Michal Granot

Prediction of chronic post-operative pain: pre-operative DNIC testing identifies patients at risk.

&NA; Surgical and medical procedures, mainly those associated with nerve injuries, may lead to chronic persistent pain. Currently, one cannot predict which patients undergoing such procedures are ‘at risk’ to develop chronic pain. We hypothesized that the endogenous analgesia system is key to determining the pattern of handling noxious events, and therefore testing diffuse noxious inhibitory control (DNIC) will predict susceptibility to develop chronic post‐thoracotomy pain (CPTP). Pre‐operative psychophysical tests, including DNIC assessment (pain reduction during exposure to another noxious stimulus at remote body area), were conducted in 62 patients, who were followed 29.0 ± 16.9 weeks after thoracotomy. Logistic regression revealed that pre‐operatively assessed DNIC efficiency and acute post‐operative pain intensity were two independent predictors for CPTP. Efficient DNIC predicted lower risk of CPTP, with OR 0.52 (0.33–0.77 95% CI, p = 0.0024), i.e., a 10‐point numerical pain scale (NPS) reduction halves the chance to develop chronic pain. Higher acute pain intensity indicated OR of 1.80 (1.28–2.77, p = 0.0024) predicting nearly a double chance to develop chronic pain for each 10‐point increase. The other psychophysical measures, pain thresholds and supra‐threshold pain magnitudes, did not predict CPTP. For prediction of acute post‐operative pain intensity, DNIC efficiency was not found significant. Effectiveness of the endogenous analgesia system obtained at a pain‐free state, therefore, seems to reflect the individual’s ability to tackle noxious events, identifying patients ‘at risk’ to develop post‐intervention chronic pain. Applying this diagnostic approach before procedures that might generate pain may allow individually tailored pain prevention and management, which may substantially reduce suffering.

Recommendations on terminology and practice of psychophysical DNIC testing

a Department of Neurology, Rambam Health Care Campus, Technion Faculty of Medicine, Haifa, Israel b Department of Diagnostic Sciences, UMDNJ, Newark, NJ, USA c Laboratory of Experimental Pain Research, Aalborg University, Aalborg, Denmark d Hopital Ambroise Pare, Boulogne Billancourt, France e Department of Anesthesiology, Brigham and Women’s Hospital, Harvard Medical School Boston, MA, USA f College of Dentistry, University of Florida, Gainesville, FL, USA g Faculty of Health and Welfare Studies, University of Haifa, Haifa, Israel h Department of Molecular Medicine and Surgery, Karolinska Hospital/Institutet, Stockholm, Sweden i Department of Psychology, Bamberg University, Bamberg, Germany j Department of Surgery and Neurosurgery, Faculty of Medicine, Sherbrooke University, Sherbrooke, QC, Canada k Department of Anesthesiology, Radboud University, Nijmegen, Netherlands

The Roles of Pain Catastrophizing and Anxiety in the Prediction of Postoperative Pain Intensity A Prospective Study

Objectives:This study was a prospective investigation of the extent to which psychologic variables could be predictive of postoperative pain. Study aims were: 1) to evaluate whether an assessment of pre-operative distress factors could predict the intensity of postoperative pain; and 2) to characterize the unique pattern in which anxiety and pain catastrophizing scores relate to postoperative pain. Methods:The Pain Catastrophizing Scale and the State-Trait Anxiety Inventory were administered to 38 patients scheduled for elective abdominal surgery. The questionnaires were completed on the day of admission, a day before the operation. On day 1 and day 2 following the operation, perception of pain intensity at the surgical wound was assessed by visual analog scale. Results:The Pain Catastrophizing Scale and State-Trait Anxiety Inventory scores were significantly correlated with the postoperative pain scores. A linear regression analysis showed that Pain Catastrophizing Scale predicted the level of postoperative pain intensity even after controlling for state anxiety and that trait anxiety was not a significant predictor. In addition, analysis of the unique pattern of each predictor related to postoperative pain intensity indicated a linear curve for the Pain Catastrophizing Scale and curvilinear curve for the state anxiety. Discussion:The results are discussed in light of appraisal and coping theories. It is suggested that a simple assessment of preoperative catastrophizing tendency and anxiety scores may assist medical teams in postoperative pain management.

