Vasopressin Versus Norepinephrine As First-Line Vasopressor Therapy for Vasoplegic Shock Following Cardiac Surgery: A Systematic Review.

Vasoplegic shock following cardiac surgery is associated with significant morbidity. While norepinephrine is recommended as first-line therapy, vasopressin has been proposed as an alternative due to catecholamine-independent mechanisms. Comparative evidence in postcardiac surgery populations remains limited. We conducted a systematic review of randomized and observational studies comparing vasopressin versus norepinephrine as initial vasopressor therapy in adults with vasoplegic shock following cardiac surgery with cardiopulmonary bypass. Primary outcomes included mortality and major postoperative complications. Risk of bias was assessed using the Cochrane Risk of Bias 2 (RoB 2) and the Risk of Bias in Non-randomized Studies of Interventions (ROBINS-I) tools. Two studies (n = 638 patients) met inclusion criteria: one randomized trial (VANCS) and one propensity score-matched observational cohort study. In the randomized trial, vasopressin was associated with a lower incidence of composite morbidity (32.2% vs 49.0%), reduced incidence of acute kidney injury requiring dialysis, and shorter ICU stay, without a difference in mortality. In contrast, the observational study in patients with severe left ventricular (LV) dysfunction showed no benefit and suggested higher rates of arrhythmias and mortality with vasopressin. Available evidence suggests that the effect of vasopressin in postcardiac surgery vasoplegia may depend on baseline ventricular function. Vasopressin may be considered as an early catecholamine-sparing strategy in selected patients with preserved ventricular function, but current evidence does not support a universal change from norepinephrine to vasopressin as first-line therapy for all patients. In patients with severe ventricular dysfunction, vasopressin should be used cautiously, and adequately powered phenotype-stratified randomized trials are needed.