Management of vasodilatory shock after cardiac surgery: Identification of predisposing factors and use of a novel pressor agent

Background: Cardiopulmonary bypass can be associated with vasodilatory hypo tension requiring presser support. We have previously found arginine vasopr essin to be a remarkably effective presser in a variety of vasodilatory sho ck states. We investigated the incidence and clinical predictors of vasodil atory shock in a general population of cardiac surgical patients and the ef fects of low-dose arginine vasopressin as treatment of this syndrome in pat ients with heart failure. Methods: patients undergoing cardiopulmonary bypa ss (n = 145) were studied prospectively, Preoperative ejection fraction, me dications, and perioperative hemodynamics mere recorded, and postbypass ser um arginine vasopressin levels were measured, Vasodilatory shock was define d as a mean arterial pressure Io cr er than 70 mm Hg, a cardiac index great er than 2.5 L/min/m(2), and norepinephrine dependence. Predictors of vasodi latory shock were investigated by logistic regression analysis, The hemodyn amic responses of patients who received arginine vasopressin infusions for vasodilatory shock after cardiopulmonary bypass for left ventricular assist device placement or heart transplantation were analyzed retrospectively. R esults: Eleven of 145 general cardiac surgery patients (8%) met criteria fo r postbypass vasodilatory shock. By multivariate analysis, an ejection frac tion lower than 0.35 and angiotensin-converting enzyme inhibitor use were i ndependent predictors of postbypass vasodilatory shock (relative risks of 9 .1 and 11.9, respectively). Vasodilatory shock was associated with inapprop riately low serum arginine vasopressin concentrations (12.0 +/- 6.6 pg/mL). Retrospective analysis found 40 patients with postbypass vasodilatory shoc k who received low-dose arginine vasopressin infusions, resulting in increa sed mean arterial pressure and decreased norepinephrine requirements. Concl usions: Low ejection fraction and angiotensin-converting enzyme inhibitor u se are risk factors for postbypass vasodilatory shock, and this syndrome is associated with vasopressin deficiency, In patients exhibiting this syndro me after high-risk cardiac operations, replacement of arginine vasopressin increases blood pressure and reduces catecholamine presser requirements.