Vasopressin and methylene blue: alternate therapies in vasodilatory shock

Cardiac surgery with cardiopulmonary bypass (CPB) is frequently complicated by vasoplegic syndrome, a vasodilatory shock state. Traditional treatment based on fluid resuscitation and catecholamine drugs is ineffective in a number of patients. Clinical trials investigating both vasopressin and methylene blue as additional rescue or preventative therapy are reviewed. Vasopressin is suggested to retain its vasoconstrictive power in hypoxemia and acidosis, lower pulmonary hypertension, reduce supraventricular arrhythmias, and accelerate intensive care unit (ICU) recovery. Safety concerns include frequent thrombocytopenia and potentially altered mesenteric and renal perfusion. Methylene blue is suggested to facilitate CPB weaning, reduce renal, respiratory, arrhythmic, and septic complications, reduce mortality, and accelerate ICU and hospital recovery. Safety concerns include oximeter interference, pulmonary hypertension, neurotoxicity, arrhythmias, and potentially altered coronary, mesenteric, and renal perfusion. Research on both molecules is ongoing and has yet to confirm on a larger scale their efficacy and safety as treatments for post-CPB vasoplegic syndrome.