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

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ObjectivesTo assess whether angiotensin II infusion increases pulmonary vascular resistance (PVR) relative to norepinephrine. DesignSecondary analysis of a double-blinded randomized feasibility study. SettingTwo tertiary metropolitan hospitals in Melbourne, Australia. ParticipantsAdult patients having cardiac surgery using cardiopulmonary bypass with an elevated risk of acute kidney injury (AKI). InterventionsAngiotensin II infusion compared with norepinephrine infusion. Measurements and main resultsWe studied 58 patients. There was no significant difference in the primary outcome of PVR both intraoperatively and postoperatively between the angiotensin II and norepinephrine groups. 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 (patient effect) (p<0.001), This effect was consistent across secondary outcomes. Randomization to norepinephrine (but not angiotensin II) was associated with reduced mean systemic arterial to mean pulmonary arterial pressure ratio postoperatively (Β=-0.65, p=0.01). ConclusionsThe results of this study suggest that, in cardiac surgery patients and compared with norepinephrine, at doses used in the prior feasibility study, angiotensin II did not have significant effects on the pulmonary vasculature. 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.