Thoresen M, Simmonds M, Satas S, Tooley J, Silver I A
Department of Child Health, St. Michael's Hospital, Level D, Southwell Street, University of Bristol, Bristol BS2 8EG, U.K.
Pediatr Res. 2001 Apr;49(4):594-9. doi: 10.1203/00006450-200104000-00024.
Selective head cooling has been proposed as a neuroprotective intervention after hypoxia-ischemia in which the brain is cooled without subjecting the rest of the body to significant hypothermia, thus minimizing adverse systemic effects. There are little data showing it is possible to cool the brain more than the body. We have therefore applied selective head cooling to our hypoxia-ischemia piglet model to establish whether it is possible. Nine piglets were anesthetized, and brain temperature was measured at the surface and in the superficial (0.2 cm) and deep (1.7-2.0 cm) gray matter. Rectal (6-cm depth), skin, and scalp temperatures (T) were recorded continuously. Lowering T-rectal from normothermia (39 degrees C) to hypothermia (33.5-33.8 degrees C) using a head cap perfused with cold (6-24 degrees C) water was undertaken for up to 6 h. To assess the impact of the 45-min hypoxia-ischemia insult on the effectiveness of selective head cooling, four piglets were cooled both before and after the insult, and four, only afterward. During selective head cooling, it was possible to achieve a lower T-deep brain than T-rectal in all animals both before and after hypoxia. However, this was only possible when overhead body heating was used. The T-rectal to T-deep brain gradient was significantly smaller after the insult (median, 5.3 degrees C; range, 4.2-8.5 degrees C versus 3.0 degrees C; 1.7-7.4 degrees C; p = 0.008). During rewarming to normothermia, the gradient was maintained at 4.5 degrees C. We report for the first time a study, which by direct measurement of deep intracerebral temperatures, validates the cooling cap as an effective method of selective brain cooling in a newborn animal hypoxia-ischemia model.
选择性头部降温已被提议作为缺氧缺血后的一种神经保护干预措施，即仅冷却大脑而不使身体其他部位出现明显低温，从而将全身不良影响降至最低。几乎没有数据表明大脑能够比身体降得更低温。因此，我们将选择性头部降温应用于我们的缺氧缺血仔猪模型，以确定是否可行。九只仔猪接受麻醉，测量其大脑表面、浅层（0.2厘米）和深层（1.7 - 2.0厘米）灰质的温度。连续记录直肠（6厘米深度）、皮肤和头皮温度（T）。使用灌注冷（6 - 24摄氏度）水的头罩将直肠温度（T）从正常体温（39摄氏度）降至低温（33.5 - 33.8摄氏度），持续长达6小时。为评估45分钟的缺氧缺血损伤对选择性头部降温效果的影响，四只仔猪在损伤前后均进行降温，另外四只仅在损伤后降温。在选择性头部降温期间，无论缺氧前后，所有动物的大脑深层温度（T）均有可能低于直肠温度（T）。然而，这只有在使用头顶身体加热时才有可能。损伤后直肠温度（T）与大脑深层温度（T）的梯度显著变小（中位数，5.3摄氏度；范围，4.2 - 8.5摄氏度，而损伤前为3.0摄氏度；1.7 - 7.4摄氏度；p = 0.008）。在复温至正常体温期间，该梯度维持在4.5摄氏度。我们首次报告了一项研究，该研究通过直接测量大脑深部温度，验证了冷却帽作为新生动物缺氧缺血模型中选择性脑冷却的有效方法。
