Developmental Considerations

At the time of birth, a neonate is considered to be fundamentally immunocompromised for several reasons.¹⁴ First, although infants born at term have passively acquired immunity from maternal antibodies that were transferred transplacentally before birth, the titers of these antibodies quickly wane, leaving the infant without immunity to most specific pathogens. Until exposure to common pathogens by natural infection or immunization, infants lack durable organism-specific immunity. In addition, the function of specific components of the immune system does not mature until approximately 2 years of age. Until that time, infants are unable to make a robust antibody response to pathogens that have polysaccharide molecules on their surface. This developmental defect explains why the incidence of invasive pneumococcal infection, an organism with a polysaccharide coat, is relatively high in young children.

The transfer of maternal antibodies during fetal life occurs chiefly in the last trimester of gestation. The premature infant, born before the last trimester, lacks those transfused maternal antibodies, and therefore has a higher risk of infection, especially during the first months of life.

Colonization and Infection

At birth, a neonate is normally essentially sterile. Within hours, however, bacteria from both the environment and people who handle the infant are transferred onto and begin to grow on the baby’s skin and mucous membranes.²⁰ These bacteria are typically referred to as colonizing flora. The predominant colonizing organisms vary with anatomic site. For example, skin organisms such as Staphylococcus epidermidis can be found on almost all keratinized skin. In contrast, anaerobic and gram-negative organisms are typically found only in the intestinal tract. Colonizing flora typically do not cause inflammation or invasive infection. Many infections, however, do arise from the patient’s colonizing flora, often when a medical device breaches the integrity of skin or mucous membranes or when skin or mucous membranes become inflamed.

Etiology

Allergic or “hypersensitivity” reactions occur when the body mounts an exaggerated or inappropriate immune response to a substance perceived as foreign, resulting in local or general tissue damage. Such reactions are usually classified by severity and involvement,¹ as in types I to IV (Table 16-1).

Table 16-1 Hypersensitivity Reactions

RBC, Red blood cell; WBC, white blood cell.

From Roberts KE, Brinker D, Murante B. Hematology and immunology. In Slota M, editor: Core curriculum for pediatric critical care nursing, ed 2. Philadelphia, 2006, Saunders Elsevier, p. 597.

Anaphylaxis is an allergic hypersensitivity reaction to a foreign protein or drug that causes a systemic response. Exposure to the antigen may be oral or intravenous, or through inhalation or via direct contact. The anaphylactic reaction can occur within seconds or minutes after exposure.⁴²

Reactions can range from mild itching and hives to life-threatening airway obstruction, hypotension, and cardiovascular collapse. Generally, the more the rapid the development of the reaction, the more severe will be the adverse reaction.

Pathophysiology

Clinical signs and symptoms usually appear within seconds to minutes of exposure to an antigen. They are caused by the action of numerous inflammatory mediators, including histamine and histamine-like substances on surrounding tissues and blood vessels. These mediators cause significant changes in capillary permeability that lead to facial edema, airway edema, and bronchoconstriction as well as vasodilation, hypotension, and possible circulatory collapse. Constriction of airway smooth muscle tissues results in wheezing, crackles, stridor, and progressive respiratory distress. Erythema and pruritus may also be seen as the result of an influx of eosinophils. Mortality from anaphylaxis results from complications of bronchospasm and airway compromise or profound hypotension.

Any medication has the potential to cause an allergic reaction, although some agents are more commonly associated with anaphylaxis than others. Agents with a higher potential for causing anaphylactic reactions include antibiotics (e.g., penicillin or sulfa drugs), chemotherapy agents (e.g., Asparaginase or Etoposide), antifungal agents, biotherapy agents (e.g., monoclonal antibodies), blood products, immunoglobins, radiologic contrast media, latex products, and food.

Clinical Signs and Symptoms

Signs and symptoms of hypersensitivity or anaphylaxis can develop within seconds or minutes after exposure. Patients often initially describe a sense of impending doom, accompanied by pruritus and flushing. This can evolve rapidly into other clinical manifestations of hypersensitivity (Table 16-2).

Table 16-2 Clinical Manifestations of Hypersensitivity Reactions

Data from Linzer JF: Pediatrics, anaphylaxis. 2008. Emedicine, http://emedicine.medscape.com/article/799744-overview.

