Cardiac Surgery

The history includes information about the patient's health status as well as the response to the disease and the recommended intervention or interventions. Patients with cardiac disease may display such symptoms as ischemic chest pain (angina pectoris), fatigue, dyspnea, and syncope. Depending on their severity, these subjective symptoms affect the patient's functional status and ability to engage in activities of daily living; the New York Heart Association's Functional Classification System (Box 25-1) is often used to assess functional ability. Updates to the classification system also include objective measurements such as x-rays and echocardiograms (American Heart Association [AHA], 2012 a,b).

Atypical ischemic chest pain is more likely in women than in men, and angina may arise from vasospastic angina, mitral valve prolapse, or psychologic factors. CAD is unusual in premenopausal women; after menses ends, however, the risk is similar to that of men (AHA, 2013; Caboral, 2013; Mosca et al, 2011; Roger et al, 2012; Wenger, 2012). Controversy exists regarding menopausal hormone therapy. Estrogen hormone replacement therapy is not recommended in postmenopausal women, according to the Evidence-Based Guidelines for Cardiovascular Disease Prevention in Women: 2011 Update (Mosca et al, 2011) (Evidence for Practice). Greater emphasis is being placed on effectiveness of interventions as well as on the evidence supporting those interventions; effective control of blood pressure, diabetes management, and maintenance of optimal lipid levels are significant risk reduction interventions for women (Caboral, 2013).

Women undergoing coronary artery bypass graft (CABG) also have some unique challenges and experiences. According to Banner and colleagues (2011), some women may minimize any public display of illness in an attempt to preserve the appearance of normalcy; they even may hesitate to tell significant others about impending surgery until the day before admission. Postoperatively they may wish to return home early in order to resume regular activities. Once home, some women were unprepared for the limitations that they faced, both physical and social; the authors recommend focused advice, support, and education (Banner et al, 2011).

A cardiovascular disease risk factor profile (Box 25-2) is helpful to plan care for hospitalization and discharge by focusing on areas that might require further patient education. For example, diabetes is a risk factor because it affects the vascular system, may retard healing, and may predispose the patient to infection. Of special concern is the epidemic growth of type 2 diabetes in particular and the role of hyperglycemia in general. Although type 2 diabetes formerly was considered an adult-onset disease, children are increasingly vulnerable because of a greater incidence of increased body weight, sedentary lifestyle, and accelerated insulin resistance (Roger et al, 2012). Altered glucose metabolism (absent diagnosed diabetes mellitus) has shown a significant correlation to atherosclerosis; control of hyperglycemia during coronary bypass surgery is an important strategy to reduce the risk of adverse clinical outcomes (Hillis et al, 2011; Nussmeier et al, 2009).

In addition to elevated lipid or cholesterol levels, inflammation increasingly has been implicated in the development of CAD. In particular, elevated homocysteine levels (which increase platelet aggregation) and high C-reactive protein (CRP) levels have been implicated (CRP is a biologic marker for inflammation and is associated with increased risk for CAD) (Horak et al, 2011). Additional recognized risk factors include metabolic syndrome (central obesity, hypertension, insulin resistance, and dyslipidemia) and obesity (Hillis et al, 2011; Roger et al, 2012). Hypertension and obesity increase the workload of the heart; obesity may also increase the risk for postoperative infection because adipose tissue vascularizes poorly. Additionally, a growing percentage of the population is aging. Age, in and of itself, rarely contraindicates intervention, but comorbidities often associated with older individuals constitute additional risk factors and areas—for example, cognitive impairment, depression, and decision-making capacity—that may require investigation (Chow et al, 2012).

Among the newer biomarkers denoting cardiovascular diseases are the natriuretic peptides—cardiac hormones synthesized and secreted by the atrium (atrial natriuretic peptide [ANP]) and the ventricle (B-type natriuretic peptide [BNP]). Discovered in 1981, natriuretic peptides have a regulatory effect that causes myocardial relaxation in response to acute increases in ventricular volume. Measurement of circulating peptides is increasingly used to identify heart failure and sudden cardiac death. Another biomarker under intensive study as a risk factor is lipoprotein(a) (Lp[a]), which has been identified from genetic studies as a causal link to MI; niacin has been shown to reduce the level of Lp(a) in some individuals (Hall, 2010).

