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.

Abstract

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). 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. 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. 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.