Once the clinical manifestations of the reaction become systemic, anaphylaxis is present. Mild symptoms include irritability, coughing, anxiety, disorientation, erythema, hives, and itching. Severe symptoms include dyspnea; cyanosis; difficulty speaking; swelling of the tongue, face, and airways; intense coughing; chest tightness; wheezing; stridor; laryngospasm; seizures; sense of impending doom; hypotension; and cardiorespiratory arrest.²³

Management

When a patient develops signs of a severe hypersensitivity reaction or anaphylaxis, immediately stop the causative infusion or remove the offending agent (if known) and call for assistance (i.e., activate emergency response and notify a physician). Support the patient’s airway, oxygenation, and ventilation and circulation as necessary and initiate cardiopulmonary resuscitation if needed. Healthcare providers should always be prepared for further patient deterioration, particularly if symptoms develop soon after the exposure.

Evaluation of airway and breathing includes assessment of oxygenation and ventilation. Administer supplementary oxygen as needed. In extreme cases, intubation and mechanical ventilation will be required. In patients with laryngeal or tracheal edema, an emergent tracheostomy may be needed.

Establish vascular access, ideally with two large-bore vascular catheters and be prepared to administer fluid boluses (to treat relative hypovolemia resulting from vasodilation and increased capillary permeability) and vasoactive support (e.g., an epinephrine infusion) to restore and maintain adequate blood pressure and systemic perfusion. (For further information, please refer to Chapter 6.)

Epinephrine 1:1000 is administered intramuscularly in the prehospital setting, but is administered intravenously (if arrest has occurred or is imminent, it can be administered by intraosseous route) in the hospital setting. Additional vasoactive medications such as norepinephrine may also be required to maintain blood pressure and systemic perfusion.

Medications typically used to treat anaphylactic reactions include oxygen, IM epinephrine (an infusion may be needed for refractory hypotension), diphenhydramine (and possibly an H₂-blocker antihistamine), albuterol nebulizer, and methylprednisolone.^10,23 Antihistamines are administered to antagonize the effects of histamine. Bronchodilators relax bronchial smooth muscles. Corticosteroids are antiinflammatory agents to enhance the effects of bronchodilators. (For further information, please refer to Chapter 6.)

Skin testing may help identify patients who may experience a hypersensitivity reaction with a known high-risk agent. Patients are given a small intradermal test dose of the agent and are monitored for at least 20   minutes.¹⁷ Emergency equipment and medications should be readily available. Patients receiving medications or agents with a higher risk of producing anaphylactic reaction and those with a history of anaphylaxis should be identified and monitored appropriately.

When a patient has a known allergy or hypersensitivity reaction to a drug, premedications may be prescribed before the agent is administered. Medications commonly used for pretreatment are corticosteroids, antihistamines, and antipyretics.¹⁷ Patients with known hypersensitivity responses should wear medical alert jewelry and should have an anaphylaxis kit (epinephrine autoinjector pen) readily available.

Etiology

In 1992, the American College of Chest Physicians (ACCP) and the Society of Critical Care Medicine (SCCM) introduced definitions³ for systemic inflammatory response syndrome (SIRS), sepsis, severe sepsis, septic shock, and multiple organ dysfunction syndrome (MODS).

SIRS is a state of inflammatory/immune activation. SIRS is present when the adult patient demonstrates two or more of the following variables^3,8a:

SIRS is nonspecific and can be caused by a number of diverse clinical conditions (Table 16-3), including ischemia, inflammation, trauma, infection, or a combination of several insults. SIRS does not always occur as a result of infection. A number of underlying conditions may predispose patients to infections with specific pathogens and the development of SIRS (Table 16-4).

Table 16-3 Infectious and Noninfectious Causes of SIRS

From Burdette SD, et al: Systemic inflammatory response syndrome. Emedicine, http://emedicine.medscape.com/article/168943-overview. Updated July 20, 2010. Accessed April 27, 2011.

Table 16-4 Predisposing Conditions/Risk Factors for Development of SIRS

Modified from Burdette SD, et al: Systemic inflammatory response syndrome. Emedicine, http://emedicine.medscape.com/article/168943-overview. Updated July 20, 2010. Accessed April 27, 2011.

Pathophysiology

Inflammation is the body’s response to nonspecific insults that arise from chemical, traumatic, or infectious stimuli. The inflammatory cascade is a complex process that involves humoral and cellular responses and complement, and cytokine cascades. This inflammatory response, regardless of cause, generally has the same pathophysiologic properties; minor differences are caused by the inciting factor.

