The latest medical research on Pain Medicine

The research magnet gathers the latest research from around the web, based on your specialty area. Below you will find a sample of some of the most recent articles from reputable medical journals about pain medicine gathered by our medical AI research bot.

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Electrical Colon Stimulation Reflexively Increases Colonic Activity.

Neuromodulation

Most individuals with spinal cord injury have neurogenic bowel dysfunction, which includes slowed colonic motility and has a significant impact on their health and quality of life. Bowel management typically includes mechanical rectal distension to evoke a recto-colic reflex and promote bowel emptying. Electrical stimulation could replace this mechanical distension. The purpose of this study was to determine the feasibility of evoking colonic activity using electrical stimulation.

Acute experiments were conducted in eight neural-intact cats under chloralose anesthesia. Patterned electrical stimulation was administered via electrodes placed on the surface of the distal colon or proximal colon. Distal and proximal colon pressures were measured using saline-filled balloon catheters. Outcome measures included peak colonic pressure; time to onset of response; and time to peak pressure compared to baseline without stimulation.

Stimulation elicited colonic activity in all animals. Peak colon pressures were 15 ± 28 cmH2 O and were proportional to stimulation amplitudes. Time to onset and time to peak pressure were 13 ± 19 s and 37 ± 49 s, respectively, and were not significantly affected by stimulus parameters. Proximal colon stimulation only resulted in pressure responses from the proximal colon, but distal colon stimulation resulted in both proximal and distal responses in 40% of trials. Adding isoflurane anesthesia removed this proximal response to distal stimulation.

Distal colon stimulation evoked colonic activity. The dependence of this response on stimulation location and anesthesia suggests that responses were reflex mediated. Colonic stimulation may have the potential to improve colonic motility for individuals with neurogenic bowel dysfunction.

Dexamethasone and dexmedetomidine as adjuvants to local anesthetic mixture in intercostal nerve block for thoracoscopic pneumonectomy: a prospective randomized study.

Regional Anesthesia and Pain Medicine

Perineural dexamethasone or dexmedetomidine prolongs the duration of single-injection peripheral nerve block when added to the local anesthetic solution. In a randomized, controlled, double-blinded study in patients undergoing thoracoscopic pneumonectomy, we tested the hypothesis that combined perineural dexamethasone and dexmedetomidine prolonged the duration of analgesia as compared with either perineural dexamethasone or perineural dexmedetomidine after intercostal nerve block (INB).

Eighty patients were randomized to receive INB using 28 mL 0.5% ropivacaine, with 2 mL normal saline (R group), with 10 mg dexamethasone in 2 mL (RS group) or 1 µg/kg dexmedetomidine in 2 mL (RM group), or with 1 µg/kg dexmedetomidine and 10 mg dexamethasone in 2 mL (RSM group) administrated perineurally. The INB was performed by the surgeon under thoracoscopic direct vision; a total of six intercostal spaces were involved, each with an injection of 5 mL. The primary outcome was the duration of analgesia. Secondary outcomes included total postoperative fentanyl consumption, visual analog scale pain score and safety assessment (adverse effects).

The duration of analgesia in RSM (824.2±105.1 min) was longer than that in RS (611.5±133.0 min), RM (602.5±108.5 min) and R (440.0±109.6 min) (p<0.001). Total postoperative fentanyl consumption was lower in RSM (106.0±84.0 µg) compared with RS (243.0±175.2 µg), RM (237.0±98.7 µg) and R (369.0±134.2 µg) (p<0.001). No significant difference was observed in the incidences of adverse effects between the four groups.

The addition of combined perineural dexmedetomidine and dexamethasone to ropivacaine for INB seemed to be an attractive method for prolonged analgesia with almost no adverse effects.

ChiCTR-IOR-17012183.

Pectoral nerve blocks and postoperative pain outcomes after mastectomy: a meta-analysis of randomized controlled trials.

Regional Anesthesia and Pain Medicine

Several studies have evaluated the effect of pectoral nerve blocks to improve postoperative analgesia following breast cancer surgery resulting in contradictory findings. The aim of this study was to examine the effect of Pecs blocks on postoperative analgesia in women following mastectomies.

We performed a quantitative systematic review in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Articles of randomized controlled trials that compared Pecs block (types I and II) to a control group in patients undergoing mastectomy were included. The primary outcome was total opioid consumption 24 hours after surgery. Secondary outcomes included pain scores and side effects. Meta-analysis was performed using the random effect model.

