Acidemia Detected on Venous Blood Gas After Out-of-Hospital Cardiac Arrest Predicts Likelihood to Survive to Hospital Discharge

Abstract

Background: Sudden cardiac arrest is the most common cause of death worldwide, and prognostication after survival remains challenging. Decisions regarding prognosis can be fraught with error in the immediate postarrest period, with guidelines recommending the use of various tests, including blood gas pH, to determine which interventions to perform. Despite these recommendations, the prognostic utility of blood gas pH remains unclear.

Objectives: In this retrospective cohort study, we aimed to demonstrate the prognostic utility of emergency department blood gas pH after return of spontaneous circulation (ROSC) in out-of-hospital cardiac arrest.

Methods: A retrospective cohort study was performed, including all adult survivors of out-of-hospital cardiac arrest (n = 79). Primary disease-oriented outcome was venous blood pH after ROSC and survival to hospital discharge.

Results: In patients with out-of-hospital cardiac arrest, pH < 7.2 was associated with decreased likelihood of survival to hospital discharge (odds ratio 0.06), with every 0.1-unit increase in pH being associated with an increased likelihood of survival (1.98). Based on the area under the receiver curve, the pH that optimizes sensitivity and specificity for predicting survival was 7.04.

Conclusion: Both presence and degree of acidemia on initial blood gas after ROSC was associated with a decreased likelihood of survival to hospital discharge. The optimal cutoff for prediction in this cohort of patients was 7.04. Using a higher pH cutoff would result in fewer patients receiving intervention that would otherwise have survived.

Keywords: acidosis; cardiopulmonary arrest; percutaneous coronary angioplasty; prognosis.