In patients resuscitated after out-of-hospital cardiac arrest, mean 24 hour PaCO₂ predicted good outcome, specifically time spent with PaCO₂ > 45 mmHg. No similar associations could be found between mean 24 h PaO₂ and outcome.

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• Jukka Vaahersalo, Stepani Bendel, Matti Reinikainen, Jouni Kurola, Marjaana Tiainen, Rahul Raj, Ville Pettilä, Tero Varpula, Markus B Skrifvars, and FINNRESUSCI Study Group.
• 1Department of Anesthesiology and Intensive Care Medicine, Helsinki University Hospital, Helsinki, Finland. 2Department of Intensive Care Medicine, Kuopio University Hospital, Kuopio, Finland. 3Department of Intensive Care, North Karelia Central Hospital, Joensuu, Finland. 4Centre for Prehospital Emergency Care, Kuopio University Hospital, Kuopio, Finland. 5Department of Neurology, Helsinki University Hospital, Helsinki, Finland.
• Crit. Care Med.. 2014 Jun 1;42(6):1463-70.

ObjectivesOptimal oxygen and carbon dioxide levels during postcardiac arrest care are currently undefined and observational studies have suggested harm from hyperoxia exposure. We aimed to assess whether mean and time-weighted oxygen and carbon dioxide levels during the first 24 hours of postcardiac arrest care correlate with 12-month neurologic outcome.DesignProspective observational cohort study.SettingTwenty-one ICUs in Finland.PatientsOut-of-hospital cardiac arrest patients treated in ICUs in Finland between March 2010 and February 2011.InterventionsNone.Measurements And Main ResultsArterial blood PaO2 and PaCO2 during the first 24 hours from admission were divided into predefined categories from the lowest to the highest. Proportions of time spent in different categories and the mean PaO2 and PaCO2 values during the first 24 hours were included in separate multivariable regression models along with resuscitation factors. The cerebral performance category at 12 months was used as primary endpoint. A total of 409 patients with arterial blood gases analyzed at least once and with a complete set of resuscitation data were included. The average amount of PaO2 and PaCO2 measurements was eight per patient. The mean 24 hours PaCO2 level was an independent predictor of good outcome (odds ratio, 1.054; 95% CI, 1.006-1.104; p = 0.027) but the mean PaO2 value was not (odds ratio, 1.006; 95% CI, 0.998-1.014; p = 0.149). With multivariate regression analysis, time spent in the PaCO2 band higher than 45 mm Hg was associated with good outcome (odds ratio, 1.015; 95% CI, 1.002-1.029; p = 0.024, for each percentage point increase in time) but time spent in different oxygen categories were not.ConclusionsIn this multicenter study, hypercapnia was associated with good 12-month outcome in patients resuscitated from out-of-hospital cardiac arrest. We were unable to verify any harm from hyperoxia exposure. Further trials should focus on whether moderate hypercapnia during postcardiac arrest care improves outcome.

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