Genetic risk factors for CAD and other cardiac disorders have been identified and are undergoing extensive study (Judge, 2012). Genetic studies have created a burgeoning body of knowledge about genetic mutations associated with risk factors such as CRP and possible pathways linking inflammatory processes with CAD (Kim et al, 2011; Roberts and Stewart, 2012a). Genetic risk variants mediate their risk in multiple ways; researchers have discovered that there are more unknown mechanisms than known mechanisms such as those associated with hypertension or lipids (Roberts and Stewart, 2012b). Soon an integral component of the preoperative assessment likely will include a genetic profile.

The risk for complications and major adverse cardiac events (MACEs) after cardiac surgery also appears to vary somewhat depending on gender (Hillis et al 2011; Newby and Douglas, 2012; Wenger, 2012). Investigations of risk factors in men and women for sternal wound infection have identified three significant risk factors that occur at significantly different rates in men and women: smoking, use of a single IMA, and age more than 70 years. Smoking and the use of a single IMA for bypass grafting are more common risk factors in men compared with women; women tend to be older than men at the time of surgery (Newby and Douglas, 2012). Fewer MACEs arose in women undergoing coronary bypass surgery without the use of cardiopulmonary bypass (CPB)—“off-pump” procedures—compared with surgery with CPB; however, malignant ventricular dysrhythmias (e.g., ventricular tachycardia), a calcified aorta, and preoperative renal failure are poor prognostic signs in women (Newby and Douglas, 2012). These findings should be incorporated into patient and family teaching plans with recommendations for lifestyle changes as indicated.

In addition to health status and risk factors, the perioperative nurse reviews patient medication history with particular attention to vasoactive drugs, anticoagulants, and other medications that can affect surgery. Nurses should note that patients taking aspirin and other antiplatelet drugs (such as 2b/IIIa inhibitors) may require intraoperative replacement of platelets. Lipid-lowering drugs (statins) have shown cardiovascular benefits, but in high doses (i.e., 80 mg, compared to moderate doses of 40 mg), they have been associated with new onset diabetes mellitus (Preiss et al, 2011). Patients taking herbal medicines may be at risk for increased bleeding, hypoglycemia, or other complications, depending on the specific side effects of some herbal drugs (see Chapter 30).

Patient knowledge and understanding of cardiovascular disease and related risk factors and their effect on functional, physiologic, and psychologic status should also be part of the perioperative nursing assessment. The patient's personal strengths, external resources, and coping strategies are important subjects to consider. The perioperative nurse also notes any cultural, ethnic, spiritual, or religious beliefs that appear relevant to perioperative patient care.

Physical assessment provides the perioperative nurse with baseline information about potential problems that might require intervention. Normal, age-specific changes in very young and elderly populations must be differentiated from pathologic conditions. Chapters 26 and 27 provide extensive age-related considerations.

In addition to age-specific changes, a growing number of adults with acquired heart disease underwent surgery in childhood to repair congenital cardiac lesions (Webb et al, 2012). For example, patients with a previous Blalock-Taussig shunt for tetralogy of Fallot (see Chapter 26) may have altered pulmonary and subclavian artery anatomy. Likewise, patients with a mechanical closure device inserted for an atrial septal defect may be at risk for endocardial injury if the heart is retracted or otherwise manipulated too forcefully. The nurse must be aware that anatomic anomalies associated with the original congenital defect, or its subsequent repair, may mandate alteration of the current surgical plan. Consultation with the surgeon can alert the cardiac team to anticipate different anatomy (and surgical landmarks), special supplies and prosthetic materials, and potential complications.

Before beginning a review of systems, it is helpful to assess the patient's functional capacity. How are activities of daily living accomplished? What are the barriers that make independent living difficult? How are activities performed when there are disabilities? What support systems are available? What educational resources are available? These and other questions will alert the clinician to the need for referrals and other resources to help the patient achieve optimal outcomes.

