The role of peripheral afferents in persistent inguinal postherniorrhaphy pain: a randomized, double-blind, placebo-controlled, crossover trial of ultrasound-guided tender point blockade.

BACKGROUND: Severe, persistent inguinal postherniorrhaphy pain (PIPP) is a debilitating condition that develops in 2-5% of patients. PIPP may be neuropathic in nature, yet the lesion in the peripheral nervous system has not been located. Most PIPP-patients demonstrate a tender point (TP) in the medial aspect of the inguinal region that triggers pain upon minimal pressure. As TPs may play a role in the pathophysiology of PIPP, the aim of this trial was to investigate the analgesic effects of local anaesthetic TP-blockade. METHODS: A randomized, double-blind, placebo-controlled, crossover trial was performed in 14 PIPP-patients and six healthy volunteers. All participated in two sessions, seven days apart, receiving 10 ml of 0.25% bupivacaine or normal saline via an ultrasound-guided fascial plane block at the TP. The TP-area was used for pain assessments (at rest, on movement, with 100 kPa pressure-algometry) and quantitative sensory testing (pressure pain thresholds, thermal detection/pain thresholds, supra-threshold heat perception), before and after the TP-blockade. RESULTS: The median (95% CI) reduction in pain was 63% (44.1 to 73.6%) after bupivacaine compared with 36% (11.6 to 49.7%; P=0.003) after placebo. Significant increases in cool detection (P=0.01) and pressure pain thresholds (P=0.009) with decreases in supra-threshold heat pain perception (P=0.003) were seen after bupivacaine only. In four out of six volunteers, increased thermal and evoked-pain thresholds after bupivacaine compared with placebo, was demonstrated. CONCLUSIONS: This trial demonstrates that peripheral afferent input from the TP-area is important for maintenance of spontaneous and evoked pain in PIPP. CLINICAL TRIAL REGISTRATION: NCT02065219.

Tachyphylaxis to local anaesthetics. What is the clinical evidence? A systematic review.

BACKGROUND: Tachyphylaxis or acute tolerance to local anaesthetics has been reported, but the prevalence in clinical analgesia is obscure, and the mechanisms behind this phenomenon remain unclear. We sought to examine the clinical significance of tachyphylaxis from the available literature. METHODS: We performed a systematic review of the literature utilising the databases PubMed and Embase employing the search terms [Tachyphylaxis AND Local Anaesthetics AND Human] AND [Tolerance AND Local Anaesthetics AND Human]. RESULTS: A total of 66 records were identified. Thirty-four articles were assessed in full text for eligibility. Twenty studies were considered relevant for qualitative analyses, but only six studies were randomised controlled trials. Because of the heterogeneity of the randomised controlled trials, it was not possible to conduct a meta-analysis. CONCLUSION: Studies documenting tachyphylaxis with clinical use of local anaesthetics are surprisingly scarce, and the mechanisms behind it remain unclear.

Effect of a high-dose target-controlled naloxone infusion on pain and hyperalgesia in patients following groin hernia repair: study protocol for a randomized controlled trial.

