Evaluation of variations in sensory and pain threshold assessments by electrocutaneous stimulation

Vasodilatory Peripheral Response and Pain Levels following Radiofrequency Stressor Application in Women with Fibromyalgia

Fibromyalgia (FM) is a syndrome of unknown pathogenesis that presents, among other symptoms, chronic widespread musculoskeletal pain. This study aims to analyze the effects of radiofrequency on core body temperature and the peripheral temperature of the dorsal surfaces and palms of the hands and its association with pain levels in patients with FM. A case-control observational study was conducted with a total of twenty-nine women diagnosed with FM and seventeen healthy women. Capacitive monopolar radiofrequency was applied to the palms of the hands using the Biotronic Advance Develops device. Peripheral hand temperature was analyzed using a thermographic camera, and core body temperature was analyzed with an infrared scanner. Pressure pain thresholds (PPTs) and electrical pain were recorded with an algometer and a Pain Matcher device, respectively. A significant decrease was observed in women with FM in pain electrical threshold (95% CI [0.01-3.56], p = 0.049), electrical pain (95% CI [2.87-10.43], p = 0.002), dominant supraspinatus PPT (95% CI [0.04-0.52], p = 0.023), non-dominant supraspinatus PPT (95% CI [0.03-0.60], p = 0.029), and non-dominant tibial PPT (95% CI [0.05-0.89], p = 0.031). Women with FM have increased hypersensitivity to pain as well as increased peripheral temperature after exposure to a thermal stimulus, such as radiofrequency, which could indicate disorders of their neurovascular response.

Painful differences between different pain scale assessments: The outcome of assessed pain is a matter of the choices of scale and statistics

OBJECTIVES

Perceived pain is a multi-factorial subjective variable, commonly measured by numeric rating scales, verbal descriptive scales (VDS), or by a position on an analogue line (VAS). A major question is whether an individual's VAS and VDS pain assessments, on the same occasion, could be comparable. The aim was to compare continuous and discretized VAS pain data with verbal descriptive pain datasets from the Oswestry Disability Index (ODI) and the European Quality of Life Scale (EQ-5D) in paired pain datasets.

METHODS

The measurement level of data from any type of scale assessments is ordinal, having rank-invariant properties only. Non-parametric statistical methods were used. Two ways of discretizing the VAS-line to VAS-intervals to fit the number of the comparing VDS-categories were used: the commonly used (equidistant VAS,VDS)-pairs and the (unbiased VAS,VDS)-pairs of pain data. The comparability of the (VAS,VDS)-pairs of data of perceived pain was studied by the bivariate ranking approach. Hence, each pair will be regarded as ordered, disordered, or tied with respect to the other pairs of data. The percentage agreement, PA, the measures of disorder, D, and of order consistency, MA, were calculated. Total interchangeability requires PA = 1 and MA = 1.

RESULTS

The wide range of overlapping of (VAS,VDS)-pairs indicated that the continuous VAS data were not comparable to any of the VDS pain datasets. The percentage of agreement, PA; in the (equidistant VAS,ODI) and (equidistant VAS, EQ-5D) pairs were 38 and 49%, and the order consistency, MA, was 0.70 and 0.80, respectively. Corresponding results for the (unbiased VAS,VDS)-pairs of pain data were PA: 54 and 100%, and MA: 0.77 and 1.0.

CONCLUSION

Our results confirmed that perceived pain is the individual's subjective experience, and possible scale-interchangeability is only study-specific. The pain experience is not possible to be measured univocally, but is possible for the individual to rate on a scale.

Enhanced pain sensitivity in obese patients with obstructive sleep apnoea syndrome is partially reverted by treatment: An exploratory study

BACKGROUND

Obesity is frequently associated with obstructive sleep apnoea syndrome (OSA) and chronic pain. OSA as well as continuous positive airway pressure (CPAP) treatment may modulate the pain perception threshold (PT) in patients with obesity.

METHODS

In this prospective, longitudinal study, all patients admitted for obesity assessment were screened for OSA by nocturnal polygraphy (SOMNOcheck^® , IAH ≥10) and performed mechanical (Von Frey electronic device) and electrical (PainMatcher^® ) pain tests. Those with severe OSA were retested for PT 1 month after initiation of CPAP therapy. Newly diagnosed patients with severe OSA (hypopnea apnoea index >30) have been offered to start CPAP treatment.

RESULTS

Among 85 patients, there were 27 OSA patients, aged between 40 ± 13.2 years with a BMI of 42 ± 7.2 kg/m² . Severe OSA patients (N = 11) showed a lower PT than non-OSA patients (N = 58) during mechanical (177 ± 120 vs. 328 ± 136 g, p < 0.01) and electrical methods (7.4 ± 6.4 vs. 12.9 ± 6.7 stimulation duration steps; p = 0.03). In the severe OSA group (N = 7), an increased PT was observed 1 month after CPAP treatment during mechanical pain testing (298 ± 69 vs. 259 ± 68 g, p < 0.05), but not during electrical pain testing (11.5 ± 3.0 vs. 12.4 ± 3.8 stimulation duration steps, p = 0.50).

