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Biomedical subjects

Serge Marchand

Publications and source records attributed to Serge Marchand.

At least 19 recordsLinked to original sources
PubMed2007

Descending analgesia--when the spine echoes what the brain expects.

Changes in pain produced by psychological factors (e.g., placebo analgesia) are thought to result from the activity of specific cortical regions. However, subcortical nuclei, including the periaqueductal gray and the rostroventral medulla, also show selective activation when subjects expect pain relief. These brainstem regions send inhibitory projections to the spine and produce diffuse analgesic responses. Regrettably the precise contribution of spinal mechanisms in predicting the strength of placebo analgesia is unknown. Here, we show that expectations regarding pain radically change the strength of spinal nociceptive responses in humans. We found that contrary to expectations of analgesia, expectations of hyperalgesia completely blocked the analgesic effects of descending inhibition on spinal nociceptive reflexes. Somatosensory-evoked brain potentials and pain ratings further confirmed changes in spino-thalamo-cortical responses consistent with expectations and with changes in the spinal response. These findings provide direct evidence that the modulation of pain by expectations is mediated by endogenous pain modulatory systems affecting nociceptive signal processing at the earliest stage of the central nervous system. Expectation effects, therefore, depend as much about what takes place in the spine as they do about what takes place in the brain. Furthermore, complete suppression of the analgesic response normally produced by descending inhibition suggests that anti-analgesic expectations can block the efficacy of pharmacologically valid treatments which has important implications for clinical practice.

Adult↗
PubMed2006

Effects of training on general practitioners' management of pain in osteoarthritis: a randomized multicenter study.

OBJECTIVE: To evaluate the effects of a short interactive training program for general practitioners (GP) on pain management in patients with osteoarthritis (OA). METHODS: A multicenter, parallel-group study. GP were randomized to receive training on relationships and communication, pain evaluation, prescription, and negotiation of a patient contract or to a control group receiving a presentation about obtaining consent in trials. Outcomes were patient assessments of pain and functional ability. We invited 1500 GP to take part in the study. Those who volunteered to receive the training recruited outpatients from May 2001 to April 2002. Patients participating in the evaluation of the effects of the general practitioners' training had lower limb OA and pain on motion [> or = 40 mm on a visual analog scale (VAS)] and had indications for treatment with acetaminophen. The primary endpoint: sum of patient pain relief based on the daily VAS self-evaluation during the 2 weeks of the trial. RESULTS: In total, 180 GP (84 trained, 96 nontrained) enrolled 842 patients (414 and 428, respectively). Mean baseline VAS pain was 63 +/- 14 mm. Patients in the trained-GP group had better overall pain relief (316 +/- 290 mm/day vs 265 +/- 243 mm; p < 0.0001), greater improvement in Lequesne and WOMAC scores (p < 0.0001), and better overall perception of treatment (p = 0.002). Acetaminophen use was slightly higher in the trained group; however, the difference in pain relief remained statistically significant (p = 0.0003) after adjustment for this difference. CONCLUSION: This is the first study to demonstrate a positive effect of physician training on patients with a painful condition.

Aged↗
PubMed2006

Endogenous pain inhibitory systems activated by spatial summation are opioid-mediated.

We previously developed a spatial summation model and demonstrated that spatial summation of pain involves the activation of both excitatory and inhibitory systems. The aim of this study was to determine whether the endogenous pain inhibitory systems recruited by the spatial summation model are opioid-mediated by verifying if they could be blocked by the opioid antagonist naloxone. Twenty healthy volunteers (10 men, 10 women) participated in a randomized, four-session, cross-over study. Each session consisted of pain perception ratings (visual analog scale) taken during the immersion of different surfaces of the arm in circulating noxious cold water (12 degrees C). The arm was arbitrarily divided into eight segments from fingertips to shoulder. Two sessions were increasing (from fingertips to shoulder) and two sessions were decreasing (from shoulder to fingertips). All sessions consisted of eight consecutive 2-min immersions separated by 5-min resting periods. Intravenous injections of naloxone hydrochloride (0.14 mg/kg) or saline (NaCl, 0.9%) were administered under double-blind conditions. We found that during the control session (saline injection) there was a significant difference in pain intensity ratings between the increasing and decreasing sessions. The decreasing session resulted in lower pain intensity. As previously demonstrated, this lowering of the perception curve seems to be due to a large recruitment of inhibitory systems at the beginning of the decreasing session as opposed to a gradual recruitment during the increasing session. However, during the opioid inhibition session (naloxone injection) no differences were found between the increasing and decreasing sessions. Naloxone inhibited the endogenous pain inhibitory systems activated by the spatial summation model, suggesting that these systems have an opioid-mediated component, as previously reported for diffuse noxious inhibitory controls.