BACKGROUND: Central sensitization is modulated by the endogenous opioid system and plays a major role in the development and maintenance of pain. Recent animal studies performed following resolution of inflammatory pain showed reinstatement of tactile hypersensitivity induced by administration of a mu-opioid-antagonist, suggesting latent sensitization is mediated by endogenous opioids. In a recent crossover study in healthy volunteers, following resolution of a first-degree burn, 4 out of 12 volunteers developed large secondary areas of hyperalgesia areas after a naloxone infusion, while no volunteer developed significant secondary hyperalgesia after the placebo infusion. In order to consistently demonstrate latent sensitization in humans, a pain model inducing deep tissue inflammation, as used in animal studies, might be necessary. The aim of the present study is to examine whether a high-dose target-controlled naloxone infusion can reinstate pain and hyperalgesia following recovery from open groin hernia repair and thus consistently demonstrate opioid-mediated latent sensitization in humans. METHODS/DESIGN: Patients submitted to unilateral, primary, open groin hernia repair will be included in this randomized, placebo-controlled, double-blind, crossover study. The experimental days take place 6-8 weeks after surgery, time-points at which patients are expected to be almost pain- free. Prior to administration of naloxone or placebo, the primary outcome (a summated measure of pain: at rest, during transition from supine to standing position, and evoked by pressure algometry) and the secondary outcomes (secondary hyperalgesia/allodynia, pressure pain thresholds, assessed at the surgical site and at the mirror-site in the contralateral groin, and, opioid withdrawal symptoms) will be assessed. These assessments will be repeated at each step of the target-controlled infusion of placebo or naloxone at estimated median (95 % CI) plasma concentrations of 344 ng/ml (130;567), 1059 ng/ml (400;1752) and 3196 ng/ml (1205;5276). DISCUSSION: We aim to demonstrate opioid-mediated latent sensitization in a post-surgical setting, using pain as a clinical relevant variable. Impairment of the protective endogenous opioid system may play an important role in the transition from acute to chronic pain. In order to sufficiently block the endogenous opioid system, a high-dose target-controlled naloxone-infusion is used, in accordance with recent findings in animal studies. EUDRACT: 2015-000793-36 (Registration date: 16 February 2015) Clinicaltrials.gov: NCT01992146 (Registration date: 12 December 2014).

Pain-related psychological distress, self-rated health and significance of neuropathic pain in Danish soldiers injured in Afghanistan.

BACKGROUND: Pain and mental health concerns are prevalent among veterans. While the majority of research has focused on chronic pain as an entity, there has been little work directed towards investigating the role of neuropathic pain in relation to psychological comorbidity. As such, we hypothesised that participants with signs of neuropathic pain would report higher levels of psychological distress and diminished self-rated health compared to those without a neuropathic component. METHODS: A retrospective review of standardised questionnaires (PainDETECT Questionnaire, Post-traumatic Stress Disorder Checklist-Civilian, the Hospital Anxiety and Depression Scale, and EuroQOL Visual Analogue Scale) administered to injured soldiers. The participants were classified into three groups according to the PainDETECT questionnaire: non-neuropathic pain, possible neuropathic pain and definite neuropathic pain. RESULTS: Fifty-three participants were included. The Post-traumatic Stress Disorder Checklist-Civilian score was in median (interquartile range) 26 (22-31), the Hospital Anxiety and Depression Scale score was 4 (2-6.5) and 2 (1-5) for anxiety and depression respectively. Evidence of neuropathic pain correlated positively with the Post-traumatic Stress Disorder Checklist-Civilian score (rho = 0.469, P < 0.001) and Hospital Anxiety and Depression Scale subscale for anxiety score (rho = 0.357, P = 0.009), and inversely with the EuroQOL Visual Analogue Scale score (rho = -0.361, P = 0.008). In multivariate regression analyses, the associations remained when adjusting for socio-demographics and clinical characteristics. CONCLUSIONS: The results from the present study suggest that neuropathic pain is related to increased psychological distress and deterioration in self-rated health in injured soldiers.

Referred pain and cutaneous responses from deep tissue electrical pain stimulation in the groin.

BACKGROUND: Persistent postherniotomy pain is located around the scar and external inguinal ring and is often described as deep rather than cutaneous, with frequent complaints of pain in adjacent areas. Whether this pain is due to local pathology or referred/projected pain is unknown, hindering mechanism-based treatment. METHODS: Deep tissue electrical pain stimulation by needle electrodes in the right groin (rectus muscle, ilioinguinal/iliohypogastric nerve and perispermatic cord) was combined with assessment of referred/projected pain and the cutaneous heat pain threshold (HPT) at three prespecified areas (both groins and the lower right arm) in 19 healthy subjects. The assessment was repeated 10 days later to assess the reproducibility of individual responses. RESULTS: Deep electrical stimulation elicited pain at the stimulation site in all subjects, and in 15 subjects, pain from areas outside the stimulation area was reported, with 90-100% having the same response on both days, depending on the location. Deep pain stimulation significantly increased the cutaneous HPT (P<0.014). Individual HPT responses before and during deep electrical pain stimulation were significantly correlated (ρ>0.474, P≤0.040) at the two test days for the majority of test areas. CONCLUSION: Our results corroborate a systematic relationship between deep pain and changes in cutaneous nociception. The individual referred/projected pain patterns and cutaneous responses are variable, but reproducible, supporting individual differences in anatomy and sensory processing. Future studies investigating the responses to deep tissue electrical stimulation in persistent postherniotomy pain patients may advance our understanding of underlying pathophysiological mechanisms and strategies for treatment and prevention. TRIAL REGISTRY NUMBERS: ClinicalTrials.gov (NCT01701427).