Trauma, inflammation, or infection leads to the activation of the inflammatory cascade. The proinflammatory interleukins either function directly on tissue or work via secondary mediators to activate the coagulation cascade, the complement cascade, and the release of nitric oxide, platelet-activating factor, prostaglandins, and leukotrienes. Activation of the white blood cells leads to secretion of tumor necrosis factor-alpha (TNF-α), a proinflammatory mediator (TNF derived its name from the fact that it causes hemorrhagic necrosis of tumors). Messenger RNA for TNF is normally present in tissues throughout the body, and levels of TNF rise early in the inflammatory process, leading to further vasodilation, capillary leak, and release or activation of additional cytokines (vasoactive peptides), including platelet-activating factor and many interleukins. The complement cascade is designed to coat invading organisms, making them vulnerable to phagocytosis. Activation of the complement cascade includes activation of the coagulation cascade (described further in the following paragraphs and later section, Sepsis and Septic Shock).

Numerous proinflammatory polypeptides are found within the complement cascade. Two of these, protein complements C3a and C5a, contribute directly to the release of additional cytokines, causing vasodilatation and increasing vascular permeability. Prostaglandins and leukotrienes incite endothelial damage, leading to multiorgan system failure (MOSF).

More than 15 years ago, Bone⁴ described the relationship between these complex inflammatory interactions. He described SIRS and MOSF as a five-stage process (Table 16-5). His definitions remain very helpful today.

Table 16-5 Bone’s Five Stages of SIRS and Multiple Organ System Failure (MOSF)

From Bone RC: Immunologic dissonance: a continuing evolution in our understanding of the systemic inflammatory response syndrome (SIRS) and the multiple organ dysfunction syndrome (MODS). Ann Intern Med 125(8):680-687, 1998.

The relationship between inflammation and coagulation directly affects the potential clinical progression of SIRS. Interleukin-1 (IL-1) and TNF-α directly affect endothelial surfaces, leading to the expression of tissue factor. Tissue factor initiates the production of thrombin, thereby promoting coagulation; tissue factor is also a proinflammatory mediator. Fibrinolysis is impaired by IL-1 and TNF-α through production of plasminogen activator inhibitor-1.

Proinflammatory cytokines also disrupt the naturally occurring antiinflammatory mediators, antithrombin, and activated protein-C (APC). If unchecked, this coagulation cascade leads to complications of microvascular thrombosis, including organ dysfunction. The complement system also plays a role in the coagulation cascade. Infection-related procoagulant activity is generally more severe than that produced by trauma.

The cumulative effect of this inflammatory cascade is an unbalanced state with inflammation and coagulation. To counteract the acute inflammatory response, the body is equipped to reverse this process via a counter-inflammatory response syndrome (CARS). Co-morbidities and other factors can influence a patient’s ability to respond appropriately. The balance of SIRS and CARS determines a patient’s prognosis after an insult. Some researchers believe that, because of CARS, many of the new medications meant to inhibit the proinflammatory mediators may lead to deleterious immunosuppression.⁴

If SIRS is identified and reversed early, the subsequent inflammatory cascade can often be avoided or mitigated. However, in some situations, the cascade continues because the insult or the resultant host inflammatory response is too great. This damage can trigger cardiovascular dysfunction (increased cardiac output, peripheral vasodilation, maldistribution of blood flow, and impaired oxygen utilization), with resultant shock and a hypermetabolic state (i.e., warm shock).

If SIRS continues to progress, cardiac output may fall, peripheral vascular resistance may increase, and shunting of blood may ensue (i.e., cold shock). This results in development of tissue hypoxia, end-organ dysfunction, metabolic acidosis, end-organ injury and/or failure, and can be fatal.³⁵

Clinical Signs and Symptoms

Fever is the most common presenting symptom of children with SIRS. Fever is one component of the triad of hyperthermia (or hypothermia), tachypnea, and tachycardia that typifies the earliest, mildest manifestation of SIRS. The international consensus terminology defines SIRS in children as present when the patient demonstrates two or more of the following (see details in Box 16-1)¹⁸:

Management

Treatment of SIRS is focused on treating the inciting cause. Empiric antibiotics are not administered routinely to all patients. Indications for empiric antimicrobial therapy include suspected or diagnosed infectious etiology, hemodynamic instability, neutropenia, and asplenia.^8a Broad spectrum antibiotics are initiated when there is concern for an infectious cause but no definitive infection has been diagnosed.