A systems review often starts with the skin. The appearance of the skin offers clues to cardiovascular status. Dryness, coolness, diaphoresis, paleness, edema, poor capillary refill, bruising, and petechiae may reflect impaired cardiovascular function. Visual problems and headaches may relate to inadequate cardiac output, atherosclerotic disease, peripheral vascular disease, aortic valve stenosis, or medications such as digitalis. The presence of chronic or local infection must be identified; if untreated, these are potential sources of postoperative infection. Nutritional status assessment (including metabolic syndrome) helps to determine increased risk for infection, skin breakdown, impaired wound healing, and other complications.

The patient's level of consciousness, memory, comprehension, and emotional status require assessment. Confusion, restlessness, slurred speech, numbness, and paralysis may signal impaired per­fusion. The perioperative nurse should note their presence pre­operatively and communicate this to nurses receiving the patient postoperatively.

During respiratory assessment the perioperative nurse should note the use of accessory muscles or nostril flaring and should auscultate breath sounds. Adventitious sounds such as crackles and wheezes may point to pulmonary edema. Orthopnea, shortness of breath, or dyspnea may require elevation of the head of the stretcher and assistance during transfer onto the OR bed. If the patient is receiving oxygen, the flow rate and method of administration should be observed.

Alleviating pain is a prime consideration in the care of the cardiovascular patient because pain is a myocardial stressor. A patient with angina may arrive in the OR after nitroglycerin tablets have been administered or transdermal patches applied. Cold also increases the workload of the heart because the shivering that accompanies chilling elevates the metabolic rate; the patient should be kept warm.

Heart sounds, murmurs, and friction rubs provide clues to congenital, ischemic, valvular heart disease, or pericarditis. The patient may experience palpitations. Apical, radial, and femoral pulses also reflect cardiac function, and their rate, rhythm, and quality should be determined. The presence of cyanosis or peripheral edema should be noted.

Blood pressure is an important assessment consideration. The hypertensive patient may have left ventricular hypertrophy, and the hypotensive patient may display changes in neurologic, gastrointestinal, and renal function. Blood pressures should be checked bilaterally. Unequal pressures in the arms may be a contraindication for the use of the IMA as a bypass graft on the side of the lower blood pressure, where perfusion may not be optimal. Radial and ulnar artery pulses should be checked bilaterally when the radial artery is to be used as a bypass graft. Patients with dissections or aneurysms may have unequal carotid, femoral, brachial, or radial artery blood pressures when the lesion occludes one or more of these vascular branches.

Cardiac function affects all the body's organ systems; therefore, assessment of the patient should be comprehensive whenever possible. A thorough assessment also alerts the physician and perioperative nurse to the need for special diagnostic tests and laboratory procedures.

Most patients referred for surgery have had clinical evaluations, including invasive and noninvasive studies (Box 25-3). After the history and physical assessment, a resting electrocardiogram (ECG) follows. An exercise ECG (stress test) is often undertaken because ST-segment changes indicating myocardial ischemia may be apparent only during or after exercise. In patients with intractable dysrhythmias, electrophysiology (EP) studies may help locate irritable atrial or ventricular foci that can be surgically ablated, excised, or controlled with pharmacologic therapy. EP studies also may determine the need for internal defibrillators or antitachycardia devices. Bradycardia may indicate the need for pacemaker insertion.

Chest radiography provides information about the size of the cardiac chambers, thoracic aorta, and pulmonary vasculature as well as the presence of calcium in valves, pericardium, coronary arteries, and aorta (Figure 25-8). Lateral chest radiographs of patients with prior sternal surgery show the chest wires and extent of pericardial adhesions. Magnetic resonance imaging (MRI) enables assessment of myocardial viability and also can image vascular structures with MRI angiograms that provide great clarity (Figure 25-9, A). In patients with suspected aortic or other vascular abnormalities, a computed tomography (CT) scan of the chest with intravenous injection of a contrast medium creates x-ray serial “slices” of the body area under study (see Figure 25-9, B). CT angiography is especially useful to image the aorta and the great vessels. CT images of the coronary arteries are used increasingly to identify areas of coronary calcification (shown in Figure 25-9, B), a recognized CV risk factor. One study demonstrated the value of coronary artery calcium scoring to identify patients who may be asymptomatic for CAD, but are at risk for increased mortality (Tota-Maharaj et al, 2012).