Hyperbaric oxygen therapy attenuates central sensitization induced by a thermal injury in humans.

BACKGROUND: Hyperbaric oxygen (HBO2 ) treatment has in animal experiments demonstrated antinociceptive effects. It was hypothesized that these effects would attenuate secondary hyperalgesia areas (SHAs), an expression of central sensitization, after a first-degree thermal injury in humans. METHODS: Seventeen healthy volunteers were examined during two sessions using a randomized crossover design. Volunteers were studied during control conditions (ambient pressure, FI O2 = 0.21) and during HBO2 (2.4 standard atmosphere, FI O2 = 1.0, 90 min) conditions in a pressure chamber. Quantitative sensory testing, including assessment of SHAs was performed. RESULTS: A statistically significant overall attenuation of SHAs was seen during the HBO2 sessions compared with the control-sessions (P = 0.011). In the eight volunteers starting with the HBO2 session, no difference in SHAs compared with control was demonstrated. However, in the nine volunteers starting with the control session, a statistical significant attenuation of SHAs was demonstrated in the HBO2 session (P = 0.004). CONCLUSIONS: The results indicate that HBO2 therapy in humans attenuates central sensitization induced by a thermal skin injury, compared with control. These new and original findings in humans corroborate animal experimental data. The thermal injury model may give impetus to future human neurophysiological studies exploring the central effects of hyperbaric oxygen treatment.

Assessment of deep tissue hyperalgesia in the groin - a method comparison of electrical vs. pressure stimulation.

BACKGROUND: Deep pain complaints are more frequent than cutaneous in post-surgical patients, and a prevalent finding in quantitative sensory testing studies. However, the preferred assessment method - pressure algometry - is indirect and tissue unspecific, hindering advances in treatment and preventive strategies. Thus, there is a need for development of methods with direct stimulation of suspected hyperalgesic tissues to identify the peripheral origin of nociceptive input. METHODS: We compared the reliability of an ultrasound-guided needle stimulation protocol of electrical detection and pain thresholds to pressure algometry, by performing identical test-retest sequences 10 days apart, in deep tissues in the groin region. Electrical stimulation was performed by five up-and-down staircase series of single impulses of 0.04 ms duration, starting from 0 mA in increments of 0.2 mA until a threshold was reached and descending until sensation was lost. Method reliability was assessed by Bland-Altman plots, descriptive statistics, coefficients of variance and intraclass correlation coefficients. RESULTS: The electrical stimulation method was comparable to pressure algometry regarding 10 days test-retest repeatability, but with superior same-day reliability for electrical stimulation (P < 0.05). Between-subject variance rather than within-subject variance was the main source for test variation. There were no systematic differences in electrical thresholds across tissues and locations (P > 0.05). CONCLUSION: The presented tissue-specific direct deep tissue electrical stimulation technique has equal or superior reliability compared with the indirect tissue-unspecific stimulation by pressure algometry. This method may facilitate advances in mechanism based preventive and treatment strategies in acute and chronic post-surgical pain states.

A systematic review of peri-operative melatonin.

We systematically reviewed randomised controlled trials of peri-operative melatonin. We included 24 studies of 1794 participants that reported eight peri-operative outcomes: anxiety; analgesia; sleep quality; oxidative stress; emergence behaviour; anaesthetic requirements; steal induction; and safety. Compared with placebo, melatonin reduced the standardised mean difference (95% CI) pre-operative anxiety score by 0.88 (0.44-1.33) and postoperative pain score by 1.06 (0.23-1.88). The magnitude of effect was unreliable due to substantial statistical heterogeneity, with I(2) 87% and 94%, respectively. Qualitative reviews suggested the melatonin improved sleep quality and emergence behaviour, and might be capable of reducing oxidative stress and anaesthetic requirements.