Drotrecogin alpha, a recombinant form of human recombinant activated protein C (APC), reduces microvascular dysfunction by reducing inflammation and coagulation and increasing fibrinolysis. It has been hypothesized that APC may be beneficial in the management of SIRS. However, the supporting evidence to date is limited. In the prospective, randomized multicenter controlled PROWESS trial,² mortality was reduced by 28% in adult patients with severe sepsis who received APC. Patients who received APC also demonstrated significantly more bleeding than control patients. However, a Cochrane meta-analysis of adult trials²⁵ involving over 4000 patients (including some children who were not randomized) did not find overall evidence of improved survival when APC was administered; a multicenter pediatric study was halted because excessive bleeding occurred when children received APC.

APC currently has no role in the routine management of SIRS unless the presentation is consistent with septic shock. Although APC may be considered in the management of severe septic shock in adolescents and adults (see section, Sepsis and Septic Shock), it is not routinely used in pediatric patients.

Fluid resuscitation should be initiated in those patients who exhibit signs of hypovolemia and hypovolemic shock (see section, Sepsis and Septic Shock and Chapter 6). All patients require establishment of adequate intravenous access. Administer isotonic fluids boluses (typically 20   mL/kg boluses; smaller volumes may be used in children with poor myocardial function) as needed to treat shock and monitor hemodynamic status closely.^22,33 If signs of shock are present, antibiotics, aggressive fluid resuscitation and vasoactive support should be provided within the first hour after the onset of symptoms (see section, Sepsis and Septic Shock and Chapter 6).⁵

Assess and support adequate oxygenation and ventilation. The oxyhemoglobin saturation in the superior vena cava (S_CVO₂) allows tracking of the balance between oxygen delivery and oxygen use; therapy should be titrated to maintain this S_CVO₂ 70% or higher.⁵ Patients with increased oxygen requirement should receive supplementary oxygen. Intubation and mechanical ventilation may be required in some patients.

Etiology

The term sepsis is often used to refer to a broad spectrum of pathophysiologic and clinical derangements ranging from initial infection and bacteremia to SIRS, generalized sepsis, severe sepsis, septic shock, and refractory septic shock. Sepsis is the systemic response to infection and is defined as the presence of SIRS in addition to a documented or presumed infection.¹⁵ Severe sepsis is defined as sepsis plus sepsis-induced MOSF or tissue hypoperfusion or insufficient end-organ perfusion.^15,43

Septic shock is defined as sepsis criteria plus persistent hypotension despite the administration of 20   mL/kg of crystalloid or colloid plus an inotrope/vasopressor requirement, a Glasgow coma score less than 15 in the absence of CNS disease, arterial lactate greater than 1.6   mmol/L (verify laboratory normal), or urine output less than 1   m/kg per hour for two consecutive hours with a urinary catheter in place.⁴³ Septic shock is addressed in greater detail in Chapter 6.

Pathophysiology

Sepsis is a complex clinical disorder that results from three potential factors that interact with one another, leading to severe sepsis and potentially to septic shock. First, an infecting pathogen can cause direct injury to the tissues, which results in the development of MOSF. Second, sepsis may develop as a secondary response to an excessive host inflammatory response. Third, sepsis may involve a failure of counter regulatory mechanisms.⁴³ The end result of sepsis is dysregulation of the inflammatory cascades leading to endothelial injury, coagulation and fibrinolytic abnormalities, microcirculatory disturbances, myocardial depression, organ dysfunction, and increased susceptibility to healthcare-acquired infections.³⁹

Clinical Signs and Symptoms

The most common clinical manifestations of sepsis include fever or hypothermia, tachycardia, tachypnea, leukocytosis or leucopenia, thrombocytopenia, and change in mental status. Fever is often the first clinical manifestation that alerts practitioners to the possibility of an infection.

Hypotension is a late sign of septic shock. Diastolic blood pressure begins to fall as sepsis produces a decrease in vascular tone. Systolic blood pressure is typically maintained for a longer period of time and only falls once a significant compromise in hemodynamic status has occurred. Clinical diagnosis is made in children with a suspected infection manifested by hypothermia or hyperthermia, and clinical signs of inadequate tissue perfusion. Hypotension is not necessary for a clinical diagnosis of septic shock. However, the presence of hypotension in a child with a clinical suspicion of infection is confirmatory for septic shock.⁵

Management

The management of pediatric sepsis and septic shock is targeted at maintaining cardiopulmonary stability and preventing or correcting metabolic abnormalities.²¹ The 2007 update to the ACCM guidelines for the hemodynamic support of pediatric and neonatal patients with septic shock⁵ emphasizes the importance of early antibiotics and aggressive fluid resuscitation and use of vasoactive agents among other age-specific therapies to achieve time-sensitive goals (Fig. 16-1).

