Chris Glynn

An fMRI study of cerebral processing of brush-evoked allodynia in neuropathic pain patients.

Previous human imaging studies have revealed a network of brain regions involved in the processing of allodynic pain; this includes prefrontal areas, insula, cingulate cortex, primary and secondary somatosensory cortices and parietal association areas. In this study, the neural correlates of the perceived intensity of allodynic pain in neuropathic pain patients were investigated. In eight patients, dynamic mechanical allodynia was provoked and brain responses recorded using functional magnetic resonance imaging (fMRI). Voxels in which the magnitude of fMRI signal correlated linearly with the ratings of allodynic pain across the group were determined in a whole brain analysis using a general linear model. To ensure that activation reflected only allodynic pain ratings, a nuisance variable containing ratings of ongoing pain was included in the analysis. We found that the magnitude of activation in the caudal anterior insula (cAI) correlates with the perceived intensity of allodynic pain across subjects, independent of the level of ongoing pain. However, the peak of activation in the allodynic condition was located in the rostral portion (rAI). This matches the representation of other clinical pain syndromes, confirmed by a literature review. In contrast, experimental pain in healthy volunteers resides predominantly in the cAI, as shown by the same literature review. Taken together, our data and the literature review suggest a functional segregation of anterior insular cortex.

A double-blind comparison between epidural morphine and epidural clonidine in patients with chronic non-cancer pain

&NA; In a randomised double‐blind study of 20 patients with chronic pain, epidural morphine 5 mg in 5 ml of saline was compared with epidural clonidine 150 &mgr;g in 5 ml of saline. Thirteen patients had a clinical and radiological diagnosis of arachnoiditis, 6 had low back pain and 1 had post‐operative scar pain. There were 18 females and 2 males with an average age of 52 years, range 22–76 years. There was no difference found between the 2 solutions in the resultant analgesia measured by the visual analogue scale for pain, pain relief or the pain word score during the 3 h period of the study. No difference was found in the patients mood which was also measured with the visual analogue scale. Two patients had no analgesia from either injection, 2 patients did not obtain any relief from clonidine and another 2 obtained no relief from morphine. Six patients reported that clonidine was better than morphine, 5 reported that morphine and clonidine were the same and 3 reported that morphine was better than clonidine. The duration of analgesia from the clonidine varied from 6 h to 1 month; the duration of analgesia from morphine varied from 6 to 24 h. Clonidine was associated with sedation and a fall in blood pressure of greater than 20 mm Hg in all patients, 1 patient required ephedrine to treat hypotension. Twelve patients had pruritus, 7 nausea and 2 vomiting following the morphine. Statistically there was no difference found between morphine and clonidine for short‐term (3 h) analgesia in these patients. The duration of analgesia from clonidine in 2 patients was about 1 month while that from morphine did not exceed 24 h. The side effects from clonidine were less than those for morphine. This group of patients was unable to differentiate between epidural morphine and clonidine for short‐term analgesia. Further evidence of the importance of the spinal noradrenergic system in the transmission and treatment of patients with chronic pain.

EMLA cream in the treatment of post-herpetic neuralgia. Efficacy and pharmacokinetic profile.

The analgesic efficacy of 5% of EMLA cream (5 or 10 g) when applied for 24 h periods was evaluated in 5 female and 7 male patients (mean age 69 years, range 50-85 years) with refractory post-herpetic neuralgia (PHN). Mean visual analogue pain intensity scores for all patients were significantly improved 6 h after application (P less than 0.05). In a subgroup of patients with facial PHN receiving EMLA cream, 5 g (n = 4), there were significant improvements in pain intensity scores at 6 h (P less than 0.05). 8 h (P less than 0.01) and 10 h (P less than 0.01) after application. Plasma lignocaine and plasma prilocaine concentrations were well below potentially toxic levels in all patients after application.

Assessment and management of persistent (chronic) and total wound pain

Persistent (chronic) wound‐related pain is a common experience that requires appropriate assessment and treatment. It is no longer adequate for health care professionals to concentrate on the acute (temporary) pain during dressing change alone. The study provides useful recommendations and statements for assessing and managing total wound‐related pain for patients, health care professionals and other policymakers. The recommendations have been developed with the involvement of an interprofessional panel of health care professionals from around the world.