Test-retest studies in quantitative sensory testing: a critical review.

Quantitative sensory testing (QST) investigates the graded psychophysical response to controlled thermal, mechanical, electrical or chemical stimuli, allowing quantification of clinically relevant perception and pain thresholds. The methods are ubiquitously used in experimental and clinical pain research, and therefore, the need for uniform assessment procedures has been emphasised. However, varying consistency and transparency in the statistical methodology seem to occur in the QST literature. Sixteen publications, evaluating aspects of QST variability, from 2010 to 2012, were critically reviewed in detail. A considerable heterogeneity in the statistical evaluations of test-retest data was demonstrated. The authors, using a secondary analysis of published data for didactic purposes, propose and present minimal requirements for reporting of test-retest QST data.

Long-term follow-up after mesh removal and selective neurectomy for persistent inguinal postherniorrhaphy pain.

PURPOSE: Persistent inguinal pain, influencing daily activities, is seen in about 5 % of patients following inguinal herniorrhaphy. Surgical treatment of patients with persistent postherniorrhaphy pain has been associated with pain relief and improvement in functional status. However, the detailed long-term outcome effects remain to be clarified. The aim of this study was to determine the long-term effects of mesh removal and selective neurectomy in patients with persistent postherniorrhaphy pain after previous open repair. METHODS: The study consecutively included 54 inguinal postherniorrhaphy pain patients treated with mesh removal and aimed neurectomy. Patients completed questionnaires evaluating pain intensity with a numerical rating scale (NRS) and pain-related functional impairment preoperatively, and, 3, 6, 12, 24, and 36 months postoperatively. Endpoints were changes in pain intensity and functional ability when comparing preoperative and postoperative assessments. RESULTS: Pain intensities (average, maximum, and during activity) were significantly lower at all time points during follow-up compared to preoperative values (p < 0.01 for all) with a reduction in median (IQR) average pain intensity from 6.0 (5.0-7.0) preoperatively to 3.0 (1.0-5.5) at 36-month follow-up. There was no association between positive pain outcome and intraoperative nerve identification (p = 0.47). The number of patients who reported a long-term negative effect of the operation (≥ 25 % increase in average pain intensity at 36-month follow-up) was 1 of 8. The functional ability was improved at 3 months after the operation (p < 0.01), but the improvement was not statistically significant in the follow-up period. Preoperative signs of depression, anxiety, and catastrophizing had no influence on outcome. CONCLUSIONS: Mesh removal and attempted neurectomy may provide long-lasting analgesic effects in most patients and with a small proportion being worse, without relation to pain history and operative findings. Detailed multicenter collaboration is required to define preoperative diagnostics and the indication for mesh removal and neurectomy, the exact surgical procedure (type of neurectomy) and with detailed follow-up.

Late sensory changes following chest drain insertion during thoracotomy.

BACKGROUND: It is well known that chest drains are associated with severe movement-related acute pain. These noxious stimuli could play a significant role in development and maintenance of persistent post-operative pain. Therefore we studied chest drain sites in post-thoracotomy pain syndrome (PTPS) patients, in regard to pain and sensory dysfunction. METHODS: We quantified thermal and pressure thresholds on both the chest drain side and the contralateral side in 11 PTPS patients and 10 pain-free post-thoracotomy patients 33 months after the thoracotomy. On average, each patient had two chest drains inserted during surgery. RESULTS: At follow up, two patients experienced pain at the chest drain sites, but had maximal pain near or at the thoracotomy scar. Comparison between chest drain side and control side for all 21 patients demonstrated significantly elevated thresholds for warmth detection and heat pain on the chest drain side (P < 0.01), but not for cool detection or pressure. No significant differences between chest drain side and control side were observed within PTPS or pain-free patients. Comparing PTPS and pain-free patients (chest drain-to-control side), no significant differences in thresholds were found. Although all 11 PTPS patients suffered from incisional pain, only two patients had pain from chest drains. CONCLUSION: Increased thresholds for thermal detection suggest that chest drain insertion is associated with late nerve injury. Because no significant differences in sensory thresholds between PTPS and pain-free patients were found, the pathophysiological role of small fibre nerve injury from chest drains in relation to PTPS remains unclear.

