Regional hypothermia improves gastric microcirculatory oxygenation during hemorrhage in dogs

Mild systemic hypothermia increases gastric mucosal oxygenation (μHbO2) during hemorrhagic shock in dogs. In the context of critical blood loss hypothermia might be fatal due to adverse side effects. Selective regional hypothermia might overcome these limitations. The aim of our study was to analyze the effects of regional gastric and oral mucosal hypothermia on μHbO2 and perfusion (μflow). In a cross-over study six anesthetized dogs were subjected to local oral and gastric mucosal hypothermia (34°C), or maintenance of local normothermia during normovolemia and hemorrhage (-20% blood volume). Macro- and microcirculatory variables were recorded continuously. During normovolemia, local hypothermia increased gastric microcirculatory flow (μflow) without affecting oxygenation (μHbO2) or oral microcirculation. During mild hemorrhagic shock gastric μHbO2 decreased from 72±2% to 38±3% in the normothermic group. This was attenuated by local hypothermia, where μHbO2 was reduced from 74±3% to 52±4%. Local perfusion, oral microcirculation and macrocirculatory variables were not affected. Selective local hypothermia improves gastric μHbO2 during hemorrhagic shock without relevant side effects. In contrast to systemic hypothermia, regional mucosal hypothermia did not affect perfusion and oxygen supply during hemorrhage. Thus, the increased μHbO2 during local hypothermia rather indicates reduced mucosal oxygen demand.

轻度全身性低温（systemic hypothermia）可提升失血性休克犬的胃黏膜氧合水平（μHbO2）。在重度失血情境中，全身性低温可能因不良反应引发致命风险，而选择性区域低温或可克服上述局限。本研究旨在分析胃与口腔黏膜区域低温对μHbO2及灌注水平（μflow）的影响。本研究采用交叉研究（cross-over study）设计，将6只麻醉犬分为两组，分别接受口腔与胃黏膜局部低温（34℃）处理，或在正常血容量（normovolemia）及失血（血容量减少20%）状态下维持局部正常体温（normothermia）。研究持续记录大循环与微循环相关指标。在正常血容量状态下，局部低温可提升胃黏膜微循环灌注水平（μflow），但不会影响胃黏膜氧合（μHbO2）及口腔微循环。在轻度失血性休克状态下，正常体温组的胃黏膜μHbO2从72±2%降至38±3%；该现象在局部低温组中得到缓解，其胃黏膜μHbO2仅从74±3%降至52±4%。局部灌注、口腔微循环及大循环指标均未受显著影响。选择性局部低温可在失血性休克过程中提升胃黏膜μHbO2，且无明显相关不良反应。与全身性低温不同，黏膜区域低温在失血过程中不会影响灌注与氧供。因此，局部低温下μHbO2的升高更提示黏膜氧需求的降低。