*The goal is to return the heart to a slow, small, perfused state.
IV = intravenous.

4. Calcium channel blockers are useful in slowing the ventricular response in atrial fibrillation and flutter, as coronary vasodilators, and in the treatment of perioperative hypertension (clevidipine better than sodium nitroprusside [SNP] or trinitroglycerin [TNG]).

G. Guidelines for Coronary Artery Bypass Graft Surgery (Table 38-4)

II. VALVULAR HEART DISEASE. Valvular heart disease is characterized by pressure or volume overload of the atria or ventricles. Transesophageal echocardiography (TEE) has become a commonly used monitor in the perioperative management of patients undergoing cardiac surgery.

A. Aortic Stenosis

1. The normal aortic valve is composed of three semilunar cusps attached to the wall of the aorta. The normal annular diameter is 1.9 to 2.3 cm with an aortic valve area of 2 to 4 cm². The normal diameter of the left ventricular outflow tract is 2.2 cm.

2. Pathophysiology (Fig. 38-1). Chronic obstruction to left ventricular ejection results in concentric ventricular hypertrophy, which makes the heart susceptible to myocardial ischemia even in the absence of CAD. Because the ventricle is stiff, atrial contraction is critical for ventricular filling and stroke volume.

3. Anesthetic Considerations. Maintenance of adequate ventricular volume and sinus rhythm is crucial. If hypotension develops, it must be treated early to prevent the catastrophic cycle of hypotension-induced ischemia, subsequent ventricular dysfunction, and worsening hypotension. Bradycardia is a common cause of hypotension in patients with aortic stenosis.

B. Hypertrophic cardiomyopathy is a genetically determined disease characterized by development of a hypertrophic intraventricular septum, resulting in left ventricular outflow obstruction (resembling aortic stenosis). Outflow obstruction is increased by increases in myocardial contractility or heart rate or decreases in preload or afterload. Anesthetic management is based on maintenance of left ventricular filling and controlled myocardial depression.

C. Aortic Insufficiency

1. Pathophysiology (Fig. 38-2). Chronic volume overload of the left ventricle evokes eccentric hypertrophy but only minimal changes in filling pressures.

2. Anesthetic Considerations. Maintenance of adequate ventricular volume in the presence of mild vasodilation and increases in heart rate is most likely to optimize forward left ventricular stroke volume. An incompetent aortic valve may prevent the delivery of cardioplegia to the coronary system to produce diastolic arrest of the heart. (The alternative is injecting cardioplegia directly into the coronary ostia or into the coronary sinus.)

D. Mitral Stenosis

1. Pathophysiology (Fig. 38-3). Increased left atrial pressure and volume overload are inevitable consequences of the narrowed mitral orifice. Persistent increases in left atrial pressure are reflected back through the pulmonary circulation, leading to right ventricular hypertrophy and perivascular edema in the lungs.

2. Anesthetic Considerations. Avoiding tachycardia is crucial for preventing inadequate left ventricular filling with concomitant hypotension. Continued preoperative administration of digitalis and β–antagonists, selection of anesthetics with minimal propensity to increase heart rate, and achievement of an anesthetic depth sufficient to suppress sympathetic nervous system responses are recommended.

E. Mitral Regurgitation

1. Pathophysiology (Fig. 38-4). Chronic volume overload of the left atrium is the cardinal feature of mitral regurgitation.

2. Anesthetic Considerations. Selection of anesthetics that promote vasodilation and increase the heart rate is useful.

III. AORTIC DISEASES

A. Aortic dissection is characterized by rapid development of an intimal flap separating the true and false lumens. Severe chest pain (dissection of the ascending aorta) or back pain (descending aorta dissections) is the most common presenting symptom. A variety of diagnostic techniques (contrast-enhanced computed tomography, TEE, magnetic resonance imaging) are accurate in the diagnosis of acute aortic dissection. Surgery is the definitive treatment for ascending aortic dissections.

1. Anesthetic Considerations. Acute aortic dissection is a surgical and anesthetic emergency necessitating IV access and invasive monitoring, including TEE.

B. Aortic Aneurysm. Thoracic aneurysms may involve one or more aortic segment (aortic root, ascending aorta, arch, descending aorta). The surgical replacement of an aortic arch aneurysm requires circulatory arrest and introduces the risk of global cerebral ischemia. Surgical replacement of the descending aorta is associated with postoperative paraplegia secondary to interruption of spinal cord blood supply.

1. Anesthetic Considerations. The anesthetic technique is focused on preservation of cardiac function (descending thoracic aortic aneurysm) and neurologic integrity (aortic arch or descending thoracic aneurysms). Drainage of cerebrospinal fluid improves spinal cord perfusion pressure. Left heart bypass (left atrium to femoral artery) provides nonpulsatile retrograde aortic perfusion.

IV. CARDIOPULMONARY BYPASS incorporates a circuit to oxygenate venous blood and return it to the patient’s arterial circulation (Table 38-5 and Fig. 38-5).

A. Blood Conservation in Cardiac Surgery

1. Intraoperative autologous hemodilution involves the removal of whole blood before bypass (spared damaging effects [coagulopathy] of the bypass circuit) for reinfusion after bypass. Red blood cells may also be salvaged from the surgical field and bypass tubing, washed, and retransfused (Cell Saver). Cell Saver blood may worsen coagulopathy because factors causing coagulopathy are not removed by the filtering process.

2. Pharmacologic measures include antifibrinolytics (epsilon-aminocaproic acid).

B. Myocardial Protection. The most common method of myocardial protection is use of intermittent hyperkalemic cold cardioplegia (diastolic electrical arrest) and moderate systemic hypothermia.

1. During CPB, the onset of left ventricular distention and lack of rapid electrical arrest may be evidence of poor myocardial protection and the possibility of difficulty in separation from bypass.

2. TEE is helpful in diagnosing ventricular distention that is relieved by venting or manual decompression.

V. PREOPERATIVE AND INTRAOPERATIVE MANAGEMENT. Data from the history, physical examination, and laboratory investigation are used to delineate the degree of left ventricular or right ventricular dysfunction (Table 38-6).

A. Current drug therapy, including β-adrenergic antagonists, calcium channel blockers, ACE inhibitors, and digitalis preparations (heart rate or rhythm control), is usually continued until the time of surgery.

B. Premedication for cardiac surgery often combines an opioid (0.1–0.2 mg/kg intramuscularly [IM] of morphine) with scopolamine (0.006 mg/kg IM) with or without a benzodiazepine (0.05–0.1 mg/kg of diazepam or 0.05–0.07 mg/kg of lorazepam orally). Patients with valvular heart disease may be more susceptible to the ventilatory depressant effects of premedication than those with CAD who are scheduled for CABG operations.

C. Monitoring should emphasize the areas particularly relevant to cardiac surgery (Table 38-7). Use of specialized equipment or procedures (hypothermia, tight glucose control) has an unproven benefit on neurologic outcomes.

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