The Effects of Angiotensin II versus Norepinephrine on Pulmonary Vascular Resistance in Cardiac Surgery: Post Hoc Analysis of a Randomized Controlled Trial

Objectives: To assess whether angiotensin II infusion increases pulmonary vascular resistance (PVR) relative to norepinephrine. Design: Secondary analysis of a double-blinded randomized feasibility study. Setting: Two tertiary metropolitan hospitals in Melbourne, Australia. Participants: Fifty-eight adult patients undergoing cardiac surgery using cardiopulmonary bypass with an elevated risk of acute kidney injury (AKI). Interventions: Angiotensin II infusion compared with norepinephrine infusion. Measurements and Main Results: There was no significant difference in the primary outcome of PVR both intraoperatively and postoperatively between the angiotensin II group and the norepinephrine group. The study drug (angiotensin II or norepinephrine) infusion rate was associated with a small increase in PVR (β = 0.08; p = 0.01). The strongest association with PVR was the random effect (ie, patient effect) (p < 0.001). This effect was consistent across secondary outcomes. Randomization to norepinephrine instead of to angiotensin II was associated with reduced mean systemic arterial to mean pulmonary arterial pressure ratio postoperatively (β = -0.65; p = 0.01). Conclusions: The results of this study suggest that in cardiac surgery patients and at doses used in the prior feasibility study, angiotensin II did not have significant effects on the pulmonary vasculature compared with norepinephrine. Moreover, at doses used in this study, neither drug appeared to have a substantial effect on the pulmonary circulation relative to surgical and patient factors.