Adult↗
PubMed2006

Direct comparison of placebo effects on clinical and experimental pain.

OBJECTIVES: Placebo effects have been suggested to be more potent on clinical than experimental pain. However, this proposition is based on the comparison of the magnitude of placebo analgesia between studies using different methodologies or between different groups of subjects within the same study. The authors sought to provide a more direct test of this hypothesis using a within-subject design and to investigate the potential mediating effect of expectancy. METHOD: Sixteen patients with low back pain rated the intensity and the unpleasantness of their clinical pain and underwent two cold pressor tests, both before and after a saline injection presented either as a potent painkiller (placebo treatment) in one session or as an inactive substance in a control session. RESULTS: The placebo treatment produced comparable increases in expected relief for clinical and experimental pain. However, ratings of pain intensity, pain unpleasantness, and perceived relief confirmed the larger placebo effect in low back pain than cold pressor pain. Retrospective ratings of perceived relief in low back pain generally showed the largest placebo effect compared with concurrent pain ratings. Furthermore, when the placebo session was performed after the control session, the placebo effect on low back pain was substantially reduced and observed only in perceived relief. Variations in expectation could not account for the large difference in placebo analgesia between clinical and experimental pain. CONCLUSIONS: The important reduction in placebo analgesia in low back pain after the single pre-exposure to the ineffective control treatment suggests the additional involvement of highly flexible mechanisms that may counteract the pro-analgesic effects of expectations.

Adolescent↗
PubMed2006

Different autonomic responses to experimental pain in IBS patients and healthy controls.

BACKGROUND: Pain perception ratings in irritable bowel syndrome (IBS) patients suggest that they present either hypoalgesia or hyperalgesia. However, little is known about the physiologic responses these patients present to a somatic painful stimulus. GOALS: The main goal of this project was to study autonomic nervous system responses and the cardiac response to experimental pain in IBS patients. STUDY: This was addressed by exposing 27 women, 14 IBS, and 13 healthy controls (HCs), to a cold water (7 degrees C) immersion test of the forefoot for 2 minutes. Pain perception, galvanic skin responses (GSR), and heart rate (HR) were monitored during and after the immersion. RESULTS: For comparable pain perception, a significant group difference (P<0.02) in the cardiac response was observed during the immersion where the peak rise in HR was much higher for HCs, reaching 22%, whereas it only reached 8% for IBS patients. Moreover, HR variability analysis demonstrated that IBS and HCs had opposite autonomic cardiac reactivity to pain, where IBS had increased parasympathetic/decreased sympathetic reactivity. CONCLUSIONS: For comparable pain perception, IBS subject demonstrated different autonomic nervous system response to pain, which supports the view of autonomic dysregulation in IBS.

Adult↗
PubMed2005

Sex differences in cardiac and autonomic response to clinical and experimental pain in LBP patients.