CT scans may be contraindicated in very unstable patients because their position in the tubelike scanner makes patient access difficult. Less frequently performed is arteriography with radiographic contrast dye to determine the size and location of the lesion and the site of the intimal tear in aortic dissections (Figure 25-10); digital subtraction angiography (DSA) provides clear images and requires less contrast material.

Echocardiography is a noninvasive test that evaluates both the structure and the function of the heart by transmitting sound waves to the heart and measuring those sound waves reflected back to the transducer (Figure 25-11). Sound waves undergo processing by the transducer, which creates visual images of the structure's movements. This test enables assessment of ventricular and valvular function before, during, and after surgery, and determination of the degree of valvular stenosis or regurgitation. It can also demonstrate a tumor, thrombus, or air in the ventricular or atrial cavities. Two-dimensional and color-flow Doppler techniques have greatly enhanced functional assessment of valvular performance and carotid artery stenoses. Echocardiography is the gold standard to diagnose mitral stenosis, and its use to assess other valvular disorders and congenital heart disease is widespread. Transesophageal echocardiography (TEE) also allows evaluation of the effectiveness of valve repairs and other surgical procedures (Table 25-1).

Cardiac catheterization provides definitive information about the extent and location of ischemic heart disease, acting as an adjunct to echocardiography to diagnose valvular heart disease (Kern, 2011). A radiopaque plastic catheter is inserted retrograde through the aortic valve into the left side of the heart by a percutaneous puncture or a cutdown to the vessels of the brachial artery (Sones technique) or the femoral artery (Judkins technique). The right side of the heart is approached percutaneously by the superior or inferior vena caval route. To perform coronary angiography that demonstrates intracoronary anatomy, a contrast medium is injected into the coronary ostia. Obstructions (Figure 25-12), flow, and distal perfusion are assessable. Ventriculography illustrates contractile weaknesses of the ventricles as well as shunting and regurgitation of blood. These studies enable assessment of the degree of myocardial dysfunction and planning for interventions such as CABG, valve repair or replacement, repair of congenital anomalies, and cardiac transplantation. The cardiologist can compute the orifice of a stenosed valve or determine the degree of regurgitation of an incompetent valve.

Ventricular, atrial, and pulmonary pressures are recorded, and cardiac output and ejection fraction estimated (Box 25-4 and Table 25-2). Oxygen saturation of cardiac chambers and the ratio of pulmonary to systemic blood flow (Q_p/Q_s) are calculated for patients with shunts and congenital or acquired defects. Cinearteriograms record the movement of the heart, and cut films or digitized versions of the cines may be displayed during surgery.

The cardiac catheterization laboratory also performs percutaneous coronary interventional (PCI) therapies for evolving and acute MIs (Morrow and Boden, 2012). Coronary thrombolysis with fibrinolytic drugs can dissolve fresh blood clots and reopen (i.e., recanalize) the artery; prescription of antiplatelet agents such as aspirin, dipyridamole, and clopidogrel often can block platelet aggregation that otherwise can lead to restenosis. Percutaneous transluminal coronary angioplasty (PTCA) followed by insertion of intracoronary (bare metal or drug-eluting) stents is often performed to dilate and maintain the patency of the recanalized artery. In many instances these interventions may obviate the need for surgical bypass grafting, although the progressive nature of CAD may eventually lead to patients requiring surgical revascularization.

EP studies enable diagnosis of conduction disturbances and allow therapeutic interventions, such as radiofrequency or cryologic ablation of foci producing atrial fibrillation or accessory pathways seen in Wolff-Parkinson-White syndrome. Insertion of a pacemaker for bradydysrhythmias or an internal cardioverter defibrillator for ventricular tachydysrhythmias commonly occurs in EP laboratories. Insertion of these devices, however, may require an OR when percutaneous access is unfeasible or when concomitant cardiac surgery is performed.

