Bedside (Percutaneous) Placement of Peritoneal Catheter

If peritoneal dialysis is expected to be required for a short time (<72   hours), the catheter can be placed percutaneously at the bedside (i.e., not surgically). When bedside placement is planned, all needed equipment is assembled and checked before the procedure (see Box 13-10). Because the incidence of catheter-related infection increases when percutaneously placed catheters remain in place beyond 72   hours, surgical catheter placement (i.e., in the operating suite) is indicated if peritoneal dialysis is expected to be required beyond 3 days.

When the decision for dialysis is first considered, the preparation of the child must begin. The discussion should be appropriate for the child's age and comprehension, and it should involve the physician, family, and nurse. The nurse must attempt to understand the aspects of the procedure that are frightening or confusing to the child and address those points directly. It is important that the parents understand the procedure and support the child throughout the dialysis.

The parents and the nurse must be comfortable with the facts before attempting to discuss them with the child. Often a sedative will be prescribed for the child to reduce pain and anxiety during the procedure.

A surgical preparation of the abdomen is performed, using a surgical skin cleaner, followed by an appropriate scrub. Sterile procedure will be used throughout catheter placement, which requires that the surgeon and any assistants wear gown, gloves, and masks. Local anesthetic is infiltrated along the lower quadrant of the abdominal wall. Before perforation of the abdominal wall, the child's vital signs should be documented for comparison during the procedure.

The 16-gauge polyethylene over-the-needle catheter is joined to the primed dialysate tubing, and the needle and catheter are inserted into the abdomen at the midline. Using the symphysis pubis and the umbilicus as distance markers, the catheter will be inserted one third of the total distance down from the umbilicus. The catheter is joined to the tubing of a warmed and primed bag of dialysate and is advanced into the peritoneal cavity until the drip chamber of the inflow line demonstrates free flow of solution into the abdomen. The inflow should be interrupted temporarily while the inflow line is disconnected and the steel needle is removed from the catheter. The catheter is then advanced into the abdomen (to the hub), the tubing is connected to the catheter, and a volume of 30   mL/kg is infused into the abdomen to distend it. Occasionally, a volume of up to 50   mL/kg is required to elevate the anterior abdominal wall sufficiently. During fluid infusion, the child's ventilation and perfusion must be monitored closely; infusion should be interrupted if cardiorespiratory distress develops.

When the peritoneal space is judged to be full and the abdominal wall is elevated and tense, the catheter is withdrawn and a small stab wound is made at the site of catheter insertion (without entering the peritoneum). The catheter and trocar are then inserted using steady pressure aimed at the right or left lower quadrant. Once the abdominal wall is penetrated, the catheter will be advanced as the trocar is withdrawn. Easy inflow and outflow of fluid should occur through the catheter.¹⁰¹

The catheter will be trimmed to leave only 4 to 6   cm outside the abdominal wall. The catheter should be secured with a silk purse-string suture and water-resistant tape. The outflow tubing is then clamped, and the first warmed exchange dialysate of 20 to 30   mL/kg is infused.

The child's blood pressure, temperature, respiratory rate, and heart rate are assessed and documented every 15   minutes for 1   hour, then every hour once the child's condition is stable. Changes in the child's level of consciousness and activity level should be noted and reported to a physician, because these can indicate serious fluid or electrolyte disturbances.

The dialysate remains in the peritoneal space for 15 to 90   minutes (this may vary), and then the outflow connection is opened and the fluid is drained slowly. All subsequent weights are obtained at the end of the outflow cycle when the peritoneal cavity is empty.

If the dialysate fails to drain easily, the catheter is probably obstructed by omentum. If the problem continues, surgical replacement of the catheter may be required. If the dialysate returns cloudy or consistently bloody, or if diarrhea or polyuria are noted, a physician should be notified immediately; these signs may indicate perforation of the bowel or bladder. The catheter must be removed and replaced, and the patient should be observed closely for evidence of further symptoms.¹⁰¹

Surgical Placement of Dialysis Catheter

When the dialysis catheter is placed surgically, a cuffed catheter is used and is inserted at the level of the umbilicus through a small incision in the rectus muscle. The catheter is inserted to the level of the Dacron cuff and is held in place with a peritoneal purse-string suture. Once the catheter is inserted, a small volume of dialysate or normal saline is infused in the catheter to ensure that the site does not leak and that fluid flows easily into and out of the catheter. Finally, the catheter is tunneled under the skin and exits through the skin at a site separate from the catheter entrance into the peritoneal cavity.³

Dialysate Solution

Commercially available dialysis solutions contain electrolytes in concentrations similar to that of normal plasma, except that potassium is absent and the concentration of glucose and osmolality vary. The absence of potassium ion creates a concentration gradient for potassium between the dialysate and the capillary vessels of the peritoneum so that potassium moves from the vascular space into the dialysate.

The dialysate is selected by glucose concentration and osmolality; the higher the glucose and osmolality of the dialysate, the greater will be the fluid shift from the vascular space to the dialysate (i.e., more fluid is withdrawn from the child). Commercially available solutions contain 1.5% (15   g glucose/L, osmolality of 347   mOsm/L), 2.5% (25   g glucose/L, osmolality of 398   mOsm/L), and 4.25% glucose (42.5   g glucose/L, osmolality of 486   mOsm/L). Because glucose can move from the dialysate into the vascular space according to a concentration gradient, the child's serum glucose must be monitored closely. In the patient without diabetes, endogenous insulin secretion should prevent hyperglycemia, but insulin should be added to the dialysate of diabetic patients (see “Fluid or Electrolyte Imbalance”).

Commercially available dialysates vary in electrolyte concentration (Table 13-6). Some critically ill infants are unable to tolerate lactate in the dialysate, because the lactate may worsen acidosis. Dialysate can be reformulated in the hospital pharmacy, using a sterile hood, to contain bicarbonate instead of lactate (see Table 13-6). When the dialysate contains bicarbonate, calcium must be administered intravenously and cannot be added to the dialysate; it will precipitate with the bicarbonate.

Table 13-6 Standard and Modified Peritoneal Dialysis Fluids

If the serum potassium concentration begins to fall after several dialysis cycles (usually 4-6 cycles are required), a small amount of potassium (typically to a maximum of 4   mEq/L) may be added to the dialysate with a physician or other on-call provider order.

Dialysis Exchange

The initial dialysate volume (inflow or exchange volume) is determined by the method of catheter placement. If the catheter is placed percutaneously at the bedside, initial exchange volumes of 20 to 30   mL/kg are used. If the catheter is placed surgically, smaller initial volumes (15-20   mL/kg) are used to reduce the likelihood of leak around the catheter.³ Small exchange volumes also may be necessary if respiratory distress is present and the child is breathing spontaneously.¹⁰¹ Heparin (500 units/L) usually is added to the dialysate for the first 24   hours of dialysis.

Exchange volumes are increased gradually as tolerated to 35 to 50   mL/kg/exchange. These volumes are ideal because they enable the correction of acidosis, electrolyte imbalance, and uremia.

Typically, 2.5% glucose dialysate is utilized for initial exchanges in the uremic child with acidosis and hyperkalemia. If fluid removal is not required, 1.5% glucose dialysate may be utilized. The 4.25% glucose dialysate is used for those patients with hypervolemia requiring fluid removal. The prolonged use of 4.25% glucose dialysate can be associated with hyperglycemia, hyponatremia, and hypovolemia.

For each exchange, dialysate is instilled over 5   minutes with a dwell time of 15 to 90 minutes (this may vary). The drain time varies with the size of the patient and the exchange volume; usually 5 to 10 minutes is sufficient, although drain times of 20   minutes may be required. Peritoneal dialysis is maximally effective during the first 15 to 90 minutes of dwell time. Therefore if maximum fluid removal and correction of hyperkalemia, acidosis, and uremia are required, frequent exchanges (often every 30   minutes) are performed.

Automated peritoneal dialysis cyclers are now available that provide exchange volumes as small as 50 to 100   mL. These cyclers incorporate a heater to warm the dialysate, and they automatically monitor the drain volume or outflow and can calculate the volume of fluid removed from the patient. Audible alarms indicate volume or infusion problems. Because the equipment manipulates the dialysate it can substantially reduce the nursing time needed for each exchange.

Manual peritoneal dialysis requires the use of buretrols or other graduated cylinders to monitor the precise volume of fluid infused and drained. When the exchange volume is small, buretrols can be used to measure both inflow and outflow (drain) volume. Graduated urine collection systems also can be utilized to measure outflow volume. Finally, the serial dialysate drainage bags used for continuous ambulatory peritoneal dialysis also can be utilized to measure the drain volume; clamps are used to direct the draining fluid into a separate bag following each exchange.

The large (2-L) dialysate bags should never be hung so they infuse directly into the child; if a clamp loosens or is inadvertently left open, the entire 2   L volume could be infused into the child's abdomen, causing respiratory distress and possible cardiovascular collapse. The dialysate fluid always should be warmed before use in infants and children to prevent heat loss and reduce discomfort. Room temperature dialysate may be used in adolescents unless it produces discomfort.

For dialysis in infants, exchange volumes will be small and tubing dead space should be minimized. Adult peritoneal dialysis Y tubing sets contain too much dead space for use in infants, so intravenous tubing (containing a Y or a stopcock) can be utilized to direct dialysate flow. Infant peritoneal dialysis circuits are commercially available.

Because dialysis removes fluid from the vascular space, the nurse should assess the child's volume status frequently. Signs of hypovolemia include tachycardia and signs of poor systemic perfusion (such as decreased intensity of pulses, pale mucous membranes, and cool extremities with weak pulses and sluggish capillary refill). The CVP will be low unless heart failure is present. The development of hypotension indicates critical hypovolemia and hypotensive shock.

If edema is present, peritoneal dialysis will not immediately abolish all fluid excess. However, as fluid is removed from the vascular compartment the intravascular proteins and sodium ions (osmolality) will draw water out of the edematous tissues into the vascular space, (where it can then be removed during dialysis).

Calculation of Fluid Balance

During peritoneal dialysis, two patient records of total fluid intake and output must be strictly maintained. One record documents the dialysate infused and the dialysate recovered (drain volume) at the end of each cycle (Fig. 13-9).

Fig. 13-9 Example of peritoneal dialysis flow chart template.

(Courtesy Children's Memorial Hospital, Chicago, IL.)

The amount of fluid recovered always should equal or exceed the amount infused; this produces a negative fluid balance. If less dialysate is recovered than was infused, the nurse should check for signs of catheter or tubing obstruction (see section, Catheter Dysfunction and Obstruction). If additional dialysate cannot be recovered, the difference between the amount infused and the amount recovered is recorded as a positive fluid balance, and a physician should be notified.