CONCLUSION

In patients with obesity, this exploratory study showed that the presence of an OSA is associated with a decreased PT, whereas implantation of a CPAP device tends to normalize pain perception.

Associations Among Nitric Oxide and Enkephalinases With Fibromyalgia Symptoms

BACKGROUND

Fibromyalgia (FM) is a complex syndrome of uncertain etiology, characterized by the presence of widespread pain. Both nitric oxide and enkephalinases modulate pain perception.

OBJECTIVES

The aim of this study was to evaluate the relationships among serum nitric oxide levels, oxytocinase activity, and enkephalin-degrading aminopeptidase (EDA) activity with pain-related clinical manifestations in women with FM.

METHODS

We performed an observational case study in a population of 58 women diagnosed with FM. Serum nitric oxide levels were analyzed by an ozone chemiluminescence-based assay. Both serum oxytocinase and EDA activities were fluorometrically determined. Pain threshold and pain magnitude were evaluated using the PainMatcher. The pressure pain thresholds were measured using a digital pressure algometer. We used a visual analog scale, the Central Sensitization Inventory, the Revised Fibromyalgia Impact Questionnaire, and the Beck Anxiety Inventory to assess the global level of pain, the symptoms associated with the central sensitization syndrome, the severity of FM, and the anxiety level, respectively.

RESULTS

Multiple linear regression analysis adjusted by age, body mass index, and menopause status revealed significant associations between nitric oxide levels and dominant occiput pressure pain thresholds, nondominant occiput pressure pain thresholds, and FM effects. Significant associations of oxytocinase activity with the visual analog scale and dominant knee pressure pain thresholds were also found. Moreover, results showed a significant association between high EDA activity levels and dominant second-rib pressure pain thresholds.

DISCUSSION

Our data have shown significant relationships of serum nitric oxide levels and oxytocinase and EDA activities with some body pressure pain thresholds, the daily activity level, and the global intensity of pain in women with FM. These results suggest that pain, which is the main symptom of this syndrome, may be related to alterations in nitric oxide levels and in oxytocinase and EDA activities in patients with FM.

Pain Intensity, Pressure Pain Hypersensitivity, Central Sensitization, and Pain Catastrophizing Related to Vascular Alterations in Raynaud's Phenomenon: A Preliminary Case-Control Study

OBJECTIVE

To evaluate pain intensity, widespread pressure pain, central sensitization (CS), and catastrophizing between subjects with primary and secondary Raynaud's phenomenon (RP) and healthy controls and to compare the relationships between vascular impairment and pain perception.

METHODS

A preliminary case-control study was performed with a total sample of 57 participants (37 with RP). Sociodemographic data, clinical/vascular data, and pain variables (pain intensity, pressure pain sensitivity, pain magnitude and threshold, CS, and catastrophizing) were registered. Results were analyzed by analysis of covariance and Pearson correlation.

RESULTS

Participants with RP had a lower basal temperature (more vasoconstriction) in their hands (P ≤ 0.012), higher pain intensity (P ≤ 0.001), higher electrical pain magnitude (P < 0.001), and lower pressure pain (P ≤ 0.05) and electrical pain (P < 0.001) thresholds in comparison with healthy controls. Secondary RP participants showed a significantly higher level of CS compared with controls and primary RP participants (P = 0.001). Catastrophizing was higher in the primary and secondary RP (P ≤ 0.001) groups than in controls. No correlations were observed between severity of vasoconstriction and pain variables.

CONCLUSIONS

RP participants showed bilateral hypersensitivity to pressure pain. However, the severity of vascular alterations seems not to be related to central pain experiences. Additional mechanisms such as catastrophizing may influence pain in RP; nevertheless, central sensitization only appears to be involved in the secondary form of RP.

Quantitative electrical pain threshold assessment in the lower urinary tract

AIMS

Assessing the reliability of electrical pain threshold (PT) and evaluating the impact of stimulation frequency at different locations in the healthy lower urinary tract (LUT).

METHODS

Ninety subjects (age: 18.3-35.8 years, 40 females, 50 males) were randomly allocated to one stimulation site (bladder dome [BD], trigone, proximal, membranous (only males), or distal urethra). Using 0.5 Hz/1.1 Hz/1.6 Hz electrical stimulation (square wave, pulse width:1 ms), current perception thresholds (CPTs), PTs and tolerance thresholds were assessed at two visits. Analyses were performed using linear mixed models, intraclass correlation coefficients (ICC) and Bland-Altman method.

RESULTS

PTs vary in relation to stimulation frequency, location and between genders. PT decreased with higher stimulation frequency. The highest PTs were measured at the BD and membranous urethra with males reporting higher PTs than females. Reliability of PT assessments according to ICC was good to excellent across all frequencies, locations, and genders (ICC = 0.61-0.97), except for BD and distal urethra in females showing poor to fair reliability (BD: all frequencies, distal urethra: 0.5 Hz).

