Transition from acute to chronic pain after surgery

Over the past decade there has been an increasing reliance on strong opioids to treat acute and chronic pain, which has been associated with a rising epidemic of prescription opioid misuse, abuse, and overdose-related deaths. Deaths from prescription opioids have more than quadrupled in the USA since 1999, and this pattern is now occurring globally. Inappropriate opioid prescribing after surgery, particularly after discharge, is a major cause of this problem. Chronic postsurgical pain, occurring in approximately 10% of patients who have surgery, typically begins as acute postoperative pain that is difficult to control, but soon transitions into a persistent pain condition with neuropathic features that are unresponsive to opioids. Research into how and why this transition occurs has led to a stronger appreciation of opioid-induced hyperalgesia, use of more effective and safer opioid-sparing analgesic regimens, and non-pharmacological interventions for pain management. This Series provides an overview of the epidemiology and societal effect, basic science, and current recommendations for managing persistent postsurgical pain. We discuss the advances in the prevention of this transitional pain state, with the aim to promote safer analgesic regimens to better manage patients with acute and chronic pain.

An Evidence-based Guideline for prehospital analgesia in trauma

BACKGROUND

The management of acute traumatic pain is a crucial component of prehospital care and yet the assessment and administration of analgesia is highly variable, frequently suboptimal, and often determined by consensus-based regional protocols.

OBJECTIVE

To develop an evidence-based guideline (EBG) for the clinical management of acute traumatic pain in adults and children by advanced life support (ALS) providers in the prehospital setting. Methods. We recruited a multi-stakeholder panel with expertise in acute pain management, guideline development, health informatics, and emergency medical services (EMS) outcomes research. Representatives of the National Highway Traffic Safety Administration (sponsoring agency) and a major children's research center (investigative team) also contributed to the process. The panel used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology to guide the process of question formulation, evidence retrieval, appraisal/synthesis, and formulation of recommendations. The process also adhered to the National Prehospital Evidence-Based Guideline (EBG) model process approved by the Federal Interagency Council for EMS and the National EMS Advisory Council.

RESULTS

Four strong and three weak recommendations emerged from the process; two of the strong recommendations were linked to high- and moderate-quality evidence, respectively. The panel recommended that all patients be considered candidates for analgesia, regardless of transport interval, and that opioid medications should be considered for patients in moderate to severe pain. The panel also recommended that all patients should be reassessed at frequent intervals using a standardized pain scale and that patients should be re-dosed if pain persists. The panel suggested the use of specific age-appropriate pain scales.

CONCLUSION

GRADE methodology was used to develop an evidence-based guideline for prehospital analgesia in trauma. The panel issued four strong recommendations regarding patient assessment and narcotic medication dosing. Future research should define optimal approaches for implementation of the guideline as well as the impact of the protocol on safety and effectiveness metrics.

Non-pharmacological management of infant and young child procedural pain

BACKGROUND

Infant acute pain and distress is commonplace. Infancy is a period of exponential development. Unrelieved pain and distress can have implications across the lifespan.  This is an update of a previously published review in the Cochrane Database of Systematic Reviews, Issue 10 2011 entitled 'Non-pharmacological management of infant and young child procedural pain'.

OBJECTIVES

To assess the efficacy of non-pharmacological interventions for infant and child (up to three years) acute pain, excluding kangaroo care, and music. Analyses were run separately for infant age (preterm, neonate, older) and pain response (pain reactivity, immediate pain regulation). 

SEARCH METHODS

For this update, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (Issue 2 of 12, 2015), MEDLINE-Ovid platform (March 2015), EMBASE-OVID platform (April 2011 to March 2015), PsycINFO-OVID platform (April 2011 to February 2015), and CINAHL-EBSCO platform (April 2011 to March 2015). We also searched reference lists and contacted researchers via electronic list-serves. New studies were incorporated into the review. We refined search strategies with a Cochrane-affiliated librarian. For this update, nine articles from the original 2011 review pertaining to Kangaroo Care were excluded, but 21 additional studies were added.