During the initial cycles of peritoneal dialysis, a larger volume may be recovered than was infused, indicating removal of intravascular fluid. When this occurs, the amount of fluid recovered in excess of the amount infused should be recorded as a negative number, because this represents fluid loss for the child. If significant fluid loss continues, a physician or on-call provider should be notified; it may be necessary to reduce the osmolality of the dialysate to prevent excessive fluid loss and dehydration.

The time and the duration of each infusion, dwell time, and drainage cycle should be recorded. Because maximum solute transfer occurs during the first 30 to 90 minutes the dialysate is in the peritoneal cavity, the dwell time is rarely longer than this. The temperature of the dialysate also should be measured and recorded; this temperature should be as close as possible to 37° C to improve the efficiency of dialysis and to minimize the child's heat loss and discomfort.

The second record of the child's fluid balance includes a total of all sources of fluid intake and output. The net dialysis balance is recorded as part of this total. It is extremely important that this record be carefully maintained, because it will aid in the evaluation of the child's progress and need for modifications in dialysis. When dialysis is begun, drug doses and administration schedules should be adjusted, because many drugs are removed by dialysis.

Potential Complications

Catheter Removal

The percutaneously placed PD catheter is removed using sterile technique. While one provider withdraws the catheter, a second provider maintains tension on the purse-string stitch that was placed during the catheter insertion. The suture is drawn tight as the catheter is withdrawn. The catheter tip can be sent to the laboratory for culture (per policy). Sterile dressings are placed over the catheterization site. If the dialysis catheter is placed surgically, it must be removed surgically.

Method

Complications

The most frequent complications associated with CAPD and CCPD are mechanical problems and infection. The mechanical problems are related to cuff erosion and fluid leaks, and the infection problems are related to peritonitis.

The cuffed peritoneal catheter can erode the abdominal wall; this can cause a fluid leak and require catheter replacement. Hernias can develop from subcutaneous fluid leaks around the dialysis incision, and these hernias often require surgical repair.

The incidence of peritonitis among children receiving CAPD and CCPD varies widely in clinical reports, but averages one infection every 14.7 patient months.³⁶ Many patients also develop local infections around the catheter site.

When selecting patients for CAPD, it is important that the child and the parents are reliable and able to follow the established protocol. Children or families must be taught the dialysis technique, and they should be instructed to contact the CAPD nurse whenever the patient experiences abdominal pain, inflow or outflow occlusion, inflammation of the catheter site, a feeling of weakness or dizziness when standing, hypotension, cloudy outflow, catheter disconnection or contamination, fever, excessive weight gain, edema, or other illness.

Because the dialysate dwells in the peritoneal cavity for a long time and the risk of peritonitis is relatively high in children receiving CAPD and CCPD, hospital protocols often try to minimize the number of personnel providing any in-hospital CAPD or CCPD that the child requires. This action minimizes the child's exposure to people and contaminants and may reduce the risk of peritonitis.

Method

Hemodialysis is one of the most efficient artificial methods of removing nitrogenous wastes from the body and of restoring fluid, electrolyte, and acid-base balance. However, pediatric hemodialysis requires the assembly of skilled personnel capable of establishing and maintaining vascular access, recognizing and responding to potential complications of dialysis, and supporting cardiorespiratory function in extremely unstable patients. If urgent dialysis is required and experienced personnel are not available, PD may be provided until the child's condition can be stabilized and the child transported to an appropriate facility.

Indications for pediatric hemodialysis are GFR <15   mL/min per 1.73   m² or intractable complications of AKI, even at a higher GFR. GFR is roughly equivalent to the creatinine clearance estimated by the Schwartz formula (see Box 13-5).

Complications of hemodialysis include but are not limited to hypervolemia, hyperkalemia, metabolic acidosis, hyperphosphatemia, hypocalcemia, hypercalcemia, and neurologic dysfunction.⁵²

Hemodialysis requires access in an artery, arterialized vessel, or large vein. If chronic hemodialysis is planned, an arteriovenous fistula may be created or a graft may be placed in a large artery. In the critical care unit, vascular access is often achieved with a single- or double-lumen catheter (at least size 6 French) placed through the subclavian vein into the right atrium, or from the femoral vein into the inferior vena cava.¹⁵

During hemodialysis, blood is withdrawn from the body and pumped at high flow rates to a blood compartment that makes contact with a semipermeable membrane. This blood compartment and semipermeable membrane are immersed in dialysate, which is pumped at rates that exceed blood flow rate by 50%. The dialysate flows in the direction opposite the blood flow.³⁷

The dialysate contains a fairly standard concentration of electrolytes, but the potassium concentration usually is determined individually (based on the amount of potassium to be removed). Nitrogenous wastes pass from the blood into the dialysate as the result of a concentration gradient. Free water will move from the blood into the dialysate if the osmolality of the dialysate is greater than the serum osmolality. Free water movement is also enhanced by a positive transmembrane hydrostatic pressure from the blood compartment to the dialysate compartment. This positive pressure can be generated by the blood pump and by manipulation of resistance to blood outflow, although newer dialysis machines automatically generate the transmembrane hydrostatic pressure required to provide the volume of ultrafiltrate prescribed.³⁷

The amount of fluid and solute removal from the blood is determined by the flow rates of the blood and dialysate, the surface area and permeability of the membrane, the concentration and osmolality gradients between the dialysate and blood, and the transmembrane pressure gradient. Electrolytes move across the semipermeable membrane as the result of concentration gradients. If the concentration of an electrolyte (e.g., potassium) or other small molecule (e.g., urea) is lower in the dialysate than in the blood, that electrolyte or molecule will move out of the blood and into the dialysate. If the concentration of an electrolyte or other molecule (e.g., glucose) is higher in the dialysate than in the blood, that electrolyte or molecule will move into the blood. Other substances can be removed from the blood as the result of ultrafiltration and solvent drag (the passive movement of solutes as the result of movement of large amounts of water).

Because hemodialysis requires that blood be drawn from and returned to the body, pumps must be present in the dialysis circuit. In addition, the filter and the tubing (the dialysis circuit) must be primed with fluid or blood before the dialysis begins. Because the circulating blood volume of the infant or child is low, extracorporeal movement of a large quantity of blood (e.g., to prime the dialysis circuit) is likely to produce hypovolemia. As a rule, the filling volume of the dialysis circuit should be no greater than the equivalent of 10% of the child's circulating blood volume. If the circuit requires a larger filling volume, the circuit should be primed with colloid (5% albumin or packed RBCs diluted with albumin to a hematocrit of 35%).³⁷ Few centers have experience in the hemodialysis of infants, and it should not be attempted by inexperienced personnel. In adolescents, the dialysis circuit can be primed with normal saline or 5% albumin.

The dialysate contains glucose, sodium, calcium, and potassium, in concentrations that are specified by the physician. The dialysate usually contains little potassium (0-4   mEq/L) and no urea, so that high concentration gradients between the dialysate and the blood will hasten removal of these solutes from the blood. The presence of glucose in the dialysate at levels of 200 to 250   mg/dL creates a high osmolality in the dialysate, favoring the movement of water from the blood to the dialysate, provided the patient's serum glucose concentration and osmolality are lower than the glucose and osmolality of the dialysate.

The glucose concentration in patients with diabetes mellitus is often higher than 200 to 250   mg/dL. As a result, the osmotic forces will favor free water movement from the dialysate into the patient's blood, exacerbating hypervolemia. This inappropriate fluid movement can be prevented by increasing the pressure gradient across the dialysis filter (creating higher pressure within the blood compartment or generating negative pressure in the dialysate compartment) or by adding albumin to the dialysate.

The high glucose concentration in the dialysate produces a serum glucose of approximately 200   mg/dL during dialysis. This mild hyperglycemia is usually well tolerated in the patients without diabetes mellitus; however, patients with diabetes will require adjustment of insulin dose (particularly long-acting insulin) in anticipation of this period of relatively low serum glucose.

The blood and the dialysate are typically pumped through the circuit in opposite directions. This pumping maximizes the concentration and osmotic gradients between the dialysate and the blood so that dialysis can be accomplished within a short period of time (exchange time of approximately 3-4   hours).

As noted previously, the creation of either positive pressure in the blood compartment or negative pressure in the dialysate compartment or both will increase the rate of fluid removal from the blood. Positive pressure is created in the blood compartment by increasing the resistance to flow on the venous side of the blood circuit. This increase in resistance usually is accomplished by placement of an adjustable clamp on the venous blood line, and the clamp is tightened until the desired pressure in the blood compartment is reached.

Negative pressure can be applied across the filter. This negative pressure draws free water and small particles from the blood, across the semipermeable membrane, and into the ultrafiltrate.

The dialysis nurse and the bedside nurse will be responsible for continuously evaluating the effect of fluid removal on the patient's systemic perfusion. If the patient's clinical condition deteriorates, some adjustment in the rate of fluid removal is often required.

When hemodialysis is initiated, a small amount of heparin is injected into the dialysis catheters and into the dialysis circuit to prevent clot formation in the filter and tubing. Heparin will then be administered at 30-minute to 1-hour intervals or by continuous infusion. The rate of infusion is adjusted based on the activated clotting time (ACT) or the Lee-White clotting time. Heparin dose and adjustment will be determined by dialysis unit policy and procedure. Citrate may be the anticoagulant of choice in hemodialysis therapy, and it is useful in the prevention of heparin-induced thrombocytopenia. Refer to protocols published on-line¹⁷ and in print⁶⁹ for additional information.

Complications

Hemodialysis is efficient, but it is extremely expensive and can produce complications that do not develop during PD or hemofiltration. These complications are related largely to hypovolemia and resultant hypotension, fluid shifts (also known as dysequilibrium), hypervolemia, bleeding, anemia, infection, or malfunction of the vascular access site. Each of these is discussed in the following sections.

Hemodialysis Access

The establishment and maintenance of vascular access in small children is one of the most challenging aspects of pediatric hemodialysis. Dependable, double lumen, cuffed venous catheters are now available and they are the acute and long-term dialysis catheters of choice. If these catheters are placed surgically in the right atrium and infused appropriately with heparin, they can be maintained for a long time. When vascular access is needed, the injection port of the catheter can be used and no skin punctures are required. The care of these catheters is identical to the care of any long-term central venous catheter; meticulous care is required to ensure catheter longevity and minimize the risk of infection. Refer to hospital policies and procedures regarding central venous catheter care (also, Box 22-6).