Preoperative laboratory tests enable assessment of physiologic function (see Appendix A). Hematologic tests include a detailed coagulation profile to uncover hemorrhagic disorders. In patients who have been taking aspirin or dipyridamole, platelet activity is decreased; this alerts the perioperative nurse to anticipate prolonged bleeding, which will require replacement. After determination of the patient's blood type, an appropriate order to the blood bank follows. The blood undergoes testing for viral contamination and for cold antibodies that could produce agglutination of the patient's blood during surgery and after patient cooling to hypothermic temperatures. A monitored blood refrigerator stores blood brought to the OR suite before surgery. Although autotransfusion techniques have reduced the use of blood bank products, the occasional, emergent need for blood requires immediate availability of blood bank packed red blood cells.

Liver and kidney function test results may be abnormal in patients with chronic heart failure, possibly because congestion related to right heart failure in the former and reduced blood flows in the latter occur with some frequency. Progressive improvement in hepatic and renal function often follows successful operative intervention. The use of statins and other cholesterol-reducing drugs that can adversely impair hepatic function also alerts the nurse to review liver function laboratory results (Pagana and Pagana, 2012). Blood glucose levels require testing, monitoring, and control, especially in patients with impaired glucose metabolism and both type 1 and type 2 diabetes.

Additional perioperative laboratory examinations may include arterial blood gases and enzyme biomarkers of myocardial damage (e.g., troponin I and troponin T; creatine kinase MB isoenzyme, known as MB bands), particularly with persistent angina (Canty, 2012). Troponin levels are the focus of a revised definition of MI. This new definition incorporates specific troponin levels and at least one of the following criteria: symptoms of ischemia, new ST-/T-wave changes or left bundle branch block on the ECG, pathologic Q waves on ECG, evidence of loss of viable myocardium or regional wall motion on diagnostic images, and documentation of an intracoronary thrombus (Thygesen et al, 2012). This new definition differentiates between infarction and injury. The distinction is important to plan treatment; it also may affect the ability to obtain insurance and participate in secondary prevention (Mitka, 2012).

Pulmonary function tests may help determine baseline data and plan postoperative care. The use of extracorporeal circulation and associated inflammatory responses, as well as the stasis of lung secretions that accompany prolonged surgery, may impair postoperative respiratory function.

The safety of the perioperative patient is a primary responsibility of the nurse. Among important National Patient Safety Goals (NPSGs) is compliance with “briefing,” “debriefing,” and other components of The Joint Commission's (TJC) Universal Protocol (TJC, 2013). The protocol consists of a checklist that addresses critical components (i.e., patient identification, confirmation of surgical procedure, availability of anticipated devices such as heart valves) that form the basis of a safe operation. Of special importance is promotion of a work culture that encourages asking questions and sharing information.

Equipment must function properly and undergo routine testing by the biomedical engineering department. Supplies should be used according to manufacturers' instructions, and instruments should be regularly scrutinized to ensure that there are no burrs that could injure tissue, that the jaws of vascular and other clamps align properly, and that small items are accounted for at the end of surgery. Toxic material, such as the glutaraldehyde storage solution of bioprosthetic valves, should be thoroughly rinsed before implantation. Monitoring aseptic practices of team members as well as visitors is important to safety.

Staff safety is also important. Protective personal equipment should be worn consistently and properly. Gloves should be used by personnel whenever contact may occur with blood or other body fluids. Injury from inadvertent effects of electrical, chemical, and other potentially hazardous materials within the OR can be minimized by reinforcing safe practices.

A growing number of hybrid suites have been designed that combine the traditional surgical controlled environment and the fluoroscopic imaging capabilities of interventional cardiology laboratories. A typical hybrid procedure may consist of a surgical coronary anastomosis under direct vision or with a robot, combined with percutaneously inserted coronary artery stents under fluoroscopy. Endovascular aneurysm (of the thoracic and abdominal aorta) and percutaneous aortic valve insertion via fluoroscopic imaging are among other procedures performed in hybrid ORs (Kpodonu, 2012).