Does nerve identification during open inguinal herniorrhaphy reduce the risk of nerve damage and persistent pain?

PURPOSE: Nerve identification during open inguinal hernia herniorrhaphy has been suggested as one of the factors that may reduce the risk of development of persistent postherniorrhaphy pain. In this prospective study, we evaluated whether intraoperative inguinal nerve identification influenced the risk of development of persistent postherniorrhaphy pain, sensory dysfunction in the groin and functional ability score after open hernia repair. METHODS: A total of 244 men with a primary inguinal hernia underwent open Lichtenstein repair in a high-volume hernia surgery centre, where information on inguinal nerve identification was registered during operation. Before the operation and 6 months postoperatively, functional pain-related impairment was assessed with Activities Assessment Scale and pain intensity scores with Numeric Rating Scale (NRS 0-10). Quantitative sensory testing in the groin was performed before operation and 6 months postoperatively, in order to investigate intraoperative inguinal nerve damage. RESULTS: The intraoperative nerve identification rates for the iliohypogastric, ilioinguinal and genitofemoral nerves were 94.7, 97.5 and 21.3 %, respectively. Thirty-nine patients (16.0 %) had substantial pain-related functional impairment at 6 months follow-up. There was no difference in risk of development of substantial pain-related functional impairment in patients with identification compared with non-identification of the iliohypogastric nerve (P = 1.0), the ilioinguinal nerve (P = 0.59), the genitofemoral nerve (P = 0.40) or all nerves (P = 0.52). There were no differences in regard to sensory loss in the groin area or in regard to improvement in functional outcome following surgery, between patients with and without nerve identification. CONCLUSIONS: Although intraoperative inguinal nerve identification should be aimed at, other factors may contribute to the risk of nerve damage and persistent pain after open groin hernia repair.

Post-operative pain treatment in Denmark from 2000 to 2009: a nationwide sequential survey on organizational aspects.

BACKGROUND: In Denmark, the first acute pain service (APS) was introduced in 1993. An important objective became to facilitate implementation of accelerated post-operative rehabilitation programmes (ACC) in selected procedures in abdominal, gynaecological and orthopaedic surgery. Therefore, it is of considerable interest to study the association between the developments of post-operative pain management and the ACC by sequential analyses from 2000 to 2009. METHODS: In 2000, 2003, 2006 and 2009, a questionnaire was mailed to all Danish anaesthesiology departments. The headings of the questionnaire were demographics of responder departments, resources allocated to pain management methods, quality assessment methods, research activities and implementation of ACC. RESULTS: The responder rates varied between 80% and 94% (mean 88%) representing a mean number of anaesthetics of 340.000 per year. The number of APSs in the study period varied in university hospitals between 52% and 71% (P = 0.01), regional hospitals between 8% and 40% (P < 0.01), and local hospitals between 0% and 47% (P < 0.01). The prevalences of departments actively engaged in ACC were 40% in 2000, 54% in 2003, 73% in 2006 and 80% in 2009 (P < 0.01). CONCLUSIONS: The study, spanning nearly a decade, illustrates that following an increase in number of APSs from 2000 to 2006, followed by a significant decline, a steadily increasing number of departments implemented ACC.

Quantitative sensory testing of persistent pain after video-assisted thoracic surgery lobectomy.

