What is the treatment for perioperative right ventricular failure?
Following mitral valve replacement, weaning from cardiopulmonary bypass is sometimes complicated by pulmonary hypertension and RV failure. Monitoring of the left atrial pressure is helpful in calculating the pulmonary vascular resistance, because a gradient is often present between the pulmonary capillary wedge and left atrial pressures. Factors that predispose to pulmonary vaso-constriction (e.g., hypoxia, hypercarbia, acidosis, and hypothermia) should be corrected.
The main goals in the anesthetic management of RV failure are to reduce RV afterload, optimize RV preload, maintain RV coronary perfusion, and support RV contractil-ity. In the presence of pre-existing pulmonary hypertension and increased pulmonary vascular resistance, RV failure will respond favorably to pulmonary vasodilatation. Drugs with pulmonary vasodilating activity that are used after termination of cardiopulmonary bypass include nitroprus-side, nitroglycerin, and prostaglandin E1. However, none of these medications is selective for the pulmonary circulation and their use may be limited due to their systemic effects. Milrinone, a phosphodiesterase III inhibitor, increases RV contractility and has pulmonary vasodilating properties. This pharmacologic profile makes phosphodiesterase III inhibitors particularly appealing in the treatment of RV failure. Inhaled aerosolized milrinone is an experimental therapy that may be used for selective pulmonary vaso-dilatation if preliminary studies prove its effectiveness.
Inhaled nitric oxide (NO) is an established therapy for pulmonary hypertension and RV failure following mitral valve surgery. NO is an endothelium-derived vasodilator and when inhaled selectively causes pulmonary vascular relaxation. Prostacyclin acts via specific prostaglandin receptors and has also been shown to reduce pulmonary hypertension after cardiac surgery. However, the vasodilation is not selective for the pulmonary vasculature and systemic hypotension may ensue. Various newer prostacyclin analogs are now given for chronic pulmonary hypertension, and may be useful for intraoperative use in the future.
Vasopressin or norepinephrine is particularly effective for the treatment of systemic hypotension in patients with RV failure. Vasopressin (antidiuretic hormone) is a posterior pituitary hormone that causes dose-dependent vasoconstric-tion and antidiuretic effects. Epinephrine is the preferred cat-echolamine in patients with pulmonary hypertension and RV failure when RV contractility is suspected to be severely impaired.