丙泊酚可线性降低血管收缩阈值和寒战阈值。

Propofol linearly reduces the vasoconstriction and shivering thresholds.

作者信息

Matsukawa T, Kurz A, Sessler D I, Bjorksten A R, Merrifield B, Cheng C

机构信息

Thermoregulation Research Laboratory, University of California, San Francisco 94143-0648, USA.

出版信息

Anesthesiology. 1995 May;82(5):1169-80. doi: 10.1097/00000542-199505000-00012.

DOI:10.1097/00000542-199505000-00012

PMID:7741292

Abstract

BACKGROUND

Skin temperature is best kept constant when determining response thresholds because both skin and core temperatures contribute to thermoregulatory control. In practice, however, it is difficult to evaluate both warm and cold thresholds while maintaining constant cutaneous temperature. A recent study shows that vasoconstriction and shivering thresholds are a linear function of skin and core temperatures, with skin contributing 20 +/- 6% and 19 +/- 8%, respectively. (Skin temperature has long been known to contribute approximately 10% to the control of sweating). Using these relations, we were able to experimentally manipulate both skin and core temperatures, subsequently compensate for the changes in skin temperature, and finally report the results in terms of calculated core-temperature thresholds at a single-designated skin temperature.

METHODS

Five volunteers were each studied on 4 days: (1) control; (2) a target blood propofol concentration of 2 micrograms/ml; (3) a target concentration of 4 micrograms/ml; and (4) a target concentration of 8 micrograms/ml. On each day, we increased skin and core temperatures sufficiently to provoke sweating. Skin and core temperatures were subsequently reduced to elicit peripheral vasoconstriction and shivering. We mathematically compensated for changes in skin temperature by using the established linear cutaneous contributions to the control of sweating (10%) and to vasoconstriction and shivering (20%). From these calculated core-temperature thresholds (at a designated skin temperature of 35.7 degrees C), the propofol concentration-response curves for the sweating, vasoconstriction, and shivering thresholds were analyzed using linear regression. We validated this new method by comparing the concentration-dependent effects of propofol with those obtained previously with an established model.

RESULTS

The concentration-response slopes for sweating and vasoconstriction were virtually identical to those reported previously. Propofol significantly decreased the core temperature triggering vasoconstriction (slope = -0.6 +/- 0.1 degrees C.micrograms-1.ml-1; r2 = 0.98 +/- 0.02) and shivering (slope = -0.7 +/- 0.1 degrees C.micrograms -1.ml-1; r2 = 0.95 +/- 0.05). In contrast, increasing the blood propofol concentration increased the sweating threshold only slightly (slope = 0.1 +/- 0.1 degrees C.micrograms -1.ml-1; r2 = 0.46 +/- 0.39).

CONCLUSIONS

Advantages of this new model include its being nearly noninvasive and requiring relatively little core-temperature manipulation. Propofol only slightly alters the sweating threshold, but markedly reduces the vasoconstriction and shivering thresholds. Reductions in the shivering and vasoconstriction thresholds are similar; that is, the vasoconstriction-to-shivering range increases only slightly during anesthesia.

摘要

背景

在确定反应阈值时，最好保持皮肤温度恒定，因为皮肤温度和核心温度都参与体温调节控制。然而，在实际操作中，很难在维持皮肤温度恒定的同时评估热阈值和冷阈值。最近的一项研究表明，血管收缩阈值和寒战阈值是皮肤温度和核心温度的线性函数，皮肤温度分别贡献20±6%和19±8%。（长期以来已知皮肤温度对出汗控制的贡献约为10%）。利用这些关系，我们能够通过实验操纵皮肤温度和核心温度，随后补偿皮肤温度的变化，并最终以单一指定皮肤温度下计算出的核心温度阈值来报告结果。

方法

五名志愿者每人接受4天的研究：（1）对照；（2）目标血丙泊酚浓度为2微克/毫升；（3）目标浓度为4微克/毫升；（4）目标浓度为8微克/毫升。在每一天，我们充分提高皮肤温度和核心温度以引发出汗。随后降低皮肤温度和核心温度以引发外周血管收缩和寒战。我们通过使用已确定的皮肤温度对出汗控制（10%）以及血管收缩和寒战控制（20%）的线性贡献，在数学上补偿皮肤温度的变化。根据这些计算出的核心温度阈值（在指定皮肤温度35.7摄氏度下），使用线性回归分析出汗、血管收缩和寒战阈值的丙泊酚浓度 - 反应曲线。我们通过将丙泊酚的浓度依赖性效应与先前使用既定模型获得的效应进行比较，验证了这种新方法。

结果

出汗和血管收缩的浓度 - 反应斜率与先前报道的几乎相同。丙泊酚显著降低触发血管收缩的核心温度（斜率 = -0.6±0.1摄氏度·微克⁻¹·毫升⁻¹；r² = 0.98±0.02）和寒战的核心温度（斜率 = -0.7±0.1摄氏度·微克⁻¹·毫升⁻¹；r² = 0.95±0.05）。相比之下，增加血丙泊酚浓度仅略微提高出汗阈值（斜率 = 0.1±0.1摄氏度·微克⁻¹·毫升⁻¹；r² = 0.46±0.39）。