BACKGROUND: Video-assisted thoracic surgery (VATS) lobectomy may potentially reduce the risk of post-thoracotomy pain syndrome (PTPS). However, it may still carry a risk of intraoperative nerve damage and thereby development of PTPS. Thus, our aim was to present a detailed long-term neurophysiological characterization of PTPS after VATS. METHODS: Quantitative sensory testing, using thermal and mechanical stimuli, was performed in 13 PTPS patients and 35 pain-free patients recruited 33 months after VATS lobectomy. RESULTS: When comparing the operated side with the control side in PTPS patients, increased thresholds of tactile and warmth detection were observed, while in pain-free patients, increased thresholds of warmth detection, cool detection, and heat pain were demonstrated. At the anterior porthole, pain-free patients displayed increased threshold to thermal detection when compared with the control side. Only side-to-side difference for tactile detection threshold was increased in PTPS patients compared with pain-free patients. Assessment of central sensitization showed no significant differences within or between PTPS and pain-free patients nor did group comparison of area of hypo- and hyperaesthesia to cool. Anxiety and depression scores (HADS) were higher in PTPS patients, but the area of hyper- and hypoaesthesia did not differ significantly between HADS groups. CONCLUSIONS: Increased sensory thresholds suggest nerve injury to be present on the operated side in both PTPS and pain-free patients. However, no significant quantitative differences between PTPS and pain-free patients could be found, implicating the presence of factors other than intercostal nerve injury as important for development of PTPS after VATS lobectomy.

Humidity affects the performance of von Frey monofilaments.

BACKGROUND: Assessment of tactile and nociceptive thresholds of the skin with calibrated polyamide monofilaments is an established testing method both in animal and in human research. It is known that changes in relative humidity may affect the physical properties of the monofilaments. As this effect has only been studied in very small diameter monofilaments, used in neonatal research, we therefore studied complete sets of polyamide monofilaments. METHODS: The effects were studied in a controlled climate chamber during six incremental changes in relative humidity from 20% to 79% (22-24°C). Following 24 h of equilibration at each humidity level, calibration with a precision scale was performed. RESULTS: A highly significant linear correlation between the natural logarithm (In) of the bending force and the von Frey number was observed at all humidity levels (r(2)>0.99, P<0.0001). An inverse linear relationship between relative humidity and In of the bending force for each monofilament was found (r(2)=0.95, P<0.0001). One percent increase in relative humidity corresponded to a 1-4% relative decrease in numerical bending force, depending on the diameter of the monofilament. A significant linear relationship was observed between the coefficient of variation and the relative humidity (r(2)=0.87, P<0.001). CONCLUSIONS: The data indicate that the hygroscopic properties of polyamide monofilaments must be taken into account for their reliable use in quantitative sensory testing.

Neurophysiological characterization of persistent pain after laparoscopic inguinal hernia repair.

PURPOSE: About 2-5% of patients undergoing laparoscopic inguinal repair experience persistent pain influencing everyday activities. However, compared with persistent pain after open repair, the combined clinical and neurophysiological characteristics have not been described in detail. Thus, the aim of the study was to describe and classify patients with severe persistent pain after laparoscopic herniorrhaphy. METHODS: Eleven patients with severe persistent pain following laparoscopic inguinal herniorrhaphy were assessed in detail by their medical history, questionnaires (impairments of daily activities, pain description, psychological parameters, socio-economic status), physical examination, sensory mapping, and quantitative sensory testing. RESULTS: The median time since operation was 2 years (range 1-14 years). Ten patients experienced pain in the inguinal region and five patients had pain outside the inguinal region. Based upon the clinical pain pattern and the detailed quantitative sensory testing, the patients could be separated into three different entities, suggesting different pathogenic mechanisms leading to the persistent pain state. Four patients experienced dysejaculation. Six patients were unemployed or retired due to the postherniorrhaphy pain. CONCLUSIONS: These results suggest that patients with severe persistent pain after laparoscopic inguinal herniorrhaphy belong to distinctive subgroups with indicators of either neuropathic, inflammatory, or mechanical irritation from the mesh, or a combination of these symptoms. The findings of a number of pain localizations outside the inguinal region demarcate it from persistent pain following open groin hernia repair. A classification based on a larger study group is required in order to define mechanism-based treatment strategies.

Prediction of post-operative pain after a laparoscopic tubal ligation procedure.

