Preliminary observations in systemic oxygen consumption during targeted temperature management after cardiac arrest

Abstract

AimLimited data suggests low oxygen consumption (VO2), driven by mitochondrial injury, is associated with mortality after cardiac arrest. Due to the challenges of measurement in the critically ill, post-arrest metabolism remains poorly characterized. We monitored VO2, carbon dioxide production (VCO2) and the respiratory quotient (RQ) in post-arrest patients and explored associations with outcome. MethodsUsing a gas exchange monitor, we measured continuous VO2 and VCO2 in post- arrest patients treated with targeted temperature management. We used area under the curve and medians over time to evaluate the association between VO2, VCO2, RQ and the VO2:lactate ratio with survival. ResultsIn 17 patients, VO2 in the first 12 h after return of spontaneous circulation (ROSC) was associated with survival (median in survivors 3.35 mL/kg/min [2.98,3.88] vs. non-survivors 2.61 mL/kg/min [2.21,2.94], p = .039). This did not persist over 24 h. The VO2:lactate ratio was associated with survival (median in survivors 1.4 [IQR: 1.1,1.7] vs. non-survivors 0.8 [IQR: 0.6,1.2] p < 0.001). Median RQ was 0.66 (IQR 0.63,0.70) and 71% of RQ measurements were <0.7. Patients with initial RQ < 0.7 had 17% survival versus 64% with initial RQ > 0.7 (p = .131). VCO2 was not associated with survival. ConclusionsThere was a significant association between VO2 and mortality in the first 12 h after ROSC, but not over 24 h. Lower VO2: lactate ratio was associated with mortality. A large percentage of patients had RQs below physiologic norms. Further research is needed to explore whether these parameters could have true prognostic value or be a potential treatment target.