Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria, Australia.
Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Victoria, Australia.
Acta Physiol (Oxf). 2022 Sep;236(1):e13860. doi: 10.1111/apha.13860. Epub 2022 Jul 29.
Cardiac surgery requiring cardiopulmonary bypass (CPB) can result in renal and cerebral injury. Intraoperative tissue hypoxia could contribute to such organ injury. Hypothermia, however, may alleviate organ hypoxia. Therefore, we tested whether moderate hypothermia (30°C) improves cerebral and renal tissue perfusion and oxygenation during ovine CPB.
Ten sheep were studied while conscious, under stable anesthesia, and during 3 h of CPB. In a randomized within-animal cross-over design, five sheep commenced CPB at a target body temperature of 30°C (moderate hypothermia). After 90 min, the body temperature was increased to 36°C (standard procedure). The remaining five sheep were randomized to the opposite order of target body temperature.
Compared with the standard procedure, moderately hypothermic CPB reduced renal oxygen delivery (-34.8% ± 19.6%, P = 0.003) and renal oxygen consumption (-42.7% ± 35.2%, P = 0.04). Nevertheless, moderately hypothermic CPB did not significantly alter either renal cortical or medullary tissue PO . Moderately hypothermic CPB also did not significantly alter cerebral perfusion, cerebral tissue PO , or cerebral oxygen saturation compared with the standard procedure. Compared with the anesthetized state, the standard procedure reduced renal medullary PO (-21.0 ± 13.8 mmHg, P = 0.014) and cerebral oxygen saturation (65.0% ± 7.0% to 55.4% ± 9.6%, P = 0.022) but did not significantly alter either renal cortical or cerebral PO .
Ovine experimental CPB leads to renal medullary tissue hypoxia. Moderately hypothermic CPB did not improve cerebral or renal tissue oxygenation. In the kidney, this is probably because renal tissue oxygen consumption is matched by reduced renal oxygen delivery.
体外循环（CPB）下心内直视手术可导致肾和脑损伤。术中组织缺氧可能导致此类器官损伤。然而，低温可减轻器官缺氧。因此，我们测试了中度低温（30°C）是否可以改善绵羊 CPB 期间的脑和肾组织灌注和氧合。
10 只绵羊在清醒、稳定麻醉和 3 小时 CPB 期间进行研究。在随机的动物内交叉设计中，5 只绵羊以 30°C 的目标体温开始 CPB（中度低温）。90 分钟后，体温升高至 36°C（标准程序）。其余 5 只绵羊按相反的目标体温顺序随机分组。
与标准程序相比，中度低温 CPB 降低了肾氧输送（-34.8%±19.6%，P=0.003）和肾氧消耗（-42.7%±35.2%，P=0.04）。然而，中度低温 CPB 并没有显著改变肾皮质或髓质组织 PO2。与标准程序相比，中度低温 CPB 也没有显著改变脑灌注、脑组织 PO2 或脑氧饱和度。与麻醉状态相比，标准程序降低了肾髓质 PO2（-21.0±13.8mmHg，P=0.014）和脑氧饱和度（65.0%±7.0%至 55.4%±9.6%，P=0.022），但并没有显著改变肾皮质或脑 PO2。
绵羊实验性 CPB 导致肾髓质组织缺氧。中度低温 CPB 并未改善脑或肾组织的氧合作用。在肾脏中，这可能是因为肾组织氧消耗与肾氧输送减少相匹配。
