• Simone K Ringer, Nicola G Clausen, Nelly Spielmann, and Markus Weiss.
• Department of Clinical Diagnostics and Services, Section Anaesthesiology, Vetsuisse Faculty University of Zurich, Zurich, Switzerland.
• Paediatr Anaesth. 2020 Sep 1; 30 (9): 970-976.

BackgroundHypothermia and its combination with hypocapnia are frequently associated with anesthesia.AimsThe goal was to investigate the effects of hypothermia and hypothermia combined with hypocapnia (hypothermia-hypocapnia) on cerebral tissue oxygenation in anesthetized piglets.MethodsTwenty anesthetized piglets were randomly allocated to hypothermia (n = 10) or hypothermia-hypocapnia (n = 10). Cerebral monitoring comprised a tissue oxygen partial pressure (PtO2 ), a laser Doppler probe, and a near-infrared spectroscopy sensor, measuring regional oxygen saturation (rSO2 ). After baseline recordings, hypothermia (35.5-36.0°C) with or without hypocapnia (target PaCO2 : 28-30 mm Hg) was induced. Once treatment goals were achieved (Tr0), they were maintained for 30 minutes (Tr30).ResultsNo changes in PtO2 but a significant increase in rSO2 (Tr0 (mean difference 8.9[95% CI for difference3.99 to 13.81], P < .001); Tr30 (10.8[6.20 to 15.40], P < .001)) were detected during hypothermia. With hypothermia-hypocapnia, a decrease in PtO2 (Tr0 (-3.2[-6.01 to -0.39], P = .021; Tr30 (-3.3[-5.8 to -0.80], P = .006)) and no significant changes in rSO2 occurred. Cerebral blood flow decreased significantly from baseline to Tr0 independently of treatment (-0.89[-0.18 to -0.002], P = .042), but this was more consistently observed with hypothermia-hypocapnia.ConclusionsThe hypothermia-induced reduction in oxygen delivery was compensated by lowered metabolic demand. However, hypothermia was not able to compensate for an additional reduction in oxygen delivery caused by simultaneous hypocapnia. This resulted in a PtO2 drop, which was not reflected by a downshift in rSO2 .© 2020 John Wiley & Sons Ltd.

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