Rehabilitation professionals are currently using heart rate (HR) in order to assess the sincerity of effort in certain evaluations. It has been shown that a relation exists between HR and pain but no study has measured cardiac response during both clinical and experimental pain among a patient population using an intra-subject design. Thirty patients with low back pain (LBP) participated in this study including 16 men. Clinical pain was induced by applying a postero-anterior pressure (PA) on a painful lumbar segment for 15 and 30s in order to reproduce the patient's typical LBP at an intensity ranging between 50 and 70/100. Experimental pain was induced with a 15s thermal stimulus at a temperature which reproduced the same pain intensity as the 15s PA. For both reproduced clinical pain durations, we observed a rise in HR ranging between 8.5% and 12.67%. However, unlike men, women's cardiac response failed to show a constant rise in HR during the 30s PA. For all subjects, the rise in HR was much lower during the experimental pain condition (p<0.001), reaching only 5%. On the other hand, galvanic skin responses were significantly higher during the experimental pain condition (p<0.001). During this same condition, women also had a greater rise in galvanic skin responses than men (p=0.04). Finally, a significant correlation was found between both types of pain. These results suggest that pain induced during a clinical evaluation will produce a significant HR augmentation. However, heart rate variability analysis showed greater sympathetic cardiac regulation for men. The sex differences observed in this study call for caution when interpreting HR during pain assessment.

Adult↗
PubMed2005

Specificity of female and male sex hormones on excitatory and inhibitory phases of formalin-induced nociceptive responses.

Several factors have been proposed to account for the differences observed between men and women in pain perception. One of these is female and male gonadal hormones. In order to verify this assumption, a hormone replacement (pellets inserted subcutaneously) of (1) 17beta-estradiol, (2) progesterone, (3) 17beta-estradiol + progesterone or (4) testosterone have been performed in gonadectomized female and male Sprague-Dawley rats. Twenty-one days after the hormonal replacement, a formalin test was performed. The nociceptive responses were divided in three distinct phases: acute (phase I), inhibitory (interphase) and tonic (phase II). After analysis, we observed that testosterone has a hypoalgesic effect on phases I and II of the formalin test. At the opposite, female hormones act only on the interphase: the combination of 17beta-estradiol and progesterone in gonadectomized rats reestablishes the weaker nociceptive pain reduction during the interphase as it is observed in the intact female. These effects were not gender specific since they had the same action in female and male. Our results permit to believe that testosterone plays a protective role in pain perception. Moreover, the female hormones act mainly on pain inhibition mechanisms (interphase), suggesting that the prevalence of certain chronic pain conditions in women could be related to a deficit of these pain inhibitory mechanisms rather than an increased nociceptive activity.

Analysis of Variance↗
PubMed2005

Randomized controlled trial on low level laser therapy (LLLT) in the treatment of osteoarthritis (OA) of the hand.

BACKGROUND AND OBJECTIVES: Low level laser therapy (LLLT) offers promising symptomatic relief of osteoarthritic (OA) pain. We examined efficacy of active LLLT versus sham LLLT on finger joints and three superficial nerves. STUDY DESIGN/MATERIALS AND METHODS: OA-patients randomly assigned, received three treatments per week for 6 weeks of LLLT (n = 42) or sham LLLT (n = 46). RESULTS: Pain relief, morning stiffness, and functional status did not significantly improve for LLLT versus placebo. No significant differences were found in finger range of motion, except carpometacarpal opposition (P = 0.011), grip strength, and patient global assessment which improved for active LLLT participants (P = 0.041). CONCLUSIONS: LLLT is no better than placebo at reducing pain, morning stiffness, or improving functional status for OA-hand patients.

Aged↗
PubMed2005

Training the next generation of researchers in work disability prevention: the Canadian Work Disability Prevention CIHR Strategic Training Program.

INTRODUCTION: There is a need to create, disseminate, and implement new knowledge in the work disability prevention (WDP) field. Training programs attracting high-quality applicants and taking into account the complexity of this emerging field are urgently needed. METHODS: An advanced training program, funded by the Canadian Institutes of Health Research (CIHR), was developed by 24 mentors affiliated with nine different universities. The main objective of this program is to develop transdisciplinary knowledge, skills, and attitudes regarding WDP. This program has been developed for PhD students or post-doctoral fellows already registered full-time in a Canadian or recognized foreign university whose main interest is WDP, regardless of the health problem. RESULTS: Since its implementation, the program received two successive cohorts of 10 students. They were registered in 13 universities in five countries and trained in nine different disciplines. CONCLUSIONS AND SIGNIFICANCES: Appropriate WDP research may save major societal costs attributable to prolonged work disability. The proposed training program will contribute to developing tomorrow's research workforce.

