title: The effects of electroacupuncture on analgesia and peripheral sensory thresholds in patients with burn scar pain.
abstract: The aim of this study is to observe if the effects of electro-acupuncture (EA) on analgesia and peripheral sensory thresholds are transposable from the model of heat pain in volunteers to the clinical setting of burn scar pain. After severe burns, pathological burn scars (PPBS) may occur with excruciating pain that respond poorly to treatment and prevent patients from wearing their pressure garments, thereby leading to unesthetic and function-limiting scars. EA might be of greater benefit in terms of analgesia and functional recovery, should it interrupt this vicious circle by counteracting the peripheral hyperalgesia characterizing PPBS. Therefore we enrolled 32 patients (22 males/10 females) aged of 46±11 years with clinical signs of PPBS and of neuropathic pain despite treatment. The study protocol consisted in 3 weekly 30-min sessions of standardized EA with extra individual needles in accordance to Traditional Chinese Medicine, in addition of previous treatments. We assessed VAS for pain and quantitative sensory testing (QST) twice: one week before and one after protocol. QST measured electrical thresholds for non-nociceptive A-beta fibers, nociceptive A-delta and C fibers in 2 dermatomes, respectively from the PPBS and from the contralateral pain-free areas. Based on heat pain studies, EA consisted in sessions at the extremity points of the main meridian flowing through PPBS (0.300s, 5Hz, sub noxious intensity, 15min) and at the bilateral paravertebral points corresponding to the same metameric level, 15min. VAS reduction of 3 points or below 3 on a 10 points scale was considered clinically relevant. Paired t-test compared thresholds (mean [SD]) and Wilcoxon test compared VAS (median [IQR]) pre and after treatment, significant p<0.05. The reduction of VAS for pain reached statistical but not clinical relevance (6.8 [3] vs. 4.5 [3.6]). This was due to a large subgroup of 14 non-responders whose VAS did not change after treatment (6.6 [2.7] vs. 7.2 [3.8]). That subgroup exhibited significant differences in sensory thresholds when compared to the 18 responders (VAS from 7 [3] to 3 [1]). First, responders' thresholds for A-delta and C fibers in the PPBS area were significantly lower than those in the pain-free area before treatment but corrected after acupuncture (from respectively 60 [30] and 63 [10]% to 91 [11] and 106 [36]%). That might account for a nociceptive hypersensitivity in the PPBS that corrected after treatment. On the contrary, in non-responders nociceptive thresholds were similar in both the PPBS and the pain-free areas before treatment and did not change after EA. However, absolute values for thresholds in the pain-free areas where significantly lower for non-responders than for responders. The fact that non-responders had significant pain scores while presenting with lowered nociceptive thresholds even in the pain-free areas might evoke the possibility of a generalized supra-spinal hyperalgesia. The fact that acupuncture did not correct the pain nor the nociceptive thresholds in this subgroup requires further investigation. We also observed a statistically and clinically relevant reduction in VAS for pruritus for all patients - even those from the subgroup of non-responders to pain - that is worth to be mentioned and requires further studies to be confirmed. This observational study is the first that confirms the effects of acupuncture on analgesia and nociceptive thresholds in the clinical setting of burn pain only for patients presenting with a burn-localized but not a generalized hyperalgesia.
authors.affiliation: Burn Center, Military Hospital, Rue Bruyn, 1120 Brussels, Belgium; Belgian Association of Physicians Acupuncturists, Rue du Serpolet 2 Bte 1, 1080 Brussels, Belgium. Electronic address: olivier.cuignet@chr-namur.be.
authors.forename: Olivier
authors.initials: O
authors.lastname: Cuignet
authors.affiliation: Burn Center, Military Hospital, Rue Bruyn, 1120 Brussels, Belgium.
authors.forename: A
authors.initials: A
authors.lastname: Pirlot
authors.affiliation: Burn Center, Military Hospital, Rue Bruyn, 1120 Brussels, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Ortiz
authors.affiliation: Burn Center, Military Hospital, Rue Bruyn, 1120 Brussels, Belgium.
authors.forename: T
authors.initials: T
authors.lastname: Rose
mesh_terms: D000328:Adult; D000698:Analgesia / Q000379:methods; D002056:Burns / Q000150:complications*; D002921:Cicatrix / Q000150:complications*; D015671:Electroacupuncture / Q000379:methods*; D005260:Female; D006801:Humans; D006930:Hyperalgesia / Q000209:etiology / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000209:etiology*; D059408:Pain Management / Q000379:methods; D010147:Pain Measurement; D017288:Pain Threshold; D012684:Sensory Thresholds; D016896:Treatment Outcome
keywords: Acupuncture; Analgesia; Burn pain; Electroacupuncture; Hyperalgesia; Pathological burn scar; Pruritus; Quantitative sensory testing