SELECTION CRITERIA

Participants included infants from birth to three years. Only randomised controlled trials (RCTs) or RCT cross-overs that had a no-treatment control comparison were eligible for inclusion in the analyses. However, when the additive effects of a non-pharmacological intervention could be assessed, these studies were also included. We examined studies that met all inclusion criteria except for study design (e.g. had an active control) to qualitatively contextualize results. There were 63 included articles in the current update.

DATA COLLECTION AND ANALYSIS

Study quality ratings and risk of bias were based on the Cochrane Risk of Bias Tool and GRADE approach. We analysed the standardized mean difference (SMD) using the generic inverse variance method.

MAIN RESULTS

Sixty-three studies, with 4905 participants, were analysed. The most commonly studied acute procedures were heel-sticks (32 studies) and needles (17 studies). The largest SMD for treatment improvement over control conditions on pain reactivity were: non-nutritive sucking-related interventions (neonate: SMD -1.20, 95% CI -2.01 to -0.38) and swaddling/facilitated tucking (preterm: SMD -0.89; 95% CI -1.37 to -0.40). For immediate pain regulation, the largest SMDs were: non-nutritive sucking-related interventions (preterm: SMD -0.43; 95% CI -0.63 to -0.23; neonate: SMD -0.90; 95% CI -1.54 to -0.25; older infant: SMD -1.34; 95% CI -2.14 to -0.54), swaddling/facilitated tucking (preterm: SMD -0.71; 95% CI -1.00 to -0.43), and rocking/holding (neonate: SMD -0.75; 95% CI -1.20 to -0.30). Fifty two of our 63 trials did not report adverse events. The presence of significant heterogeneity limited our confidence in the findings for certain analyses, as did the preponderance of very low quality evidence.

AUTHORS' CONCLUSIONS

There is evidence that different non-pharmacological interventions can be used with preterms, neonates, and older infants to significantly manage pain behaviors associated with acutely painful procedures. The most established evidence was for non-nutritive sucking, swaddling/facilitated tucking, and rocking/holding. All analyses reflected that more research is needed to bolster our confidence in the direction of the findings. There are significant gaps in the existing literature on non-pharmacological management of acute pain in infancy.

Factors Associated With Acute Pain Estimation, Postoperative Pain Resolution, Opioid Cessation, and Recovery: Secondary Analysis of a Randomized Clinical Trial

Importance

Acute postoperative pain is associated with the development of persistent postsurgical pain, but it is unclear which aspect is most estimable.

Objective

To identify patient clusters based on acute pain trajectories, preoperative psychosocial characteristics associated with the high-risk cluster, and the best acute pain predictor of remote outcomes.

Design, Setting, and Participants

A secondary analysis of the Stanford Accelerated Recovery Trial randomized, double-blind clinical trial was conducted at a single-center, tertiary, referral teaching hospital. A total of 422 participants scheduled for thoracotomy, video-assisted thoracoscopic surgery, total hip replacement, total knee replacement, mastectomy, breast lumpectomy, hand surgery, carpal tunnel surgery, knee arthroscopy, shoulder arthroplasty, or shoulder arthroscopy were enrolled between May 25, 2010, and July 25, 2014. Data analysis was performed from January 1 to August 1, 2018.

Interventions

Patients were randomized to receive gabapentin (1200 mg, preoperatively, and 600 mg, 3 times a day postoperatively) or active placebo (lorazepam, 0.5 mg preoperatively, inactive placebo postoperatively) for 72 hours.

Main Outcomes and Measures

A modified Brief Pain Inventory prospectively captured 3 surgical site pain outcomes: average pain and worst pain intensity over the past 24 hours, and current pain intensity. Within each category, acute pain trajectories (first 10 postoperative pain scores) were compared using a k-means clustering algorithm. Fifteen descriptors of acute pain were compared as predictors of remote postoperative pain resolution, opioid cessation, and full recovery.