7 randomized controlled trials with 458 patients were included in the analysis. The effect of pectoral nerve blocks on postoperative opioid consumption compared with control revealed a significant effect, weighted mean difference (WMD) (95% CI) of --4.99 (-7.90 to -2.08) mg intravenous morphine equivalents (p=0.001). In addition, postoperative pain compared with control was reduced at 6 hours after surgery: WMD (95% CI) of -0.72 (-1.37 to -0.07), p=0.03, and at 24 hours after surgery: WMD (95% CI) of -0.91 (-1.81 to -0.02), p=0.04.

This quantitative analysis of randomized controlled trials demonstrates that the Pecs block is effective for reducing postoperative opioid consumption and pain in patients undergoing mastectomy. The Pecs block should be considered as an effective strategy to improve analgesic outcomes in patients undergoing mastectomies for breast cancer treatment.

Nocebo Hyperalgesia can be Induced by the Observation of a Model Showing Natural Pain Expressions.

Clin J Pain

Nocebo hyperalgesia is an increase in pain through the expectation of such an increase as a consequence of a sham treatment. Nocebo hyperalgesia can be induced by observation of a model demonstrating increased pain via verbal pain ratings. The aim of the present study was to investigate whether observing natural pain behavior, such as facial pain expressions, can also induce nocebo responses.

Eighty female participants (age: 22.4 y±4.8) underwent a pressure-pain procedure (algometer) on both hands and rated their pain on a numerical rating scale. All participants received ointment on one of their hands, but no explanation was given for this. Before their own participation, the participants watched a video in which a woman underwent the same procedure and who either modeled increased pressure pain upon ointment application (nocebo condition) or showed a neutral facial expression throughout (control condition).

A 2×2 analysis of variance with condition (nocebo; control) as a between-subjects factor and ointment application (with; without) as a within-subject factor revealed a main effect for ointment and a condition×ointment interaction. In the nocebo condition, pain ratings were higher with ointment than without.

For the first time, it was shown that watching a model demonstrating pain through facial expressions induced nocebo hyperalgesia. As we mostly express pain through natural pain behavior rather than through pain ratings, this paradigm extends our knowledge of observational learning about pain and may have implications for contexts in which persons watch others undergo painful procedures.

Sensory Function and Pain Experience in Arthritis, Complex Regional Pain Syndrome, Fibromyalgia Syndrome and Healthy Volunteers: A Cross-sectional Study.

Clin J Pain

This study aimed to identify relationships between sensory function and pain in common pain conditions (Arthritis, Complex Regional Pain Syndrome (CRPS) and Fibromyalgia Syndrome (FMS)) and healthy participants. Sensory abnormalities are known to be concomitant with some types of chronic pain but comparison across pain conditions using existing research is difficult due to methodological differences. Pragmatic Quantitative Sensory Testing (QST) methods were used.

Hot and cold sensitivity, light touch threshold (LTT), two-point discrimination (TPD) and pressure pain threshold (PPT) were assessed in 143 participants (n=37 Healthy, n=34 Arthritis, n=36 CRPS, n=36 FMS). Outcomes were assessed in the index ("affected" or right) and contralateral arm. Participants also completed the Brief Pain Inventory and McGill Pain Questionnaire.

There were statistically significant differences between groups for all QST outcomes except TPD. Relative to healthy participants, FMS displayed heat hyperesthesia in both arms and cold hyperesthesia in the contralateral arm. CRPS demonstrated no changes in thermal sensitivity. Both CRPS and FMS exhibited bilateral pressure hyperalgesia. LTT hypoesthesia was observed bilaterally for CRPS but only in the contralateral arm for FMS. CRPS and FMS had pressure hyperalgesia in the index arm relative to Arthritis patients. There were no differences between Arthritis and Healthy participants for any QST outcome. In CRPS there were significant correlations between LTT and pain outcomes bilaterally.

People with FMS and CRPS demonstrate extensive sensory dysfunction. Arthritis patients had sensory profiles closer to healthy participants. LTT may provide a clinically relevant and accessible assessment for CRPS.

A Subgroup of Chronic Low Back Pain Patients with Central Sensitization.

