Wang Kelun, Luo Yi, Asaki Toshiyuki, Graven-Nielsen Thomas, Cairns Brian E, Arendt-Nielsen Thomas, Arendt-Nielsen Lars
SMI, Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Denmark.
SMI, Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Denmark.
Scand J Pain. 2017 Oct;17:260-266. doi: 10.1016/j.sjpain.2017.07.012. Epub 2017 Jul 24.
Acid has long been thought to play an important role in the pain process. Animal study showed that repeated acid stimulation induced central sensitization. The purpose of the study is to investigate muscle pain and hyperalgesia evoked by intramuscular infusion of saline at different pH levels, and to compare the effect of a single versus repeated acid infusions.
Twenty healthy subjects received infusions of buffered saline (pH 5.0, 6.0, and 7.4) into the brachioradialis muscle in a randomized order. Twelve of the subjects received repeated infusions. The subjects rated the pain intensity on visual analogue scale (VAS). Thermal pain sensitivity, and pressure pain threshold (PPT) were assessed in both arm before, during, immediately after, one hour after, and one day after the infusion. A McGill Pain Questionnaire and pain mapping were completed after each infusion.
The pH 5 solution caused significantly higher pain and larger areas than pH 6.0 or 7.4. The local PPTs were significantly decreased (hyperalgesia) during and immediately after infusion of all three solutions. No significant differences were detected between the first and second infusion.
The intensity of acid-induced muscle pain is pH-dependent. All three solutions induced pressure hyperalgesia at the infusion site. Repeated infusions did not induce increased pain or prolonged hyperalgesia as compared with a single injection. Human intramuscular acidic saline infusion could not produce chronic pain model.
The acid-induced pain model may reflect the early stage responses to tissue injury of clinical conditions. Repeated intramuscular acidic saline injection model of prolonged hyperalgesia in rodents could not be translated into a human for modelling chronic musculoskeletal pain.
长期以来，人们一直认为酸在疼痛过程中起重要作用。动物研究表明，反复的酸刺激会诱发中枢敏化。本研究的目的是调查不同pH值的生理盐水肌肉内输注所诱发的肌肉疼痛和痛觉过敏，并比较单次与反复酸输注的效果。
20名健康受试者以随机顺序接受将缓冲生理盐水（pH 5.0、6.0和7.4）输注到肱桡肌中。其中12名受试者接受反复输注。受试者用视觉模拟量表（VAS）对疼痛强度进行评分。在输注前、输注期间、输注后即刻、输注后1小时和输注后1天，对双臂的热痛敏感性和压痛阈值（PPT）进行评估。每次输注后完成麦吉尔疼痛问卷和疼痛定位。
pH 5的溶液所引起的疼痛和疼痛面积明显高于pH 6.0或7.4的溶液。在输注所有三种溶液的过程中及输注后即刻，局部PPT均显著降低（痛觉过敏）。第一次和第二次输注之间未检测到显著差异。
酸诱导的肌肉疼痛强度取决于pH值。所有三种溶液均在输注部位诱发压痛觉过敏。与单次注射相比，反复输注并未导致疼痛增加或痛觉过敏持续时间延长。人体肌肉内输注酸性生理盐水不能产生慢性疼痛模型。
酸诱导的疼痛模型可能反映了临床情况下对组织损伤的早期反应。啮齿动物中反复肌肉内注射酸性生理盐水导致痛觉过敏持续延长的模型不能转化用于人类慢性肌肉骨骼疼痛的建模。
