Hypothermia Improves Oral and Gastric Mucosal Microvascular Oxygenation during Hemorrhagic Shock in Dogs

Hypothermia is known to improve tissue function in different organs during physiological and pathological conditions. The aim of this study was to evaluate the effects of hypothermia on oral and gastric mucosal microvascular oxygenation ( μ HbO 2 ) and perfusion ( μ flow) under physiological and hemorrhagic conditions. Five dogs were repeatedly anesthetized. All animals underwent each experimental protocol (randomized cross-over design): hypothermia (34°C), hypothermia during hemorrhage, normothermia, and normothermia during hemorrhage. Microcirculatory and hemodynamic variables were recorded. Systemic (DO 2 ) and oral mucosal ( μ DO 2 ) oxygen delivery were calculated. Hypothermia increased oral μ HbO 2 with no effect on gastric μ HbO 2 . Hemorrhage reduced oral and gastric μ HbO 2 during normothermia (−36 ± 4% and −27 ± 7%); however, this effect was attenuated during additional hypothermia (−15 ± 5% and −11 ± 5%). The improved μ HbO 2 might be based on an attenuated reduction in μ flow during hemorrhage and additional hypothermia (−51 ± 21 aU) compared to hemorrhage and normothermia (−106 ± 19 aU). μ DO 2 was accordingly attenuated under hypothermia during hemorrhage whereas DO 2 did not change. Thus, in this study hypothermia alone improves oral μ HbO 2 and attenuates the effects of hemorrhage on oral and gastric μ HbO 2 . This effect seems to be mediated by an increased μ DO 2 on the basis of increased μ flow.