Petersen-Felix Steen, Arendt-Nielsen Lars, Bak Peter, Fischer Michael, Bjerring Peter, Zbinden Alex M
Department of Anaesthesiology and Intensive Care, University Hospital of Bern, Bern 3010 Switzerland Center for Sensory-Motor Interaction, Laboratory for Experimental Pain Research, University of Aalborg, Aalborg, Denmark Department of Dermatology, University Hospital of Aarhus, Aarhus, Denmark.
Pain. 1996 Feb;64(2):277-281. doi: 10.1016/0304-3959(95)00111-5.
Central temporal summation of afferent nociceptive stimuli is involved in central hyperexcitability. This is assumed to be an important mechanism in the nociceptive system which is probably activated during surgery and trauma. The purpose of the present study was to investigate if isoflurane has a specific effect on central temporal summation in humans. Facilitation of the nociceptive reflex to repeated stimuli can be used to assess central summation in subjects unable to cooperate due to an anaesthetic procedure. The nociceptive reflex to single and repeated (5 pulses delivered at 2 Hz) electrical surface stimuli of the sural nerve were measured in 6 healthy volunteers anaesthetized with isoflurane. A reflex was defined as an EMG signal from the rectus and biceps femoris exceeding 20 microV for more than 10 msec in the 80-200 msec interval after the stimulus. The end-tidal isoflurane concentration was increased in steps of 0.25 vol% from 0.25 to 1.50 vol%. For each concentration the thresholds for the nociceptive reflex were determined as the current intensity that could just elicit a reflex response to single stimulations, and for the repeated stimulations as the current intensity that could just elicit a reflex response to the 4th and/or 5th stimuli in the train of 5 stimuli. The nociceptive reflex to single stimuli was depressed at isoflurane concentrations producing sedation or light anaesthesia (0.25-0.50 vol% end-tidal). In contrast, 2-4-fold higher isoflurane concentrations (1.00-1.50 vol% end-tidal) that normally produce surgical anaesthesia were required to depress the nociceptive reflex to repetitive stimuli. This indicates that central temporal summation in the nociceptive system is a potent mechanism, and that isoflurane has a weak potency for depressing temporal summation in humans. As such isoflurane alone is not adequate for inhibiting surgically evoked hyperexcitability.
传入性伤害性刺激的中枢性时间总和与中枢性兴奋性过高有关。这被认为是伤害性系统中的一个重要机制，在手术和创伤期间可能会被激活。本研究的目的是调查异氟烷是否对人类的中枢性时间总和有特定影响。对于因麻醉程序而无法配合的受试者，伤害性反射对重复刺激的易化作用可用于评估中枢性总和。在6名接受异氟烷麻醉的健康志愿者中，测量了对腓肠神经单次和重复（以2Hz施加5个脉冲）体表电刺激的伤害性反射。反射被定义为在刺激后80 - 200毫秒间隔内，来自直肌和股二头肌的肌电图信号超过20微伏且持续超过10毫秒。呼气末异氟烷浓度从0.25体积%以0.25体积%的步长增加到1.50体积%。对于每个浓度，伤害性反射的阈值被确定为刚好能引发对单次刺激的反射反应的电流强度，对于重复刺激，则为刚好能引发对5次刺激序列中第4次和/或第5次刺激的反射反应的电流强度。在产生镇静或浅麻醉（呼气末0.25 - 0.50体积%）的异氟烷浓度下，对单次刺激的伤害性反射受到抑制。相比之下，通常产生手术麻醉的2 - 4倍高的异氟烷浓度（呼气末1.00 - 1.50体积%）才能抑制对重复刺激的伤害性反射。这表明伤害性系统中的中枢性时间总和是一种强大的机制，并且异氟烷抑制人类时间总和的效力较弱。因此，单独使用异氟烷不足以抑制手术诱发的兴奋性过高。