CONCLUSIONS

PTs can be safely and reliably assessed from bladder and urethral locations. Semi-objective PT assessment may provide additional information on functionality and sensitivity of the LUT slow fiber afferents and complement findings from urodynamic investigations and CPT assessments. In conclusion, the developed methodology may open new opportunities for using electrical stimulation paradigms for LUT PT assessments and diagnostics. All this allows a more precise, location-specific characterization of pain origin and pain reaction towards therapy.

Aspects of Pain, Its Assessment and Evaluation from An Acupuncture Perspective

Pain is a major clinical problem that causes great suffering for the individual and incurs costs for society. Accurate assessment and evaluation of perceived pain is necessary for diagnosis, for choice of treatment, and for the evaluation of treatment efficacy. The assessment of an individual's pain is a challenge since pain is a subjective, multidimensional experience, and assessment is based on the person's own self-report. The results are often varied, possibly due to inter-individual variation, but also in relation to gender and aetiology.

A gold standard for pain assessment is still lacking, but rating scales, questionnaires, and methods derived from psychophysical concepts, such as threshold assessments and perceptual matching, are used. In the evaluation of pain and associated variables, both systematic and individual variation should be taken into account, as should pain-associated symptoms.

Recommendations for pain treatment should be based on the patient's specific needs. Therefore, it is important to assess the level of perceived pain taking individual variation into account. The methods used should preferably have proved to be useful in randomised controlled trials, and analysis of pain assessment should consider its non-metric properties. In the future, the use of studies with a naturalistic protocol together with individual assessment of individual pain responses could increase the internal and external validity.

Effect of postoperative pneumatic compression after volar plate fixation of distal radial fractures: a randomized controlled trial

We investigated the difference between postoperative rehabilitation with or without adjunctive intermittent pneumatic compression therapy following distal radial fracture treated with volar plating. A total of 115 patients were randomized to a control or to an experimental group. After 4 weeks of immobilization the experimental group received intermittent pneumatic compression therapy in addition to conventional postoperative rehabilitation. Primary outcome up to 1 year postoperatively was assessed using the Canadian Occupational Performance Measure. No significant differences between groups were found. There were no clinically relevant differences regarding the secondary outcome measures swelling, strength, pain and flexibility. We conclude that postoperative intermittent pneumatic compression treatment had no major benefits. The results of the present study do not support general use of intermittent pneumatic compression initiated 4 weeks following volar plating surgery for distal radial fracture.

LEVEL OF EVIDENCE

I.

Higher preoperative sensitivity to pain and pain at rest are associated with worse functional outcome after stemless total shoulder arthroplasty

Aims

The aims of this study were to investigate any possible relationship between a preoperative sensitivity to pain and the degree of pain at rest and on exertion with postoperative function in patients who underwent stemless total shoulder arthroplasty (TSA).

Patients and Methods

In this prospective study, we included 63 patients who underwent stemless TSA and were available for evaluation one year postoperatively. There were 31 women and 32 men; their mean age was 71 years (53 to 89). The pain threshold, which was measured using a Pain Matcher (PM) unit, the degree of pain (visual analogue scale at rest and on exertion, and function using the short version of the Disabilities of the Arm, Shoulder and Hand questionnaire (QuickDASH), were recorded preoperatively, as well as three and 12 months postoperatively.

Results

We found an inverse relationship between both the preoperative PM threshold and pain (VAS) at rest and the 12-month postoperative QuickDASH score (Pearson correlation coefficient (r) ≥ 0.4, p < 0.05). A linear regression analysis showed that the preoperative PM threshold on the affected side and preoperative pain (VAS) at rest were the only factors associated with the QuickDASH score at 12 months.

Conclusion

These findings indicate the importance of central sensitization in the restoration of function after TSA. Further studies are required to investigate whether extra analgesia and rehabilitation could influence the outcome in at risk patients. Cite this article: Bone Joint J 2018;100-B:480–4.

Prediction of emergence agitation using withdrawal reaction following rocuronium injection in preschool-aged patients undergoing inguinal herniorrhaphy: a preliminary exploratory observational trial

Purpose

The development of emergence agitation (EA) is associated with several factors including age, preoperative anxiety, postoperative pain, anesthesia method, and surgery type. No studies have investigated whether the withdrawal reaction following rocuronium injection can predict the occurrence of EA. Therefore, we investigated this relationship in preschool-aged children undergoing inguinal herniorrhaphy, and which grade of withdrawal reaction is appropriate for identifying patients at risk of experiencing EA.

Methods

A total of 40 patients were enrolled in this study. During anesthesia induction, the withdrawal reaction after loss of consciousness following rocuronium injection was assessed using a 4-point scale. After surgery, EA was assessed using the Watcha scale.

Results

There was a correlation between withdrawal reaction and EA on admission to the postanesthesia care unit (PACU). Patients with a severe withdrawal reaction (grade 3) showed a significantly higher incidence of severe EA requiring medication on admission to the PACU.