Fig. 16-1 Suggestions for hemodynamic support in pediatric septic shock.

BP, Blood pressure; CI, cardiac index; SVRI, systemic vascular resistance index.

Based on recommendations of Brierley J, Carcillo JA, Choong K, Cornell T, et al: Clinical practice parameters for hemodynamic support of pediatric and neonatal septic shock: 2007 update from the American College of Critical Care Medicine. Crit Care Med 37:666–688, 2009.

Standard Precautions

Standard precautions apply to all patients, regardless of diagnosis, and describe the appropriate handling of all human body substances, including blood, secretions, excretions (except sweat), non-intact skin, and mucous membranes. These precautions presume that all patients may have unidentified blood-borne pathogens such as HIV, or Hepatitis B or C virus.

Implementation of these precautions includes: (1) hand hygiene; (2) gloves when at risk of exposure to blood, body fluids, or mucus membranes; (3) masks, eye protection, and face shields when there is a risk of splashes or sprays of blood or body substances; and (4) gowns when soiling of clothing is possible as the result of either direct contact or splashing or spray of body substances.

Contact Precautions

Contact is the most common mode of transmission of potentially pathogenic organisms within the hospital setting. The pathogens in this category include many viruses and bacteria that can live for variable lengths of time on the hands of healthcare workers or inanimate objects. The most important actions to prevent this mode of transmission are the use of gloves and nonsterile gowns when in contact with the patient or the patient care environment. To interrupt patient-to-patient transmission, healthcare providers must change gowns and gloves between patients and perform hand hygiene before and after every patient contact.

Droplet Precautions

Pathogens in this category are usually spread by larger droplets expelled from the respiratory tract by the infected person. Because the droplets are large in size, transmission usually only occurs when the source patient is relatively close to a healthcare worker or another susceptible patient. Thus, droplet precautions focus on protecting the healthcare workers and other patients by the use of masks by anyone who will be within three feet of a source patient.

Airborne Precautions

This category of infections involves organisms with very small particle size, such as varicella and measles viruses. These droplets may be carried through the air over long distances and they can infect patients who are positioned at great distances from the source patient. Methods used to limit spread of these pathogens include appropriate patient placement (usually a single bed in a room with a closed door, and possible use of a negative air pressure isolation room) as well as the use of protective equipment, such as masks or respirators, for healthcare workers.

When the child is critically ill or injured, infection control isolation precautions may add to the stress of hospitalization, especially if the child is too young to understand the purpose of the isolation precautions. The involvement of developmentally appropriate support (e.g., child life specialists) should be requested as indicated.

Etiology

Severe combined immunodeficiency disorder (SCID) is a rare combined B- and T-lymphocyte disorder. Estimations of incidence range from 1:70,000 to 1:1,000,000 live births, but may be as frequent as 1:35,000.^27,44 The majority of cases are inherited in an X-linked or autosomal recessive pattern. SCID is fatal if untreated and is considered a pediatric emergency. In most cases survival requires expeditious stem cell transplantation.

Pathophysiology

SCID occurs as the result of mutations in 1 of 10 known genes.³⁶ There are many variants of the disorder ranging from partial to almost complete loss of T-lymphocyte function. X-linked SCID is the most common form. Other forms of SCID usually follow an autosomal recessive inheritance pattern or are the result of spontaneous mutations. One of these other forms is linked to a deficiency of the enzyme adenosine deaminase (ADA). B and T lymphocytes produce chemicals that can accumulate to toxic levels within these cells. Normally, these cells produce an enzyme (ADA) that destroys the excess toxins. When this vital “detoxifying enzyme” is missing, these toxins accumulate, “poisoning” the B and T lymphocytes.

Clinical Signs and Symptoms

SCID is characterized by multiple severe or recurrent illnesses such as dermatitis, otitis media, and diarrhea.³⁶ Infection is not present at birth, because the infant is protected from bacterial infections by transplacental delivery of maternal IgG antibody. However, signs and symptoms of infection develop soon after birth with the majority of cases presenting in patients less than 3 months of age.³⁶

Infants with SCID frequently develop a severe skin rash with red, peeling skin during the first few weeks of life. This rash may resemble eczema, but is more diffuse and typically does not respond to topical corticosteroids. Superinfection of the skin with Staphylococcus aureus is often seen.

Infections are characteristic in terms of severity, recurrence (persistent in nature), type of organism, and location. Common sites of infection include the respiratory tract, mucous membranes, liver, GI tract, and blood. Bacterial infections such as otitis media, pneumonia, and skin infections develop frequently. Infants have recurrent mucocutaneous infections with Candida that is resistant to therapy. This candidal esophagitis can result in poor feeding and poor weight gain. Chronic diarrhea responds weakly to alterations in diet and may become life threatening.

