Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN.
Department of Psychology, Ohio University, Athens, OH.
Clin J Pain. 2021 Jan;37(1):20-27. doi: 10.1097/AJP.0000000000000887.
Conditioned pain modulation (CPM) protocols index magnitude of descending pain inhibition. This study evaluated whether the degree of CPM, controlling for CPM expectancy confounds, was associated with analgesic and subjective responses to morphine and whether chronic pain status or sex moderated these effects.
Participants included 92 individuals with chronic low back pain and 99 healthy controls, none using daily opioid analgesics. In a cross-over design, participants attended 2 identical laboratory sessions during which they received either intravenous morphine (0.08 mg/kg) or saline placebo before undergoing evoked pain assessment. In each session, participants engaged in ischemic forearm and heat pain tasks, and a CPM protocol combining ischemic pain (conditioning stimulus) and heat pain (test stimulus). Placebo-controlled morphine outcomes were derived as differences in pain and subjective effects across drug conditions.
In hierarchical regressions controlling for CPM expectancies, greater placebo-condition CPM was associated with less subjective morphine unpleasantness (P=0.001) and greater morphine analgesia (P's<0.05) on both the ischemic pain task (Visual Analog Scale Pain Intensity and Unpleasantness) and heat pain task (Visual Analog Scale Pain Intensity, McGill Pain Questionnaire-Sensory, and Present Pain Intensity subscales). There was no moderation by sex or chronic low back pain status, except for the ischemic Present Pain Intensity outcome for which a significant 2-way interaction (P<0.05) was noted, with men showing a stronger positive relationship between CPM and morphine analgesia than women.
Results suggest that CPM might predict analgesic and subjective responses to opioid administration. Further evaluation of CPM as an element of precision pain medicine algorithms may be warranted.
条件性疼痛调制（CPM）方案指数下行性疼痛抑制的幅度。本研究评估了 CPM 的程度，是否控制了 CPM 预期的混杂因素，与吗啡的镇痛和主观反应相关，以及慢性疼痛状态或性别是否调节了这些效应。
参与者包括 92 名慢性腰痛患者和 99 名健康对照者，均未使用每日阿片类镇痛药。采用交叉设计，参与者参加了 2 个相同的实验室会议，在每个会议中，他们接受了静脉内吗啡（0.08mg/kg）或生理盐水安慰剂，然后进行诱发疼痛评估。在每个会议中，参与者进行了缺血性前臂和热痛任务，以及结合缺血性疼痛（条件刺激）和热痛（测试刺激）的 CPM 方案。通过比较药物条件下的疼痛和主观效应，得出了安慰剂对照吗啡的结果。
在控制 CPM 预期的层次回归中，较大的安慰剂条件 CPM 与主观上吗啡不愉快感降低（P=0.001）和吗啡镇痛增加（P<0.05）相关，在缺血性疼痛任务（视觉模拟量表疼痛强度和不愉快感）和热痛任务（视觉模拟量表疼痛强度、麦吉尔疼痛问卷-感觉和现在疼痛强度子量表）上均如此。性别或慢性腰痛状态没有调节作用，但缺血性现在疼痛强度结果存在显著的 2 向交互作用（P<0.05），男性的 CPM 与吗啡镇痛之间的正相关关系强于女性。
结果表明，CPM 可能预测阿片类药物给药的镇痛和主观反应。进一步评估 CPM 作为精准疼痛医学算法的一个元素可能是必要的。
