Background: Vasodilatory shock requiring catecholamine pressors occurs in some patients following cardiopulmonary bypass. Prompted by a clinical observation, we investigated the use of vasopressin as a treatment for this syndrome in a randomized, controlled trial.
Methods and results: Patients undergoing placement of a left ventricular assist device (n=23) were evaluated for post-bypass vasodilatory shock requiring catecholamine pressors, and consecutive eligible subjects (n=10) were evenly randomized to blinded intravenous vasopressin or saline placebo. Vasopressin (0.1 U/min) increased mean arterial pressure (57+/-4 to 84+/-2 mm Hg, P<.001) and systemic vascular resistance (813+/-113 to 1188+/-87 dyne-s/cm5, P<.001), with decreased norepinephrine administration. There was no significant response to saline, but in three subjects who crossed over, blinded vasopressin increased mean arterial pressure (69+/-8 to 93+/-4 mm Hg) and systemic vascular resistance (898+/-88 to 1443+/-72 dyne-s/cm5) with decreased norepinephrine administration. Plasma vasopressin concentrations prior to randomization clustered in two groups: one (n=5) with concentrations inappropriately low for the degree of hypotension (8.4+/-2.1 pg/mL) and a second (n=3) with moderately elevated levels (33.7+/-1.6 pg/mL); vasopressin increased mean arterial pressure in the low vasopressin group from 57+/-4 to 85+/-2 mm Hg (P<.01) and in the high vasopressin group from 68+/-8 to 86+/-4 mm Hg.
Conclusions: Vasopressin is an effective pressor in vasodilatory shock after cardiopulmonary bypass. An absolute vasopressin deficiency was observed in the majority of patients, but all subjects responded to vasopressin administration.