Managing painful chronic wounds: the Wound Pain Management Model.

Chronic wound pain is not well understood and the literature is limited. Six of 10 patients venous leg ulcer experience pain with their ulcer, and similar trends are observed for other chronic wounds. Chronic wound pain can lead to depression and the feeling of constant tiredness. Pain related to the wound should be handled as one of the main priorities in chronic wound management together with addressing the cause. Management of pain in chronic wounds depends on proper assessment, reporting and documenting patient experiences of pain. Assessment should be based on six critical dimensions of the pain experience: location, duration, intensity, quality, onset and impact on activities of daily living. Holistic management must be based on a safe and effective mix of psychosocial approaches together with local and systemic pain management. It is no longer acceptable to ignore or inadequately document persistent wound pain and not to develop a treatment and monitoring strategy to improve the lives of persons with chronic wounds. Unless wound pain is optimally managed, patient suffering and costs to health care systems will increase.

An evaluation of a single dose of magnesium to supplement analgesia after ambulatory surgery: randomized controlled trial.

BACKGROUND:Previous studies have suggested that magnesium may be a useful adjuvant to postoperative analgesia. METHODS:We randomized adults undergoing ambulatory ilioinguinal hernia repair or varicose vein operation under general anesthesia (propofol, fentanyl, isoflurane-N2O) to receive magnesium sulfate 4 g IV or physiological saline after induction. All patients preoperatively received diclofenac 100 mg rectally and those undergoing hernia repair had a postoperative ilioinguinal-iliohypogastric nerve block done. Pain, analgesic consumption, and adverse effects were recorded in the recovery room and, using a questionnaire, up to 3 days postoperatively. RESULTS:We randomized 200 patients (101 magnesium, 99 placebo). There were no differences in hemodynamic variables before and immediately after study drug injection. Pain intensity at rest and on movement after 1, 2, and 4 h, time to first rescue analgesic, and cumulative numbers of non-opioid and opioid analgesics were similar among groups. There was no difference in the incidence of postoperative nausea and vomiting, dizziness, headache, or fainting. The incidence of postoperative shivering was significantly lower in the magnesium group (4% vs 13.1%, P = 0.0232). Adequately completed questionnaires were returned by 84 placebo and 82 magnesium patients. There was no difference between groups for any of the analyzed outcomes during the first three postoperative days, neither for patients undergoing inguinal hernia repair nor for those undergoing varicose vein stripping. CONCLUSIONS:In patients undergoing ambulatory ilioinguinal hernia repair or varicose vein operations under general anesthesia supplemented with other analgesic adjuvants, pretreatment with IV magnesium sulfate 4 g has no impact on postoperative pain and analgesic consumption.

Cerebrospinal fluid kinetics of epidural clonidine in man

&NA; Ten patients with deafferentation pain after spinal cord injury were given 150 &mgr;g clonidine epidurally. CSF and plasma samples were collected over the following 24 h, and drug concentrations were measured by radio‐immunoassay. The results of only 6 patients are included in the pharmacokinetic analysis because the catheters were not in the epidural space in the remaining 4 patients. These analyses revealed a mean maximum CSF concentration of 228 ng/ml whereas the mean plasma concentration at all time points was less than 0.7 ng/ml. The elimination half‐life of epidural clonidine was 66 ± 2 min, while the absorption half‐life was 31 ± 7 min, Tmax was 60 ± 7 min and Cmaxwas 228 ± 56 ng/ml. The ratio of the area under the curve (AUC) for CSF and plasma was 52. One patients catheter was intrathecal and 3 were not in the epidural space. The measured plasma concentrations were similar after all injections. As 4 of 6 patients with epidural catheters obtained pain relief and all 3 patients with spasms obtained relief from epidural clonidine, these data suggest that clonidine has a place in the treatment of patients with spinal cord injury.

