Targeting two different levels of both arterial carbon dioxide and arterial oxygen after cardiac arrest and resuscitation: a randomised pilot trial

PurposeWe assessed the effects of targeting low-normal or high-normal arterial carbon dioxide tension (PaCO2) and normoxia or moderate hyperoxia after out-of-hospital cardiac arrest (OHCA) on markers of cerebral and cardiac injury.MethodsUsing a 2(3) factorial design, we randomly assigned 123 patients resuscitated from OHCA to low-normal (4.5-4.7kPa) or high-normal (5.8-6.0kPa) PaCO2 and to normoxia (arterial oxygen tension [PaO2] 10-15kPa) or moderate hyperoxia (PaO2 20-25kPa) and to low-normal or high-normal mean arterial pressure during the first 36h in the intensive care unit. Here we report the results of the low-normal vs. high-normal PaCO2 and normoxia vs. moderate hyperoxia comparisons. The primary endpoint was the serum concentration of neuron-specific enolase (NSE) 48h after cardiac arrest. Secondary endpoints included S100B protein and cardiac troponin concentrations, continuous electroencephalography (EEG) and near-infrared spectroscopy (NIRS) results and neurologic outcome at 6months.ResultsIn total 120 patients were included in the analyses. There was a clear separation in PaCO2 (p<0.001) and PaO2 (p<0.001) between the groups. The median (interquartile range) NSE concentration at 48h was 18.8 mu g/l (13.9-28.3 mu g/l) in the low-normal PaCO2 group and 22.5 mu g/l (14.2-34.9 mu g/l) in the high-normal PaCO2 group, p=0.400; and 22.3 mu g/l (14.8-27.8 mu g/l) in the normoxia group and 20.6 mu g/l (14.2-34.9 mu g/l) in the moderate hyperoxia group, p=0.594). High-normal PaCO2 and moderate hyperoxia increased NIRS values. There were no differences in other secondary outcomes.ConclusionsBoth high-normal PaCO2 and moderate hyperoxia increased NIRS values, but the NSE concentration was unaffected.RegistrationClinicalTrials.gov, NCT02698917. Registered on January 26, 2016.