Effect of hypothermia on cerebral blood flow and metabolism in the pig
Effect of hypothermia on cerebral blood flow and metabolism in the pig
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DOI：
10.1016/s0003-4975(01)03273-8
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发表时间：
2002-01-01
影响因子：
4.6
通讯作者：
Griepp, RB
中科院分区：
文献类型：
--
作者：
Ehrlich, MP;McCullough, JN;Griepp, RB
背景近年来，猪已成为心胸外科手术中脑保护研究的一个越来越受欢迎的模型，但有关低温猪生理学的信息很少。由于脑保护的功效在很大程度上取决于代谢抑制，我们研究了脑氧代谢在不同温度下使用两种不同的方法来评估脑血流量（CBF）。12头猪（7 - 13公斤）在体外循环中接受冷却至8 ℃，这是由放置在脑实质深处的电极记录的。用放射性微球测定6只动物的CBF，用荧光微球测定6只动物的CBF。在37 ℃、28 ℃、18 ℃和8 ℃下测定CBF、脑耗氧量和脑血管阻力。这两种方法产生了非常相似的数据。CBF随着温度降低至18 ℃而稳定下降，但随着更深的低温而未能进一步下降。两组合并后，37 ℃时平均脑氧代谢为2.63 mL/100 g/min。28 ℃时代谢活性为基线值的50%，18 ℃时为19%，8 ℃时为11%。猪的Q（10）值-温度下降10 ℃所达到的代谢抑制程度-为2.46（95%置信区间为2.1至2.9）;该值与人类的类似研究一致。在18 ℃时存在显著的残余代谢活性表明，这种程度的低温可能在CBF长时间中断期间提供不完全的脑保护。这项研究表明，在猪中冷却到18摄氏度以下的温度可以实现更大的代谢抑制，尽管它可能与大脑自动调节的丧失有关。(C)2002年由胸外科医师协会出版。
Background. The pig has become an increasingly popular model for the study of cerebral protection during cardiothoracic surgery in recent years, but little information is available concerning hypothermic porcine physiology. Because the efficacy of cerebral protection depends largely upon metabolic suppression, we studied cerebral oxygen metabolism at various temperatures using two different methods to assess cerebral blood flow (CBF).Material and Methods. Twelve pigs (7 to 13 kg) underwent cooling on cardiopulmonary bypass to 8degreesC as recorded by an electrode placed deep in the parenchyma of the brain. CBF was measured in 6 animals using radioactive microspheres and in the other 6 using fluorescent microspheres. CBF, cerebral oxygen consumption, and cerebral vascular resistance were determined at 37degreesC, 28degreesC, 18degreesC, and 8degreesC.Results. Both methods produced very similar data. CBF fell steadily with decrease in temperature to 18degreesC but failed to drop further with more profound hypothermia. With both groups combined, mean cerebral oxygen metabolism was 2.63 mL/100 g per minute at 37degreesC. Metabolic activity was 50% of base line values at 28degreesC, 19% at 18degreesC, and 11% at 8degreesC. The Q(10) value in the pig-the degree of metabolic suppression achieved by a 10degreesC drop in temperature-is 2.46 (95% confidence interval 2.1 to 2.9); this value is consistent with similar studies in humans.Conclusions. The presence of significant residual metabolic activity at 18degreesC suggests that this degree of hypothermia may provide incomplete cerebral protection during prolonged interruption of CBF. This study demonstrates that cooling to temperatures below 18degreesC in the pig can achieve greater metabolic suppression although it may be associated with loss of cerebral autoregulation. (C) 2002 by The Society of Thoracic Surgeons.