Increase in end-tidal carbon dioxide after defibrillation predicts sustained return of spontaneous circulation during out-of-hospital cardiac arrest.

Introduction: Guidelines recommend monitoring end-tidal carbon dioxide (ECO) during out-of-hospital cardiac arrest (OHCA), though its prognostic value is poorly understood. This study investigated the relationship between ECO and return of spontaneous circulation (ROSC) after defibrillation in intubated non-traumatic OHCA patients.

Methods: This retrospective, observational cohort analysis included adult OHCA patients who received a defibrillation shock during treatment by an urban EMS agency from 2015 to 2021. Peak ECO values were determined for the 90-second periods before and after the first defibrillation in an intubated patient (shock of interest [SOI]). Values were analyzed for association between the change in ECO from pre- to post-shock and the presence of ROSC on the subsequent pulse check.

Results: Of 518 eligible patients, mean age was 61, 72% were male, 50% had a bystander-witnessed arrest, and 62% had at least one episode of ROSC. The most common arrest etiology was medical (92%). Among all patients, peak ECO during resuscitation prior to SOI was 36.8 mmHg (18.6). ECO increased in patients who achieved ROSC immediately after SOI (from 38.3 to 47.6 mmHg; +9.3 CI: 6.5, 12.1); patients with sustained ROSC experienced the greatest increase in ECO after SOI (from 37.8 to 48.2 mmHg; +10.4 CI: 7.2, 13.6), while ECO in patients who did not achieve ROSC after SOI rose (from 36.4 to 37.8 mmHg; +1.4 CI: -0.1, 2.8).

Conclusions: ECO rises after defibrillation in most patients during cardiac arrest. Patients with sustained ROSC experience larger rises, though the majority experience rises of less than 10 mmHg.