Iwata Sachiko, Tachtsidis Ilias, Takashima Sachio, Matsuishi Toyojiro, Robertson Nicola J, Iwata Osuke
Centre for Developmental and Cognitive Neuroscience, Department of Paediatrics and Child Health, Kurume University School of Medicine, Kurume, Fukuoka, Japan; Institute for Women's Health, University College London, London, UK.
Department of Medical Physics and Bioengineering, University College London, London, UK.
Int J Dev Neurosci. 2014 Oct;37:1-7. doi: 10.1016/j.ijdevneu.2014.05.010. Epub 2014 Jun 4.
Small shifts in brain temperature after hypoxia-ischaemia affect cell viability. The main determinants of brain temperature are cerebral metabolism, which contributes to local heat production, and brain perfusion, which removes heat. However, few studies have addressed the effect of cerebral metabolism and perfusion on regional brain temperature in human neonates because of the lack of non-invasive cot-side monitors. This study aimed (i) to determine non-invasive monitoring tools of cerebral metabolism and perfusion by combining near-infrared spectroscopy and echocardiography, and (ii) to investigate the dependence of brain temperature on cerebral metabolism and perfusion in unsedated newborn infants. Thirty-two healthy newborn infants were recruited. They were studied with cerebral near-infrared spectroscopy, echocardiography, and a zero-heat flux tissue thermometer. A surrogate of cerebral blood flow (CBF) was measured using superior vena cava flow adjusted for cerebral volume (rSVC flow). The tissue oxygenation index, fractional oxygen extraction (FOE), and the cerebral metabolic rate of oxygen relative to rSVC flow (CMRO₂ index) were also estimated. A greater rSVC flow was positively associated with higher brain temperatures, particularly for superficial structures. The CMRO₂ index and rSVC flow were positively coupled. However, brain temperature was independent of FOE and the CMRO₂ index. A cooler ambient temperature was associated with a greater temperature gradient between the scalp surface and the body core. Cerebral oxygen metabolism and perfusion were monitored in newborn infants without using tracers. In these healthy newborn infants, cerebral perfusion and ambient temperature were significant independent variables of brain temperature. CBF has primarily been associated with heat removal from the brain. However, our results suggest that CBF is likely to deliver heat specifically to the superficial brain. Further studies are required to assess the effect of cerebral metabolism and perfusion on regional brain temperature in low-cardiac output conditions, fever, and with therapeutic hypothermia.
缺氧缺血后大脑温度的微小变化会影响细胞活力。大脑温度的主要决定因素是大脑代谢（它会产生局部热量）和脑灌注（它会带走热量）。然而，由于缺乏非侵入性的床边监测仪，很少有研究探讨大脑代谢和灌注对人类新生儿局部脑温的影响。本研究旨在：（i）通过结合近红外光谱和超声心动图来确定大脑代谢和灌注的非侵入性监测工具，以及（ii）研究未使用镇静剂的新生儿脑温对大脑代谢和灌注的依赖性。招募了32名健康的新生儿。对他们进行了脑近红外光谱、超声心动图和零热流组织温度计检查。使用根据脑容量调整的上腔静脉血流（rSVC血流）来测量脑血流量（CBF）的替代指标。还估算了组织氧合指数、氧提取分数（FOE）以及相对于rSVC血流的脑氧代谢率（CMRO₂指数）。rSVC血流增加与脑温升高呈正相关，尤其是对于浅表结构。CMRO₂指数与rSVC血流呈正相关。然而，脑温与FOE和CMRO₂指数无关。环境温度较低与头皮表面和身体核心之间的温度梯度较大有关。在未使用示踪剂的情况下对新生儿的脑氧代谢和灌注进行了监测。在这些健康的新生儿中，脑灌注和环境温度是脑温的重要独立变量。CBF主要与从大脑带走热量有关。然而，我们的结果表明，CBF可能专门将热量传递到浅表脑区。需要进一步研究来评估在低心输出量状态、发热和治疗性低温情况下大脑代谢和灌注对局部脑温的影响。
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