The basic setup described for thoracic procedures (see Chapter 23) is used, along with specialized cardiovascular instruments and equipment.

Vascular clamps, designed to occlude blood flow partially or completely, must be maintained in good condition if they are to prevent fracture of the delicate tunica intima of the blood vessels and still retain their specific holding qualities. There are many variations in construction of vascular instruments. Jaws may consist of single or double rows of fine, sharp, or blunt teeth or special crosshatching or longitudinal serrations. The working angles of the clamps also vary. All clamps are designed to hold vessels securely, without causing trauma (Figure 25-13).

Minimally invasive procedures require special instrumentation to access the heart through smaller incisions in the anterior and lateral aspects of the chest wall (Figure 25-14). Retractors, dissecting instruments, suturing devices, coronary artery stabilizers, and vascular clamps are available.

Sternal and rib retractors are available to meet specific needs. IMA retractors expose the retrosternal artery bed by elevating the sternal border (Figure 25-15). Some sternal retractors have attachments to provide improved exposure of the LA during mitral valve replacement (MVR) (Figure 25-16). Handheld retractors can also expose the left or RA or the aortic root. Special rib spreaders provide exposure for mini-thoracotomy procedures. Coronary artery stabilizer systems with left ventricular apical suction retractors are widely used for beating heart coronary bypass surgery (described later).

Other equipment commonly used (or available) for cardiac surgery may include the following:

A variety of nonabsorbable cardiovascular sutures with atraumatic needles are available from most suture manufacturers. Synthetic sutures of Teflon, Dacron, polyester, or polypropylene are usually selected for insertion of prostheses and for vascular anastomoses. Most sutures are double armed with a needle on each end. Given the numerous stitches required for prosthetic valve repair and replacement, alternately colored suture and slotted, numbered suture holders may help avoid confusion. Polytetrafluoroethylene (PTFE) sutures can be used for replacement of mitral valve chordae. Vessel loops and umbilical tapes are commonly used to identify and to retract blood vessels and other structures. Wire (monofilament or twisted cable) commonly is used to approximate the sternum (Figure 25-18), with plastic, metal, or nylon bands occasionally added to reinforce fragile bone. Skin staplers may be used to close skin incisions; a staple remover must accompany the patient to the postanesthesia area if staples have been used to close the chest.

The following supplies are used in most cardiac procedures. Depending on the surgeon's preference, other items may be added or substituted.

In addition to these general supplies, special supplies are needed to repair or replace cardiovascular structures. Intracardiac patches, heart valves, and synthetic grafts should be handled with care to prevent damage or the introduction of foreign materials. Teflon, a fluorocarbon fiber, and Dacron, a polyester fiber, come in a variety of meshes, fabrics, felts, tapes, and sutures, and it is possible to combine them with other materials in prosthetic heart valves (Figure 25-19).

Use of Dacron arterial tube grafts is common in cardiac surgery, although reinforced expanded PTFE grafts are also available. There are two types of Dacron grafts: knitted and woven. Woven prosthetic grafts are usually used when the patient has been fully heparinized because the interstices of woven grafts are tighter than those in knitted grafts and bleeding is usually less. Compared with woven grafts, the advantages of knitted grafts are that they do not fray as readily, they are easier to handle, and they reendothelialize more quickly. Grafts come in a variety of sizes and may be straight or bifurcated (Figure 25-20). Knitted and woven grafts impregnated with collagen to reduce interstitial bleeding are useful in the thoracic aorta and do not have to be preclotted, even when the patient is fully heparinized for cardiopulmonary bypass. Graft sizers are available to determine correct size.

Specially designed tube grafts for the aortic arch incorporate prosthetic branches for the head vessels (bracheocephalic, left common carotid, and subclavian arteries); and tube grafts for replacement of the aortic root and ascending aorta are available with preformed sinuses of Valsalva incorporated into the prosthesis (David, 2009).

