Arterial blood gas parameters during cardiopulmonary resuscitation and sustained return of spontaneous circulation in out-of-hospital cardiac arrest: a preplanned secondary analysis of the AMCPR trial.

AIM: Arterial blood gas analysis (ABGA) is not routinely performed during cardiopulmonary resuscitation (CPR) for out-of-hospital cardiac arrest (OHCA), and is not recommended by current guidelines. This preplanned secondary analysis of the Augmented-Medication CardioPulmonary Resuscitation (AMCPR) trial evaluated whether intra-arrest PaO2 was associated with sustained return of spontaneous circulation (ROSC).

METHODS: Adult OHCA patients treated at a tertiary emergency department were included. ABGA samples were obtained immediately after ultrasound-confirmed arterial catheterization and 10 and 20 min after the start of ED resuscitation; parameters included pH, PaO2, PaCO2, bicarbonate (HCO3-), and lactate. PaO2 at the protocol-defined 10-min time point was the primary exposure and sustained ROSC the outcome; other parameters and sampling times were examined as secondary exploratory analyses.

RESULTS: Among 251 patients, 93 (37.1%) achieved sustained ROSC and 135 had a 10-min sample. In the primary analysis of these 135 patients, higher PaO2 at 10 min was independently associated with sustained ROSC (adjusted odds ratio 1.02; 95% CI 1.01-1.02). In secondary exploratory analyses, optimal cut-offs were PaO2 >60 mmHg and PaCO2 <70 mmHg, whereas pH and lactate showed no consistent pattern. Twenty patients (8.0%) survived to discharge and 2 (0.8%) had a favorable neurological outcome.

CONCLUSION: During monitored ED resuscitation for OHCA, higher intra-arrest PaO2 was associated with sustained ROSC, although this association was only partly separable from resuscitation duration. Arterial line placement during CPR may provide physiologic information beyond hemodynamic monitoring.