Conditioned pain modulation predicts duloxetine efficacy in painful diabetic neuropathy

Summary Conditioned pain modulation (CPM) predicts efficacy of duloxetine in painful diabetic neuropathy; patients with less efficient CPM are more likely to benefit from the drug. ABSTRACT This study aims to individualize the selection of drugs for neuropathic pain by examining the potential coupling of a given drug’s mechanism of action with the patient’s pain modulation pattern. The latter is assessed by the conditioned pain modulation (CPM) and temporal summation (TS) protocols. We hypothesized that patients with a malfunctioning pain modulation pattern, such as less efficient CPM, would benefit more from drugs augmenting descending inhibitory pain control than would patients with a normal modulation pattern of efficient CPM. Thirty patients with painful diabetic neuropathy received 1 week of placebo, 1 week of 30 mg/d duloxetine, and 4 weeks of 60 mg/d duloxetine. Pain modulation was assessed psychophysically, both before and at the end of treatment. Patient assessment of drug efficacy, assessed weekly, was the study’s primary outcome. Baseline CPM was found to be correlated with duloxetine efficacy (r = 0.628, P < .001, efficient CPM is marked negative), such that less efficient CPM predicted efficacious use of duloxetine. Regression analysis (R2 = 0.673; P = .012) showed that drug efficacy was predicted only by CPM (P = .001) and not by pretreatment pain levels, neuropathy severity, depression level, or patient assessment of improvement by placebo. Furthermore, beyond its predictive value, the treatment‐induced improvement in CPM was correlated with drug efficacy (r = −0.411, P = .033). However, this improvement occurred only in patients with less efficient CPM (16.8 ± 16.0 to −1.1 ± 15.5, P < .050). No predictive role was found for TS. In conclusion, the coupling of CPM and duloxetine efficacy highlights the importance of pain pathophysiology in the clinical decision‐making process. This evaluative approach promotes personalized pain therapy.

Postcesarean section pain prediction by preoperative experimental pain assessment.

Background Postcesarean section pain is a common cause of acute pain in obstetrics, yet pain relief and patient satisfaction are still inadequate in many cases. The present study was conducted to determine whether preoperative assessment of experimental pain perception by quantitative sensory tests could predict the level of postcesarean section pain. Methods Fifty-eight women who were scheduled for elective cesarean section were enrolled in the study. Heat pain threshold and magnitude estimation of suprathreshold pain stimuli at 44°–48°C were assessed for both algosity (the sensory dimension of pain intensity) and unpleasantness 1 or 2 days before surgery. The day after the operation, the women reported the level of pain at the surgical wound on a visual analog scale at rest and during activity. Regression analysis was performed to evaluate the usefulness of preoperative scores in predicting postcesarean section pain. Results Postoperative visual analog scale scores at rest and during activity significantly correlated with preoperative suprathreshold pain scores at 44°–48°C (r = 0.31–0.58 for algosity and r = 0.33–0.74 for unpleasantness). The stimulus of 48°C was found to be the best predictor of postoperative pain for both conditions (r = 0.434–0.527;P < 0.01). In contrast to suprathreshold pain stimuli, pain threshold was not correlated with postoperative pain. Conclusions The results show that a simple and quick preoperative test is useful in identifying those women who will experience greater pain after a cesarean section. This test may be suggested for caregivers to tailor the postoperative treatment to specific patient needs and to improve postoperative outcome and patient satisfaction.

Determinants of endogenous analgesia magnitude in a diffuse noxious inhibitory control (DNIC) paradigm: Do conditioning stimulus painfulness, gender and personality variables matter?

&NA; Descending modulation of pain can be demonstrated psychophysically by dual pain stimulation. This study evaluates in 31 healthy subjects the association between parameters of the conditioning stimulus, gender and personality, and the endogenous analgesia (EA) extent assessed by diffuse noxious inhibitory control (DNIC) paradigm. Contact heat pain was applied as the test stimulus to the non‐dominant forearm, with stimulation temperature at a psychophysical intensity score of 60 on a 0–100 numerical pain scale. The conditioning stimulus was a 60 s immersion of the dominant hand in cold (12, 15, 18 °C), hot (44 and 46.5 °C), or skin temperature (33 °C) water. The test stimulus was repeated on the non‐dominant hand during the last 30 s of the conditioning immersion. EA extent was calculated as the difference between pain scores of the two test stimuli. State and trait anxiety and pain catastrophizing scores were assessed prior to stimulation. EA was induced only for the pain‐generating conditioning stimuli at 46.5 °C (p = 0.011) and 12 °C (p = 0.003). EA was independent of conditioning pain modality, or personality, but a significant gender effect was found, with greater EA response in males. Importantly, pain scores of the conditioning stimuli were not correlated with EA extent. The latter is based on both our study population, and on additional 82 patients, who participated in another study, in which EA was induced by immersion at 46.5 °C. DNIC testing, thus, seems to be relatively independent of the stimulation conditions, making it an easy to apply tool, suitable for wide range applications in pain psychophysics.