Arterial access can be provided by a graft. Grafts consist of tubes made of Teflon or polytetrafluoroethylene. The tube is attached to an artery and then looped subcutaneously and connected to a parallel large vein.¹⁵ After surgical placement, time is allowed for the graft to become coated with the patient's endothelial cells (i.e., the graft endothelializes) before it is used for dialysis. Vascular access is achieved by piercing the graft with standard large-bore needles.

Arteriovenous fistulae can still be created in older children to provide vascular access for hemodialysis. The fistula is surgically created in the nondominant arm by connection of the radial artery to the cephalic vein.¹⁵ Soon after the fistula is created, the vein distends and is punctured easily to obtain vascular access. The risk of infection in the fistula is low because no prosthetic material is involved in its construction. However, any arteriovenous shunt will increase venous return to the heart and may precipitate or worsen congestive heart failure.

Continued Problems of Uremia

The patient requiring hemodialysis is still susceptible to complications of uremia. Although dialysis may provide temporary relief of some fluid and electrolyte or acid-base imbalances, anemia, hypertension, infection, osteodystrophy, endocrine imbalance, pruritus, anorexia, nausea, vomiting, fatigue, ulcers, and depression can persist (see section, Chronic Kidney Disease).

Throughout the care of the child with renal failure, the nurse should consult support personnel to assist in the psychosocial care of the child and family. Frequent multidisciplinary conferences and meetings with the social worker, dietician, financial counselor, physicians, and primary nurses will help the family to be aware of the support systems available to them and ensure that communication is optimal among team members and the family. As appropriate, the bedside nurse or case manager should begin to plan for the child's discharge to home or to another unit.

Whenever the critically ill child requires dialysis, the bedside nurse remains responsible for coordinating the care of the child and family. Although a dialysis nurse may be present and responsible for the dialysis procedure and circuit, the bedside nurse still must assess and document the child's fluid balance and systemic perfusion. The dialysis nurse and the bedside nurse should coordinate efforts. It is important to time the administration of medications, blood products, and fluids based on the timing and effectiveness of the dialysis. Both the dialysis nurse and the bedside nurse must provide the child and family with skilled support and compassion.

Definition

Hemoperfusion is a treatment which exposes blood or plasma to an adsorbent material for the removal of toxins, solutes, or other materials. Adsorbent materials used can include charcoal, resin, protein A, synthetic materials, and monoclonal antibodies.²¹

Although hemodialysis is highly efficient at removing water-soluble drugs with low molecular weights (e.g., salicylates, ethanol, methanol, lithium) from the blood, it does not remove protein and lipid-bound substances; therefore it is not effective in the treatment of hypercholesterolemia, hyperbilirubinemia, toxicity associated with fulminant hepatic failure, or ingested toxins. Hemoperfusion is extremely effective in the treatment of these problems.²¹ Large molecules such as β₂-microglobulin have been successfully removed by hemoperfusion with lower cardiovascular mortality,⁸⁷ and clinical trials are currently underway with new adsorbents that are effective in removing β₂-microglobulin.²¹

Hemoperfusion uses a hemodialysis circuit; however, the blood is passed through a cartridge containing the adsorbent surface, and no dialysate is present. Life-threatening poisonings from theophylline, carbamazepine, phenobarbital, and phenytoin may be an indication for charcoal hemoperfusion.⁷⁴ With the use of activated charcoal, substances normally bound by lipid or protein are quickly and effectively removed from the intravascular space. Because hemoperfusion will not remove urea, it is not the treatment of choice for uremia.

Method

In the following discussion, a charcoal filter or cartridge will be used as the example of the adsorbent surface. As noted previously, the vascular access and circuit tubing used for hemoperfusion are often identical to those required for hemodialysis.

The charcoal filter is prepared, and the filter is given a glucose-heparin rinse. Because most commercially available cartridges require a priming volume of 50 to 300   mL, the total hemoperfusion circuit is primed with the equivalent of more than 10% of the circulating volume of a small child. As a result, the circuit usually is primed with blood before initiation of hemoperfusion.²⁴

Some anticoagulation must be provided to prevent clot formation in the cartridge. Heparin usually is infused into the inflow tubing, between the patient and the cartridge. To minimize the risk of bleeding, protamine sulfate usually is added to the blood in the circuit beyond the cartridge (i.e., between the cartridge and the patient) to bind the heparin before the blood is returned to the patient.

Approximately 3   hours are required for hemoperfusion. The activated charcoal quickly will become saturated with the drug or substance removed from the blood. Frequently, several cartridges are required to complete one treatment. To determine the amount of toxin binding provided by the cartridge, blood levels of the toxic substance are drawn from the circuit immediately proximal to and distal from the cartridge. If these levels become nearly identical or if clotting is observed in the cartridge, the cartridge should be changed.

Complications

The activated charcoal binds lipid or protein-bound toxins. In addition, it binds glucose, calcium, and platelets; therefore serum concentrations of these substances must be monitored closely during hemoperfusion. Severe thrombocytopenia is the most common complication observed during this procedure.²⁴

Occasionally, hemoperfusion effectively removes the toxins from the blood, but rebound toxicity develops several hours later as tissue-bound toxins move into the vascular space. For this reason, serum levels of the toxin should be monitored during the hemoperfusion and at regular intervals for several hours following hemoperfusion.

Bleeding can result from thrombocytopenia or heparinization. Because the half-life of protamine sulfate is shorter than the therapeutic effect of heparin, it may be necessary to administer additional protamine sulfate several hours after hemoperfusion is performed. During and after the procedure, the child should be observed closely for any evidence of bleeding, and all body secretions should be checked for the presence of blood.

Definition

CRRT performs the work of the kidney through an extracorporeal system designed to run continuously. The patient's blood flows through a filter to remove excess fluid, waste products, and toxins and to establish electrolyte and pH balance before it is returned to the patient. CRRT is similar to hemodialysis, but treatment is continuous rather than intermittent. The continuous aspect of CRRT provides more gradual fluid and electrolyte shifts and enables more tightly calibrated fluid management. CRRT as provided by current technology enables minute-to-minute adjustments in therapy titrated to patient need.

Indications for Continuous Renal Replacement Therapy

In the setting of AKI, the indications for renal replacement therapy are fluid and solute removal. Similar to PD, CRRT provides a gradual fluid and solute removal, but CRRT allows more sensitive fluid control than PD.¹⁰¹ Comparable to HD, CRRT can treat hypervolemia and electrolyte imbalance but instead of correcting these imbalances over 3 to 4 hours as with HD, CRRT will correct them over 1 day or more. For these reasons, CRRT is a valuable treatment choice in critically ill pediatric patients with AKI who are hemodynamically unstable with signs of multiorgan dysfunction syndrome. In data from the ppCRRT Registry, the most common acute diagnoses in patients receiving CRRT were sepsis and cardiogenic shock, and the most common comorbid conditions were bone marrow transplant and solid organ transplants—primarily the liver.^38,88

In data from the ppCRRT Registry, immediate indications for CRRT include: fluid overload and electrolyte imbalance, fluid overload only, electrolyte imbalance only, prevention of fluid overload to allow intake, or other indications such as intoxications and inborn errors of metabolism. The combination of fluid overload and electrolyte imbalance was the most frequently encountered indication and had the lowest survival.

Recent experience supports the use of CRRT as a treatment modality for sepsis, not only for the management of fluids and electrolytes but also for the removal of inflammatory mediators of sepsis.^26,28,33 CRRT has been effective after stem cell transplant, for treatment of drug toxicities, in acute solute removal in tumor lysis syndrome with associated hyperkalemia and hyperuricemia and to treat inborn error of metabolism.

Continuous Renal Replacement Therapy Modalities

CRRT is a broad term that encompasses treatment modalities involving an extracorporeal system and water removal by filtration. The treatment modalities include continuous arteriovenous hemofiltration (CAVH) and a variety of modalities provided by continuous venovenous hemofiltration.

The mechanism of solute transport is the distinguishing feature of the CRRT modalities. Solutes are removed by diffusion, convection, or both.

When solute is removed by diffusion, the process is similar to that described in the hemodialysis portion of this chapter. Solutes are removed from the blood through the filter's semipermeable membrane as the result of concentration gradients. Solutes move from the area of high concentration (blood) through the semipermeable membrane into an area of low concentration (i.e., fluid on the opposite side of the membrane).

The second mechanism of solute transport is convection. Solutes in solution are carried with the water across the semipermeable membrane in response to a transmembrane pressure gradient. Convection has been described as “solvent drag”: the bulk water flow literally drags the solutes through the semipermeable membrane. In venovenous CCRT, the transmembrane pressure gradient is generated by the speed of the blood pump or blood flow rate (BFR), which transmits a positive hydrostatic pressure inside the blood tubule of the filter. The rate of the effluent pump, or effluent and dialysate pump if dialysis is used, creates a negative pressure in the space surrounding the blood tubules, therefore increasing the transmembrane pressure gradient.

Definition

CAVH uses an extracorporeal circuit and a small filter that is highly permeable to water and small solutes, but is impermeable to proteins and formed elements of the blood. The filter system is joined to both an arterial and a venous catheter. Passage of arterial blood through the filter results in the formation of an ultrafiltrate of plasma that consists of water and nonprotein bound solutes. The filtered blood is then returned to the patient through the venous catheter.

Because the filter used for CAVH contains no dialysate there are no concentration gradients established across the filter. The volume and content of the ultrafiltrate is determined by the rate of blood flow through the filter (essentially determined by the patient's blood pressure), the permeability of the filter, and the transmembrane pressure. The transmembrane pressure is created largely by the patient's arterial pressure, but it also can be augmented by elevating the patient above the fluid drainage bag. The transmembrane pressure also will be enhanced by the oncotic pressure difference between the patient blood and the ultrafiltrate, which is protein-free with an oncotic pressure of zero.

The volume of ultrafiltrate can also be adjusted through the use of negative pressure generated on one side of the filter by the use of a volume-controlled infusion pump that draws ultrafiltrate at a set hourly rate. The faster the rate set for the volume-controlled pump, the more ultrafiltrate drawn from the blood through the filter every hour. The infusion pump can create resistance to flow if it is adjusted to a relatively slow hourly rate. As a result, resistance to ultrafiltrate production will be created by slow flow through the infusion pump circuit. The use of infusion pumps in this setting is not optimal for neonates and small infants, because the pumps may be inaccurate and might remove fluid at an unreliable rate. For example, the amount of ultrafiltrate could actually be greater than the hourly rate set on the infusion pump.

