Iwata Osuke, Iwata Sachiko, Tamura Masanori, Nakamura Tomohiko, Sugiura Masatoshi, Ogiso Yoshifumi
Division of Neonatology, Perinatal Center, Nagano Children's Hospital, Toyoshina, Nagano, Japan.
Pediatr Int. 2003 Apr;45(2):163-8. doi: 10.1046/j.1442-200x.2003.01682.x.
Although selective brain hypothermia is expected to be a promising neuroprotective treatment, the thermal distribution under hypothermia is not fully investigated. We applied selective head cooling to seven newborn piglets under general anesthesia in order to investigate the mechanism of cooling.
Seven healthy, large white piglets aged within 5 days after birth were studied. Temperatures were monitored at the superficial brain (0.5 cm), deep brain (2.0 cm), scalp skin, nasopharynx, tympanum, esophagus, and rectum. A radiant heater and a warmer blanket were used to maintain the normal rectal temperature (38.5-39 degrees C). For the first piglet, the coolant temperature was widely changed from 15 degree C to - 20 degree C in order to define the practical range. Subsequently, the coolant temperature was set at 10 degree C, 0 degree C, and - 10 degree C for the remaining six piglets. The target deep brain temperature was set at 35 degree C, as the same reduction of brain temperature might provide moderate brain hypothermia in the human neonate.
With 0 degree C coolant temperature, the deep brain temperature was cooled to 35 degree C; however, the scalp skin attached to the cooling cap became broadly blotchy and injured in all animals. When we induced minimal systemic hypothermia by 1C for a cohort of three piglets, the deep brain temperature decreased in parallel with the rectal temperature, which enabled us to achieve the target temperature with 10 degrees C coolant without injuring the scalp skin. The scalp skin and nasopharyngeal temperatures were good predictors of both superficial and deep-brain temperatures throughout the experiment.
Our results suggest that moderate brain hypothermia may be applied to newborn infants without inducing moderate systemic hypothermia.
尽管选择性脑低温有望成为一种有前景的神经保护治疗方法，但低温下的热分布尚未得到充分研究。我们对七只新生仔猪在全身麻醉下应用选择性头部降温，以研究降温机制。
研究了七只出生后5天内的健康大白仔猪。在浅表脑（0.5厘米）、深部脑（2.0厘米）、头皮、鼻咽、鼓膜、食管和直肠监测温度。使用辐射加热器和暖毯维持正常直肠温度（38.5 - 39摄氏度）。对于第一只仔猪，冷却液温度在15摄氏度至 - 20摄氏度之间广泛变化，以确定实际范围。随后，其余六只仔猪的冷却液温度设定为10摄氏度、0摄氏度和 - 10摄氏度。目标深部脑温度设定为35摄氏度，因为相同程度的脑温降低可能为人类新生儿提供中度脑低温。
冷却液温度为0摄氏度时，深部脑温度降至35摄氏度；然而，所有动物中与冷却帽相连的头皮均出现广泛的斑点状损伤。当我们对一组三只仔猪诱导1摄氏度的轻度全身低温时，深部脑温度与直肠温度平行下降，这使我们能够在冷却液温度为10摄氏度的情况下达到目标温度，且不会损伤头皮。在整个实验过程中，头皮和鼻咽温度是浅表和深部脑温度的良好预测指标。
我们的结果表明，中度脑低温可应用于新生儿，而不会诱导中度全身低温。
