Aortorenal Bypass for Renovascular Hypertension in Adults

Preoperative Preparation

Antihypertensive medications are reduced during the preoperative period to the minimum necessary for blood pressure control. Many patients who require large doses of multiple medications for control have reduced requirements while hospitalized and on bed rest. If continued antihypertensive therapy is required, peripheral vasodilators (e.g., amlodipine) and selective β-adrenergic blocking agents (e.g., atenolol or metoprolol) are the agents of choice. There are few adverse hemodynamic effects when these agents are combined with general anesthesia. If an adult’s diastolic blood pressure exceeds 120 mm Hg, it is essential that operative treatment be postponed until the blood pressure is controlled. In this instance, the combination of intravenous nitroprusside and esmolol is administered in an intensive care setting with continuous intraarterial blood pressure monitoring. Similarly, if the patient has significant heart disease, pulmonary artery wedge pressure, cardiac index, and oxygen delivery are monitored to optimize cardiac performance before and after operation. Information about regional myocardial performance and left ventricular preload is provided by transesophageal echocardiography in high-risk cardiac patients.

Although new diagnostic imaging techniques might have future application, digital subtraction aortography remains an essential diagnostic study before renal artery reconstruction. This is particularly important in planning branch renal artery bypass. Arteriography better defines the distal extent of renal artery disease and intrarenal disease consistent with nephrosclerosis. Although 70% of the patients treated at the author's center have at least mild ischemic nephropathy, no patient has been made permanently dependent on dialysis after digital subtraction arteriography.

Finally, certain measures are used in almost all renal artery operations. Mannitol is administered intravenously in 12.5-g doses early in the operation. Repeated doses are administered before and after periods of renal ischemia, up to a total dose of 1 g/kg body weight. Just before renal artery cross clamping, unfractionated heparin sodium, 100 U/kg, is given intravenously, and systemic anticoagulation is verified by measuring activated clotting time. Unless required for hemostasis, protamine is not routinely administered to reverse the heparin effect at the completion of the operation.

Operative Management