CAVH can provide effective therapy for the treatment of AKI complicated by hypervolemia or electrolyte or acid-base disturbances. It is particularly useful in patients with extremely limited venous access, in neonates or small infants, and in patients with unstable cardiovascular function or multisystem organ failure who are likely to be intolerant of hemodialysis. This form of renal replacement is not recommended for the rapid treatment of hyperkalemia, because the rate of ultrafiltration is low and potassium removal is slower than with hemodialysis.¹⁹

CAVH may be used to remove a small but predictable volume of fluid from the vascular space. This procedure is helpful in the management of chronically ill patients with oliguria and hypervolemia (e.g., those with severe congestive heart failure), because excess fluid can be removed and replaced with parenteral fluid that has high nutrient value.

With the appropriate equipment, CAVH systems can be assembled and implemented relatively quickly. CAVH also can provide a useful option when resources are scarce. However, in many critical care areas CAVH has been replaced by venovenous hemofiltration machines with more precise technology to provide safer and more predictable blood flow and precise ultrafiltation.^12,69

Contraindications

There are few contraindications to the use of CAVH. Active bleeding is a relative contraindication; PD is preferred in such patients. A severe coagulopathy is not a contraindication to the use of CAVH, although the risk of bleeding at the access site is increased.

Method

Preparation for Continuous Arteriovenous Hemofiltration

To begin CAVH, arterial and venous access must be achieved. It is extremely important to catheterize an artery large enough to allow sufficient flow into the filter; the femoral artery is used most frequently, although the umbilical artery may be catheterized in neonates. The femoral and external jugular veins are used most frequently for venous access.

The circuit tubing should contain multiple sampling ports, and it should be primed before use. A heparin infusion system (with appropriate infusion pump) should be joined to the arterial side of the circuit, and stopcocks and tubing should be placed in the circuit to enable bypass of the filter; these stopcocks will be used when the filters are changed. The filter and circuit are prepared, and the prime fluid should be warmed to no more than 37° C.

Many CAVH filters are commercially available, and most use a hollow fiber design. It is preferable to use small filters (20-mL prime volume) designed for use in small children to keep the volume in the circuit as low as possible during treatment. The ideal filter has a short fiber length, a large surface area, and a small priming volume. If the entire extracorporeal circuit must be primed with a volume exceeding 10% of the patient's blood volume, fresh bank blood should be used to prime the circuit.

As noted previously, a volume-controlled infusion pump may be required to enhance or limit the formation of ultrafiltrate. Occasionally, an additional fluid infusion pump and infusion system are prepared to administer fluid to the patient to enable replacement of ultrafiltrate with fluid that differs in solute or nutritional content (Fig. 13-10).

Fig. 13-10 Continuous arteriovenous hemofiltration. A, The rate of fluid removal can be controlled if a pediatric volume infusion pump is joined to the hemofilter. The variable resistance generated by the infusion pump will control the hemofilter transmembrane pressure and the filtration rate. B, Continuous hemofiltration generally requires infusion of replacement fluid to prevent volume depletion and to control the electrolytes lost through hemofiltration. Use of two pediatric infusion pumps enables controlled removal of fluid and controlled replacement of fluid and electrolytes.

(From Stark JE, Hammed J: Continuous hemofiltration and dialysis. In Blumer J, editor: A practical guide to pediatric intensive care, ed 3. St Louis, 1990, Mosby-Year Book.)

Pediatric Considerations

Access issues are extremely important in all patients who need renal replacement therapy, but these challenges become much more difficult in small, critically ill patients. Access is the most important consideration contributing to the effectiveness of therapy, and constant problems can arise when access is inadequate.¹⁰⁰

Data from the ppCRRT Registry indicate that femoral access is used most often.⁸⁸ Care must be taken with femoral catheters in neonates and young children to prevent thrombosis and bleeding at the site. Femoral catheters are subject to kinking and are positional, and high negative pressures may lodge the catheter tip against the wall of the vessel, impeding flow. Femoral catheters may also have draw and inflow problems caused by increased intraabdominal pressure. These issues can be alleviated by careful positioning and switching the outflow (arterial) port with the inflow (venous) port of the catheter.

Catheter placement and size are based on the optimal site determined for the patient based on the risk of thrombosis and infection, ease of placement, and adequacy of function. Most pediatric practitioners recommend short, large-bore catheters in the right internal jugular vein or access in the femoral vein using the shortest possible catheter that will reach the inferior vena cava.¹⁶

Circuit volume must be considered. The CRRT circuit volume can represent a large percentage of the total blood volume in neonates or infants, especially if the patient is hemodynamically unstable as the result of sepsis, shock, or cardiac failure. The guidelines^17,61 recommend a blood prime if the circuit volume represents >10% of the patient's blood volume or if the patient is hemodynamically unstable. It is important to remember that packed RBCs from the blood bank have high potassium concentration and a hematocrit of approximately 80%; therefore they should be diluted by 50% using either normal saline or albumin before the circuit prime.

Blood priming can cause early clotting and in some filters may cause acute hypotension that is thought to be caused by bradykinin release.¹⁷ If a blood prime is required, several procedures may help maintain hemodynamic stability while connecting the patient to the circuit.

The first procedure prepares the bank blood for infusion into the patient. This procedure, called zero balance ultrafiltration,⁴⁶ circulates the bank blood through the CRRT circuit to normalize electrolytes and improve the acid-base status of the blood before connecting the circuit to the patient.

A second procedure uses a priming mixture of 75   mL of PRBCs, 75   mL of sodium bicarbonate, and 300   mg of calcium gluconate to be transfused post hemofilter.¹⁷ In a third option, called the bypass maneuver, RBCs are administered to the patient at the same rate that the patient's blood is entering the circuit. The heparinized priming solution is discarded as it is displaced by the patient's blood. When the circuit is completely primed with the patient's blood, the venous line of the circuit is attached to the patient and CRRT treatment is begun.³⁵

Hypothermia is a significant problem in pediatrics, especially in neonates or small infants, whenever an extracorporeal system is used. Heat loss is related to the blood flow rate (BFR) and the volume of blood in the circuit. Heat loss can be problematic even in children with higher BFR and smaller circuit volume-to-blood volume ratios. All possible measures should be instituted to maintain normothermia. Newer machines incorporate blood warmers. However, if a warmer is not included in the circuit, the nurse should institute some method of providing external warming. Blood warmers can be attached to the patient return line of the circuit to warm the blood just before it is returned to the patient. Potential external warming devices include radiant warmers, body warmers, heating mattresses, and solution heaters.

Most commercially available systems have membrane choices that will meet the patient's needs and the prescribed therapy that is based on those needs. For a list of access catheters see Table 13-8. Table 13-9 lists characteristics of CRRT hemofilters used for children, including priming volume, and Table 13-10 lists machines.

Table 13-8 Recommended Catheter Sizes and Sites for Pediatric Continuous Renal Replacement Therapy

Data supplied by Cook Critical Care, Bloomington, IN.; Mahurkar catheters are marketed by Kendall Company, Mansfield, MA; Medcomp, Harleysville, PA.; The Kendall Company, Mansfield, MA. Adapted from McBryde KD, Bunchman TE: Continuous renal replacement therapy. In Wheeler DS, Wong HR and Shanley TP, editors: Pediatric critical care medicine basic science and clinical evidence, London, 2007, Springer-Verlag.

Table 13-9 Hemofilters for Continuous Renal Replacement Therapy in Children

Table 13-10 Hemofiltration Machines

Baxter, Baxter Healthcare Corporation, Deerfield, IL; Braun, Braun Medical Incorporated, Renal Therapies Division, Bethleham, PA; Edwards Lifesciences, Draper UT: Fresenius, Fresdius Medical Care North America, Waltham, MA; Gambro, Gambro USA, Lakewood, CO; Hospal, Meyzieu, France.

* Prisma system no longer available, but supported by Gambro.

† Blood pump only; need the addition of the BM 14 to make the total of a BM 25 for the blood and ultrafiltration monitor together.

From Brophy PD, Bunchman TE: References and overview for hemofiltration in pediatrics and adolescents. Available at http://www.pcrrt.com/Protocols%20PCRRT%20Zurich.pdf, Accessed January 14, 2010.

Nutritional considerations in the pediatric patient during CRRT are focused on protein requirements. In critically ill children or in children during the postoperative period, provision of adequate dietary protein is the most important nutritional intervention. Recommended daily amounts of protein to be administered to these children range from 1.5 g/kg for patients with AKI who are not receiving dialysis to 3 to 4   g/kg for patients receiving CRRT.¹⁷ When critical illness is complicated by renal injury or failure, protein loss increases and it is imperative to consider this loss in planning the child's nutritional support. Protein loss in this setting results from increased muscle protein catabolism from insulin resistance, acidosis, and the presence of catabolic hormones and mediators.⁶⁸

CRRT prescription variables include selecting the CRRT modality, the blood flow rate (BFR), the ultrafiltration rate, the dialysate rate, and the replacement fluid rate appropriate for the patient's clinical condition. In pediatric CVVH, a BFR of 4 to 6   mL/kg per minute is used, while attempting to keep the venous return pressure below 200   mm Hg. Dialysate and replacement fluid rates at 2000   mL/1.73   m² per hour have historically been used with a minimum rate of 35   mL/kg per hour.^17,100 The available data are insufficient to guide dialysate or replacement fluid rates, and wide variations exist worldwide in dialysis dosing.^78,81,100 Because of the many options available, prescription decisions should be tailored to the needs of the patient.¹⁰⁰

Contraindications and Indications

As with CAVH, there are few contraindications to venovenous CRRT. It is often the treatment of choice for critically ill pediatric patients who are hemodynamically unstable as a result of shock, sepsis, or poor cardiac function. It is also used in patients after transplant (e.g., liver, bone marrow, stem cell transplant) who are fragile and have a metabolic milieu that does not promote optimal organ function. Even bleeding is not a contraindication to venovenous CRRT.¹⁹ The patient must always be observed for bleeding at catheter sites, and vigilance must be heightened if the patient exhibits severe coagulopathy.

Method

Etiology

NS is primarily a pediatric disease, developing in approximately 2 to 5 in 100,000 children per year.⁹¹ It is 15-fold more common in children than in adults. Although NS can occur at any age, the initial onset of the disease is most often between 2 and 7 years of age. NS is seen approximately twice as often in boys as in girls in this age group.⁹¹

NS is currently categorized into primary and secondary forms. Primary or idiopathic NS is the most common form of NS in children (90% of cases); the cause remains unclear. Secondary NS is seen less frequently (10% of cases) in children and results from infections, drugs or toxins,⁹⁷ systemic diseases, or glomerular disease (e.g., membranous nephropathy, membranoproliferative glomerulonephritis).

