Urine output following vasopressin initiation in children in intensive care

Vasopressin is commonly used as an adjunct vasoactive infusion in paediatric intensive care. We aimed to describe changes in urine output, after vasopressin initiation, in children admitted to a paediatric intensive care unit (PICU). We performed a retrospective cohort study of patients aged < 18 years who received a vasopressin infusion between 2017 and 2023. Urine output in the 6 h prior to vasopressin commencement was compared with four subsequent 6-hour epochs over the following 24 h. Average percentage change in urine output was estimated using linear regression on the log scale, accounting for repeated measures with generalised estimating equations. Prespecified subgroup analyses were conducted in children with acute kidney injury (AKI), and contemporaneous changes in serum sodium were described. Among 247 children who received vasopressin, the most common diagnostic groups were congenital heart disease 131(53%) and sepsis 35(14%). The median starting dose was 0.02 Units/kg/hr (IQR 0.02–0.03). Median baseline urine output was 1.4 mL/kg/hr (IQR 0.6–3.2). Overall, urine output changed little after vasopressin initiation; in the first 0–6 h the relative change, compared with baseline, was 5.2% (95% CI − 1.5% to 12.0%). In the 228/247 (92%) children with AKI, patterns of urine output change were similar. Serum sodium decreased modestly over time (mean difference − 0.6 mmol/L at 0–6 h and − 1.3 mmol/L at 18–24 h). In this single-centre study, vasopressin was not associated with a clinically meaningful increase in urine output over 24 h, while a small fall in sodium suggests a predominant antidiuretic effect.