Rogers Richard, Wise Richard G, Painter Deborah J, Longe Sarah E, Tracey Irene
Nuffield Department of Anesthetics, John Radcliffe Hospital, Oxford, Oxfordshire, OX3 9DU, United Kingdom.
Anesthesiology. 2004 Feb;100(2):292-301. doi: 10.1097/00000542-200402000-00018.
Anatomic sites within the brain, which activate in response to noxious stimuli, can be identified with the use of functional magnetic resonance imaging. The aim of this study was to determine whether the analgesic effects of ketamine could be imaged.
Ketamine was administered to eight healthy volunteers with use of a target-controlled infusion to three predicted plasma concentrations: 0 (saline), 50 (subanalgesic), and 200 ng/ml (analgesic, subanesthetic). Volunteers received noxious thermal stimuli and auditory stimuli and performed a motor task within a 3-T human brain imaging magnet. Activation of brain regions in response to noxious and auditory stimuli and during the motor task was compared with behavioral measures.
The analgesic subanesthetic dose of ketamine significantly reduced the pain scores, and this matched a decrease in activity within brain regions that activate in response to noxious stimuli, in particular, the insular cortex and thalamus. A different pattern of activation was observed in response to an auditory task. In comparison, smaller behavioral and imaging changes were found for the motor paradigm. The lower dose of ketamine gave similar but smaller nonsignificant effects.
The analgesic effect can be measured within a more global effect of ketamine as shown by auditory and motor tasks, and the analgesia produced by ketamine occurs with a smaller degree of cortical processing in pain-related regions.
大脑中对伤害性刺激产生反应而激活的解剖部位可通过功能磁共振成像来识别。本研究的目的是确定氯胺酮的镇痛效果是否可以成像。
对8名健康志愿者使用靶控输注给予氯胺酮，使其达到三个预测的血浆浓度：0（生理盐水）、50（亚镇痛剂量）和200纳克/毫升（镇痛、亚麻醉剂量）。志愿者接受伤害性热刺激和听觉刺激，并在3-T的人脑成像磁体中执行一项运动任务。将大脑区域对伤害性和听觉刺激以及运动任务期间的激活情况与行为测量结果进行比较。
氯胺酮的亚麻醉镇痛剂量显著降低了疼痛评分，这与对伤害性刺激产生反应而激活的脑区活动减少相匹配，特别是岛叶皮质和丘脑。对听觉任务观察到不同的激活模式。相比之下，运动范式的行为和成像变化较小。较低剂量的氯胺酮产生了类似但较小的不显著效果。
如听觉和运动任务所示，镇痛效果可在氯胺酮的更全面效应中测量，并且氯胺酮产生的镇痛作用在疼痛相关区域的皮质处理程度较小的情况下发生。