Pathophysiology

Primary NS is believed to have immune pathogenesis, although the precise mechanism remains to be elucidated.⁹¹ Primary NS may be related to lymphocyte dysfunction and suppressor cytokines, or lymphocytes may initiate the syndrome. The permeability of the glomerular filtering membrane is increased, with electron microscopy revealing effacement or fusion of foot processes of podocytes (cells forming the outer layer of the glomerular capillary). The foot processes of the podocytes normally interconnect, leaving small filtration slits that normally do not allow filtration of protein.

The increase in glomerular capillary permeability may be related to a change in the electrostatic charge of the glomerular capillary wall by a highly cationic plasma protein. Under normal conditions, the glomerular endothelial cells and basement membrane express negatively charged glycoproteins, and they repel negatively charged proteins. If the charge becomes positive, then large, negatively charged proteins are no longer electrically repelled, and they begin to pass through the glomerular membrane, resulting in severe proteinuria.¹⁰²

Clinical Signs and Symptoms

Periorbital edema is often the first sign noted by parents of children with NS. Initially the eyes are puffy only in the morning and appear normal later in the day. Soon, however, the child develops dependent edema. If the child is ambulatory, the edema will first be apparent in the ankles and feet. It is common for children to be diagnosed with allergies during this time. As the edema becomes more generalized, it will be noted in the abdomen. The development of abdominal distension may accentuate inguinal and umbilical hernias, and labial and scrotal edema may be excessive. Moderate hepatomegaly often is noted. If ascites becomes severe, it may compromise diaphragm excursion and cause respiratory distress.

Generalized edema may also produce diarrhea, vomiting, and anorexia. These gastrointestinal symptoms and the presence of a generalized catabolic state further deplete body protein stores. Malnutrition and loss of muscle mass may become severe, but may not become apparent until the edema resolves. During the edematous phase, fever may be absent despite the presence of infection.

The patient with NS is oliguric; the urine has an acid pH and contains large quantities of protein, so it foams. Urine may be tinted pink or red from microscopic hematuria; it may contain granular and cellular casts and lipid bodies. Severe hypoalbuminemia is generally present among children with NS, and most have albumin levels of less than 2.5   g/dL. Serum complement levels are low in some patients with nephritic syndrome (e.g., membranoproliferative glomerulonephritis or systemic lupus erythematosus nephritis), but are normal in children with MCNS.

Total serum calcium concentration may be falsely low. Because hypoalbuminemia is present, the fraction of the total calcium bound to protein is reduced; therefore serum ionized calcium concentration may be normal. The patient with chronic NS, however, may demonstrate genuine hypocalcemia resulting from loss of vitamin products, including vitamin D. Water retention may contribute to the development of hyponatremia; hyperaldosteronism and poor dietary intake may produce hypokalemia.¹⁰ Approximately one fourth of the children with MCNS demonstrate an increase in serum creatinine and BUN. Children who have focal glomerulosclerosis may demonstrate glycosuria and bicarbonaturia, with only moderate reduction of creatinine clearance.

A secondary anemia may be present and may be severe when significant glomerular disease is associated with renal failure. Because the patient's skin is edematous, the pallor of anemia may be more pronounced. If the child's intravascular volume is reduced, hemoconcentration may maintain the measured hematocrit within normal limits.

The risk of thromboembolism is high among patients with NS. These children demonstrate a hypercoagulability that may be related to increased platelet aggregation and increased levels of beta-thromboglobulin, as well as decreased fibrinolytic activity. As a result, the nurse should monitor for signs of thromboembolic events and minimize venipunctures and use of longdwelling central venous or arterial catheters.

During NS relapse, edema can accumulate rapidly in tissues, depleting the intravascular volume. If this fluid shift from the intravascular space occurs during sodium restriction and diuretic therapy, hypovolemia may result in circulatory collapse.

Children with NS usually develop anorexia and demonstrate growth failure. The administration of steroids and immunosuppressive agents can further compromise the child's growth. In addition, the steroids and immunosuppressive agents increase the child's risk of infection, as does the loss of immune proteins in the urine. Sepsis, especially gram-positive sepsis, frequently occurs among children with NS in relapse.

A renal biopsy is necessary to firmly establish the degree of glomerular damage associated with NS, but it may not be performed as part of the initial workup. Because MCNS is the most common form of NS occurring in children, a 4-week course of corticosteroid therapy abolishes symptoms in approximately 93% of children with NS who are between 1 and 7 years of age.⁶⁷

If the child with NS does not respond to the initial steroid therapy, a renal biopsy is often indicated.⁶⁷ The biopsy specimen is examined using both electron and light microscopy techniques. Identification of the degree of glomerular involvement will enable better evaluation of therapy and establishment of prognosis.

Management

Treatment of the child with NS is aimed at restoration or maintenance of adequate circulating blood volume and systemic perfusion, minimization of glomerular damage and maximization of renal function, maintenance of fluid and electrolyte balance, maximization of patient comfort, and prevention of infection. Respiratory function also must be monitored and supported.

If the child with NS has signs of poor systemic perfusion (e.g., tachycardia, cool, clammy extremities, and decreased intensity of peripheral pulses) and intravascular volume depletion (no hepatomegaly, low CVP, small heart silhouette on chest radiograph), then a large-bore central venous catheter should be inserted if one is not already in place. This catheter will enable measurement of CVP and infusion of intravenous fluids. Usually bolus administration of 10 to 20   mL/kg of saline, Ringer's lactate, albumin, or a mixture of saline and albumin (80   mL of saline plus 20   mL of 25% albumin) will reestablish adequate intravascular volume (see “Management of Shock” in Chapter 6). Fluid resuscitation should proceed with care to avoid pulmonary edema, and the healthcare team should be prepared to support ventilation.

The use of albumin may cause rapid fluid shift from the third space into the vascular space. If the child is oliguric, fluid administration probably should be curtailed as soon as intravascular volume is adequate as indicated by a CVP >5   mm Hg, with good systemic perfusion and a heart rate that is appropriate for age and clinical condition.

Once systemic perfusion is acceptable, laboratory studies should be performed, including complete blood count, serum electrolytes, calcium, phosphorus, BUN, creatinine, total protein, albumin, globulin, cholesterol, triglycerides, complement (C₃), and urinalysis. Each time the child voids, the urine should be measured and tested for proteins. The urine specific gravity will be falsely elevated in the presence of proteinuria or with administration of osmotic diuretics. The urine osmolality is the best indicator of renal function, because it reflects renal concentrating ability and is not affected by the presence of large molecules in the urine.

Collection of urine samples from the infant or child with NS may be difficult. Catheterization should be avoided if possible, because it introduces risk of infection. Adhesive urine collection bags can irritate the edematous perineal skin; therefore they should be avoided. Small children may be allowed to void on nonabsorbant surfaces, such as the outside of a disposable diaper, so that some urine can be collected for analysis. Cotton balls may be placed in the diaper to catch the urine; the urine is then squeezed out of the cotton ball into a container to be sent for analysis. The specimen should be labeled as that collected into a cotton ball, because it will not yield reliable cell counts.

The child with NS requires careful measurement of all sources of fluid intake and output. The child's daily weight should be measured using the same scale and technique at the same time of day. Frequent, but rough, estimates of the degree of edema should be made. If ascites is present, the child's abdominal girth should be measured at least once daily.

Usually, children with NS are asymptomatic except for the discomfort caused by edema. Bed rest is necessary only during acute infections or when severe incapacitating edema is present. Because bed rest is associated with problems of large vessel venous stasis, possible decubitus, and possible development of contractures, mobility is encouraged as soon as it is feasible.

Salt restriction, albumin infusion, or diuretics may be necessary to reduce edema. All of these methods of reducing edema, except albumin infusion, can result in intravascular volume depletion, so they should be used with caution. In addition, the hemoconcentration produced by edema and vigorous diuresis can aggravate the hypercoagulability, resulting in increased risk of thromboembolic events.

If a diuretic is prescribed, the nurse should assess the child's systemic perfusion carefully before administering the drug, and then monitor perfusion during and after diuresis. Furosemide is the most commonly used diuretic for children with NS, whether administered by scheduled doses or by infusion⁶⁷ (see Table 13-2).

Furosemide (1-2   mg/kg per intravenous dose) may be prescribed; this dose can be increased each time the drug is given until a maximum of 4 to 5   mg/kg every 12   hours is reached. If the patient develops resistance to furosemide, other diuretics such as metolazone, hydrochlorothiazide, and spironolactone (an aldosterone antagonist) can be used.

For maximal diuretic effect, the infusion of salt-poor albumin may be ordered to be followed by intravenous administration of furosemide (1-2   mg/kg) within 30   minutes. The administration of 25% albumin before diuresis will diminish the risk of hypovolemia, and a target albumin level of approximately 2.8   g/dL is considered sufficient to restore intravascular volume and oncotic pressure.⁶⁷ The nurse should monitor for signs of hypervolemia after albumin administration, although risks can be reduced by infusing albumin at a slow continuous rate. Signs of hypervolemia include tachycardia, hypertension, and congestive heart failure. The increase in intravascular volume is usually only transient while the albumin remains in the vascular space.

If the child is between 1 and 7 years of age with a normal complement (C₃) concentration and minimal hematuria, MCNS is likely to be present, and steroid therapy is the treatment of choice. Prednisone is given in a dose of 2   mg/kg per 24 hours, for a maximum total daily dose of 80   mg in divided doses.⁶⁵ Proteinuria should disappear within the first 2 weeks of therapy in most children. Once the child responds to the prednisone, the dose can be tapered over a period of several months while the child or parents continue to test the child's urine for proteinuria.

If the child continues to demonstrate proteinuria after 28 days of continuous prednisone therapy, a renal biopsy usually is planned to determine the etiology of the NS. NS that is unresponsive to prednisone may include MCNS or mesangial proliferation or focal glomerulosclerosis.

Treatment of steroid-resistant or relapsed NS may require the use of alkylating agents such as cyclophosphamide or chlorambucil. These drugs can produce alopecia, leukopenia, and increased susceptibility to infection, so careful evaluation and preparation of the child and family is required before such drugs are prescribed. Cyclosporine has become one of the most commonly used drugs for children with steroid-resistant NS (SRNS). More recently, tacrolimus has been used with prednisone to treat SRNS, with a high rate of complete remission reported.⁶⁷

The child will be extremely uncomfortable if severe edema is present. Measures should be taken to avoid friction between adjacent skin surfaces, such as between the inner leg and the scrotum or between the chest and under arm areas. Rolls of cotton can be placed in these areas, or nonperfumed talc or cornstarch can be placed over friction points. Because the skin is extremely fragile, tape or adhesive dressings should be avoided. The bedridden child should be turned frequently to avoid pressure sores over bony prominences.