Conclusion

The findings of this preliminary exploratory observational study suggest that it is possible for withdrawal movement following rocuronium injection during anesthesia induction to reflect pain sensitivity of pediatric patients, which in turn may be useful in identifying those at risk of severe EA on admission to the PACU among preschool children undergoing inguinal herniorrhaphy. Further studies with a larger sample size are required to validate these findings. The exact correlation between pain reaction following rocuronium injection and postoperative pain or pain-related phenomenon should be elucidated.

High Power Laser for Treatment of Achilles Tendinosis - a Single Blind Randomized Placebo Controlled Clinical Study

INTRODUCTION

Pain in the Achilles tendon during loading is a very common condition. Conservative treatments, such as low level laser therapy (LLLT) have been reported to give varying results. Recently, a new laser treatment technique, high power laser treatment (HPLT) (Swiss DynaLaser®), was introduced in Scandinavia, but has not, to our knowledge, been systematically tested before. The objective of this study was to evaluate the effects of HPLT compared to placebo HPLT in rated pain and assessed pain threshold in patients with chronic Achilles tendinosis.

METHODS

The study was a randomized, single blind, placebo controlled trial. Patients were randomized to receive 6 treatments of either HPLT or placebo HPLT during a period of 3-4 weeks with a follow up period of 8-12 weeks. Outcome measures were rated pain according to questions of the Foot and Ankle Outcome Score (FAOS, Swedish version LK1.0) and assessment of electro-cutaneous stimulated pain threshold and matched pain (PainMatcher).

RESULTS

The results of the study demonstrated significant changes of assessments within groups, that were more pronounced towards lower levels of rated pain in the HPLT group than in the placebo HPLT group. The between group difference were significant in four of nine questions regarding loading activities of the FAOS subscale. Assessed pain thresholds were found increased in the HPLT group, as compared to the placebo HPLT group. At individual level, the results varied.

CONCLUSION

The results indicate that HPLT may provide a future option for treatment of Achilles tendinosis related pain, but further studies are warranted.

Low-dose progestin-releasing contraceptives are associated with a higher pain threshold in healthy women

OBJECTIVE

To determine the pain thresholds of women taking different formulations of hormonal contraceptives.

DESIGN

Cross-sectional study.

SETTING

Basic health care unit.

PATIENT(S)

Eighty-nine healthy nonusers and 188 users of hormonal contraceptives.

INTERVENTION(S)

Subject interviews were followed by the application of a semistructured questionnaire, including a psychometric assessment with the Beck Depression Inventory and the State-Trait Anxiety Inventory. After the interview, a 10-mL peripheral blood sample was collected. Pain thresholds were obtained by performing pressure algometry.

MAIN OUTCOME MEASURE(S)

Serum concentrations of E2, P, and T (free fraction) were determined via chemoluminescence. The menstrual cycle phase was determined according to hormonal level and identification of an LH surge in urine. Pain threshold was evaluated with a dynamometer applied to the forearm skin of the nondominant limb and abdominal wall.

RESULT(S)

Progestin-only contraceptive users showed a higher pain pressure threshold in the forearm (2.94 ± 0.96 vs. 2.74 ± 0.89 vs. 2.62 ± 0.92) and right (2.11 ± 0.87 vs. 1.83 ± 0.81 vs. 1.78 ± 0.77) and left abdomen (2.12 ± 0.88 vs. 1.79 ± 0.76 vs. 1.73 ± 0.70) than did combined hormonal contraceptive users and nonusers of hormonal contraceptives, respectively. Users of contraceptives that continuously release etonogestrel (subcutaneous implant, vaginal ring) or levonorgestrel (intrauterine devices) had higher pain thresholds.

CONCLUSION(S)

Women who used hormonal contraceptives enabling continuous release of etonogestrel or levonorgestrel tended to have higher pain thresholds than did nonusers of hormonal contraceptives.

Evaluation of pain associated with chronic venous insufficiency in Spanish postmenopausal women

OBJECTIVE

Menopause status has been associated with an increase in venous diseases and lower limb-related symptoms. The purpose of our study was to evaluate pain associated with chronic venous insufficiency and its risk factors in postmenopausal women.

METHODS

A controlled cross-sectional study was performed in 139 postmenopausal women with chronic venous insufficiency and 40 control women. Pain was assessed with a visual analogue scale, the McGill Pain Questionnaire, and the Pain Matcher (Cefar Medical AB, Lund, Sweden). The influence of several demographic and clinical risk factors was analyzed using bivariate and multivariate regression analyses.

RESULTS

Women in the chronic venous insufficiency group had significantly higher pain intensity and significantly lower pain threshold (P = 0.001) than the control group. The level of pain was independently and significantly associated with venous refill time and osteoarthritis index scores. It was not associated with other risk factors or with disease severity according to the clinical, etiological, anatomical, and pathophysiological classification.