Attitude of Health Personnel↗
PubMed2005

Establishing a link between heart rate and pain in healthy subjects: a gender effect.

UNLABELLED: Heart rate (HR) is currently used by rehabilitation clinicians as a complementary objective measure of pain. The premise is that, as pain increases, HR should also increase. However, this relationship is not clearly established. The goal of this study was to verify the relationship between HR and pain perception. Thirty-nine healthy volunteers participated in this experimental study. Painful stimuli were induced by a 2-minute immersion of the hand in hot water (47 degrees C). HR was recorded before and during the stimulation and was matched to a pain rating. We observed a rise of 11% in HR after 2 minutes of immersion. There was a significant intrasubject correlation between HR and pain intensity (r = 0.50, P < .001) and pain unpleasantness (r = 0.55, P < .001). Furthermore, there was a strong gender effect in the intersubject correlations. Men presented a strong correlation between mean HR and mean pain perception (intensity: r = 0.77, unpleasantness: r = 0.86), whereas this relationship was absent in women (intensity: r = -0.2, unpleasantness: r = 0.001). In conclusion, results show that, for healthy volunteers, experimental pain can elicit a rise in HR up to 11%. Moreover, the relationship between HR response and pain is gender related. Considering that a positive relationship between HR and pain perception was only found in men, these results do not support a clinical significance of the use of HR for pain evaluation in women. Clinical implications need to be further evaluated with patients before clinicians can use HR as a complementary tool in pain assessment. PERSPECTIVE: A positive correlation between HR and pain was observed for men but not for women. These differences underline the importance of taking into account gender differences in the development of complementary pain assessment. Further research should be conducted to verify the role of sex hormones on heart rate and pain.

Adult↗
PubMed2005

Widespread pain in fibromyalgia is related to a deficit of endogenous pain inhibition.

A deficit of endogenous pain inhibitory systems has been suggested to contribute to some chronic pain conditions, one of them being fibromyalgia. The aim of the investigation was to test whether endogenous pain inhibitory systems were activated by a spatial summation procedure in 30 fibromyalgia, 30 chronic low back pain, and 30 healthy volunteers who participated in a cross-over trial (two sessions). Each session consisted of visual analog scale ratings of pain during the immersion of different surfaces of the arm in circulating noxious cold (12 degrees C) water. The arm was arbitrarily divided into eight segments from the fingertips to the shoulder. One session was ascending (from the fingertips to the shoulder) and the other was descending (from the shoulder to the fingertips); they included eight consecutive 2-min immersions separated by 5-min resting periods. For healthy and low back pain subjects, pain was perceived differently during the ascending and descending sessions (P=0.0001). The descending session resulted in lower pain intensity and unpleasantness. This lowering of the perception curve seems to be due to a full recruitment of inhibitory systems at the beginning of the descending session as opposed to a gradual recruitment during the ascending session. For fibromyalgia subjects, no significant differences were found between the increasing and decreasing sessions (P>0.05). These data support a deficit of endogenous pain inhibitory systems in fibromyalgia but not in chronic low back pain. The treatments proposed to fibromyalgia patients should aim at stimulating the activity of those endogenous systems.

Adult↗
PubMed2003

Analgesic and placebo effects of thalamic stimulation.

Numerous clinical studies have reported successful relief of chronic pain with sensory thalamic stimulation. However, even with the extensive use of sensory thalamic stimulation as a clinical tool in the relief of chronic pain, the results are still inconsistent. This discrepancy could probably be explained by the fact that the majority of these studies are case reports or retrospective analyses, which have often used imprecise pain measurements that do not allow a rigorous statistical evaluation of pain relief. None of these studies measured the effect of stimulation on clinical pain for longer than a few hours per day, which is an important aspect considering that clinical pain can vary over time. Moreover, placebo controls are seldom included. In the current study, we measured patients' pain perception at home over a 2-week period, both during days of normal stimulation of the sensory thalamus and during days without stimulation. Patients also came to the laboratory to assess the effects of thalamic and placebo stimulation on clinical pain, experimental heat pain, innocuous air puff and visual stimulation. A potential relation between the perceived paresthesia and analgesic efficacy during thalamic and placebo stimulation was also explored. We found that thalamic stimulation significantly affected clinical and experimental pain perception, but that an important placebo component also exists. On the other hand, neither thalamic nor placebo stimulation affected air puff and visual ratings, suggesting that the effect applies specifically to pain and hence is not caused by a general change in attention. The level of paresthesia elicited during the placebo manipulation was also directly correlated with the degree of placebo pain relief. These results suggest that thalamic stimulation produces a small but significant reduction in pain perception, but that a significant placebo effect also exists.

