Vasoplegia during cardiac surgery is common and associated with perioperative mortality. Hydroxocobalamin is a catecholamine-sparing approach for treating vasoplegia. However, there is currently limited evidence to inform its use.

We conducted a single-centre retrospective propensity-matched cohort study of patients who developed vasoplegia after cardiopulmonary bypass. Our primary outcome was vasopressor requirement, expressed as norepinephrine equivalents (NEE), at 1, 4, 24, and 48 h after treatment. Our secondary outcome was a collapsed composite of in-hospital complications comprising stroke, sternal wound infection, mesenteric ischaemia, renal failure, and death.

We identified 2727 (11%) patients with vasoplegia from 2018 to 2024. The final analysis cohort included 229 matched pairs. Hydroxocobalamin administration was associated with a significant reduction in median NEE infusion rates of −0.04 (95% confidence interval [CI]: −0.07 to −0.02; P=0.008) μg kg⁻¹ min⁻¹ at 1 h, −0.05 (95% CI: −0.07 to −0.02; P<0.001) μg kg⁻¹ min⁻¹ at 4 h, and −0.04 (95% CI: −0.06 to −0.02; P=0.004) μg kg⁻¹ min⁻¹ at 24 h, but not at 48 h, −0.02 (95% CI: −0.05 to 0.0; P=0.220) μg kg⁻¹ min⁻¹. Over the initial 24 h, hydroxocobalamin reduced NEE by 14% compared with the reference group. The risk of in-hospital complications was similar in each group (odds ratio: 1.06; 95% CI: 0.74–1.54; P=0.745).

Hydroxocobalamin administration was associated with reduced vasopressor requirement over 24 h, but not thereafter. Robust trials are needed to determine whether this relationship is causal, and whether a reduction in vasopressor use improves substantive clinical outcomes.