BACKGROUND: Pre-operative identification of reliable predictors of post-operative pain may lead to improved pain management strategies. We investigated the correlation between pre-operative pain, psychometric variables, response to heat stimuli and post-operative pain following a laparoscopic tubal ligation procedure. METHODS: Assessments of anxiety, mood, psychological vulnerability and pre-operative pain were made before surgery using the State-Trait Anxiety Inventory (STAI), the Hospital Anxiety Depression Scale (HADS), a psychological vulnerability test and the Short-Form McGill Pain Questionnaire (SF-MPQ), respectively. Pre-operative assessments of thermal thresholds and pain response to randomized series of heat stimuli (1 s, 44-48 degrees C) were made with quantitative sensory testing technique. Post-operative pain intensity was evaluated daily by a visual analogue scale during rest and during standardized dynamic conditions for 10 days following surgery. Univariate and multivariate regression analyses were used to construct prediction models. RESULTS: Fifty-nine patients completed the study. Post-operative pain was significantly correlated with pre-operative pain (SF-MPQ), heat pain perception, psychological vulnerability, STAI and HADS. In the multiple regression model pre-operative pain and heat pain perception were significant predictive factors (R=0.537-0.609). CONCLUSION: The study indicates that pre-surgical pain and heat pain sensitivity are important pre-operative indicators of post-operative pain intensity, while psychological factors like vulnerability and anxiety seem to contribute to a lesser degree after laparoscopic tubal ligation. The prediction model accounted for 29-43% of the total variance in post-operative movement-related pain.

Development and validation of a brief, descriptive Danish pain questionnaire (BDDPQ).

BACKGROUND: A new pain questionnaire should be simple, be documented to have discriminative function, and be related to previously used questionnaires. METHODS: Word meaning was validated by using bilingual Danish medical students and asking them to translate words taken from the Danish version of the McGill pain questionnaire into English. Evaluative word value was estimated using a visual analog scale (VAS). Discriminative function was assessed by having patients with one of six painful conditions (postherpetic neuralgia, phantom limb pain, rheumatoid arthritis, ankle fracture, appendicitis, or labor pain) complete the questionnaire. RESULTS: We were not able to find Danish words that were reliably back-translated to the English words 'splitting' or 'gnawing'. A simple three-word set of evaluative terms had good separation when rated on a VAS scale ('let' 17.5+/-6.5 mm; 'moderat' 42.7+/-8.6 mm; and 'staerk' 74.9+/-9.7 mm). The questionnaire was able to discriminate among the six painful conditions with 77% accuracy by just using the descriptive words. The accuracy of the questionnaire increased to 96% with the addition of evaluative terms (for pain at rest and with activity), chronicity (acute vs. chronic), and location of the pain. CONCLUSIONS: A Danish pain questionnaire that subjects and patients can self-administer has been developed and validated relative to the words used in the English McGill Pain questionnaire. The discriminative ability of the questionnaire among some common painful conditions has been tested and documented. The questionnaire may be of use in patient care and research.

Effects of gabapentin in acute inflammatory pain in humans.

BACKGROUND AND OBJECTIVES: The aim of the study was to examine the analgesic effects of the anticonvulsant, gabapentin, in a validated model of acute inflammatory pain. METHODS: Twenty-two volunteers were investigated in a double-blind, randomized, placebo-controlled cross-over study. Gabapentin 1,200 mg or placebo was given on 2 separate study days. Three hours after drug administration, a first-degree burn injury was produced on the medial aspect of the nondominant calf (12.5 cm(2), 47 degrees C for 7 minutes). Quantitative sensory testing (QST) included pain ratings to thermal and mechanical stimuli (visual analog scale [VAS]), assessments of thermal and mechanical detection thresholds, and areas of secondary hyperalgesia. Side effects drowsiness and postural instability were assessed by subjective ratings (VAS). RESULTS: The burn injury induced significant primary and secondary hyperalgesia (P <.0001). Gabapentin diminished the decrease in mechanical pain threshold in the burn area (P =.04) and reduced secondary hyperalgesia, but the reduction was not significant (P =.06). Heat pain thresholds, pain during the burn, and mechanical pain in the area of secondary hyperalgesia were not significantly changed by gabapentin (P <.2). Ratings of drowsiness and unsteadiness during walking were significantly higher for gabapentin than for placebo (P <.05). CONCLUSIONS: The study indicates that gabapentin has no analgesic effect in normal skin, but may reduce primary mechanical allodynia in acute inflammation following a thermal injury. These observations suggest a clinical potential of gabapentin in the treatment of postoperative pain.