Associations between early intra-arrest blood acidaemia and outcomes of adult in-hospital cardiac arrest: A retrospective cohort study

Abstract

Resuscitation guidelines list acidaemia as a potentially reversible cause of cardiac arrest without specifying the threshold defining acidaemia. We examined the association between early intra-arrest arterial blood gas (ABG) data and outcomes of in-hospital cardiac arrest (IHCA). This single-centred retrospective study reviewed patients with IHCA between 2006 and 2015. Early intra-arrest ABG data were measured within 10min of initiating cardiopulmonary resuscitation. The ABG analysis included measurements of blood pH, PaCO2, and HCO3-. Among the 1065 included patients, 60 (5.6%) achieved neurologically intact survival. Mean blood pH was 7.2. Mean PaCO2 and HCO3- levels were 59.7mmHg and 22.1mmol/L, respectively. A blood pH of 7.2 was identified by a generalised additive models plot to define severe acidaemia. The PaCO2 level was higher in patients with severe acidaemia (mean: 74.5 vs. 44.1mmHg) than in those without. Multivariable logistic regression analyses indicated that blood pH>7.2 was associated with a favourable neurological recovery (odds ratio [OR]: 2.79, 95% confidence interval [CI]: 1.43-5.46; p-value=0.003) and blood pH was positively associated with survival at hospital discharge (OR: 5.80, 95% CI: 1.62-20.69; p-value=0.007). Early intra-arrest blood pH was associated with IHCA outcomes, while levels of PaCO2 and HCO3- were not. A blood pH of 7.2 could be used as the threshold defining severe acidaemia during arrest and help profile patients with IHCA. Innovative interventions should be developed to improve the outcomes of patients with severe acidaemia, such as novel ventilation methods.