Clin J Pain

Our knowledge of central sensitization (CS) in chronic low back pain (CLBP) is limited. 2011 fibromyalgia criteria and severity scales (2011 FM survey) has been used to determine FM positive as a surrogate of CS. The major features of CS including widespread hyperalgesia and dysfunction of the descending inhibitory pathways can be identified by pressure pain threshold (PPT) and conditioned pain modulation (CPM) tests. The purpose of the study was to examine neurophysiological characteristics and psychosocial symptoms in a subgroup of FM positive CLBP compared to FM negative CLBP patients.

46 participants with CLBP and 22 healthy controls completed outcome measures of the 2011 FM survey, PPT and CPM tests, and psychosocial questionnaires. Differences between FM positive and FM negative CLBP participants on these measures and correlations were analyzed.

The 2011 FM survey identified 22 (48%) participants with CLBP as FM positive. FM positive CLBP participants showed lower PPT values of the thumbnail (P=0.011) and lower back (P=0.003), lower CPM values of the thumbnail (P=0.002), and more severe pain catastrophizing, anxiety and depression symptoms (P<0.05) than FM negative CLBP participants. The 2011 FM scores were significantly correlated with the PPT and CPM values of the thumbnail and with psychosocial symptoms (P<0.001).

Our findings suggest a subgroup of CLBP patients exhibiting with signs and symptoms of CS. Associations between subjective and objective CS measures indicate that the 2011 FM survey can be utilized to identify the presence of CS in CLBP in clinical practice.

Sleep restriction does not potentiate nocebo-induced changes in pain and cortical potentials.

Eur J Pain

The increased pain sensitivity following reduced sleep may be related to changes in cortical processing of nociceptive stimuli. Expectations shape pain perception and can inhibit (placebo) or enhance (nocebo) pain. Sleep restriction appears to enhance placebo responses; however, whether sleep restriction also affects nocebo responses remains unknown. The aim of the present study was to determine whether sleep restriction facilitates nocebo-induced changes in pain and pain-evoked cortical potentials.

In an experimental study with a crossover design, the sensitivity to electrically induced pain was determined in 53 nurses under two sleep conditions, after habitual sleep and after two consecutive nights at work. Nocebo was induced by conditioning one-third of the pain stimuli. Pain-elicited cortical event-related potentials were recorded by electroencephalography (EEG). Data were analysed both in the time-domain (N2P2 amplitude) and in the time-frequency domain (ERP magnitude). Sleepiness and vigilance were also assessed.

Both nocebo alone and sleep restriction alone increased the sensitivity to electrically induced pain. However, no interaction effect was found. Moreover, the magnitude of the pain-elicited responses increased after sleep restriction and decreased after nocebo expectation, suggesting that nocebo is probably not an underlying mechanism for the commonly observed hyperalgesia induced by sleep restriction.

The present work addresses whether sleep restriction, known to increase the sensitivity of the pain system, facilitates nocebo-induced hyperalgesia. Our findings suggest that this is not the case, indicating that the increased sensitivity of the pain system following nocebo and sleep restriction are mediated by different cortical mechanisms. This article is protected by copyright. All rights reserved.

Exercise-induced hypoalgesia in young adult females with long-standing patellofemoral pain - A randomized crossover study.

Eur J Pain

Patellofemoral pain (PFP) is a common knee pain condition where hip and knee exercises help improve treatment outcomes. This study compared the acute effect of hip versus knee exercises on anti-nociceptive and pro-nociceptive mechanisms in young females with long-standing PFP.

In this randomized cross-over study, 29 females with PFP performed hip and knee exercises in randomized order during a single day. Pressure pain thresholds (PPTs) were assessed by handheld pressure algometry at the patella, the tibialis anterior muscle, and the contralateral elbow. Cuff pressure algometry at the lower legs was used to assess pain detection threshold (cPDT) and tolerance (cPTT) as well as conditioned pain modulation (CPM: change in cPDT during contralateral cuff pain conditioning) and temporal summation of pain (TSP: ten painful cuff stimulations assessed on a visual analogue scale [VAS]).

PPTs at the tibialis anterior muscle but not at the patella increased compared with baseline following both exercises (p < .002). Compared with baseline, the cPDTs and cPTTs increased after both types of exercises (p < .001). The cPTTs increased more after knee compared to hip exercises (p < .007). VAS scores for TSP were increased following hip exercises (p < .001) although the rate of VAS increase over repeated stimulations was not significantly affected by exercises. The CPM-effect was reduced after both types of exercises (p < .001).