Resistance to infection is compromised by loss of immune proteins in the urine, poor systemic perfusion, steroid and/or immunosuppressive therapy, poor nutrition, and appetite loss. The nurse and dietician should make every effort to provide the child with small, frequent, nutritious, and appetizing meals.

The development of significant abdominal effusion can increase the risk of peritonitis, causing unexplained fever and ascites. Administration of prophylactic antibiotics usually is not indicated, because it can foster the growth of resistant organisms. The pneumococcal vaccine should be administered to any patient with new onset NS and every 5 years thereafter to reduce the risk of infection.

The mortality rate of NS is low (3% to 7%), and the prognosis for children with MCNS is best if the child has only signs of proteinuria and responds immediately to prednisone therapy. If the child has nonresponsive (i.e., steroid-resistant) or steroid-dependent NS, recovery is less complete, and relapses may occur frequently. If the child is unresponsive to steroids (i.e., has SRNS), immunosuppressive drugs, and alkylating agents, the prognosis is poor because many of these patients (estimated risk >40% within 5 years of diagnosis) develop end-stage renal disease (ESRD). SRNS causes greater than 10% of pediatric ESRD.⁶⁷ Severe glomerular sclerosis that is resistant to treatment often is associated with a fulminant and fatal course.

Because the child's illness is often sudden and the prognosis is usually uncertain for several weeks, it is imperative that the child and family receive adequate support and consistent information from all members of the healthcare team.

Etiology

Acute glomerulonephritis is a significant cause of AKI in pediatric patients and among children who require acute dialysis.⁶⁷ Glomerulonephritis can be a primary or secondary disease resulting in glomerular injury leading to hematuria, mild proteinuria, edema, hypertension, and oliguria. The injury to the glomerulus is characterized by glomerular inflammation and cellular proliferation. Nephritogenic forms of streptococcus have been associated with the most common form of glomerulonephritis in children, though other bacterial, viral, parasitic, pharmacologic, and toxic agents have also been implicated.²⁵

Pathophysiology

When antibody reacts with circulating antigen that is unrelated to the kidney and forms immune complexes, these complexes are deposited in the glomerulus. The deposits contain immunoglobulins and complement that can be visualized with immunofluorescence microscopy. This deposition stimulates glomerular endothelial proliferation, mesangial proliferation, and invasion of white blood cells. When antibody reacts with antigen located on the glomerular basement membrane, the deposition of immunoglobulin and complement forms crescents.^59,77 These deposits also activate the inflammatory response.

Clinical Signs and Symptoms

The onset of glomerulonephritis is usually abrupt with manifestations of nephritis: azotemia (excess of urea or other nitrogenous wastes), oliguria, edema, hypertension, proteinuria, and active urine sediment.⁵⁷ If glomerulonephritis is related to a nephritogenic streptococcal infection, it generally develops in children between the ages of 2 and 12 years, and symptoms develop approximately 7 to 14 days after a group A beta-hemolytic streptococcal pharyngitis or 21 to 40 days after streptococcal skin infection (impetigo).⁵⁹ The symptoms are usually self limiting, although prolonged hematuria and proteinuria occasionally occur.

Macroscopic hematuria (excretion of rusty colored urine) is a frequent presenting sign, although microscopic hematuria is occasionally present. The child usually develops systemic edema; periorbital edema may be noted initially, although generalized edema is often present. Proteinuria is present, but is not as severe as that seen with NS.

Hypertension is present in 50% to 60% of children with acute streptococcal glomerulonephritis,^25,67 and it can be severe. Occasionally, hypertensive encephalopathy develops and will be associated with signs of altered level of consciousness, irritability, and increased intracranial pressure.

Signs of hypervolemia may be associated with signs of congestive heart failure, including tachycardia, hepatomegaly, high CVP, tachypnea, and increased respiratory effort. Radiologic evidence of cardiomegaly and pulmonary edema are often apparent.

The child with glomerulonephritis is often oliguric but rarely anuric. The GFR is reduced, but renal concentrating ability may be normal. The fractional excretion of sodium often is reduced, and sodium and water retention develop (see “Acute Kidney Injury” earlier in this chapter for information regarding fractional excretion of sodium). Hematuria with RBC casts are the characteristic urinalysis findings associated with acute glomerulonephritis and are documented in nearly half of involved patients.⁵⁷ A renal biopsy rarely is indicated to confirm the diagnosis of glomerulonephritis.

Changes in the child's serum and urinary electrolyte concentrations often resemble those associated with prerenal failure (see Table 13-4). The creatinine is often normal, but the BUN typically is elevated. The child may demonstrate dilutional hyponatremia, and the serum albumin concentration will be low. Serum hyperkalemia also may develop and produce associated changes in cardiac rhythm (see “Hyperkalemia” earlier in this chapter, and in Chapter 12). A dilutional anemia may also be observed.

Antibodies to streptococcal products (such as antistreptolysin-O) usually can be documented in patients with poststreptococcal glomerulonephritis from pharyngeal infection, but may not be present after a skin infection. The most consistent indicators of a recent streptococcal infection are serum titers of antihyaluronidase and antideoxyribonuclease B (antiDNAase B). High serum immunoglobulin (Ig) G levels and low C₃ levels will be present.⁵⁹

Management

Most children with acute glomerulonephritis will recover completely if complications of renal disease can be prevented.²⁵ If AKI failure develops, fluid restriction will be required, and treatment of electrolyte and acid-base imbalances will be necessary (see section, Acute Renal Failure and Acute Kidney Injury). In general, treatment is symptomatic and supportive.

Sixty percent of children with acute glomerulonephritis will develop hypertension.²⁵ The nurse should notify the on-call provider if hypertension develops and perform frequent neurologic examinations to detect any deterioration in the child's level of consciousness. The child with significant hypertension may develop headaches and signs of encephalopathy, including nausea, vomiting, irritability, lethargy, seizures, coma, and increased intracranial pressure. Standard therapies to treat hypertension include sodium restriction and drug therapy including diuretic therapy with furosemide, calcium channel blockers, vasodilators and ACE inhibitors.²⁵

Significant hyperkalemia must be treated on an urgent basis to prevent the development of malignant arrhythmias. Administration of calcium, sodium bicarbonate, glucose and insulin, or a sodium polystyrene sulfonate (Kayexalate) enema may be needed (see “Hyperkalemia” in this chapter and in Chapter 12).

If signs of congestive heart failure develop, the child will require treatment with fluid restriction and diuretics. Intravenous inotropic agents and/or vasodilators may be necessary. (See “Management of Shock” in Chapter 6, and “Congestive Heart Failure” in Chapter 8).

Because antibiotic administration does not influence the recovery of children with glomerulonephritis, antibiotic administration is indicated only if the child has positive bacterial cultures.

Etiology

Hemolytic uremic syndrome (HUS) is a thrombotic microangiopathic disease involving endothelial damage, which leads to platelet and fibrin deposition in small vessels. It has several etiologies.

HUS is characterized by a triad of symptoms: acute hemolytic anemia, thrombocytopenia, and AKI causing uremia. HUS is classified as postdiarrheal (D+HUS, the typical form) or nondiarrheal (D-HUS, the atypical form). HUS is the most common cause of AKI in children^25,59; it affects both sexes equally and most cases occur in children younger than 4 years of age. Advances in treatment of the D+HUS have greatly improved prognosis with most children regaining normal renal function.⁷⁵

Pathophysiology

The inciting event most commonly associated with D+HUS is the absorption of verotoxin (also called a Shiga toxin) from a form of Escherichia coli, known collectively as Shiga toxin-producing E. coli (STEC). In North America, the most commonly identified STEC is E. coli O157:H7 (also called E. coli O157).⁴¹ STEC is transmitted through ingestion of contaminated and undercooked or uncooked beef, or contaminated milk or cheese. Contaminated water, fruits, vegetables, and juices have been implicated less frequently.⁷⁵

The primary site of injury with hemolytic uremic syndrome is the endothelial lining of the small arteries and arterioles, particularly in the kidney. This microangiopathic process results in the intravascular deposition of platelets and fibrin, resulting in partial or complete occlusion of small arterioles and capillaries in the kidney. As erythrocytes and platelets traverse these partially occluded vessels, they are fragmented by mechanical injury from the narrowed vessels and the fibrin strands. RBC fragmentation also results from oxidative damage.⁷⁵ The life span of the erythrocytes is reduced, and the damaged erythrocytes are removed from the circulation by the spleen; this results in a severe and often rapidly progressing anemia.

Most patients with HUS also demonstrate thrombocytopenia for 1 to 2 weeks. It is not clear whether this thrombocytopenia results from destruction of platelets, consumption of the platelets, or aggregation of the platelets within the kidney. Platelet survival time is drastically reduced, from a normal survival of 7 to 10 days to approximately 1.5 to 5 days. Platelet antigen has been found in the kidneys of affected patients and HUS patients often demonstrate a thrombocytopathia. In addition, there is evidence of peripheral platelet destruction.

As noted previously, HUS is associated with damage to the glomerular endothelial cells. The cells tend to swell and detach from the glomerular basement membrane, and the space between the cells and the membrane becomes filled with lipid, fibrin strands, platelets, and cell fragments. The glomerular capillary lumen often is occluded by fibrin, thrombi, and platelets. As a result, renal blood flow and GFR can be reduced in a degree proportional to the glomerular injury.

Renal ischemia may produce cortical necrosis, and renal tubular injury also may be seen. Although much of this damage is reversible, recurrences can occur or progressive renal failure can develop.

HUS may involve the gastrointestinal or central nervous systems. Young children often have a mild gastroenteritis that can progress to bloody diarrhea. The development of neurologic symptoms, particularly coma, is associated with a poor prognosis. The patient may develop irritability, seizures, abnormal posturing, hemiparesis, or hypertensive encephalopathy.

In contrast to D+HUS, the presentation of D-HUS (the atypical form) does not include a prodrome of enterocolitis and diarrhea. D-HUS can be genetic, acquired, or idiopathic in origin. Atypical HUS also predominantly affects children, and the glomerular endothelial pathology is similar to that of D+HUS. However, D-HUS has a worse prognosis and a tendency to recur, and a large percentage of the patient's progress to end-stage renal disease.²⁵ D-HUS is likely to recur even after renal transplant.