Recurrent, severe, and sometimes fatal infections occur with common viruses such as adenovirus, parainfluenza, and varicella. Opportunistic infections including Pneumocystis carinii pneumonia (PCP) and cytomegalovirus (CMV) are the hallmarks of a T-cell immune defect. Their presence should immediately prompt investigation for an underlying immune defect. In children with SCID, PCP infection is frequently fatal.

Management

Early immune reconstitution offers the best chance of long-term survival. Bone marrow or stem cell transplantation can be performed within the first 3 months of life, with reported survival as high as 97%.⁷ Donors may be human leukocyte antigen-identical siblings, cord blood units, or matched unrelated donors identified through the national registries or haploidentical parents. Bone marrow transplantation (BMT) using stem cells obtained from a related, HLA-identical donor (RID) is the optimal treatment for patients with SCID. In the absence of a RID, HLA-mismatched related donors (MMRDs) are often used. However, compared with RIDs, use of MMRDs for BMT is associated with reduced survival and inferior long-term immune reconstitution. Grunebaum and co-workers¹⁹ found that use of HLA-matched unrelated donors (MUDs) had an 80% cure rate for SCID and are associated with long-term robust immune reconstitution. They suggest that this mode of treatment may be an important therapeutic alternative for patients with SCID when a RID is not available.

Before transplantation, supportive care is essential. This includes prophylaxis against PCP pneumonia with trimethoprim-sulfamethoxazole and administration of intravenous gammaglobulin. Infants with SCID may have severe, sometimes fatal reactions after vaccination with live vaccines (e.g., for measles-mumps-rubella or varicella). As a result, these live vaccines are contraindicated for all children with SCID.

When transfusion is required, CMV-negative, leuko-depleted, irradiated blood products are administered. The development of graft-versus-host disease has been described in infants with SCID after a blood transfusion. Because more than half of SCIDs are caused by an X-linked defect, genetic counseling is important for parents and siblings to determine their carrier status.

Diarrhea may result from persistent infection, rotavirus, Giardia lamblia, or malabsorption. The use of an elemental formula may be helpful to reduce the diarrhea. If there is severe weight loss or failure to thrive, parenteral nutrition may be necessary.

Etiology

Meningococcemia is a rare but frequently devastating condition. It primarily affects children and is the leading cause of bacterial meningitis in the United States. N. meningitidis (the meningococcus) is an encapsulated gram-negative diplococcus that causes infections with a broad spectrum of clinical involvement and severity of symptoms, including meningitis, sepsis, conjunctivitis, pericarditis, epiglottitis, pneumonia, and arthritis. Meningitis, sepsis, or a combination of the two is most frequently seen in the pediatric critical care unit.

Pathophysiology

N. meningitidis is transmitted from person to person via direct contact with infected droplets of respiratory secretions. Carriers are often asymptomatic at the time of transmission. Immunity to N. meningitidis is thought to be acquired through intermittent nasal carriage of meningococci and antigenic cross-reaction with enteric flora during the first two decades of life.¹⁶ Once the bacteria colonize and cross the nasal mucosa, disease symptoms often appear within 10 days.

The virulence or severity of meningococcemia is related to the release of endotoxin. The endotoxin of meningococcus is structurally different from that of other gram-negative bacteria.³⁴ Levels of endotoxin correlate with the severity of illness and may be 50- to 100-fold that occurring with other gram-negative infections.

The clinical manifestations of meningococcemia result from capillary leak, myocardial failure, coagulopathy, and metabolic derangement. These processes work together to produce a state of multisystem organ failure that typically causes cardiorespiratory dysfunction and, frequently, renal, neurologic, and gastrointestinal dysfunction.³⁰

In the first 2 to 4 days after onset of illness, there is a massive increase in vascular permeability with resulting capillary leak. Initially, the body compensates through normal homeostatic mechanisms, including vasoconstriction. As the capillary leak continues, hypovolemia develops. This hypovolemia leads to decreased venous return and cardiac output. Vasodilation and maldistribution of blood flow contribute to inadequate tissue perfusion, tissue hypoxia, and lactic acidosis, and may produce cell death and organ dysfunction. For additional information, see Chapter 6.

