Laboratory research suggests that vasopressin restores systemic arterial pressure without significantly increasing pulmonary artery pressures, compared with norepinephrine. We therefore tested the hypotheses that treatment of intraoperative vasoplegia with vasopressin rather than norepinephrine induces less pulmonary hypertension and improves right ventricular function during cardiac surgery.

Our single-center cluster-randomized multiple cross-over trial enrolled patients having elective cardiac surgery who developed systemic hypotension (mean arterial pressure <70 mmHg) and cardiac index greater than 2.2 L/min/m². Randomization was performed in one-week blocks (total of 46 weeks) where vasopressin or norepinephrine were assigned as the initial vasopressor. Our primary outcome was the time-weighed average mean pulmonary artery pressure to systemic mean arterial pressure ratio (mPAP-to-MAP) and our secondary outcome was right ventricular free wall strain by transesophageal echocardiography, both measured between start and end of chest closure. A pre-defined sub-analysis examined the effect of norepinephrine versus vasopressin in patients with preoperative pulmonary hypertension.

We analyzed 153 patients, with 70 assigned to vasopressin and 83 to norepinephrine. There were no significant differences in mPAP-to-MAP ratio [0.02 (95% CI: -0.02, 0.05; P = 0.646)] or in right ventricular free wall strain [3.45 (95% CI: 0.17, 6.73; P = 0.078) %] in patients given vasopressin vs norepinephrine infusion. There was no evidence of an interaction between preoperative pulmonary hypertension status and mPAP-to-MAP ratio (interaction P value = 0.781) or right ventricular strain (interaction P value = 0.780).

We found no evidence to support the preferential use of Vasopressin over norepinephrine in cardiac surgery patients.