Joakim M. Bischoff

Ultrasound-guided ilioinguinal/iliohypogastric nerve blocks for persistent inguinal postherniorrhaphy pain: a randomized, double-blind, placebo-controlled, crossover trial.

BACKGROUND: Ilioinguinal and iliohypogastric nerve blocks are used in the clinical management of persistent inguinal postherniorrhaphy pain, but no controlled studies have been published on the subject. In this controlled study, we investigated the analgesic and sensory effects of ultrasound-guided blocks of the ilioinguinal and iliohypogastric nerves with lidocaine. METHODS: A randomized, double-blind, placebo-controlled, crossover trial in 12 patients with severe persistent inguinal postherniorrhaphy pain, including a control group of 12 healthy controls, was performed. Assessments included pain ratings under standardized conditions with numerical rating scale (0–10), sensory mapping to a cool roller, and quantitative sensory testing (QST), in the groin regions, before and after each ultrasound-guided block. A needle approach of 1 to 2 cm superior and medial to the anterior superior iliac spine was used. Outcomes were changes in pain ratings, sensory mapping, and QST compared with preblock values. Lidocaine responders were a priori defined by a pain reduction of ≥80% after lidocaine block and ⩽25% after placebo block, nonresponders by pain reduction of <80% after lidocaine block and ⩽25% after placebo block, and placebo responders by pain reduction of >25% after placebo block. RESULTS: One of 12 pain patients was a lidocaine responder, 6 patients were nonresponders, and 5 patients were placebo responders. No consistent QST changes were observed in patients after the lidocaine block. In 10 of 12 healthy controls, a cool hypoesthesia area developed in the groin after the lidocaine block. Furthermore, QST assessments demonstrated significantly decreased suprathreshold heat pain perception in the groin after lidocaine versus placebo blocks (95% confidence interval = −3.5 to −0.5, P = 0.008). CONCLUSION: Ultrasound-guided lidocaine blocks of the ilioinguinal and iliohypogastric nerves, at the level of the anterior superior iliac spine, are not useful in diagnosis and management of persistent inguinal postherniorrhaphy pain.

Lidocaine patch (5%) in treatment of persistent inguinal postherniorrhaphy pain: a randomized, double-blind, placebo-controlled, crossover trial.

Background:Evidence-based pharmacological treatment options for patients with persistent inguinal postherniorrhaphy pain are lacking. Methods:Twenty-one male patients, with severe, unilateral, persistent inguinal postherniorrhaphy pain, participated in a randomized, double-blind, placebo-controlled crossover trial, receiving lidocaine patch (5%) and placebo patch treatments in periods of 14 days separated by a 14-day wash-out period. Pain intensities (at rest, during movement, and pressure evoked [Numerical Rating Scale]) were assessed before treatment and on the last 3 days of each treatment period. Patients were a priori divided into two subgroups based on quantitative sensory testing (+/− thermal “hyposensitivity”). Skin biopsies for intraepidermal nerve fiber density assessment were taken at baseline, and quantitative sensory testing was performed before and after each treatment period. The primary outcome was change in pain intensity assessed as the difference in summed pain intensity differences between lidocaine and placebo patch treatments. Results:There was no difference in summed pain intensity differences between lidocaine and placebo patch treatments in all patients (mean difference 6.2% [95% CI = −6.6 to 18.9%]; P = 0.33) or in the two subgroups (+/− thermal “hyposensitivity”). The quantitative sensory testing (n = 21) demonstrated an increased pressure pain thresholds after lidocaine compared with placebo patch treatment. Baseline intraepidermal nerve fiber density (n = 21) was lower on the pain side compared with the nonpain side (−3.8 fibers per millimeter [95% CI = −6.1 to −1.4]; P = 0.003). One patient developed mild erythema in the groin during both treatments. Conclusions:Lidocaine patch treatment did not reduce combined resting and dynamic pain ratings compared with placebo in patients with severe, persistent inguinal postherniorrhaphy pain.

Pulsed radiofrequency in the treatment of persistent pain after inguinal herniotomy: a systematic review.