Clinical Signs and Symptoms

The appearance of D+HUS closely follows or is coincident with an episode of mild gastroenteritis that may include bloody stools. HUS also may follow upper respiratory infections, urinary tract infections, measles, or varicella.⁴¹ Within 1 to 2 days, the child demonstrates a notable pallor, with purpura, rectal bleeding, or other signs of hemorrhage (e.g., petechiae or ecchymoses).

The child's peripheral blood smear shows fragmented RBCs (a microangiopathic hemolytic anemia), fibrin split products, and a decreased platelet count (thrombocytopenia) seen in 90% of patients. The hemoglobin concentration is typically 5 to 9   g/dL. Within a few days of the onset of anemia, the reticulocyte count will be high. The serum bilirubin level usually is not elevated, although hepatosplenomegaly is often present.

Renal manifestations range from mild insufficiency to AKI. If the child exhibits oliguria or anuria, the serum creatinine, BUN, phosphate, and potassium will be elevated. Hyperkalemia can develop and progress rapidly if gastrointestinal bleeding and gastrointestinal reabsorption of blood products occurs. Congestive heart failure, pulmonary edema, and hypertension can result from decreased renal function, hypervolemia, and increased plasma renin activity.

Examination of the child's urine reveals the presence of fibrin, proteinuria, microscopic or macroscopic hematuria, and urinary cell casts. Evidence of consumptive coagulopathy (decreased levels of fibrinogen, factor V, and factor VIII) is not present.

Most children younger than 2 years demonstrate mild hemolytic anemia and renal involvement, and the course of the disease is short. Mortality has declined to less than 10% as a result of aggressive treatment focused on the support of fluid and electrolyte balance and nutrition, with early dialysis. A small number of patients recover renal function slowly, whereas some will develop chronic renal failure. Recurrence of HUS has been reported after renal transplantation, particularly in patients with D-HUS.²⁵

Management

The management of the child with hemolytic uremic syndrome requires assessment and support of fluid and electrolyte balance, administration of RBCs as needed, management of hypertension, and recognition and treatment of neurologic complications. Insensible fluid loss (300-400   mL/m² per day) is replaced with 5% dextrose and 0.45% sodium chloride without potassium supplement. Urine output is typically replaced milliliter for milliliter with 0.45% sodium chloride. Furosemide is given intravenously in a dose of 1 to 5   mg/kg every 6   hours to convert oliguric renal failure to the polyuric form, which is ostensibly easier to treat.⁷⁵

Approximately one third to half of children with D+HUS⁷⁵ and the majority of those with D-HUS become anuric or develop oliguric renal failure, and fluid and electrolyte therapy must be adjusted accordingly. Renal replacement therapy, usually in the form of PD, may be necessary. If the illness is severe and is complicated by intestinal perforation or severe neurologic symptoms, CVVH is used (see Care of the Child During Dialysis, earlier in this chapter). The healthcare team should review doses and dosing intervals of all drugs that the child is receiving and adjust as needed.

Anemia is treated through careful administration of packed RBCs whenever the child becomes symptomatic or the hematocrit falls below 20%. Frequent transfusions may be required, because the life span of transfused erythrocytes is shortened in the presence of HUS. Only small amounts (3-5   mL/kg) of blood should be administered at any one time if hypervolemia, hypertension, or hyperkalemia are complicating the renal failure. Often transfusions will be planned around the institution of CRRT to manage fluid balance. Fresh packed RBCs are preferable to older bank blood, because the potassium content of fresh blood is low. Administration of leukocyte-poor packed RBCs may be ordered if irreversible renal failure and ultimate renal transplantation are anticipated. Platelet transfusions should be avoided, because they can create further consumptive coagulopathy and microthrombosis.⁷⁵

Hypertension related to hypervolemia should be managed with hemofiltration or dialysis. Pharmacologic agents may be needed (see Box 13-7).¹⁰⁴ Doses and dosing intervals should be adjusted as needed in the presence of renal dysfunction.

The nurse should perform careful neurologic assessments at least every hour. Signs of irritability, lethargy, seizures, posturing, or hemiparesis should be reported immediately. If the child develops signs of neurologic deterioration, refer to Increased Intracranial Pressure in Chapter 11.

If bloody diarrhea persists or the child develops abdominal distension with decreased intestinal motility, provide nothing by mouth and plan to administer caloric requirements through parenteral alimentation. Calories should be provided chiefly with glucose, using less protein than would be provided for patients without renal failure. Maximize caloric intake within the fluid restrictions necessary to prevent hypervolemia.

The parents of the child with hemolytic uremic syndrome will require a great deal of support. They will require reassurance that there was no way they could have known that the child's prodromal illness would lead to serious illness. It is imperative that all members of the healthcare team use consistent terminology and provide a consistent prognosis to minimize confusion.

Etiology

Chronic kidney disease (CKD) is an irreversible, progressive decrease in renal function that leads to ESRD. CKD is defined by the Kidney Disease Outcome Quality Initiative (KDOQI) as either kidney damage or a decreased level of kidney function as measured by the GFR. The criteria for kidney damage (with or without a decrease in GFR) specify damage for 3 months or more as defined by pathologic abnormalities or markers of kidney damage, such as abnormalities in the blood or urine or abnormal imaging tests. The second defining criterion of CKD is a GFR of <60   mL/minute per 1.73   m² body surface area (BSA) for 3 or more months with or without kidney damage. Regardless of the etiology of the renal injury, the continued decline in GFR reflects the process of sclerosis and nephron loss, which is irreversible.²²

The KDOQI has published a classification system for the stages of CKD, with emphasis on early detection and treatment to prevent or delay the progression of the disease. This staging of CKD²² is as follows:

The kidney reserve function is such that more than 50% of renal capacity must be lost before imbalances occur. Although manifestations of renal insufficiency vary, continued dialysis will be necessary for the patient with severe renal insufficiency, whereas the patient with moderate renal impairment typically responds to careful medical and dietary management.

Functional disturbances associated with CKD involve impaired removal of metabolic byproducts as well as fluid excess and electrolyte and acid-base imbalances. Renal dysfunction will affect the growth and formation of bones, RBC formation, and general body growth and will greatly alter the child's daily life.

Pathophysiology

Chronic kidney disease may result from malformation of the renal system, infections, inherited renal disorders, severe trauma, or glomerular disease. The leading causes of CKD in young children are congenital defects, and cystic and hereditary diseases. ESRD from glomerulonephritis, hereditary diseases, and acquired diseases such as HUS are seen in older children.¹⁰

At stage III, chronic renal disease is associated with moderate reduction in the GFR with or without kidney damage. At this level the serum urea is greater than 20   mg/dL, and serum creatinine is greater than 1.5   mg/dL. (Normal creatinine concentration in infants and small children is approximately 0.3-0.8   mg/dL; the creatinine concentration in larger children and adults is approximately 0.7-1.5   mg/dL.)⁴⁰

Calcium, Phosphate, and Bone

Patients with CKD have reduced intestinal absorption of calcium. This reduced absorption may result from deficiency in the active form of vitamin D that is produced by the kidney.

When the GFR falls below 25% of normal, the plasma phosphate concentration begins to rise. Under normal conditions, a reciprocal fall in the serum level of ionized calcium follows phosphate retention, because the ionized calcium and phosphate form a precipitate. This lowering of the ionized calcium stimulates release of parathyroid hormone (PTH). PTH normally increases renal excretion of phosphate and promotes bone reabsorption, liberating calcium and phosphate ions. It simultaneously reduces renal phosphate reabsorption. PTH also assists the kidney in the formation of active vitamin D, which increases intestinal calcium absorption and bone reabsorption. The net result of PTH secretion is normally a fall in serum phosphate and a rise in serum ionized calcium, removing the stimulus for PTH secretion.

When renal disease is present, the rise in phosphate concentration results in a fall in serum ionized calcium. The low serum calcium level stimulates PTH release. Because the kidneys are impaired, they are unable to excrete more phosphate and cannot synthesize vitamin D to increase intestinal calcium absorption. The serum calcium remains low, triggering an increase in PTH synthesis and secretion, causing chronic bone reabsorption. This excessive secretion of PTH by the parathyroid is referred to as secondary hyperparathyroidism, and it causes renal osteodystrophy (Fig. 13-11).

Fig. 13-11 Advanced concepts: pathophysiology of hyperphosphatemia in chronic kidney disease.

Clinical Signs and Symptoms

Patients with CKD often have vague complaints of fatigue, weakness, anorexia, nausea, abdominal pain, and headaches. Growth failure is usually present. Specific signs and symptoms include an initial polyuria and polydipsia, mild edema (especially around the eyes), and oliguria. The child's complexion may be sallow or pale with a faint uremic tint. Skin rashes or arthritis also may be present. The child usually has a history of previous kidney or urologic disease or of an episode of renal injury.

Initial evaluation includes analysis of serum electrolytes, phosphate, pH, bicarbonate, BUN, creatinine, PCO₂ and base deficit or excess, hematocrit, hemoglobin, white cell count, and blood culture. Urine is collected for culture, sediment, pH, osmolality, and sodium. A 24-hour or timed urine collection may be performed to quantify urine volume and creatinine and protein excretion.

The child with CKD usually demonstrates a normal serum sodium and potassium concentration (unless chronic diuretic therapy is provided, and then hypokalemia may be present), a high serum phosphate and low serum calcium concentration, a high BUN, high uric acid, and an elevated serum creatinine concentration. Metabolic acidosis may be present, and serum bicarbonate ion concentration is low. If an infection is present, the child's white blood cell count may be elevated. In addition, the child is usually anemic, with a prolonged bleeding time resulting from thrombocytopathia.

If uremic encephalopathy develops, the child may demonstrate signs of increased intracranial pressure, such as irritability, lethargy, or seizures. If a uremic neuropathy is present, the child may develop muscle cramps, tetany, weakness, or muscle wasting.⁶⁴

Management

The hospitalized child with CKD requires careful fluid and electrolyte therapy. Parents or primary caregivers of children with CKD are often valuable resources regarding the child's food preferences and feeding techniques. The dietician will assist by helping plan menus on an individual basis.

Children with CKD are more susceptible to infections and need careful skin and wound attention. The staff must be extremely careful to use good hand-washing technique before and after examining the child.

Once the child develops any form of renal failure, doses of medications must be adjusted (see section, Adjustment of Medication Dosages in the Management of Acute Renal Injury earlier in this chapter).

