GENERAL SURGERY IN THE PATIENT WITH HEART DISEASE



Noncardiac surgery is particularly stressful in patients with pre-existing heart disease. The bur­dens of anesthesia, surgical trauma, wound heal­ing, infection, hemorrhage, and pulmonary in­sufficiency may overwhelm the diseased heart. The internist is often asked to assess cardiovas­cular risk in patients undergoing noncardiac sur­gery and to aid in their preoperative and post­operative management.

General anesthetics reduce myocardial con-tactility and also have autonomic nervous sys­tem effects that may cause either hypotension or hypertension. Regional, spinal, or epidural anesthesia minimizes myocardial depression, but sympathetic blockade and hypotension still may result. In general, there appears to be no difference in risk between general anesthesia and spinal anesthesia in cardiac patients. The anesthesiolo­gist must maintain adequate ventilation, oxygenation, and blood pH throughout the procedure. The ECG is routinely monitored throughout sur­gery. If cardiac disease is significant, arterial blood pressure, central venous pressure and/or pulmonary arterial wedge pressure may need to be monitored throughout the procedure. Cardiac arrhythmias are particularly likely in patients with heart disease and occur most commonly dur­ing induction of anesthesia and intubation. Ex­cessive vagal tone can cause bradyarrhythmias and usually responds to adjusting the depth of anesthesia or administering atropine. Antiar­rhythmic agents may be administered if needed.

Some patients have life-threatening indications for surgery, and cardiac risk does not affect whether or not the surgery should be performed. In elective surgery, however, the timing of the op­eration or even whether the operation should be done may depend upon a preoperative estimation of surgical risk. Cardiac risk is strongly associated with the type of surgical procedure. Hernior­rhaphy and transurethral resection of the prostate carry relatively low risk, whereas chest, abdom­inal, and retroperitoneal surgery have a relatively high risk. Emergency surgery is associated with greater risk than nonemergent surgery because there is no time to optimize the patient’s cardiac status.

Ischemic heart disease is one of the major de­terminants of cardiac risk. The incidence of per­ioperative myocardial infarction is 4 to 8 per cent in patients who have had remote prior infarctions. In addition, the mortality from perioperative my­ocardial infarction is two to three times greater in patients with previous infarction as compared to those without previous infarction. Particularly high risk of reinfarction occurs if surgery is per­formed early after infarction, but levels off if sur­gery is delayed until six months after infarction. The surgical risk in patients with stable angina pectoris is about the same as that in patients with remote myocardial infarction. Patients with un­stable angina pectoris should not have elective surgery until the angina is stabilized and possibly invasive evaluation of the coronary arteries ob­tained.

Decompensated congestive heart failure is an­other major operative risk factor and should be treated vigorously prior to noncardiac surgery. Pa­tients with congestive heart failure or atrial tachy arrhythmias should probably receive digitalis prior to surgery.
Patients with symptomatic heart block may need prophylactic pacing prior to surgery. Pa­tients with chronic bifascicular block or asymp­tomatic type I second-degree AV block probably do not require prophylactic pacemaker placement prior to anesthesia. Patients with frequent or symptomatic atrial or ventricular tachyarrhyth­mias should be treated prior to surgery.
Patients with valvular heart disease tend to tol­erate the operation according to their pre-existing functional status. Patients with critical aortic or mitral stenosis are at particularly high risk. Treat­ment of heart failure should be optimized pre-operatively, and those with severe valvular le­sions should be considered for corrective surgery prior to elective noncardiac operation. In patients with valvular disease or prosthetic heart valves, endocarditis prophylaxis should be administered if appropriate (see Chapter 10). In patients with prosthetic heart valves, anticoagulation can usu­ally be stopped temporarily immediately preop-eratively and in the early postoperative period in order to prevent bleeding complications.

Mild to moderate hypertension does not alter surgical risk. Severe hypertension should be con­trolled prior to surgery, as should heart failure or angina associated with it.

Patients with congenital heart disease are at in­creased risk according to their functional disabil­ity. Patients with cyanotic congenital heart dis­ease and polycythemia have an increased risk of hemorrhage due to coagulation defects and throm­bocytopenia, and they may tolerate hypotension and hypoxia poorly. Appropriate endocarditis prophylaxis should be administered. Patients with right-to-left shunts are at risk for paradoxical emboli.

In addition to evaluating and optimizing the pa­tient’s cardiac status, the general medical status should also be optimized. Pulmonary function is especially important; cessation of smoking and treatment of chronic bronchitis may improve risk.