Haemodynamic trajectories around prehospital adrenaline infusion start after return of spontaneous circulation

Post-return of spontaneous circulation (ROSC) hypotension is common and associated with worse outcomes, but the immediate haemodynamic response to prehospital adrenaline infusion is poorly described. We examined minute-level blood pressure trajectories around documented infusion initiation in out-of-hospital cardiac arrest (OHCA) patients who achieved sustained ROSC and arrived at hospital with a pulse present.

We performed a retrospective linked cohort study of adult emergency medical services-treated out-of-hospital cardiac arrest cases in Victoria, Australia, from 2019 to 2023, who achieved sustained ROSC, had available linked ZOLL® monitor-defibrillator data, and arrived at hospital with a pulse present. Patients started on prehospital adrenaline infusion within 60 min of ROSC were included. Minute-level mean arterial pressure (MAP) and systolic blood pressure (SBP) trajectories from 10 min before to 20 min after infusion start were analysed using segmented mixed-effects models adjusted for pre-infusion mean pressure and pre-infusion slope.

Of 3655 eligible adult ROSC cases with linked monitor data and pulse present on hospital arrival, 1920 received prehospital adrenaline infusion within 60 min of ROSC. Blood pressure generally declined in the 10 min before infusion, reached a nadir at or near infusion start, and then rose over the next 20 min. In the primary models, MAP fell by 1.64 mmHg/min before infusion and rose by 1.15 mmHg/min after infusion, a slope change of 2.79 mmHg/min (95% CI 2.48-3.09). SBP fell by 2.25 mmHg/min before infusion and rose by 1.71 mmHg/min after infusion, a slope change of 3.96 mmHg/min (95% CI 3.55-4.38). These changes reflected a marked reversal in trajectory around infusion start. Descriptively, mean MAP increased from 81.2 mmHg at 5 min after infusion start to 95.4 mmHg at 20 min, while mean SBP increased from 107.9 to 128.4 mmHg.

Documented adrenaline infusion start coincided with reversal of a falling blood pressure trajectory and a sustained rise in MAP and SBP over the next 20 min. These findings help define prehospital post-ROSC adrenaline arterial-pressure responsiveness and support further study of vasopressor timing, targets, and trial design.