Women's sexual pain disorders

INTRODUCTION Womens sexual pain disorders include dyspareunia and vaginismus and there is need for state-of-the-art information in this area. AIM To update the scientific evidence published in 2004, from the 2nd International Consultation on Sexual Medicine pertaining to the diagnosis and treatment of womens sexual pain disorders. METHODS An expert committee, invited from six countries by the 3rd International Consultation, was comprised of eight researchers and clinicians from biological and social science disciplines, for the purpose of reviewing and grading the scientific evidence on nosology, etiology, diagnosis, and treatment of womens sexual pain disorders. MAIN OUTCOME MEASURE Expert opinion was based on grading of evidence-based medical literature, extensive internal committee discussion, public presentation, and debate. Results. A comprehensive assessment of medical, sexual, and psychosocial history is recommended for diagnosis and management. Indications for general and focused pelvic genital examination are identified. Evidence-based recommendations for assessment of womens sexual pain disorders are reviewed. An evidence-based approach to management of these disorders is provided. CONCLUSIONS Continued efforts are warranted to conduct research and scientific reporting on the optimal assessment and management of womens sexual pain disorders, including multidisciplinary approaches.

Enhancement of the perception of systemic pain in women with vulvar vestibulitis

Objective The aim of this study was to determine whether the characteristics of systemic pain perception and anxiety differ between women with vulvar vestibulitis and healthy women.

Contact heat-evoked temporal summation: Tonic versus repetitive-phasic stimulation

Abstract Temporal summation (TS) is usually evoked by repetitive mechanical or electrical stimuli, and less commonly by tonic heat pain. The present study aimed to examine the TS induction by repetitive‐phasic versus tonic heat pain stimuli. Using 27 normal volunteers, we compared the extent of summation by three calculation methods: start‐to‐end pain rating difference, percent change, and double‐logarithmic regression of successive ratings along the stimulation. Subjects were tested twice, and the reliability of each of the paradigms was obtained. In addition, personality factors related to pain catastrophizing and anxiety level were also correlated with the psychophysical results. Both paradigms induced significant TS, with similar increases for the repetitive‐phasic and the tonic paradigms, as measured on 0–100 numerical pain scale (from 52.9 ± 11.7 to 80.2 ± 15.5, p < 0.001; and from 38.5 ± 13.3 to 75.8 ± 18.3, p < 0.001, respectively). The extent of summation was significantly correlated between the two paradigms, when calculated by absolute change (r = 0.543, p = 0.004) and by regression (r = 0.438, p = 0.025). Session‐to‐session variability was similar for both paradigms, relatively large, yet not biased. As with other psychophysical parameters, this poses some limitations on TS assessment in individual patients over time. The extent of TS induced by both paradigms was found to be associated with anxiety level and pain catastrophizing. Despite some dissimilarity between the repetitive‐phasic and the tonic paradigms, the many similarities suggest that the two represent a similar physiological process, even if not precisely the same. Future clinical applications of these tests will determine the clinical relevance of the TS paradigms presented in this study.

Psychological Factors Associated with Perception of Experimental Pain in Vulvar Vestibulitis Syndrome

This study assessed the association between pain perception and psychological variables in women with vulvar vestibulitis syndrome (VVS) by comparing 28 VVS women with 50 healthy women. We assessed non genital systemic pain perception with quantitative sensory testing by administering experimental pain stimuli to the forearm. The VVS women demonstrated a lower pain threshold and a higher magnitude estimation of pain, combined with a higher trait anxiety, increased somatization, and a lower body image. Among the VVS women, nonvaginal pain catastrophizing was significantly related to reported pain during coitus. A cluster analysis revealed four subtypes of VVS women, as characterized by levels of pain and personality variables. I suggest implications for the assessment and treatment of women suffering from painful coitus.