Adult↗
PubMed2002

The role of sex hormones on formalin-induced nociceptive responses.

Many chronic pain conditions are more frequent in women than in men. This observation suggests that there is a potential role of sex hormones on pain perception. In the present study, we measured nociceptive responses to the formalin test in normal and gonadectomized male and female rats. The nociceptive responses to formalin injection were divided in four phases: acute (phase I), interphase and late phases (phases II and III). Four groups of rats were tested: (a) males (n = 15), (b) females (n = 16), (c) ovariectomized females (OVX) (n = 15) and (d) castrated males (CAST) (n = 15). Females presented significantly more nociceptive responses than males during phase I, interphase and phase II (P < 0.01). They also presented significantly more nociceptive responses than OVX females during the interphase (P < 0.05). CAST males presented significantly more nociceptive responses during the phases I (P < 0.01), II (P < 0.01) and III (P < 0.05) than the male rats. Finally, the responses of CAST males and OVX females were virtually identical, suggesting that the differences recorded between males and females in the formalin test were related to an activational effect of the sex hormones rather than an organizational effect. In conclusion, these results permit the support of the role of sex hormones on the modulation of pain perception. Interestingly, male and female sex hormones seem to act specifically on the different phases of the formalin test, suggesting some specific roles for sex hormones in different pain conditions.

Animals↗
PubMed2002

Odors modulate pain perception: a gender-specific effect.

Odors naturally provoke emotions that are pleasant or unpleasant. Prior studies have demonstrated the effects of pleasing odors on cognition and mood perception, but no studies have reported if they influence pain perception. In the present study, we measured the effect of, and relationship between, different odors on mood and experimental pain perception. Results show that odors significantly influence mood in both women and men. Compared to a neutral odor, pleasant odors produced a positive mood while unpleasant odors produced a negative mood. However, the effect of odor on pain was gender specific, as only women experienced the effects of odor on pain perception. Because no relationship was found between mood and pain perception, it could suggest that different mechanisms are involved in the emotional aspects of mood and pain perception. These results and their potential clinical implications are discussed.

Adolescent↗
PubMed2002

Efficacy of the transcutaneous electrical nerve stimulation for the treatment of chronic low back pain: a meta-analysis.

BACKGROUND: Low back pain affects a large proportion of the population. Transcutaneous electrical nerve stimulation (TENS) was introduced more than 30 years ago as an alternative therapy to pharmacologic treatments for chronic pain. However, despite its widespread use, the efficacy of TENS is still controversial. PURPOSE: The aim of this meta-analysis was to determine the efficacy of TENS in the treatment of chronic low back pain. METHODS: The authors searched MEDLINE, EMBASE, PEDro, and the Cochrane Controlled Trials Register up to June 1, 2000. Only randomized controlled clinical trials of TENS for the treatment of patients with a clinical diagnosis of chronic low back pain were included. Abstracts were excluded unless further data could be obtained from the authors. Two reviewers independently selected trials and extracted data using predetermined forms. DATA ANALYSIS: Heterogeneity was tested with Cochrane's Q test. A fixed effects model was used throughout for continuous variables, except where heterogeneity existed, in which case, a random effects model was used. Results are presented as weighted mean differences with 95% confidence intervals, where the difference between the treated and control groups was weighted by the inverse of the variance. Standardized mean differences were calculated by dividing the difference between the treated and control by the baseline variance. Standardized mean differences were used when different scales were integrated to measure the same concept. Dichotomous outcomes were analyzed with odds ratios. MAIN RESULTS: Five trials were included, with 170 subjects randomized to the placebo group receiving sham TENS and 251 subjects receiving active TENS (153 for conventional mode, 98 for acupuncture-like TENS). The schedule of treatments varied greatly between studies ranging from one treatment/day for 2 consecutive days, to three treatments/day for 4 weeks. There were no statistically significant differences between the active TENS group compared with the placebo TENS group for any outcome measures. Subgroup analysis performed on TENS application and methodologic quality did not demonstrate a significant statistical difference (P > 0.05). Remaining preplanned subgroup analysis was not conducted because of the small number of included trials and the variety of outcome measures reported. CONCLUSION: The results of the meta-analysis present no evidence to support the use or nonuse of TENS alone in the treatment of chronic low back pain. Considering the small number of studies responding to the criteria to be included in this meta-analysis, it is clear that more appropriately designed studies are needed before a final conclusion. Clinicians and researchers should consistently report the characteristics of the TENS device and the application techniques used. New trials on TENS should make use of standardized outcome measures. This meta-analysis lacked data on how TENS efficacy is affected by four important factors: type of applications, site of application, treatment duration of TENS, and optimal frequencies and intensities.

