Støen R, Sessler D I
Department of Anesthesia, University of California, San Francisco 94143-0648.
Anesthesiology. 1990 May;72(5):822-7. doi: 10.1097/00000542-199005000-00009.
This study tested the hypothesis that the threshold for thermoregulatory vasoconstriction is lowered as isoflurane concentration increases, but the intensity of vasoconstriction, once triggered, is well preserved during isoflurane anesthesia. The thermoregulatory threshold was prospectively defined as the central temperature at which vasoconstriction occurred, and significant vasoconstriction was defined as a skin-surface temperature gradient (forearm-fingertip) greater than or equal to 4 degrees C. The threshold for thermoregulatory vasoconstriction and the intensity of vasoconstriction, measured as maximum skin-temperature gradient, was determined in six unpremedicated patients electively donating a kidney during isoflurane anesthesia, and in four healthy, awake volunteers. All anesthetized patients were deliberately cooled and became hypothermic. Vasoconstriction occurred in five of six at central temperatures between 35.3 and 32.4 degrees C, at end-tidal isoflurane concentrations between 0.74 and 1.65%. The patient who did not vasoconstrict received the highest isoflurane concentration (approximately 2.5%) and reached a central temperature of 31 degrees C. Unanesthetized volunteers also were exposed to cold and each vasoconstricted at a temperature near 37 degrees C. The threshold for thermoregulatory cutaneous vasoconstriction was inversely correlated with anesthetic dose, the thermoregulatory threshold decreasing approximately 3 degrees C/% isoflurane concentration. There were no statistically significant differences between maximum skin-surface temperature gradients in awake volunteers and patients given isoflurane, or between any of the groups when patients from previous studies given halothane or nitrous oxide/fentanyl anesthesia were included in the comparison. These data indicate that the intensity of vasoconstriction, once triggered, is similar during several different types of anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)
随着异氟烷浓度的增加，体温调节性血管收缩的阈值会降低，但一旦触发，血管收缩的强度在异氟烷麻醉期间能得到很好的维持。体温调节阈值被前瞻性地定义为发生血管收缩时的中心温度，显著血管收缩被定义为皮肤表面温度梯度（前臂-指尖）大于或等于4摄氏度。在6例异氟烷麻醉下择期捐献肾脏的未用术前药患者以及4名健康清醒志愿者中，测定了体温调节性血管收缩的阈值以及以最大皮肤温度梯度衡量的血管收缩强度。所有麻醉患者均被故意降温并出现体温过低。6例患者中有5例在中心温度35.3至32.4摄氏度、呼气末异氟烷浓度0.74至1.65%时发生血管收缩。未发生血管收缩的患者接受了最高异氟烷浓度（约2.5%），中心温度达到31摄氏度。未麻醉的志愿者也暴露于寒冷环境中，每例在接近37摄氏度时发生血管收缩。体温调节性皮肤血管收缩的阈值与麻醉剂量呈负相关，体温调节阈值每增加1%异氟烷浓度约降低3摄氏度。清醒志愿者和接受异氟烷麻醉患者的最大皮肤表面温度梯度之间，以及在比较中纳入既往接受氟烷或氧化亚氮/芬太尼麻醉患者的任何组之间，均无统计学显著差异。这些数据表明，一旦触发，血管收缩强度在几种不同类型的麻醉期间是相似的。（摘要截短至250字）