Endovascular, expandable stented tube grafts are available for both the abdominal aorta and the descending portion of the thoracic aorta (Figure 25-21). The endovascular graft is inserted percutaneously into the femoral artery and advanced to the desired position in the abdominal or descending thoracic aorta, where the prosthesis is opened, implanted, and secured (Thompson and Bertling, 2009; Tinkham, 2009).

Valve prosthesis selection depends on multiple factors: hemodynamics, thromboresistance, durability, ease of insertion, anatomic suitability, and patient acceptability; cost, patient outcome, and value are also important (Manji et al, 2012; Rahimtoola, 2010, 2011). Most mechanical prostheses use a tilting disk design. The ball-and-cage prosthesis was the first mechanical valve implanted in the anatomic position but is no longer available. Prosthetic valves allow complete closure with slight regurgitation to prevent stasis of blood (Figures 25-22 to 25-24). Prosthetic valves are manufactured with an attached annular sewing ring (often made of Dacron). The surgeon places sutures into the native valve annulus and then into the prosthesis sewing ring. The sewing ring occupies space within the valvular orifice and may affect the amount of flow through the valve orifice. This is especially significant in the small aortic root (the location of the valve annulus). Aortic prostheses, especially in the smaller sizes (e.g., 21 mm), tend to have minimal sewing ring material to avoid taking up space so as to minimize cardiac reduction of cardiac output that can flow through the prosthetic orifice. When blood flow through the prosthetic valve fails to meet metabolic demands, a prosthesis-patient mismatch is said to exist (Daneshvar and Rahimtoola, 2012; Head et al, 2012; Rahimtoola, 2011). The deleterious effect of such a mismatch eventually produces deterioration of cardiac function. Surgeons, increasingly aware of the problem, select the prosthesis with the best hemodynamics for the patient. If a suitable prosthesis is unavailable, the surgeon may opt to perform a procedure to enlarge the aortic root in order to insert a larger, more hemodynamically suitable valve.

Bioprostheses derive from porcine, bovine, or equine tissue (Figures 25-25 to 25-27). Porcine valves consist of an aortic valve from a pig that can be sutured to a Dacron-covered stent (Figure 25-25, A); alternatively, the porcine aortic valve may be “stentless” (without a sewing ring) to enhance the hemodynamics, especially in patients with a small aortic root (see Figure 25-25, B). The bovine (calf) (see Figure 25-26) pericardial bioprosthesis is created by cutting leaflet-shaped pieces from the pericardium and sewing them onto a Dacron ring; more recently, a newer bovine pericardial prosthesis (Kocher et al, 2013) can be rapidly deployed by sliding the valve into position in the aortic annulus and inflating the frame to sit firmly in place (three commissural stitches also help to anchor the prosthesis). The equine (horse) (see Figure 25-27, A) pericardial prosthesis is created by cutting pieces of the pericardium, shaping the pieces into a tube, and attaching the prosthesis to a ring of Dacron material. The advantage of these biologic valves is that administration of long-term anticoagulants is not necessary in most patients. Obturators to size prosthetic valves as well as valve holders are specific to the prostheses (see Figures 25-24, B, and 25-27, B). Tables 25-3 and 25-4 compare mechanical and biologic prosthetic heart valves. Tissue-engineered heart valves may offer a future potential cure for valvular heart disease (Rahimtoola, 2011).

Transcatheter, percutaneously inserted aortc valves come from bovine pericardium (Figure 25-28). These may be inserted in a hybrid OR with fluoroscopy.

Aortic valve allografts (homografts) pose little or no risk of thromboembolism, offer optimal hemodynamic function, require no anticoagulation drugs, and raise virtually no risk of sudden catastrophic failure. Moreover, they demonstrate a lower incidence of infective endocarditis than that found in mechanical or biologic valves, and their long-term durability is comparable with that of bioprostheses. Allograft root replacement is also a valuable technique in the context of prosthetic valve endocarditis. The entire ascending aorta and valve (Figure 25-29) or the valve alone (Figure 25-30) may be inserted. Allografts are cryopreserved and must be thawed in saline according to the vendor's protocol before implantation. Because stentless aortic valves (see Figure 25-25, B) are more easily available than allografts, they are increasingly preferred for aortic root replacement.

