• Chiara Robba, Rafael Badenes, Denise Battaglini, Lorenzo Ball, Filippo Sanfilippo, Iole Brunetti, Janus Christian Jakobsen, Gisela Lilja, Hans Friberg, Pedro David Wendel-Garcia, Paul J Young, Glenn Eastwood, Michelle S Chew, Johan Unden, Matthew Thomas, Michael Joannidis, Alistair Nichol, Andreas Lundin, Jacob Hollenberg, Naomi Hammond, Manoj Saxena, Annborn Martin, Miroslav Solar, Fabio Silvio Taccone, Josef Dankiewicz, Niklas Nielsen, Anders Morten Grejs, Florian Ebner, Paolo Pelosi, and TTM2 Trial collaborators.
• Anesthesia and Critical Care, San Martino Policlinico Hospital, IRCCS for Oncology and Neuroscience, Genoa, Italy. kiarobba@gmail.com.
• Crit Care. 2022 Oct 21; 26 (1): 323323.

BackgroundOptimal oxygen targets in patients resuscitated after cardiac arrest are uncertain. The primary aim of this study was to describe the values of partial pressure of oxygen values (PaO2) and the episodes of hypoxemia and hyperoxemia occurring within the first 72 h of mechanical ventilation in out of hospital cardiac arrest (OHCA) patients. The secondary aim was to evaluate the association of PaO2 with patients' outcome.MethodsPreplanned secondary analysis of the targeted hypothermia versus targeted normothermia after OHCA (TTM2) trial. Arterial blood gases values were collected from randomization every 4 h for the first 32 h, and then, every 8 h until day 3. Hypoxemia was defined as PaO2 < 60 mmHg and severe hyperoxemia as PaO2 > 300 mmHg. Mortality and poor neurological outcome (defined according to modified Rankin scale) were collected at 6 months.Results1418 patients were included in the analysis. The mean age was 64 ± 14 years, and 292 patients (20.6%) were female. 24.9% of patients had at least one episode of hypoxemia, and 7.6% of patients had at least one episode of severe hyperoxemia. Both hypoxemia and hyperoxemia were independently associated with 6-month mortality, but not with poor neurological outcome. The best cutoff point associated with 6-month mortality for hypoxemia was 69 mmHg (Risk Ratio, RR = 1.009, 95% CI 0.93-1.09), and for hyperoxemia was 195 mmHg (RR = 1.006, 95% CI 0.95-1.06). The time exposure, i.e., the area under the curve (PaO2-AUC), for hyperoxemia was significantly associated with mortality (p = 0.003).ConclusionsIn OHCA patients, both hypoxemia and hyperoxemia are associated with 6-months mortality, with an effect mediated by the timing exposure to high values of oxygen. Precise titration of oxygen levels should be considered in this group of patients.Trial Registrationclinicaltrials.gov NCT02908308 , Registered September 20, 2016.© 2022. The Author(s).

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