CONCLUSIONS

Venous pain is a consistent symptom in postmenopausal women with chronic venous insufficiency, in whom nociceptive thresholds are generally decreased. Reduced physical activity, venous reflux, and osteoarthritis seem to influence pain level in chronic venous insufficiency.

The functional barometer -a self-report questionnaire in accordance with the International Classification of Functioning, Disability and Health for pain related problems; validity and patient-observer comparisons

Background

The International Classification of Functioning, Disability and Health, (ICF) provides a unified, international standardized framework for describing and classifying health and health-related functioning and disability. Based on an ICF core sets the Functional Barometer, (FB), was developed for assessments of perceived pain-related problems with functions, activity and quality-of-life by patients suffering from long-term pain. The aim was to evaluate the construct validity, and to compare the assessments of a patient’s problems from the perspectives of the patient and of the examining professional when using the validated FB and corresponding ICF-classification form, respectively.

Methods

Patients with long-term pain for more than 3 months that visited one of four pain clinics during specified time periods of data collections were eligible. The self-report Balanced Inventory for Spinal disorders was used for validation of the FB. Correspondingly to the validated FB an ICF-classification form for professional’s assessment was developed. The data sets for these inter-scale and the patient-professional comparisons were collected adjacent to the clinical examination. By the statistical method used for evaluation of the pairs of ordinal data presence of systematic disagreement was identified and measured separately from additional individual variations.

Results

The validation process resulted in a revised FB(2.0) that meets the requirements of good construct and content validity. The professionals’ ICF-classifications of the patients’ problems disagreed with the patients’ assessments on the FB(2.0); the percentage agreements ranged from 18% to 51%. The main reason was that the practitioners systematically underestimated the patients’ levels of problems but the different professionals contributed also to a large individual variability (noise) in assessment.

Conclusions

This study presents an ICF-based validated self-report questionnaire, The FB, to be used for identifying and describing pain-related problems with current functioning, activities and quality-of-life as perceived by patients suffering from long-term pain. The strong evidences of underestimation of the patients’ problems and the variability in the professionals’ ICF-classifications demonstrated the importance of describing the patient’s problems both from the patient’s and the professional’s perspective beneficial for the patient’s rehabilitation.

The validity of using an electrocutaneous device for pain assessment in patients with cervical radiculopathy

The purpose of this study was to evaluate the validity and preference for assessing pain magnitude with electrocutaneous testing (ECT) compared to the visual analogue scale (VAS) and Borg CR10 scale in men and women with cervical radiculopathy of varying sensory phenotypes. An additional purpose was to investigate ECT sensory and pain thresholds in men and women with cervical radiculopathy of varying sensory phenotypes. This is a cross-sectional study of 34 patients with cervical radiculopathy. Scatterplots and linear regression were used to investigate bivariate relationships between ECT, VAS and Borg CR10 methods of pain magnitude measurement as well as ECT sensory and pain thresholds. The use of the ECT pain magnitude matching paradigm for patients with cervical radiculopathy with normal sensory phenotype shows good linear association with arm pain VAS (R(2) = 0.39), neck pain VAS (R(2) = 0.38), arm pain Borg CR10 scale (R(2) = 0.50) and neck pain Borg CR10 scale (R(2) = 0.49) suggesting acceptable validity of the procedure. For patients with hypoesthesia and hyperesthesia sensory phenotypes, the ECT pain magnitude matching paradigm does not show adequate linear association with rating scale methods rendering the validity of the procedure as doubtful. ECT for sensory and pain threshold investigation, however, provides a method to objectively assess global sensory function in conjunction with sensory receptor specific bedside examination measures.

Pre-operative pain sensitivity: A prediction of post-operative outcome in the obstetric population

CONTEXT

Experimental assessments can determine pain threshold and tolerance, which mirror sensitivity to pain. This, in turn, influences the post-operative experience.

AIMS

The study intended to evaluate whether the pre-operative pressure and electrical pain tests can predict pain and opioid requirement following cesarean delivery.

SETTINGS AND DESIGN

Research was conducted on females scheduled for cesarean section at a tertiary care hospital of the state. Twenty women were enrolled, after obtaining written informed consent.

MATERIALS AND METHODS

PAIN ASSESSMENT WAS PERFORMED ON THE EVE OF CESAREAN SECTIONS USING THREE DEVICES: PainMatcher(;) determined electrical pain threshold while the algometers PainTest(™) FPN100 (manual) and PainTest(™) FPX 25 (digital) evaluated pressure pain threshold and tolerance. Post-operative pain relief included intravenous morphine administered by patient-controlled analgesia, diclofenac (100 mg, every 12 h, rectally, enforced) and paracetamol (1000 mg, every 4-6 h, orally, on patient request). Pain scores were reported on numerical rating scales at specified time intervals.

STATISTICAL ANALYSIS USED

Correlational and regression statistics were computed using IBM SPSS Statistics 21 software (IBM Corporation, USA).