A general hypoalgesic response to slowly increasing pressure stimuli was observed following both hip and knee exercises as well as decreased conditioned pain modulation, potentially indicating an attenuated ability from exercise to inhibit pain.

Sympathetic efferent neurons are less sensitive than nociceptors to 4 Hz sinusoidal stimulation.

Eur J Pain

Sinusoidal current stimuli preferentially activate C-nociceptors. Sodium channel isoforms NaV1.7 and NaV1.8 have been implicated in this. Sympathetic efferent neurons lack NaV1.8 and were explored upon sinusoidal activation.

Quantitative Sudomotor Axon Reflex Test (QSART) was performed in hairy (n=16) and glabrous (n=12) skin. Responses of sympathetic efferents (n=10) and nociceptive afferents (n=21) to sinusoidal current stimulation (4 Hz, 0.05 - 0.15 mA) were recorded in humans by microneurography (n=11). Activation of sympathetic units upon supra-threshold sinusoidal currents (> 0.8 mA) was recorded in pigs (n=8).

Sinusoidal stimuli (4 Hz, 0.4 mA) evoked weak sweat output (30 ml/h/m2 ) in hairy skin compared to rectangular pulses (4 Hz, 5 mA, 53 ml/h/m2 , p < 0.00001, ANOVA). No change in sweat output was recorded from glabrous skin to sine wave stimuli. Sinusoidal current at intensities ranging from 0.05 - 0.15 mA activated almost all (85%) nociceptors but only 40% of sympathetic units in human. Stimuli lead to a significantly lower activation in sympathetic vs. nociceptive fibers as measured by activity dependent slowing (ADS) of conduction (sympathetic efferents average ADS 100 ± 0.2% vs. C-nociceptors average ADS 113 ± 4%, p < 0.003, ANOVA).

Sympathetic efferent neurons are less apt to convert slow depolarizations into action potentials as compared to nociceptors. Distinctive sodium channel expression patterns between nociceptors and sympathetic efferent neurons may account for this difference. Sinusoidal stimulation therefore provokes weak sweat responses and provides no alternative for clinical assessment of autonomic function. This article is protected by copyright. All rights reserved.

Exercise in Parkinson's disease: experimental-induced pain sensitivity is reduced already after short term training.

Eur J Pain

This journal recently published a paper by Nguy et al. titled 'Exercise induced hypoalgesia is present in people with Parkinson's disease: two obse...

Comment on "Sándor Márai and painful Guillain-Barré syndrome" by Alamos et al.

Eur J Pain

Alamos et al. (2019) discuss Hungarian author Sándor Márai's description of pain in Guillain-Barré syndrome (GBS) in his novel "The Sister" (1946) ...

The responsiveness and interpretability of psychosocial patient-reported outcome measures in chronic musculoskeletal pain rehabilitation.

Eur J Pain

For several widely-used patient-reported outcome measures (PROMs) in chronic musculoskeletal pain (CMSP) rehabilitation, it is still not known whether they are responsive to change, and what the smallest detectable change (SDC) and minimal clinically important change (MCIC) are. Knowledge of these values can be used to accurately interpret change scores in research and clinical practice.

In this retrospective cohort study, the responsiveness, the SDC, and the MCIC of the mental components of the Research and Development 36-Item Health Survey (RAND-36), the Pain Catastrophizing Scale (PCS), and the Tampa Scale of Kinesiophobia (TSK) were investigated in CMSP patients. Responsiveness, the SDC, and MCIC were determined by using both anchor and distribution-based methods.

For all outcome measures, there was a progression from smallest to largest mean change scores between participants who did not perceive change and those who reported change after treatment. However, correlations of the Global Perceived Effect (GPE) with the change scores on the outcome measures were low. For all outcome measures, the SDC was larger than the MCIC.

For this population, the questionnaires were shown not to be responsive. Furthermore, the questionnaires appeared not to be able to distinguish clinically important change from measurement error in individual patients. The finding of large measurement errors of PROMs is in line with previous research in pain rehabilitation. Using generic PROMs only, to examine changes in psychosocial status due to a pain rehabilitation programme, is therefore questionable. This article is protected by copyright. All rights reserved.