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 (ET CO2 ) during out-of-hospital cardiac arrest (OHCA), though its prognostic value is poorly understood. This study investigated the relationship between ET CO2 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 ET CO2 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 ET CO2 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 ET CO2 during resuscitation prior to SOI was 36.8 mmHg (18.6). ET CO2 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 ET CO2 after SOI (from 37.8 to 48.2 mmHg; +10.4 CI: 7.2, 13.6), while ET CO2 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: ET CO2 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.