Oxygen metabolism after cardiac arrest: Patterns and associations with survival

Whether changes in oxygen metabolism, as measured by oxygen consumption (VO₂), carbon dioxide production (VCO₂) and the respiratory exchange ratio (RER), are associated with survival after cardiac arrest is poorly understood. In this prospective observational study, we investigated the association between VO₂, VCO₂, and RER in the initial 12 and 24 h after return of spontaneous circulation (ROSC) and survival to hospital discharge.

Adults with ROSC after cardiac arrest, admitted to the intensive care unit, requiring mechanical ventilation and treated with targeted temperature management were included. VO₂ and VCO₂ were measured continuously for 24 h after ROSC, using a noninvasive anesthesia monitor. Area under the curve for VO₂, VCO₂ & RER was calculated using all available values over 12 and 24 h after ROSC. Using logistic regression, we evaluated the relationship between these metabolic variables and survival to hospital discharge. Analyses were adjusted for temperature, vasopressors, and neuromuscular blockade.

Sixty four patients were included. Mean age was 64 ± 16 years, and 59% were women. There was no significant association between the area under the curve of VO₂ or VCO₂ and survival. A higher RER in the initial 12 h was associated with better survival (aOR = 3.97, 95% CI [1.01,15.6], p = 0.048). Survival was lower in those with median RER < 0.7 in the initial 12 h compared with those with a median RER ≥ 0.7 (25% vs 67%, p = 0.011).

Higher RER in the initial 12 h was associated with survival after cardiac arrest. The etiology of unusually low RERs in this patient population remains unclear.