Hypovolemia and maldistribution of blood flow are primary causes of cardiovascular collapse, although they may be further complicated by development of myocardial dysfunction. Myocarditis, pericarditis, or direct bacterial invasion of the heart may contribute to this cardiac dysfunction.

Patients with meningococcemia often present with disseminated intravascular coagulation (DIC). The combination of microvascular thrombosis and bleeding (caused by initiation of the clotting cascade) is particularly challenging to manage. DIC, in combination with the described hypoxia and hypovolemia, can cause significant end-organ damage. Waterhouse-Friderichsen syndrome (massive adrenal hemorrhage) can complicate meningococcemia and may further exacerbate cardiovascular collapse. See Chapter 15 for additional information about DIC.

Clinical Signs and Symptoms

The clinical manifestations of meningococcal disease can be extremely variable, ranging from the typical signs of meningitis to full-blown septic shock (Table 16-10). In cases of severe meningococcemia, the disease may progress extremely quickly, with death occurring within a few hours of the onset of symptoms. The classic petechial rash is considered to be pathognomic for meningococcemia. However, up to 20% of children with this disorder have no rash or petechiae at presentation.²⁶

Table 16-10 Clinical Manifestations of Meningococcemia

Management

Antibiotic therapy is the only definitive treatment for meningococcemia and should be initiated as soon as the diagnosis is made. The sequelae of this disease may be devastating, but N. meningitidis itself is relatively easy to eradicate. A blood culture should be obtained before initiation of antibiotic therapy but should not delay treatment. In a stable patient, a lumbar puncture may be performed. However, it may be deferred in those who are considered unstable or are exhibiting signs of increased intracranial pressure. Recommended antibiotic therapy may include cefotaxime, ceftriaxone, or penicillin G.^28,32,41 Doses vary based on the patient’s clinical condition (i.e., presence or absence of associated meningitis).

Further management is aimed at restoring adequate oxygen and substrate delivery to the tissues. This is achieved through aggressive fluid resuscitation to replete intravascular volume, correction of DIC, and optimization of oxygenation and ventilation. Patients with meningococcemia may require as much as 80   mL/kg of crystalloid during the first hour of therapy and 240 mL/kg or more during the first 8   hours of therapy. This fluid is administered in boluses of 20   mL/kg per Pediatric Advanced Life Support (PALS) guidelines.^10,22,33 The child’s hemodynamic and cardiovascular status should be reassessed after each intervention. If shock persists after initial volume therapy, inotropic support is recommended, and should be instituted within the first hour of therapy, even if this requires administration via peripheral venous access. Epinephrine and dopamine may be used to improve myocardial contractility and enhance vasoconstriction.

After initial resuscitation and stabilization, afterload reducing agents such as milrinone are often needed. Arterial and central venous catheters should be placed to allow for close monitoring of hemodynamic status and response to interventions. Insertion of a central venous catheter should not delay administration of fluid boluses and vasoactive support; both can be initiated through large-bore peripheral venous catheters until a central venous catheter is placed. For additional information about management of septic shock, see Chapter 6.

Administration of corticosteroids in the pediatric patient with meningococcemia is controversial. In those patients who are at risk for adrenal insufficiency (those with chronic steroid use, recent steroid use, purpura fulminans, or hypothalamic, pituitary, or adrenal disease) or those with persistent hypotension after adequate volume resuscitation and initiation of inotropic support, it may be prudent to administer hydrocortisone.²⁸ However, the safety and efficacy of stress-dose steroids as adjunctive therapy for pediatric septic shock have not been established.⁴⁶ Glucocorticoid administration does add potential risks, including anti-anabolic effects, attenuated immunity, depressed wound healing, calcium mobilization, impaired insulin action, and associated hyperglycemia and possible alteration in brain development.⁴⁶

Correction of DIC is essential to prevent complications such as intracranial bleeding, GI hemorrhage, and bleeding into skin lesions. Fresh-frozen plasma, platelets, cryoprecipitate, and factor VII are administered as indicated to correct specific deficiencies. Packed red blood cells are administered to restore hemoglobin concentration and improve oxygen carrying capacity. For additional information about management of DIC, see Chapter 15.

Optimizing oxygenation and ventilation typically requires the use of supplementary oxygen and mechanical ventilation. The patient with depressed level of consciousness may require endotracheal intubation to establish a patent airway and reduce risk of aspiration. If increased capillary permeability produces pulmonary edema, noninvasive positive pressure ventilation (e.g., bi-level positive airway pressure) or ventilation with positive end-expiratory pressure will be needed. For additional information, see Chapter 9.

Treatment of septic shock is presented in more detail in Chapter 6.