Abstract In the United States, it is estimated that between 6000 and 18,000 individuals each year present with disabling pain after inguinal hernia repair. Although surgical treatment with mesh removal is one of few options available, effective alternatives to nonsurgical management are needed. The use of pulsed radiofrequency (PFR), leading to nondestructive lesions of nerve structures, has been proposed as a treatment option. To examine the evidence of treatment efficacy, a systematic literature search was made. From the databases PubMed, Embase, and CINAHL, 4 case reports were retrieved and 8 patients were included for analysis. The PFR treatment was peripheral (n = 4) and central (n = 4). Pain relief varied between 63% and 100%, the follow-up period was 3 to 9 months, and no adverse effects or complications were reported. In conclusion, the evidence base of PRF in persistent pain after inguinal herniotomy is fairly limited. Suggestions for improved research strategies are presented.

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.

A Capsaicin (8%) Patch in the Treatment of Severe Persistent Inguinal Postherniorrhaphy Pain: A Randomized, Double-Blind, Placebo-Controlled Trial

Background Persistent pain after inguinal herniorrhaphy is a disabling condition with a lack of evidence-based pharmacological treatment options. This randomized placebo-controlled trial investigated the efficacy of a capsaicin 8% cutaneous patch in the treatment of severe persistent inguinal postherniorrhaphy pain. Methods Forty-six patients with persistent inguinal postherniorrhaphy pain were randomized to receive either a capsaicin 8% patch or a placebo patch. Pain intensity (Numerical Rating Scale [NRS 0–10]) was evaluated under standardized conditions (at rest, during movement, and during pressure) at baseline and at 1, 2 and 3 months after patch application. Skin punch biopsies for intraepidermal nerve fiber density (IENFD) measurements were taken at baseline and 1 month after patch application. Quantitative sensory testing was performed at baseline and at 1, 2, and 3 months after patch application. The primary outcome was comparisons of summed pain intensity differences (SPIDs) between capsaicin and placebo treatments at 1, 2 and 3 months after patch application (significance level P<0.01). Results The maximum difference in SPID, between capsaicin and placebo treatments, was observed at 1 month after patch application, but the pain reduction was not significant (NRS, mean difference [95% CI]: 5.0 [0.09 to 9.9]; P = 0.046). No differences in SPID between treatments were observed at 2 and 3 months after patch application. Changes in IENFD on the pain side, from baseline to 1 month after patch application, did not differ between capsaicin and placebo treatment: 1.9 [−0.1 to 3.9] and 0.6 [−1.2 to 2.5] fibers/mm, respectively (P = 0.32). No significant changes in sensory function, sleep quality or psychological factors were associated with capsaicin patch treatment. Conclusions The study did not demonstrate significant differences in pain relief between capsaicin and placebo treatment, although a trend toward pain improvement in capsaicin treated patients was observed 1 month after patch application. Trial Registration Clinicaltrialsregister.eu 2012-001540-22 ClinicalTrials.gov NCT01699854

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.

Good from far. Far from good.

i t To the Editor Geber et al. have taken up an interesting and relevant topic in evaluation of quantitative sensory testing (QST) data [2]. Estimation of variability components is important for calculating sample power, planning statistical data handling, and especially for correctly interpreting research data. In the abstract, the authors 11 times refer to correlation coefficients (r), with values of 0.35 to 0.93, to substantiate their conclusion ‘‘that standardized QST performed by trained examiners is a

Intraoperative nerve identification and chronic postherniorrhaphy pain

First of all, we thank Drs. Chen and Amid [1] for their very thoughtful comments and update on the role of intraoperative nerve identification during groin hernia repair and the risk of development of chronic pain. We agree with all their comments, except that our conclusions in the abstract does not ‘‘conclude that nerve identification does not decrease rates of pain in routine practice’’ as quoted, but rather that ‘‘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’’ [2]. This conclusion supports the comments by Chen and Amid [1], despite that we in the present study were not able to demonstrate any influence of nerve identification on signs of nerve damage or on development of persistent pain. The discussion on identification of the ‘‘genitofemoral nerve’’ (which we entirely agree should be named ‘‘genital branch’’) is to some extent semantic as we agree that routine direct identification should not be done, but only if necessary for the herniotomy per se. This may explain our low identification rate of the genital branch (21.3 %) which, interestingly, is within the same range as reported from a recent hernia specialist publication on persistent pain problems, with an identification rate of 26.5 % [3]. Also, we agree that the use of heavy-weight mesh may have contributed to the pain problems, but when the study was conducted there was little conclusive evidence for differences between mesh type and persistent pain. In summary, the valuable comment by Drs. Chen and Amid provides a sound balance on this important (but also difficult) topic of persistent postherniorrhaphy pain compared to our rather negative findings [1]. We entirely support their conclusion that surgical technique is a crucial component to reduce this disturbing problem.