Results

Of the 422 patients enrolled, 371 patients (≤10% missing pain scores) were included in the analysis. Of these, 146 (39.4%) were men; mean (SD) age was 56.67 (11.70) years. Two clusters were identified within each trajectory category. The high pain cluster of the average pain trajectory significantly predicted prolonged pain (hazard ratio [HR], 0.63; 95% CI, 0.50-0.80; P < .001) and delayed opioid cessation (HR, 0.52; 95% CI, 0.41-0.67; P < .001) but was not a predictor of time to recovery in Cox proportional hazards regression (HR, 0.89; 95% CI, 0.69-1.14; P = .89). Preoperative risk factors for categorization to the high average pain cluster included female sex (adjusted relative risk [ARR], 1.36; 95% CI, 1.08-1.70; P = .008), elevated preoperative pain (ARR, 1.11; 95% CI, 1.07-1.15; P < .001), a history of alcohol or drug abuse treatment (ARR, 1.90; 95% CI, 1.42-2.53; P < .001), and receiving active placebo (ARR, 1.27; 95% CI, 1.03-1.56; P = .03). Worst pain reported on postoperative day 10 was the best predictor of time to pain resolution (HR, 0.83; 95% CI, 0.78-0.87; P < .001), opioid cessation (HR, 0.84; 95% CI, 0.80-0.89; P < .001), and complete surgical recovery (HR, 0.91; 95% CI, 0.86-0.96; P < .001).

Conclusions and Relevance

This study has shown a possible uniform predictor of remote postoperative pain, opioid use, and recovery that can be easily assessed. Future work is needed to replicate these findings.

Trial Registration

ClinicalTrials.gov Identifier: NCT01067144.

Transcutaneous electrical nerve stimulation for acute pain

BACKGROUND

This is a second update of a Cochrane Review originally published in Issue 2, 2009. Transcutaneous Electrical Nerve Stimulation (TENS) is a non-pharmacological agent, based on delivering low voltage electrical currents to the skin. TENS is used by people to treat a variety of pain conditions.

OBJECTIVES

To assess the analgesic effectiveness of TENS, as a sole treatment, for acute pain in adults.

SEARCH METHODS

We searched the following databases up to 3 December 2014: the Cochrane Central Register of Controlled Trials (CENTRAL), in the Cochrane Library; MEDLINE; EMBASE; CINAHL; and AMED. We also checked the reference lists of included trials.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of adults with acute pain (< 12 weeks) if they examined TENS given as a sole treatment and assessed pain with subjective pain scales. Trials were eligible if they compared TENS to placebo TENS, no treatment controls, pharmacological interventions or non-pharmacological interventions. We excluded trials on experimental pain, case reports, clinical observations, letters, abstracts or reviews. Also we excluded trials investigating the effect of TENS on pain during childbirth (labour), primary dysmenorrhoea or dental procedures. Studies where TENS was given with another treatment as part of the formal trial design were excluded. We did not restrict any articles based on language of publication.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility and carried out study selection, data extraction, 'Risk of bias' assessment and analyses of data. We extracted data on the following: types of participants and pain condition, trial design and methods, treatment parameters, adverse effects, and outcome measures. We contacted trial authors for additional information if necessary.

MAIN RESULTS

We included 12 trials in the original review (2009) and included no further trials in the first update (2011). An additional seven new trials met the inclusion criteria in this second update. In total, we included 19 RCTs involving 1346 participants at entry, with 11 trials awaiting classification either because the full text was unavailable or information in the full text failed to clarify eligibility. We excluded most trials because TENS was given in combination with another treatment as part of the formal study design or TENS was not delivered using appropriate TENS technique. The types of acute pain included in this Cochrane Review were procedural pain, e.g. cervical laser treatment, venepuncture, screening flexible sigmoidoscopy and non-procedural pain, e.g. postpartum uterine contractions and rib fractures. We pooled data for pain intensity for six trials (seven comparisons) comparing TENS with placebo but the I(2) statistic suggested substantial heterogeneity. Mean difference (MD) with 95% confidence intervals (CIs) on a visual analogue scale (VAS, 100 mm) was -24.62 mm (95% CI -31.79 to -17.46) in favour of TENS. Data for the proportion of participants achieving ≥ 50% reduction in pain was pooled for four trials (seven comparisons) and relative risk was 3.91 (95% CI 2.42 to 6.32) in favour of TENS over placebo. We pooled data for pain intensity from five trials (seven comparisons) but the I(2) statistic suggested considerable heterogeneity. MD was -19.05 mm (95% CI -27.30 to -10.79) in favour of TENS using a random-effects model. It was not possible to pool other data. There was a high risk of bias associated with inadequate sample sizes in treatment arms and unsuccessful blinding of treatment interventions. Seven trials reported minor adverse effects, such as mild erythema and itching underneath the electrodes and participants disliking TENS sensation.

