The restoration of the systemic vascular resistance employing methylene blue (MB) in 6 patients after cardiac surgery with and without cardiopulmonary bypass is reported. All patients presented, during the immediate postoperative period, tachycardia, oligury, good peripheral perfusion and important systemic arterial hypotension not responsible to large doses of catecholamines infusion. The hemodynamic analysis, using the Swan-Ganz thermodilution technique, showed a profile compatible with vasoplegic syndrome, with the mean index of systemic vascular resistance of 868 dyne.s.cm5, similarly to the endotoxic shock this syndrome was assumed to be caused by nitric oxide synthase stimulation and release of nitric oxide (NO), by endothelial cells. Once released, NO stimulates solube guanylate cyclase, and thereby activates the production of cyclic guanosine 3',5' monophosphate (cGMP) resulting in relaxation. Methylene blue was administered to block the NO action by inhibiting the soluble guanylate cyclase at doses of 1.5 mg/kg during one hour intravenous infusion. Systemic vascular tone restoration (IRVS = 1693 dyne.s.cm5), with normal arterial pressure and clinical performance, were effective and fast, showing MB as a pharmacological tool able to reduce morbidity and mortality of the vasoplegic syndrome.
Methylene blue; Heart surgery; Extracorporeal circulation; Postoperative complications; Hypotension; Vascular resistance