• Sylvain Diop, Elie Fadel, Pauline Valentini, Alexandre Thepaut, Thibaut Genty, Iolanda Ion, Filip De Somer, and Jacques Thes.
• Department of Anesthesiology, Marie Lannelongue Hospital, Paris Saint Joseph Hospital, Le Plessis Robinson, France; Cardiothoracic Intensive Care Unit, Marie Lannelongue Hospital, Paris Saint Joseph Hospital, Le Plessis Robinson, France. Electronic address: menes.diop@gmail.com.
• J. Cardiothorac. Vasc. Anesth. 2024 Sep 19.

ObjectivesThe aim of this physiological pilot study was to investigate the effect of deep hypothermia on oxygen extraction (OE) and consumption (VO2) in normothermic conditions (36-37°C), and at different stages of cooling: 30°C, 25°C, and 18°C.DesignFor 3 months, a prospective study was conducted on patients who underwent pulmonary thromboendarterectomy.SettingsThis was a single-center study done in a university teaching hospital.ParticipantsPatients who underwent pulmonary thromboendarterectomy during the inclusion period.InterventionsHemodynamic and biological data were recorded from arterial and venous blood gas samples withdrawn first at normothermia, then at 30°C, 25°C, and 18°C.Measurements And Main Results24 patients were included in the final analysis. Indexed VO2 decreased from 65.9 mL to 25.1 mL of O2/min/m2 between 36°C and 18°C (p < 0.001). The OE decreased from 18% to 9% between 36°C and 18°C (p < 0.001). At normal temperature and 18°C, the median venoarterial difference of O2 bound to hemoglobin was 2.22 [1.68-2.58] and 0.03 mL [0.01-0.07] of O2/100 mL of blood, respectively (p < 0.001). Whereas the median venoarterial differences in dissolved O2 were 0.78 [0.66-0.92] and 1.09 mL [1.03-1.32] of O2/100 mL of blood, respectively (p = 0.0013).ConclusionThere were VO2 and OE decreases of more than half their baseline values at 18°C. Given that metabolic needs are essentially supplied by dissolved O2 during cooling from 30°C to 18°C, the authors suggest that PaO2 should be increased during the period of cooling and/or deep hypothermia to prevent hypoxia.Copyright © 2024 Elsevier Inc. All rights reserved.

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