Adult↗
PubMed2002

Spatial summation for pain perception: interaction of inhibitory and excitatory mechanisms.

To study the relation between size of the surface stimulated and perceived pain intensity (spatial summation effect), subjects sequentially immersed predetermined segments of the surface of their arm, between the fingertips and the shoulder, in circulating nociceptive hot water. Immersion sessions were of three types: (i) increasing session (immersion beginning at fingertips and increasing to shoulder); (ii) decreasing session (immersion beginning at shoulder and decreasing to fingertips); and (iii) whole arm+increasing session (preliminary immersion of the whole arm up to shoulder, followed by an increasing session from fingertips to shoulder). Results showed a positive spatial summation effect (pain perception positively correlated to the size of the surface stimulated) during both the decreasing session and the whole arm+increasing session. However, no spatial summation effect was found during the increasing session (fingertips to shoulder). In addition, pain perceived for a surface area was less intense during the decreasing session compared to the increasing session. One possible explanation for the lack of a spatial summation effect during the increasing session is that inhibitory mechanisms are gradually recruited at the same time as excitatory afferences, thus 'cancelling out' any measurable spatial summation effect. The results obtained during the decreasing session and the whole arm+increasing session may be explained by inhibitory mechanisms being fully recruited at the beginning of the session with the immersion of the largest surface area (whole arm). The results are a shift of the pain perception curve and a positive relation between the surface stimulated and pain perception.

Adolescent↗
PubMed1993

Is TENS purely a placebo effect? A controlled study on chronic low back pain.

Although high-frequency low-intensity transcutaneous electric nerve stimulation (TENS) has been extensively used to relieve low back pain, experimental studies of its effectiveness have yielded contradictory findings mainly due to methodological problems in pain evaluation and placebo control. In the present study, separate visual analog scales (VAS) were used to measure the sensory-discriminative and motivational-affective components of low back pain. Forty-two subjects were randomly assigned to 1 of 3 groups: TENS, placebo-TENS, and no treatment (control). In order to measure the short-term effect of TENS, VAS pain ratings were taken before and after each treatment session. Also, to measure long-term effects, patients rated their pain at home every 2 h throughout a 3-day period before and 1 week, 3 months and 6 months after the treatment sessions. In comparing the pain evaluations made immediately before and after each treatment session, TENS and placebo-TENS significantly reduced both the intensity and unpleasantness of chronic low back pain. TENS was significantly more efficient than placebo-TENS in reducing pain intensity but not pain unpleasantness. TENS also produced a significant additive effect over repetitive treatment sessions for pain intensity and relative pain unpleasantness. This additive effect was not found for placebo-TENS. When evaluated at home, pain intensity was significantly reduced more by TENS than placebo-TENS 1 week after the end of treatment, but not 3 months and 6 months later. At home evaluation of pain unpleasantness in the TENS group was never different from the placebo-TENS group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