Central Venous Catheter Infections

Catheter-associated bloodstream infections are among the most common healthcare-acquired infection in hospitalized children. Catheter-associated infections include localized infection at the site of catheter entry, phlebitis, or bloodstream infection.

Evidence-based practices that are associated with a reduced risk of catheter-associated infections include: (1) use of maximal sterile barrier precautions (e.g., cap, mask, sterile gown, sterile gloves, and large sterile drape) during catheter placement; (2) use of 2-3% chlorhexidine gluconate/70% isopropyl alcohol or other appropriate antiseptic agents to prepare the skin before placement or during routine care of the catheter; (3) prompt removal of catheters as soon as they are no longer required; and (4) strict adherence to appropriate hand hygiene practices.²⁹ For additional information, see Box 22-6.

In studies performed in adult critical care units, antiseptic impregnated catheters have been associated with reduced rates of catheter associated bloodstream infection^8b,10b (Box 16-4). Studies performed in children have described delayed time to infection but not reduced infection rate associated with use of antibiotic-impregnated catheters.^10a

Complications of catheter-related infection include sepsis and septic shock, endocarditis, septic thrombophlebitis, and metastatic infection with seeding of bone and organs (lung, kidneys, liver, spleen, brain, and skin). The prognosis for patients with a catheter-related infection is influenced by factors related to the pathogen, host, and therapy. If the infection is promptly identified and appropriate antimicrobial therapy is instituted, there can be a high rate of cure and salvage of the catheter. Delayed recognition or therapy for an infection is associated with increased morbidity and mortality. Overall, fatality rates for central catheter bacteremia are 10% to 25%, with rates as high as 50% in critically ill patients.

Urinary Tract Infections

Experts estimate that catheter-associated urinary tract infections are the most common device-associated infection among hospitalized patients, although the burden of disease is likely greater in adult, as compared with pediatric patients. Inappropriate and prolonged use of urinary catheters has been found in as many as 50% of patients who develop a catheter-associated urinary tract infection. Important strategies to prevent urinary catheter infections are: (1) limiting catheterization to those for whom it is medically necessary; (2) attention to strict aseptic technique during catheter insertion; and (3) removal of the catheter as soon as possible.²⁴ Catheters are commonly left in place for too long; one study of adult medical inpatients revealed that clinicians were unaware that their patients had a catheter 28% of the time.^34a

Ventilator-Associated Pneumonia (VAP)

An endotracheal tube provides an ideal portal of entry for the many organisms colonizing the oropharynx to migrate into the lower respiratory tract. The tube itself is an ideal substrate for the formation of biofilm. Pediatric patients appear to have lower risk of ventilator-associated pneumonia than adults, likely because they have fewer co-morbid conditions such as chronic heart or lung disease or immunosuppressing conditions. However, pediatric critical care clinicians have embraced strategies to reduce the risk of VAP, including whenever possible: (1) the use of noninvasive ventilation; (2) the avoidance of nasotracheal intubation; (3) the use of in-line suctioning to prevent the aspiration of pooled tracheal sections; and (4) the elevation of the head of the bed at 45 degrees from horizontal, especially for patients receiving enteral nutrition.¹² Additional information is included in Box 22-7.

Clostridium difficile Colitis

In both children and adults, the most important cause of healthcare-acquired gastrointestinal disease is C. difficile. The epidemiology of C. difficile colitis is complex and somewhat confusing in the pediatric population.⁶ Up to 50% of healthy neonates may be colonized with toxigenic forms of C. difficile. After the age of 2 years, colonization rates decrease to adult levels of less than 5%, although higher levels are seen in hospitalized patients with or without exposure to antimicrobial agents.

Clinically apparent disease occurs when the microbial ecology of the gut is upset, for example, when a patient is undergoing antimicrobial therapy. With the decline of normal intestinal flora, C. difficile proliferates and elaborates potent toxins A and B, which lead to secretory diarrhea and inflammatory colitis. The major risk factor for pseudomembranous colitis is exposure to antimicrobial agents. Other risk factors include underlying gastrointestinal disease, bowel stasis, and anatomic obstructions.

Symptoms of C. difficile colitis typically begin 4 days (range, 1 to 21 days) after initiation of antimicrobial therapy. Associated signs and symptoms include fever, cramping abdominal pain, distension, nausea, and vomiting. Typically, hematochezia does not occur. Although symptoms often resolve when antibiotics are discontinued, oral metronidazole or vancomycin are typically given to critically ill children with C. difficile colitis.