AUTHORS' CONCLUSIONS

This Cochrane Review update includes seven new trials, in addition to the 12 trials reviewed in the first update in 2011. The analysis provides tentative evidence that TENS reduces pain intensity over and above that seen with placebo (no current) TENS when administered as a stand-alone treatment for acute pain in adults. The high risk of bias associated with inadequate sample sizes in treatment arms and unsuccessful blinding of treatment interventions makes definitive conclusions impossible. There was incomplete reporting of treatment in many reports making replication of trials impossible.

A potent oral P-selectin blocking agent improves microcirculatory blood flow and a marker of endothelial cell injury in patients with sickle cell disease

Abnormal blood flow accounts for most of the clinical morbidity of sickle cell disease (SCD) [1,2]. Most notably, occlusion of flow in the microvasculature causes the acute pain crises [3] that are the commonest cause for patients with SCD to seek medical attention [4] and major determinants of their quality of life [5]. Based on evidence that endothelial P-selectin is central to the abnormal blood flow in SCD we provide results from four of our studies that are germane to microvascular blood flow in SCD. A proof-of-principle study established that doses of heparin lower than what are used for anticoagulation but sufficient to block P-selectin improved microvascular blood flow inpatients with SCD. An in vitro study showed that Pentosan Polysulfate Sodium (PPS) had greater P-selectin blocking activity than heparin. A Phase I clinical study demonstrated that a single oral dose of PPS increased microvascular blood flow in patients with SCD. A Phase II clinical study that was not completed documented that daily oral doses of PPS administered for 8 weeks lowered plasma levels of sVCAM-1 and tended to improve microvascular blood flow in patients with SCD. These data support the concept that P-selectin on the microvascular endothelium is critical to both acute vascular occlusion and chronically impaired microvascular blood flow in SCD. They also demonstrate that oral PPS is beneficial to microvascular sickle cell blood flow and has potential as an efficacious agent for long-term prophylactic therapy of SCD.

Post-operative patient-related risk factors for chronic pain after total knee replacement: a systematic review

OBJECTIVE

To identify postoperative patient-related risk factors for chronic pain after total knee replacement (TKR).

DESIGN

The systematic review protocol was registered on the International Prospective Register of Systematic Reviews (CRD42016041374). MEDLINE, Embase and PsycINFO were searched from inception to October 2016 with no language restrictions. Key articles were also tracked in the Institute for Scientific Information (ISI) Web of Science. Cohort studies evaluating the association between patient-related factors in the first 3 months postoperatively and pain at 6 months or longer after primary TKR surgery were included. Screening, data extraction and assessment of methodological quality were undertaken by two reviewers. The primary outcome was pain severity in the replaced knee measured with a patient-reported outcome measure at 6 months or longer after TKR. Secondary outcomes included adverse events and other aspects of pain recommended by the core outcome set for chronic pain after TKR.

RESULTS

After removal of duplicates, 16 430 articles were screened, of which 805 were considered potentially relevant. After detailed evaluation of full-text articles, 14 studies with data from 1168 participants were included. Postoperative patient-related factors included acute pain (eight studies), function (five studies) and psychosocial factors (four studies). The included studies had diverse methods for assessment of potential risk factors and outcomes, and therefore narrative synthesis was conducted. For all postoperative factors, there was insufficient evidence to draw firm conclusions about the association with chronic pain after TKR. Selection bias was a potential risk for all studies, as none were reported to be conducted at multiple centres.