Treatment of uremia in children with CKD can be accomplished through dietary restrictions, dialysis, or both. Because protein is essential for normal growth and development in children, dietary protein restriction is generally not recommended.⁹⁸

Indications for dialysis in children with chronic kidney disease include: hypervolemia or congestive heart failure, deterioration in neurologic status, severe bleeding, metastatic calcification as a result of calcium phosphate precipitation, severe hyperkalemia, acidosis, BUN greater than 125 to 150   mg/dL, serum sodium concentration above 160   mEq/L, or serum calcium concentration above 12   mg/dL.

Generally, once the child with CKD is in stable condition, dialysis can be scheduled at relatively regular intervals. Next, hemodialysis or a form of PD can be used to maintain fluid and electrolyte balance (see “Dialysis,” earlier in this chapter). Whenever possible, children with CKD are prepared for renal transplantation.

Nutritional support for children with chronic renal failure is extremely challenging. Anorexia is common among patients with CKD, and inadequate ingestion of protein and carbohydrates compounds the severe growth failure associated with the disease. Tube feedings can provide 100% of the recommended dietary allowances for infants (100   Kcal/kg per day) and older children (40-70   Kcal/kg per day) for normal growth (see Chapter 14). However, no catch-up growth can be achieved by providing calories exceeding recommended daily allowances.

Daily protein requirement for children is approximately 2.5   g/kg. The aim should be to provide proteins that are metabolized into useable amino acids—that is, amino acids that do not produce as much nitrogenous wastes. These proteins include: eggs, milk, meat, fish, and foul (listed from lowest to highest in nitrogenous waste production).⁹⁸ Patients receiving PD should receive the higher ranges of protein. Meals must be appetizing, and the caloric content of foods should be maximized. For example, if the child enjoys drinking milkshakes, then they should contain protein and caloric supplements so that the child ingests more than milk and ice cream. Regular consultation with a dietician is usually necessary.

Fluid, sodium, and potassium restrictions usually are not required when the patient is receiving PD. If hemodialysis is provided, the need for fluid restrictions is determined by the amount of remaining renal function and urine output present, by the child's volume status, and by the success of fluid removal during dialysis.

If the patient develops mild hyperkalemia, treatment should focus on elimination of the cause of the elevation. If the hyperkalemia is severe, however, and ECG changes develop, urgent treatment with calcium, sodium bicarbonate, glucose plus insulin, sodium polystyrene sulfonate, or dialysis are indicated (see “Hyperkalemia” and “Acute Kidney Injury,” this chapter).

It is important to regulate the child's phosphate intake and intestinal absorption. Phosphate binders, especially calcium-based phosphate binders, should be prescribed when phosphate cannot be controlled by dietary restriction.²² Control of the serum phosphate concentration helps prevent hypocalcemia and hyperparathyroidism and the bone mineral disease that results.

Anemia is often present in children with CKD. The 2007 clinical practice guidelines recommend maintaining the hemoglobin concentration in children with CKD between 11 and 12   g/dL using erythropoietin stimulating agents.²²

Oral hygiene and skin care are extremely important because urea tends to accumulate in the mouth and on the skin, which can cause odor, irritation, and discomfort. Uremia is usually especially high just before dialysis treatments.

Indications

The major indication for renal transplantation is deterioration in renal function leading to ESRD, requiring chronic dialysis therapy. Children in ESRD have the greatest chance of surviving 5 years with transplantation (93% compared with 79% for hemodialysis and 82% for peritoneal dialysis).⁹² Although transplantation is virtually always preferable to dependence on dialysis, the availability of continuous ambulatory peritoneal dialysis and continuous cycled peritoneal dialysis offers tolerable options for support of the child while awaiting transplantation, and they probably offer improved transplantation selection criteria and survival.

Preemptive transplantation (transplantation before dialysis is required) has the benefit of preventing potential complications of dialysis as well as limiting the adverse effects created by complete kidney failure. This strategy is challenging because it requires predicting when kidney failure will become significant, transplanting only when necessary and avoiding dialysis. As stated in the KDOQI Guidelines, “the initiation of dialysis therapy remains a decision informed by clinical art, as well as by science and the constraints of regulation and reimbursement.”²²

If transplantation is considered, the nephrologist, the transplant surgeon, and the nurse transplant coordinator will each discuss with the child (as age-appropriate) and family the type of transplant recommended (cadaver versus living related), and the expected posttransplant care regimen. The child's role in postoperative activities and the immunosuppressive regimen should be discussed before the procedure takes place.

Preparation for Transplantation

Multiple diagnostic studies will be necessary to evaluate the renal transplant recipient (Table 13-14). Because many children with renal disease demonstrate associated anomalies of the urinary tract, a voiding cystourethrogram (VCUG) is performed to ensure that drainage of the urinary system is normal. If abnormalities, such as reflux are detected, they usually are repaired surgically before the child is listed for transplantation.

Table 13-14 Preoperative Evaluation of the Renal Transplant Patient

The child must be free of infection at the time of transplantation. In addition, a social worker interviews the family and determines the support they will require and their ability to comply with the child's posttransplant care requirements. A psychosocial evaluation of the child and family is required by federal law. There should also be a discussion with the family regarding alternative therapies and the option to decline escalation of care. Families will need support for their decisions.

Blood type identification and tissue typing is performed to identify the category of tissue that is most likely to result in successful transplantation. Use of a living donor is preferable to a cadaver donor for long-term outcome. The most important factors in finding a suitable donor have been shown to be ABO blood type compatibility and youth.

Typing of human leukocyte antigens (HLAs) is performed on all potential donors and recipients. These antigens are located on the sixth chromosome, and three pairs of antigens—including A, B, and DR antigens—are present in each patient. Long-term graft survival is best if the transplant recipient and the kidney are HLA-compatible.

Each child receives a haploid or haplotype from each parent; the haploid contains the genetic material from either the sperm or egg (half of the genetic material required). Therefore a biologic parent always shares one haplotype with the child. Siblings may demonstrate identical haplotypes (25% probability), share one haplotype (50% probability), or share no haplotype (25% probability). Transplants from living related donors with identical haplotypes are more successful than all other transplants, because the donor will share identical chromosomal material with the recipient.⁹⁴

Parents and family members of the patient will be tissue typed. Identical twins will, of course, match all six antigens. If a compatible family donor is identified, baseline laboratory studies must be performed, including complete blood count with white cell differential, serum electrolytes, liver and renal function studies, and cytomegalovirus, HIV, and hepatitis B antigen screening. An ECG and chest radiograph also are performed. If the results of all serum studies are acceptable, a renal computed axial tomography scan, renal arteriograms, and psychiatric evaluation are performed. These studies are more extensive than those required of a cadaver donor, because the family member must be assured of adequate renal function even after the donation of one kidney; two functioning structurally normal kidneys must be present in order for one kidney to be donated. The donor must be prepared for surgery and a potentially painful recovery. Laparoscopic kidney donation has minimized the risk to the donor with far quicker recovery time. In addition, the donor and recipient must be prepared for the psychological stress of possible rejection of the transplanted kidney.

A cadaver kidney is obtained when a kidney to be donated is matched with a computerized listing of potential recipients available from the United Network of Organ Sharing and regional organ procurement organizations. This network lists the age; ABO blood type, presence or absence of Rh (rhesus) D-antigen (i.e., Rh⁺ or Rh^-), and tissue type; antigen sensitivity; time on list; and urgency status of recipients on the network roster. When a kidney is donated, it becomes available to the patient with the highest priority based on time waiting, urgency of condition, tissue matching, percentage of reactive antibody, and age.

The United Network of Organ Sharing agrees that children younger than 18 years have priority on the list. This priority of pediatric over adult transplant recipients was approved because significant deleterious effects of transplant delay on growth and development have been documented in pediatric patients with renal failure. Current policies give pediatric transplant candidates priority for kidneys from donors younger than 35 years.⁹³ The impetus for this prioritization was an attempt to decrease the need for a second transplant in pediatric patients and to attempt to provide more effective use of organs. In the past, older transplant patients were dying with functioning grafts from younger donors, and children were requiring second transplants after they received initial grafts from older donors.

Kidneys are preferentially allocated locally, then regionally, and then cross-regionally. A cadaver kidney should ideally be transplanted within 24   hours of harvest, because longer preservation times are associated with a higher incidence of acute tubular necrosis and primary nonfunction.

The final step in matching the donated kidney and the recipient is the panel reactive antibody (PRA) which is used to detect antibodies in the recipient to the HLA antigens in the potential donor. The PRA test is reported as a percentage; a high percentage means that the recipient possesses preformed antibodies to the donor cells and will reject the kidney acutely.

If all crossmatches, the PRA test, and assessment of the donor, the donated kidney, and the recipient indicate that the donor is healthy and infection free and the donor and recipient are compatible, the transplant is performed. The procedure lasts approximately 4   hours. In children larger than approximately 20   kg, the new kidney is placed in the retroperitoneal space in the right or left iliac fossa. The renal artery of the donated kidney is sewn to the recipient iliac artery, the donor vein is sewn to the recipient's external iliac vein, and the ureter is implanted into the posterior wall of the recipient bladder. In small children (less than 20   kg), the kidney can be placed in the intraperitoneal space. It is routinely attached to the aorta and vena cava. The dialysis catheter remains in place if kidney function is not immediately observed during surgery, so the dialysis catheter will be available if needed for dialysis postoperatively.

Posttransplant Care

The child usually returns from renal transplantation with a urinary catheter, large-bore peripheral intravenous catheters, and one central venous monitoring catheter. A multilumen central venous catheter will enable simultaneous CVP measurement and intravenous access. The first dose of immunosuppressive agent can be administered preoperatively or intraoperatively.

The goals of posttransplant care include maintenance of effective circulating blood volume, maintenance of systemic and kidney perfusion, and prevention of infection. Fluid balance and daily weight must be monitored closely and reported to the on-call provider. Routine postoperative cardiorespiratory support and psychosocial and family support also will be required.

The transplant surgery and flank incision will create a significant amount of pain postoperatively. Adequate analgesia must be provided (see Chapter 5 for further information).

Late Complications

The most common cause of death during the first year after renal transplantation is infection, especially from Epstein-Barr virus (EBV) and cytomegalovirus (CMV). Antibody titers for both of these viruses are screened in the donor and recipient before transplantation. Cytomegalovirus can lead to direct graft tissue injury and loss.⁹⁴

Malignancies are another serious complication that can lead to death. Most (up to 73%) result from posttransplantation lymphoproliferative disease caused by Epstein-Barr virus (EBV) infection during aggressive immunosuppressive therapy.⁹⁴ Other complications include, but are not limited to, recurrence of glomerular disease in the new kidney, ATN, bleeding, and drug toxicity.³²