• Sebastian Voicu, Nicolas Deye, Isabelle Malissin, Bernard Vigué, Pierre-Yves Brun, William Haik, Sebastien Champion, Bruno Megarbane, Georgios Sideris, Alexandre Mebazaa, Pierre Carli, Philippe Manivet, and Frédéric J Baud.
• 1Medical and Toxicological Intensive Care Department, Lariboisière University Hospital, APHP, Paris, France. 2INSERM U942, Université Paris Diderot, Paris, France. 3Cardiology Department, Lariboisière University Hospital, APHP, Paris, France. 4Department of Anesthesiology and Critical Care, CHU Bicêtre, APHP, Le Kremlin-Bicêtre, France. 5INSERM U705, Université Paris Denis Diderot, Paris, France. 6Department of Anaesthesia and Intensive care, Lariboisière University Hospital, APHP, Paris, France. 7SAMU 75 and Department of Anesthesiology, Necker Hospital, APHP, Paris Descartes University, Medical School, Paris, France. 8Biochemical Laboratory, Lariboisière University Hospital, APHP, Paris, France.
• Crit. Care Med. 2014 Aug 1;42(8):1849-61.

ObjectivesIn patients treated with therapeutic hypothermia after out-of-hospital cardiac arrest, two blood gas management strategies are used regarding the PaCO2 target: α-stat or pH-stat. We aimed to compare the effects of these strategies on cerebral blood flow and oxygenation.DesignProspective observational single-center crossover study.SettingICU of University hospital.PatientsTwenty-one therapeutic hypothermia-treated patients after out-of-hospital cardiac arrest more than 18 years old without history of cerebrovascular disease were included.InterventionsCerebral perfusion and oxygenation variables were compared in α-stat (PaCO2 measured at 37 °C) versus pH-stat (PaCO2 measured at 32-34 °C), both strategies maintaining physiological PaCO2 values: 4.8-5.6 kPa (36-42 torr).Measurements And Main ResultsBilateral transcranial middle cerebral artery flow velocities using Doppler and jugular vein oxygen saturation were measured in both strategies 18 hours (14-23 hr) after the return of spontaneous circulation. Pulsatility and resistance indexes and cerebral oxygen extraction were calculated. Data are expressed as median (interquartile range 25-75) in α-stat versus pH-stat. No differences were found in temperature, arterial blood pressure, and oxygenation between α-stat and pH-stat. Significant differences were found in minute ventilation (p = 0.006), temperature-corrected PaCO2 (4.4 kPa [4.1-4.6 kPa] vs. 5.1 kPa [5.0-5.3 kPa], p = 0.0001), and temperature-uncorrected PaCO2 (p = 0.0001). No differences were found in cerebral blood velocities and pulsatility and resistance indexes in the overall population. Significant differences were found in jugular vein oxygen saturation (83.2% [79.2-87.6%] vs. 86.7% [83.2-88.2%], p = 0.009) and cerebral oxygen extraction (15% [11-20%] vs. 12% [10-16%], p = 0.01), respectively. In survivors, diastolic blood velocities were 25 cm/s (19-30 cm/s) versus 29 cm/s (23-35 cm/s) (p = 0.004), pulsatility index was 1.10 (0.97-1.18) versus 0.94 (0.89-1.05) (p = 0.027), jugular vein oxygen saturation was 79.2 (71.1-81.8) versus 83.3% (76.6-87.8) (p = 0.033), respectively. However, similar results were not found in nonsurvivors.ConclusionsIn therapeutic hypothermia-treated patients after out-of-hospital cardiac arrest at physiological PaCO2, α-stat strategy increases jugular vein blood desaturation and cerebral oxygen extraction compared with pH-stat strategy and decreases cerebral blood flow velocities in survivors.

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