RESULTS

A SIGNIFICANT CORRELATION WAS OBSERVED BETWEEN MORPHINE REQUIREMENT AND: (1) electrical pain threshold (r = -0.45, P = 0.025), (2) pressure pain threshold (r = -0.41 P = 0.036) and (3) pressure pain tolerance (r = -0.44, P = 0.026) measured by the digital algometer. The parsimonious regression model for morphine requirement consisted of electrical pain threshold (r(2)= 0.20, P = 0.049). The dose of morphine consumed within 48 h of surgery decreases by 0.9 mg for every unit increment in electrical pain threshold.

CONCLUSIONS

The predictive power of pain sensitivity assessments, particularly electrical pain threshold, may portend post-cesarean outcomes, including opioid requirements.

Prediction of post-operative pain following arthroscopic subacromial decompression surgery: an observational study

Background: Arthroscopic shoulder surgery is increasingly performed as a day case procedure. Optimal post-operative pain relief remains a challenge due to considerable variations in the level of pain experienced between individuals. Our aim was to examine whether the preoperative electrical pain threshold was a strong predictor of elevated postoperative pain levels following arthroscopic subacromial decompression (ASD) surgery. Methods: Forty consenting patients with American Society of Anesthesiologists (ASA) grade 1-2 presenting for elective ASD surgery were recruited. Patients’ electrical pain thresholds were measured preoperatively using a PainMatcher® (Cefar Medical AB, Lund, Sweden) device. Following surgery under general anaesthesia, the maximum pain experienced at rest and movement was recorded using a visual analogue scale until the end of postoperative day four. Results: In univariate analyses (t-test), the postoperative pain experienced (Area Under Curve) was significantly greater in patients with a low pain threshold as compared with a high pain threshold at both rest (mean 12.5, S.E. 1.7 v mean 6.5, S.E.1.2. P=0.008) and on movement (mean 18.7, S.E. 1.5 v mean 14.1, S.E.1.4. P=0.031). In multivariate analyses, adjusting for additional extra analgesia, the pain experienced postoperatively was significantly greater in the low pain threshold group both at rest (mean difference 4.9, 95% CI 1.5 to 8.4, P=0.007) and on movement (mean difference 4.1, 95%CI 0.03 to 8.2, P=0.049). Conclusions: Preoperative pain threshold can predict postoperative pain level following ASD of the shoulder. Trial registration: Clinicaltrials.gov identifier: NCT01351363 Level of Evidence: II

Possible effects of mobilisation on acute post-operative pain and nociceptive function after total knee arthroplasty

BACKGROUND

Experimental studies in animals, healthy volunteers, and patients with chronic pain suggest exercise to provide analgesia in several types of pain conditions and after various nociceptive stimuli. To our knowledge, there is no data on the effects of exercise on pain and nociceptive function in surgical patients despite early mobilisation being an important factor to enhance recovery. We therefore investigated possible effects of mobilisation on post-operative pain and nociceptive function after total knee arthroplasty (TKA).

METHODS

Thirty patients undergoing TKA under standardised anaesthesia and analgesia underwent an exercise (mobilisation) strategy on the first post-operative morning consisting of 25-m walking twice, with a 20-min interval. Pain was assessed at rest and during passive hip and knee flexion before, and 5 and 20 min after walk, as well as during walk. Nociceptive function (pain threshold and tolerance) was assessed with pressure algometry and an electrical stimulus.

RESULTS

Pain at rest (supine) and during hip and knee flexion was significantly reduced 5 min (P < 0.03) and 20 min (P < 0.003) after walk compared with before walk, and pain was reduced during the second walk compared with the first walk (P < 0.034). Knee pain pressure threshold (P = 0.002) but not tolerance (P = 0.27) was increased following walk compared with before walk.

CONCLUSION

This first exploratory hypothesis-generating pilot study suggests mobilisation to promote analgesic effects after TKA calling for future studies with a randomised, controlled design on exercise dose-response effects in post-surgical patients.

On the threshold - evaluation of variability in effects of acupuncture in a gender perspective

Variable results of pain alleviation in response to acupuncture have been reported, complicating its interpretation. Sources of variability are probably multi-factorial, including the contribution of gender related effects. Gender related variation in perceived pain has been discussed frequently, but documented effects of acupuncture referring to gender are sparse. Furthermore, factors such as operationalisation of the outcome variable and the statistical method for evaluation could also be sources of variability. When pain is regarded as subjective, the produced data should be treated as ordinal. The rank-based method by Svensson, taking the non-metric qualities of the ordinal data into account as well as the variability at the group and the individual level, is therefore an alternative. The present commentary aims to (1) evaluate changes in electrical sensory thresholds and electrical pain thresholds after low frequency electro-acupuncture separately in healthy women and men; (2) introduce and exemplify the method by Svensson in a user-friendly approach. To analyze the systematic patterns of change in thresholds, indicating evidence of treatment on a group level, the relative position (RP) and relative concentration (RC), were measured. The variation related to the individual, the relative rank variation (RV) was also measured. The results were divergent between women (n = 23) and men (n = 22), i.e. unchanged sensory threshold after acupuncture at the group level in women while changed in men. The assessed pain threshold after acupuncture on the other hand was changed towards higher levels in women and unchanged in men. The individual variation was apparent in both women and men but larger in women. For statistical analysis of the variability for both group and individual related effects, the rank-based method by Svensson could be used. The present study indicates that evaluation of sensory and pain threshold response should be analysed separately in women and men.