CONCLUSION

This systematic review found insufficient evidence to draw firm conclusions about the association between any postoperative patient-related factors and chronic pain after TKR. Further high-quality research is required to provide a robust evidence base on postoperative risk factors, and inform the development and evaluation of targeted interventions to optimise patients' outcomes after TKR.

Topical NSAIDs for acute musculoskeletal pain in adults

BACKGROUND

Use of topical NSAIDs to treat acute musculoskeletal conditions has become widely accepted because they can provide pain relief without associated systemic adverse events. This review is an update of 'Topical NSAIDs for acute pain in adults' originally published in Issue 6, 2010.

OBJECTIVES

To determine the efficacy and safety of topically applied NSAIDs in acute musculoskeletal pain in adults.

SEARCH METHODS

We searched the Cochrane Register of Studies Online, MEDLINE, and EMBASE to February 2015. We sought unpublished studies by asking personal contacts and searching online clinical trial registers and manufacturers websites. For the earlier review, we also searched our own in-house database and contacted manufacturers.

SELECTION CRITERIA

We included randomised, double-blind, active or placebo (inert carrier)-controlled trials in which treatments were administered to adults with acute pain resulting from strains, sprains or sports or overuse-type injuries (twisted ankle, for instance). There had to be at least 10 participants in each treatment arm, with application of treatment at least once daily.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion, and extracted data. We used numbers of participants achieving each outcome to calculate the risk ratio and numbers needed to treat for an additional beneficial outcome (NNT) or additional harmful outcome (NNH) compared with placebo or other active treatment. We reported 95% confidence intervals (CI). We were particularly interested to compare different formulations (gel, cream, plaster) of individual NSAIDs.

MAIN RESULTS

For this update we added 14 new included studies (3489 participants), and excluded four studies. We also identified 20 additional reports of completed or ongoing studies that have not been published in full. The earlier review included 47 studies.This update included 61 studies. Most compared topical NSAIDs in the form of a gel, spray, or cream with a similar topical placebo; 5311 participants were treated with a topical NSAID, 3470 with placebo, and 220 with an oral NSAID. This was a 63% increase in the number of included participants over the previous version of this review. We also identified a number of studies in clinical trial registries with unavailable results amounting to about 5900 participants for efficacy and 5300 for adverse events.Formulations of topical diclofenac, ibuprofen, ketoprofen, piroxicam, and indomethacin demonstrated significantly higher rates of clinical success (more participants with at least 50% pain relief) than matching topical placebo (moderate or high quality data). Benzydamine did not. Three drug and formulation combinations had NNTs for clinical success below 4. For diclofenac, the Emulgel® formulation had the lowest NNT of 1.8 (95% CI 1.5 to 2.1) in two studies using at least 50% pain intensity reduction as the outcome. Diclofenac plasters other than Flector® also had a low NNT of 3.2 (2.6 to 4.2) based on good or excellent responses in some studies. Ketoprofen gel had an NNT of 2.5 (2.0 to 3.4), from five studies in the 1980s, some with less well defined outcomes. Ibuprofen gel had an NNT of 3.9 (2.7 to 6.7) from two studies with outcomes of marked improvement or complete remission. All other drug and formulation combinations had NNT values above 4, indicating lesser efficacy.There were insufficient data to compare reliably individual topical NSAIDs with each other or the same oral NSAID.Local skin reactions were generally mild and transient, and did not differ from placebo (high quality data). There were very few systemic adverse events (high quality data) or withdrawals due to adverse events (low quality data).

AUTHORS' CONCLUSIONS

Topical NSAIDs provided good levels of pain relief in acute conditions such as sprains, strains and overuse injuries, probably similar to that provided by oral NSAIDs. Gel formulations of diclofenac (as Emugel®), ibuprofen, and ketoprofen, and some diclofenac patches, provided the best effects. Adverse events were usually minimal.Since the last version of this review, the new included studies have provided additional information. In particular, information on topical diclofenac is greatly expanded. The present review supports the previous review in concluding that topical NSAIDs are effective in providing pain relief, and goes further to demonstrate that certain formulations, mainly gel formulations of diclofenac, ibuprofen, and ketoprofen, provide the best results. Large amounts of unpublished data have been identified, and this could influence results in updates of this review.