Magnesium bier's block for treatment of chronic limb pain: a randomised, double-blind, cross-over study

&NA; Magnesium is a physiological antagonist of both calcium and the NMDA receptor. Patients with chronic pain of a limb (>1 months duration) were treated with two Biers blocks (250 mmHg, 10 m) in a randomised, double‐blind, cross‐over design. They received once 20% magnesium sulphate (500 mg) + lignocaine 1% (75 mg), and once physiological saline + lignocaine 1% (75 mg). The volume of both treatments was 10 ml. Efficacy data from 49 treatments (25 magnesium, 24 placebo) could be analysed. With magnesium–lignocaine, the duration of pain relief as reported by the patients was on average 23 days (95% CI 8–38) compared with 6 days (95% CI 2–10) with lignocaine alone (P=0.043). With magnesium–lignocaine, 54.2% of patients had more than 50% pain relief compared with 25% with lignocaine alone (number‐needed‐to‐treat 3.5, P=0.075). With magnesium–lignocaine, 20% of patients had a treatment failure (i.e. pain relief <24 h) compared with 50% with lignocaine alone (number needed‐to‐treat 3.3, 95% CI 1.8–29, P=0.038). The magnesium–lignocaine treatment was painful in 52% of patients compared with 8% with lignocaine alone (number‐needed‐to‐harm 2.3, 95% CI 1.5–4.5, P=0.0008). For patients with chronic limb pain, the addition of magnesium to a Biers block with lignocaine improves and prolongs pain relief and reduces the number of treatment failures. The optimal dose of lignocaine to prevent magnesium‐induced aching of the treated limb needs to be established. Biers block with magnesium–lignocaine may provide a possible treatment alternative in these patients.

Morphine injected around the stellate ganglion does not modulate the sympathetic nervous system nor does it provide pain relief

&NA; Six patients with a presumptive diagnosis of upper limb reflex sympathetic dystrophy and 1 patient with anaesthesia dolorosa had pain and sympathetic activity assessed before and after injection of bupivacaine and morphine around the stellate ganglion. Sympathetic modulation was assessed by measuring the effect of each injection on the inspiratory gasping response (IGR), a measure of central arousal, the sympathetic skin response (SSR), a measure of peripheral sudomotor activity and the plethysmographic wave (PW), a measure of peripheral vasomotor activity. There were 5 women and 2 men with a mean age of 49 years (range: 41–66 years). The duration of pain varied from 9 months to 7 years. Bupivacaine abolished the IGR and SSR and increased the amplitude of the PW in all patients without any demonstrable sensory or motor blockade in the treated limb, nor did it have any effect on the contralateral IGR or PW. Bupivacaine did provide short‐term pain relief in 4 out of 7 patients. Morphine did not produce any demonstrable effect on the sympathetic nervous system nor did it provide pain relief for any patient. Thus these data do not support injection of morphine around the stellate ganglion as it neither modulated sympathetic activity nor provided pain relief.

Why combine a foam dressing with ibuprofen for wound pain and moist wound healing

Six out of ten patients with chronic wounds suffer from persistent wound pain (1). A novel dressing combination has been formulated to provide pain relief and moisture balance at the local wound site (ibuprofen-foam, Biatain-Ibu foam dressing, Coloplast A/S). Foam dressings with polyurethane cells have been known to absorb moisture and provide moisture balance. These second generation foams have the ability to partially retain some fluids and to exchange other fluid, providing moisture balance to the wound surface. This type of foam is less likely to cause maceration of the periwound skin (2). Healing wounds requires five initial important components: debridement, prevention of bacterial damage, pain and prolonged inflammation and maintaining moisture balance. Painful wounds take longer time to heal, and some patients cannot tolerate the treatment of wounds and some can become immobile, which in turn can lead to social isolation, depression and feelings of hopelessness (3). Non steroidal anti-inflammatory drugs (NSAIDs) are excellent pain-reducing agents, but when administered systemically in the elderly patients, they may cause side effects such as gastrointestinal bleeding, decreased renal function and even deaths. To overcome the safety concern, very small doses of ibuprofen can have an excellent local effect on the superficial wound compartment, without detectable systemic levels. The equivalent of a quarter tablet (50 mg, 1010-cm dressing) of ibuprofen can exert adequate anti-inflammatory and pain-reducing effects up to 7 days. Conceptually, we have a safe combination of moisture-balancing foams with continuousrelease, low-dose ibuprofen to exert a local pain-reducing effect.