Transcutaneous electrostimulation for osteoarthritis of the knee

BACKGROUND

Osteoarthritis is the most common form of joint disease and the leading cause of pain and physical disability in the elderly. Transcutaneous electrical nerve stimulation (TENS), interferential current stimulation and pulsed electrostimulation are used widely to control both acute and chronic pain arising from several conditions, but some policy makers regard efficacy evidence as insufficient.

OBJECTIVES

To compare transcutaneous electrostimulation with sham or no specific intervention in terms of effects on pain and withdrawals due to adverse events in patients with knee osteoarthritis.

SEARCH STRATEGY

We updated the search in CENTRAL, MEDLINE, EMBASE, CINAHL and PEDro up to 5 August 2008, checked conference proceedings and reference lists, and contacted authors.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials that compared transcutaneously applied electrostimulation with a sham intervention or no intervention in patients with osteoarthritis of the knee.

DATA COLLECTION AND ANALYSIS

We extracted data using standardised forms and contacted investigators to obtain missing outcome information. Main outcomes were pain and withdrawals or dropouts due to adverse events. We calculated standardised mean differences (SMDs) for pain and relative risks for safety outcomes and used inverse-variance random-effects meta-analysis. The analysis of pain was based on predicted estimates from meta-regression using the standard error as explanatory variable.

MAIN RESULTS

In this update we identified 14 additional trials resulting in the inclusion of 18 small trials in 813 patients. Eleven trials used TENS, four interferential current stimulation, one both TENS and interferential current stimulation, and two pulsed electrostimulation. The methodological quality and the quality of reporting was poor and a high degree of heterogeneity among the trials (I(2) = 80%) was revealed. The funnel plot for pain was asymmetrical (P < 0.001). The predicted SMD of pain intensity in trials as large as the largest trial was -0.07 (95% CI -0.46 to 0.32), corresponding to a difference in pain scores between electrostimulation and control of 0.2 cm on a 10 cm visual analogue scale. There was little evidence that SMDs differed on the type of electrostimulation (P = 0.94). The relative risk of being withdrawn or dropping out due to adverse events was 0.97 (95% CI 0.2 to 6.0).

AUTHORS' CONCLUSIONS

In this update, we could not confirm that transcutaneous electrostimulation is effective for pain relief. The current systematic review is inconclusive, hampered by the inclusion of only small trials of questionable quality. Appropriately designed trials of adequate power are warranted.

Comparison of the PainMatcher and the Visual Analogue Scale for assessment of labour pain following administered pain relief treatment

OBJECTIVE

during childbirth, it is necessary to assess and monitor experienced pain and to evaluate the effect of pain relief treatment. The aim of this study was to compare the PainMatcher (PM) with the Visual Analogue Scale (VAS) for the assessment of labour pain and the effect of pain relief treatment.

DESIGN

randomised controlled trial.

SETTING

labour ward with approximately 2500 childbirths per year in western Sweden.

PARTICIPANTS

57 women with labour pain treated with acupuncture or sterile water injections scored their electrical pain threshold and pain intensity with the PM. Pain intensity was also assessed with the VAS. Electrical pain threshold and pain intensity were assessed immediately after a uterine contraction before and 30, 60, 90, 120, 150 and 180 minutes after treatment.

MEASUREMENTS AND FINDINGS

the results showed a weak correlation (r=0.13, p<0.05) between the pain intensity scores on the PM and the VAS. The PM detected changes (decrease) in pain intensity to a lower degree than the VAS. Surprisingly, in over 10% of sessions, women scored their pain intensity during a uterine contraction lower than their electrical pain threshold with the PM. However, electrical pain thresholds with the PM correlated well throughout all measurements.

CONCLUSIONS

the PM is a reliable tool for the assessment of electrical pain threshold; however, the VAS is more sensitive than the PM for recording changes in pain intensity when assessing the effects of treatment on labour pain.

IMPLICATIONS FOR PRACTICE

the PM and the VAS are not interchangeable in the case of labour pain, and there is still a need for research in this area to find a more suitable assessment instrument for the evaluation of labour pain.

Prediction of persistent pain after total knee replacement for osteoarthritis

We suggest that different mechanisms underlie joint pain at rest and on movement in osteoarthritis and that separate assessment of these two features with a visual analogue scale (VAS) offers better information about the likely effect of a total knee replacement (TKR) on pain. The risk of persistent pain after TKR may relate to the degree of central sensitisation before surgery, which might be assessed by determining the pain threshold to an electrical stimulus created by a special tool, the Pain Matcher. Assessments were performed in 69 patients scheduled for TKR. At 18 months after operation, separate assessment of pain at rest and with movement was again carried out using a VAS in order to enable comparison of pre- and post-operative measurements. A less favourable outcome in terms of pain relief was observed for patients with a high pre-operative VAS score for pain at rest and a low pain threshold, both features which may reflect a central sensitisation mechanism.

