Ikeda T, Sessler D I, Marder D, Xiong J
Department of Anesthesia, University of California, San Francisco 94143-0648, USA.
Anesthesiology. 1997 Mar;86(3):603-12. doi: 10.1097/00000542-199703000-00012.
Recently, liquid crystal skin-surface thermometers have become popular for intraoperative temperature monitoring. Three situations during which cutaneous liquid-crystal thermometry may poorly estimate core temperature were monitored: (1) anesthetic induction with consequent core-to-peripheral redistribution of body heat, (2) thermoregulatory vasomotion associated with sweating (precapillary dilation) and shivering (minimal capillary flow), and (3) ambient temperature variation over the clinical range from 18-26 degrees C.
The core-to-forehead and core-to-neck temperature difference was measured using liquid-crystal thermometers having an approximately 2 degrees C offset. Differences exceeding 0.5 degree C (a 1 degree C) temperature range) were a priori deemed potentially clinically important. Seven volunteers participated in each protocol. First, core-to-peripheral redistribution of body heat was produced by inducing propofol/desflurane anesthesia; anesthesia was then maintained for 1 h with desflurane. Second, vasodilation was produced by warming unanesthetized volunteers sufficiently to produce sweating; intense vasoconstriction was similarly produced by cooling the volunteers sufficiently to produce shivering. Third, a canopy was positioned to enclose the head, neck, and upper chest of unanesthetized volunteers. Air within the canopy was randomly set to 18, 20, 22, 24, and 26 degrees C.
Redistribution of body heat accompanying induction of anesthesia had little effect on the core-to-forehead skin temperature difference. However, the core-to-neck skin temperature gradient decreased approximately 0.6 degree C in the hour after induction of anesthesia. Vasomotion associated with shivering and mild sweating altered the core-to-skin temperature difference only a few tenths of a degree centigrade. The absolute value of the core-to-forehead temperature difference exceeded 0.5 degree C during approximately 35% of the measurements, but the difference rarely exceeded 1 degree C. The core-to-neck temperature difference typically exceeded 0.5 degree C and frequently exceeded 1 degree C. Each 1 degree C increase in ambient temperature decreased the core-to-fore-head and core-to-neck skin temperature differences by less than 0.2 degree C.
Forehead skin temperatures were better than neck skin temperature at estimating core temperature. Core-to-neck temperature differences frequently exceeded 1 degree C (a 2 degrees C range), whereas two thirds of the core-to-forehead differences were within 0.5 degree C. The core-to-skin temperature differences were, however, only slightly altered by inducing anesthesia, vasomotor action, and typical intraoperative changes in ambient temperature.
近年来，液晶体表温度计在术中体温监测中已广泛应用。本研究监测了三种可能导致皮肤液晶测温法难以准确估计核心体温的情况：（1）麻醉诱导导致体热从核心向外周重新分布；（2）与出汗（毛细血管前扩张）和寒战（最小毛细血管血流）相关的体温调节性血管运动；（3）临床范围内环境温度从18℃至26℃的变化。
使用偏移约2℃的液晶温度计测量核心体温与额头及颈部体温的差值。差值超过0.5℃（1℃温度范围）被预先认定为可能具有临床重要性。每个方案有7名志愿者参与。首先，通过诱导丙泊酚/地氟醚麻醉使体热从核心向外周重新分布；然后用地氟醚维持麻醉1小时。其次，通过充分温暖未麻醉志愿者使其出汗来产生血管扩张；同样，通过充分冷却志愿者使其寒战来产生强烈血管收缩。第三，放置一个罩子覆盖未麻醉志愿者的头部、颈部和上胸部。罩内空气随机设置为18、20、22、24和26℃。
麻醉诱导伴随的体热重新分布对核心体温与额头皮肤温度差值影响不大。然而，麻醉诱导后1小时内，核心体温与颈部皮肤温度梯度下降约0.6℃。与寒战和轻度出汗相关的血管运动仅使核心体温与皮肤温度差值改变了几十分之一摄氏度。核心体温与额头温度差值的绝对值在约35%的测量中超过0.5℃，但差值很少超过1℃。核心体温与颈部温度差值通常超过0.5℃，且经常超过1℃。环境温度每升高1℃，核心体温与额头及核心体温与颈部皮肤温度差值下降不到0.2℃。
在估计核心体温方面，额头皮肤温度优于颈部皮肤温度。核心体温与颈部温度差值经常超过1℃（2℃范围），而三分之二的核心体温与额头温度差值在0.5℃以内。然而，麻醉诱导、血管运动和术中环境温度的典型变化仅使核心体温与皮肤温度差值略有改变。
