ADRENALINE AND/OR ISOPROTERENOL IN PATIENTS WITH LOW CARDIAC OUTPUT AND PULMONARY HYPIERTENSION UNDERGOING OPEN HEART SURGERY

Abstract

Patients with mitral stenosis undergoing valve replacement surgery have preoperative low cardiac output and pulmonary hypertension which may limit the potential for recovery of full cardiac function. Pulmonary hypertension remams a significant problem in the treatment of patients undergoing cardiac surgery. Such pulmonary hypertension is one of the most important determinants of perioperative morbidity and mortality and oflong term survival after cardiac operations.

Inotropes are frequently required to improve myocardial performance following cardiopulmonary bypass sympathomimetic amines are the most widely used agents for the management of low cardiac output syndrome that follows weaning from cardiopulmonary bypass.

Adrenaline is a potent alpha- and beta-adrenergic agonist, but effects on beta-adrenergic receptors predominate at lower doses. Profound vasoconstriction makes it difficult to use adrenaline in large doses, so a vasodilator e.g. (nitroglycerin) is usually added to adrenaline to control afterload and offset the impairment of splanchnic and renal blood flow produced by the adrenaline alone and to further augment cardiac output.

Isoproterenol is a synthetic catecholamine derivative. It is the only clinically available drug with pure beta-adrenergic agonist activity.