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

PURPOSE: We assessed the effects of targeting low-normal or high-normal arterial carbon dioxide tension (PaCO(2)) and normoxia or moderate hyperoxia after out-of-hospital cardiac arrest (OHCA) on markers of cerebral and cardiac injury. METHODS: Using a 2(3) factorial design, we randomly assigned 123 patients resuscitated from OHCA to low-normal (4.5–4.7 kPa) or high-normal (5.8–6.0 kPa) PaCO(2) and to normoxia (arterial oxygen tension [PaO(2)] 10–15 kPa) or moderate hyperoxia (PaO(2) 20–25 kPa) and to low-normal or high-normal mean arterial pressure during the first 36 h in the intensive care unit. Here we report the results of the low-normal vs. high-normal PaCO(2) and normoxia vs. moderate hyperoxia comparisons. The primary endpoint was the serum concentration of neuron-specific enolase (NSE) 48 h 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 6 months. RESULTS: In total 120 patients were included in the analyses. There was a clear separation in PaCO(2) (p < 0.001) and PaO(2) (p < 0.001) between the groups. The median (interquartile range) NSE concentration at 48 h was 18.8 µg/l (13.9–28.3 µg/l) in the low-normal PaCO(2) group and 22.5 µg/l (14.2–34.9 µg/l) in the high-normal PaCO(2) group, p = 0.400; and 22.3 µg/l (14.8–27.8 µg/l) in the normoxia group and 20.6 µg/l (14.2–34.9 µg/l) in the moderate hyperoxia group, p = 0.594). High-normal PaCO(2) and moderate hyperoxia increased NIRS values. There were no differences in other secondary outcomes. CONCLUSIONS: Both high-normal PaCO(2) and moderate hyperoxia increased NIRS values, but the NSE concentration was unaffected. REGISTRATION: ClinicalTrials.gov, NCT02698917. Registered on January 26, 2016. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00134-018-5453-9) contains supplementary material, which is available to authorized users.