Chapter 21

• Cardiopulmonary bypass (CPB) diverts venous blood away from the heart, adds oxygen, removes CO2, and returns the blood to a large artery (usually the aorta). As a result, nearly all blood flow through the heart and most of the flow through the lungs cease.
• The fluid level in the reservoir of the CPB machine is critical: If the reservoir is allowed to empty, air can enter the main pump and cause a fatal air embolism.
• Initiation of CPB is associated with a marked increase in stress hormones and a variable systemic inflammatory response.
• Establishing the adequacy of cardiac reserve should be based on exercise (activity) tolerance, measurements of myocardial contractility such as ejection fraction, the severity and location of coronary stenoses, ventricular wall motion abnormalities, cardiac end-diastolic pressures, cardiac output, and valvular areas and gradients.
• Blood should be available for immediate transfusion if the patient has already had a midline sternotomy (a “redo”); in these cases, the right ventricle or coronary grafts may be adherent to the sternum and may be inadvertently entered during the repeat sternotomy.
• In general, pulmonary artery catheterization should be used in patients with compromised ventricular function (ejection fraction < 40–50%) or pulmonary hypertension and in those undergoing complicated procedures.
• Transesophageal echocardiography (TEE) provides valuable information about cardiac anatomy and function during surgery. Two-dimensional, multiplane TEE can detect regional and global ventricular abnormalities, chamber dimensions, valvular anatomy, and the presence of intracardiac air.
• Anesthetic dose requirements are extremely variable and generally are inversely related to ventricular function. Severely compromised patients should be given anesthetic agents in small doses, slowly, and in increments.
• Anticoagulation must be established before CPB to prevent acute disseminated intravascular coagulation and formation of clots in the CPB pump.
• Aprotinin therapy should be considered for patients who are undergoing a repeat operation; who refuse blood products, such as Jehovah’s Witnesses; who are at high risk for postoperative bleeding because of recent administration of glycoprotein IIb/IIIa inhibitors (abciximab, eptifibatide, or tirofiban); who have preexisting coagulopathy; and who are undergoing long and complicated procedures involving the heart or aorta.
• Hypotension from impaired ventricular filling often occurs during manipulation of the venae cavae and the heart.
• Hypothermia (< 34°C) itself is usually anesthetic, but failure to give anesthetic agents, particularly during rewarming on CPB, frequently results in light anesthesia that may result in awareness and recall.
• Protamine administration can result in a number of adverse hemodynamic effects, which appear to be either immune or idiosyncratic nonimmune reactions. Although protamine given slowly (5–10 min) usually has minimal effects, hypotension from acute systemic vasodilation, myocardial depression, and marked pulmonary hypertension may be encountered.
• Persistent bleeding following bypass may be due to inadequate surgical control of bleeding sites, inadequate reversal of heparin, reheparinization, thrombocytopenia, platelet dysfunction, hypothermia, undiagnosed preoperative hemostatic defects, or newly acquired defects. If oozing continues despite adequate surgical hemostasis and the activated clotting time (ACT) is normal or the heparin–protamine titration assay shows no residual heparin, thrombocytopenia or platelet dysfunction is most likely.
• Chest tube drainage in the first 2 h of more than 250–300 mL/h (10 mL/kg/h)—in the absence of a hemostatic defect—is excessive and often requires surgical reexploration. Intrathoracic bleeding at a site not adequately drained causes ...

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