The effects of mild hypothermia on neonatal hypoxic-ischemic brain injury in the newborn piglets

最近开始了对窒息婴儿进行低温治疗的临床试验。然而，由于难以选择神经预后异常的婴儿以及对低温不良反应的担忧，临床研究一直被推迟。本研究旨在探讨全身降温对新生仔猪脑代谢（CMR）和局部脑血流量（rCBF）的影响。用彩色微球测量大脑七个部位的rCBF。取脐动脉和上矢状窦血测脑耗氧量（cro_2）和脑葡萄糖耗氧量（CMRglc）。当大脑皮层温度降低到32℃时，所有脑区的血流量都会减少。特别是，脑干的血流量比其他区域减少得更明显。32℃时，脑总血流量（CBF）、CMRglc分别为32.3±3.9 mL/100 g / min、2.8±1.0 mL/100 g / min和22±12 mmol/100 g / min（分别为初始值的41%、53%和46%）。在35℃以下，CBF与cmoro_2和CMRglc平行减小，但在35℃以下CBF的减小幅度大于cmoro_2和CMRglc。低温治疗的指示和降温的程度必须非常仔细地执行。全身降温对完全窒息的婴儿尤其危险，因为在体温过低的情况下，脑干的血流量明显减少，可能会损害脑干。

Clinical trials of hypothermic therapy in asphyxiated infants have started recently. However, clinical studies have been delayed by the difficulty in selecting infants with an abnormal neurological prognosis and by the concern regarding adverse effects of hypothermia. The purpose of this study is to examine the effects of systemic cooling on cerebral metabolism (CMR) and the regional cerebral blood flow (rCBF) in newborn piglets. The rCBF in the seven parts of the brain were measured with colored microspheres. The blood samples for the measurement of cerebral oxygen consumption (CMRO_2) and cerebral glucose consumption (CMRglc) was collected from the umbilical artery and the superior sagittal sinus.Reductions of cerebral cortex temperature to 32 ℃ decreased blood flow in all brain regions. In particular, blood flow in the brainstem decreased more significantly than in any other region. The total cerebral blood flow (CBF), CMRO_2 and CMRglc, respectively, decreased to 32.3 ± 3.9 mL/100 g per min, 2.8 ±1.0 mL 0_2/100 g per min and 22 ± 12 mmol/100 g per min at 32 ℃(41, 53 and 46% of the initial value). The CBF decreased in parallel with CMRO_2 and CMRglc down to 35 ℃, but CBF decreased to a greater extent than CMRO_2 and CMRglc at below 35 ℃.The indication of hypothermic therapy and the degree of cooling have to be performed very carefully. Systemic cooling is especially dangerous for the total asphyxiated infants who might have damage to the brainstem because the blood flow in the brainstem has significantly decreased during hypothermia.