Are reviews based on sham acupuncture procedures in fibromyalgia syndrome (FMS) valid?

In recent reviews regarding the efficacy of acupuncture in fibromyalgia syndrome (FMS) it has been concluded that acupuncture has no specific effect since the control procedure (superficial needling and/or needling away from 'specific' points) had similar effects. These conclusions may be questioned since superficial needling and/or needling away from specific trigger points is not inert. Also, manual acupuncture or mild electroacupuncture (EA) may not be sufficient to activate the endogenous pain inhibiting system. Patients with FMS suffer from allodynia, fatigue and muscle ache, which is partly explained by peripheral and central sensitisation. Sensitisation results in augmented and altered stimulus responses whereby light stimulation of the skin has as strong an effect as regular needling on the pain inhibitory system in FMS. Central sensitisation in FMS is also associated with expanded receptive fields of central neurons resulting in a larger topographic distribution of the pain. This would suggest that control procedures using needling away from the 'specific site' might have as strong an effect as needling within the most painful area. Also, repeated nociceptive input from muscles (as obtained by de qi) results in expansion of receptive fields which in turn may result in activation of descending pain inhibition outside the stimulated myotome. Sensitisation to pain, such as in FMS, may also be related to abnormalities in descending efferent pathways. As there is likely to be an imbalance between excitatory and inhibitory systems in FMS, stronger stimulation may therefore be needed to activate the descending pain inhibitory system. In studies using mild manual acupuncture or weak EA stimulation optimal pain inhibition may therefore not have been obtained. When conducting studies on acupuncture, the clinical condition or syndrome needs to be taken into account and the control procedure designed accordingly.

Prediction of post-operative pain by an electrical pain stimulus

BACKGROUND

Treatment of post-operative pain is still a significant problem. Recently, interest has focused on pre-operative identification of patients who may experience severe post-operative pain in order to offer a more aggressive analgesic treatment. The nociceptive stimulation methods have included heat injury and pressure algometry. A simple method, Pain Matcher (PM), using electrical stimulation, is validated for pain assessment, but has not been evaluated as a tool for prediction of post-operative pain. Our aim was to assess the predictive value of pre-caesarean section pain threshold on intensity of post-caesarean section pain using the PM.

PATIENTS AND METHODS

Thirty-nine healthy women scheduled for elective caesarean section were studied. The anaesthetic/analgesic procedures included spinal anaesthesia, paracetamol, diclofenac, controlled-release (CR) oxycodone and morphine on request. Pre-operatively, the sensory and pain thresholds were measured using the PM. Post-operatively, a midwife, blinded for pre-caesarean pain threshold assessments, assessed the pain at rest and during mobilization every 12 h for 2 days. Consumption of analgesics was also recorded.

RESULTS

Pre-operative pain threshold correlated significantly with post-caesarean pain score (VAS) at rest and mobilization: [Spearman's rho =-0.65 (-0.30 to -0.75), P < 0.01] and [Spearman's rho =-0.52 (-0.23 to -0.72), P < 0.01], respectively. There was no significant correlation between pre-operative PM assessment of sensory threshold and post-operative pain.

CONCLUSION

Electrical pain threshold before caesarean section seems to predict the intensity of post-operative pain. This method may be used as a screening tool to identify patients at high risk of post-operative pain.

Gender differences in electrical pain threshold responses to transcutaneous electrical nerve stimulation (TENS)

Gender differences in pain perception have been frequently discussed, but the documented gender-related pain-alleviating effects of non-pharmacological methods are sparse. In this study we aimed to investigate changes in electrical sensory thresholds and electrical pain thresholds, in response to high frequency transcutaneous electrical nerve stimulation, TENS, for 20 min in healthy women (n=29) and men (n=29). The thresholds were assessed pre-, during-, and post-TENS. The pattern of change in thresholds was evaluated with a rank-based statistical method regarding the level of systematic change, expressed as relative position (RP) and additional individual changes, expressed as relative rank variance (RV), with its 95% confidence intervals. Equal levels of systematic changes towards increased electrical sensory thresholds were seen in women and men post-TENS (RP, 0.35; 95% CI, 0.07, 0.63, and RP, 0.36; 95% CI, 0.17, 0.53, respectively). At the same point of time, systematic changes towards increased electrical pain thresholds were only seen in women (RP, 0.43; 95% CI, 0.27, 0.60), while they were unchanged in men (RP, -0.01; 95% CI, -0.13, 0.10). Significant additional individual variations were found in the women's responses of assessed electrical sensory and pain thresholds but not in the men's. It is concluded that both women and men responded with a significant increase of the electrical sensory threshold to high frequency TENS, but only women responded with increase of the electrical pain thresholds. The individual variation of the responses was greater in the women than in the men.