The effects of electroacupuncture on analgesia and peripheral sensory thresholds in patients with burn scar pain.

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.

Effects of gabapentin on morphine consumption and pain in severely burned patients.

OBJECTIVE: Nociception is the major cause of burn pain and leads to central hyperalgesia. Gabapentin (Gp) is an antihyperalgesic drug that selectively affects central sensitization. We studied the opioid-sparing and analgesic effects of Gp in severely burned patients. METHODS: Ten patients (mean total burned body surface area (TBSA), 25%), received 2400 mg of oral Gp daily from after burn days 3-24 in addition to standard pain therapy. They were compared to a retrospective matching group. Outcomes were cumulative morphine consumption and mean daily pain scores. Outcomes were recorded during treatment (21 days) and 21 days after treatment. RESULTS: During treatment and post-treatment phases, patients receiving Gp had cumulative morphine consumption and a mean daily pain score significantly lower than controls. CONCLUSION: Gp use reduced opioid consumption and lowered pain scores that seemed to extend beyond its pharmacologic action probably result from the ability of Gp to prevent central hyperalgesia induced by burns.

The efficacy of continuous fascia iliaca compartment block for pain management in burn patients undergoing skin grafting procedures.

UNLABELLED: Postoperative pain from split skin donor sites is often more intense than the pain at the grafted site. In this prospective, randomized, double-blind study we assessed the efficacy of a continuous fascia iliaca compartment block (FICB) in reducing the pain at the thigh donor site. Twenty patients, with a total burn surface area of 16% +/- 13% (mean +/- SD) were randomized 1:1 to receive either ropivacaine 0.2% or saline 0.9%. All patients received a general anesthesic followed by preincision continuous FICB with 40 mL of the randomized solution, then an infusion of 10 mL/h of either ropivacaine or saline until the first dressing change (72 h later). Postoperative analgesia consisted of propacetamol 2g/6h, IV patient-controlled analgesia of morphine chlorhydrate (2 mg/mL), and morphine hydrochlorate 0.5 mg/kg PO once 60 min before first dressing change. The visual analog scale (VAS) scores were compared using the Mann-Whitney U-test preoperatively, 24 and 48 h postoperatively, and during the first dressing change. The cumulative morphine consumption was compared with repeated-measures analysis of variance followed by Scheffé's method if indicated. Patients with continuous FICB had significantly reduced postoperative morphine consumption at all time points (23 +/- 20 versus 88 +/- 29 mg after 72 h, study versus control groups, respectively; P < 0.05). In both groups, VAS scores remained low but were only significantly lower for patients with continuous FICB during the first dressing change (3 [1] versus 7 [3]; median [interquartile range]; P < 0.05). We conclude that continuous FICB is an efficient method for diminishing pain at the thigh donor site. (250 words) IMPLICATIONS: Postoperative pain at the split skin donor sites is often more intense than the pain at the grafted site. This prospective, randomized, double-blind study assessed the efficacy of a continuous fascia iliaca compartment block in reducing the pain at the thigh donor site.

A second-generation blood substitute (perflubron emulsion) increases the blood solubility of modern volatile anesthetics in vitro.

UNLABELLED: Perfluorocarbon-based emulsions increase the blood solubility of isoflurane, enflurane, and halothane, with a maximal effect reported for the less soluble isoflurane. Current volatile anesthetics are less soluble and may be more affected by this phenomenon. Perflubron (Oxygent(TM)) is a perfluorocarbon-based emulsion in late-stage clinical testing in surgical patients for use as a temporary oxygen carrier. We tested the hypothesis that perflubron increases the solubility of isoflurane, sevoflurane, and desflurane, as reflected by their blood/gas partition coefficient (lambda(Bl:g)). Fresh whole-blood samples were drawn from eight volunteers and mixed with perflubron to obtain concentrations of 1.2%, 1.8%, and 3.6% by volume (equivalent to in vivo doses of 1.8 to 5.4 g/kg, which represent up to twice the intended clinical dose range). By using the double-extraction method, we demonstrated increased lambda(Bl:g) for isoflurane, sevoflurane, and desflurane. However, the solubility in blood does not really change, because volatile anesthetics are actually partitioning into perflubron. Increasing the amount of emulsion in the blood consequently increases the amount of gas carried, as reflected by the measured linear correlation between the lambda(Bl:g) values of all three volatile anesthetics and perflubron doses. Even though the increase ranges from 0.9 (desflurane) to 2.6 (sevoflurane) times the normal value, the apparent lack of clinical implications in current trials with perflubron may trigger further in vivo experiments. IMPLICATIONS: Perflubron increases the in vitro solubility of volatile anesthetics when present in the blood at clinically relevant concentrations. Volatile anesthetics actually partition into the emulsion, but the solubility in the blood does not change. Further studies are needed to assess whether perflubron will affect the pharmacokinetics of volatile anesthetics in vivo.