Lenhardt R, Greif R, Sessler D I, Laciny S, Rajek A, Bastanmehr H
Department of Anesthesia and Perioperative Care, University of California, San Francisco 94143-0648, USA.
Anesthesiology. 1999 Aug;91(2):422-9. doi: 10.1097/00000542-199908000-00016.
Thermoregulatory control is based on both skin and core temperatures. Skin temperature contributes approximately 20% to control of vasoconstriction and shivering in unanesthetized humans. However, this value has been used to arithmetically compensate for the cutaneous contribution to thermoregulatory control during anesthesia--although there was little basis for assuming that the relation was unchanged by anesthesia. It even remains unknown whether the relation between skin and core temperatures remains linear during anesthesia. We therefore tested the hypothesis that mean skin temperature contributes approximately 20% to control of vasoconstriction and shivering, and that the contribution is linear during general anesthesia.
Eight healthy male volunteers each participated on 3 separate days. On each day, they were anesthetized with 0.6 minimum alveolar concentrations of isoflurane. They then were assigned in random order to a mean skin temperature of 29, 31.5, or 34 degrees C. Their cores were subsequently cooled by central-venous administration of fluid at approximately 3 degrees C until vasoconstriction and shivering were detected. The relation between skin and core temperatures at the threshold for each response in each volunteer was determined by linear regression. The proportionality constant was then determined from the slope of this regression. These values were compared with those reported previously in similar but unanesthetized subjects.
There was a linear relation between mean skin and core temperatures at the vasoconstriction and shivering thresholds in each volunteer: r2 = 0.98+/-0.02 for vasoconstriction, and 0.96+/-0.04 for shivering. The cutaneous contribution to thermoregulatory control, however, differed among the volunteers and was not necessarily the same for vasoconstriction and shivering in individual subjects. Overall, skin temperature contributed 21+/-8% to vasoconstriction, and 18+/-10% to shivering. These values did not differ significantly from those identified previously in unanesthetized volunteers: 20+/-6% and 19+/-8%, respectively.
The results in anesthetized volunteers were virtually identical to those reported previously in unanesthetized subjects. In both cases, the cutaneous contribution to control of vasoconstriction and shivering was linear and near 20%. These data indicate that a proportionality constant of approximately 20% can be used to compensate for experimentally induced skin-temperature manipulations in anesthetized as well as unanesthetized subjects.
体温调节控制基于皮肤温度和核心温度。在未麻醉的人体中，皮肤温度对血管收缩和寒战控制的贡献约为20%。然而，该数值已被用于算术补偿麻醉期间皮肤对体温调节控制的贡献——尽管几乎没有依据假设这种关系在麻醉状态下保持不变。甚至在麻醉期间皮肤温度与核心温度之间的关系是否保持线性仍不清楚。因此，我们检验了以下假设：平均皮肤温度对血管收缩和寒战控制的贡献约为20%，并且在全身麻醉期间这种贡献是线性的。
八名健康男性志愿者每人在三个不同日期参与实验。每天，他们吸入0.6最低肺泡浓度的异氟烷进行麻醉。然后，他们被随机分配到平均皮肤温度为29、31.5或34摄氏度的组。随后通过中心静脉输注约3摄氏度的液体使他们的核心体温降低，直至检测到血管收缩和寒战。通过线性回归确定每个志愿者每种反应阈值时皮肤温度与核心温度之间的关系。然后从该回归的斜率确定比例常数。将这些值与先前在类似的未麻醉受试者中报告的值进行比较。
每个志愿者在血管收缩和寒战阈值时，平均皮肤温度与核心温度之间存在线性关系：血管收缩时r2 = 0.98±0.02，寒战 时r2 = 0.96±0.04。然而，皮肤对体温调节控制的贡献在志愿者之间有所不同，并且在个体受试者中血管收缩和寒战的贡献不一定相同。总体而言，皮肤温度对血管收缩的贡献为21±8%，对寒战的贡献为18±10%。这些值与先前在未麻醉志愿者中确定的值（分别为20±6%和19±8%）没有显著差异。
麻醉志愿者的结果与先前在未麻醉受试者中报告的结果几乎相同。在这两种情况下，皮肤对血管收缩和寒战控制的贡献都是线性的，且接近20%。这些数据表明，约20%的比例常数可用于补偿麻醉和未麻醉受试者中实验诱导的皮肤温度变化。