Conduits consisting of mechanical or biologic aortic valves attached to a tube graft (Figure 25-31) are used in procedures such as repair of aortic dissections requiring replacement of the aortic valve and ascending aorta. If vein grafts must be inserted into the conduit or if a direct coronary ostial anastomosis is required, the surgeon uses an electrocoagulator to make the opening into the graft and at the same time heat-seals the cut edges of the prosthesis. Conduits with biologic valves interposed between tube graft materials may be used when patients are at increased risk for bleeding complications associated with the need for chronic anticoagulation therapy. Allograft conduits may be used for these procedures as well.

Although allografts and stentless bioprostheses may minimize prosthesis-patient mismatch and avoid the complications associated with prosthetic mechanical valve replacement, valve repair rather than replacement is preferred, particularly for mitral and tricuspid valve lesions. Numerous mitral valve rings and bands are available for both surgical and interventional percutaneous reparative procedures. Consult with the surgeon about the intended prosthesis as well as alternative devices should another prosthesis be required (Otto and Bonow, 2012). When repairing the native valve with an annuloplasty ring, obturators specific to various kinds of annuloplasty rings are used to size the annulus (Figure 25-32, A, B, C). Ensure that the sizers appropriate for the desired prosthesis are available.

Additional safety considerations include storing prosthetic materials in a clean, protected environment and using them according to manufacturers' instructions. Before implantation, biologic valves (including the biologic valves within transcatheter aortic valve implantation [TAVI] systems) must be rinsed in three saline baths to remove the glutaraldehyde (or other) storage solution. The prescribed number of baths, the amount of physiologic fluid in each rinsing bath, and the recommended rinsing time for each bath vary among bioprosthetic manufacturers (Table 25-5). Adhere to the specific manufacturer's instructions for each prosthesis. Some bioprostheses do not require rinsing because their storage is in a physiologically neutral solution (i.e., not glutaraldehyde). However, before and during insertion, all bioprostheses should be kept moist with saline. Mechanical valves should be protected from scratching and other injury as well.

Preoperatively, cardiac surgical patients may exhibit more stress and anxiety than other surgical patients. Perioperative nurses should anticipate and prepare for this because stress and anxiety increase myocardial oxygen consumption. Efforts to reduce the family's stress and anxiety level are also important and may result in less communication of stress and anxiety to the patient. Often patients and family members ask questions about the surgery and the immediate postoperative appearance of the patient. It is helpful to prepare the family for some of the physical changes (e.g., edema, multiple tubes and lines) they can expect to see in their loved one postoperatively, and to encourage talking and touching the patient—even if the patient seems unable to respond (Patient-Centered Care).

In addition to communication with the patient, members of the team prepare the patient by ensuring vascular access for pressure monitoring and medication infusion. They insert a peripheral arterial pressure line and venous infusion lines. They may use a local anesthetic at insertion sites and may inject an IV sedative. Occasionally a patient's response to sedation results in impaired respiration, as evidenced by shallow respirations, decreased oxygen saturation, and a reduced respiratory rate (e.g., eight breaths per minute or less) (Nussmeier et al, 2009; Reich et al, 2011). The nurse noticing these respiratory changes can call a rapid response team (RRT) to assess the patient and initiate treatment before the patient develops more serious reactions, such as cardiopulmonary arrest. In this situation the RRT may consist of the anesthesia providers and staff in the immediate preoperative area rather than a specific hospital-wide RRT. For patients awaiting transfer from the preoperative area to the OR for cardiac surgery, the concept of a clinician acting promptly on changes in a patient's status and initiating a “rapid response” is an important aspect of enhancing a culture of patient safety.

After application of the ECG leads and the pulse oximeter finger cot, padding of the hands, elbows, and feet follows. The perioperative nurse confirms that the peripheral arterial pressure line functions properly, may reposition the arm as necessary in collaboration with the anesthesia provider, and confirms that pulse oximetry functions properly. Additional monitoring devices appear in Table 25-6. A time-out commences to comply with TJC's Universal Protocol (see Chapter 2).