Acute kidney injury during a pediatric sickle cell vaso-occlusive pain crisis

BACKGROUND

Patients who develop sickle cell disease (SCD) nephropathy are at a high risk for mortality. The pathophysiology of vaso-occlusive pain crisis may contribute to acute kidney injury (AKI). Non-steroidal anti-inflammatory drugs, known inducers of AKI, are used to treat pain crises. Multiple gaps exist in the knowledge about the impact of AKI in SCD.

METHODS

We conducted a 2-year retrospective review of AKI events in patients admitted for vaso-occlusive crisis. AKI was defined by an increase of ≥0.3 mg/dL or 50% in serum creatinine from baseline. Laboratory values and ketorolac administration by days and dose (mg/kg) were identified from hospital records. A generalized mixed effects model for binary outcomes evaluated AKI based on laboratory variables and ketorolac administration. A generalized mixed Poisson effects model analyzed the association of AKI with hospital length of stay.

RESULTS

Thirty-three out of 197 admissions for vaso-occlusive pain crisis (17%) were associated with AKI. Fifty-two percent of the cases presented to the Emergency Room (ER) with AKI. Every one unit decrease in hemoglobin from baseline to admission increased the risk of AKI by 49%. Among patients who received ketorolac for pain, both total days and doses of ketorolac were associated with AKI. Finally, patients with pain and AKI required longer periods of hospitalization than patients without AKI.

CONCLUSION

Acute kidney injury during sickle cell pain crisis is common and may be an important modifiable risk factor for developing chronic kidney disease (CKD). Further studies are needed to determine the impact of nephrotoxic medications on progressive SCD nephropathy.

A meta-analysis of the preoperative use of gabapentinoids for the treatment of acute postoperative pain following spinal surgery

BACKGROUND

Gabapentinoid drugs, which include gabapentin and pregabalin, play an established role in the management of neuropathic pain. However, whether preoperative administration of gabapentinoids has a beneficial role in controlling acute pain after spinal surgery is unknown. We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) to determine the efficacy and safety of the preoperative use of gabapentinoids (gabapentin and pregabalin) for the treatment of acute postoperative pain following spinal surgery.

METHODS

In March 2017, a systematic computer-based search was conducted in PubMed, EMBASE, Web of Science, Cochrane Library, and Google databases. RCTs comparing gabapentinoids (gabapentin and pregabalin) with placebo in patients undergoing spine surgery were retrieved. The primary endpoint was the visual analogue scale (VAS) score with rest or mobilization at 6, 12, 24, and 48 hours and cumulative morphine consumption at 24 and 48 hours. The secondary outcomes were complications of nausea, vomiting, sedation, dizziness, headache, urine retention, pruritus, and visual disturbances. After tests for publication bias and heterogeneity among studies were performed, data were aggregated for random-effects models when necessary.

RESULTS

Sixteen clinical studies (gabapentin group n = 8 and pregabalin group n = 8) were ultimately included in the meta-analysis. Gabapentinoids were associated with reduced pain scores at 6, 12, 24, and 48 hours. Similarly, gabapentinoids were associated with a reduction in cumulative morphine consumption at 24 and 48 hours. Furthermore, gabapentinoids can significantly reduce the occurrence of nausea, vomiting, and pruritus. There were no significant differences in the occurrence of sedation, dizziness, headache, visual disturbances, somnolence, or urine retention.

CONCLUSIONS

Preoperative use of gabapentinoids was able to reduce postoperative pain, total morphine consumption, and morphine-related complications following spine surgery. Further studies should determine the optimal dose and whether pregabalin is superior to gabapentin in controlling acute pain after spine surgery.

New Insights in Understanding and Treating Bone Fracture Pain

PURPOSE OF REVIEW

This paper describes recent advances in understanding the mechanisms that drive fracture pain and how these findings are helping develop new therapies to treat fracture pain.

RECENT FINDINGS

Immediately following fracture, mechanosensitive nerve fibers that innervate bone are mechanically distorted. This results in these nerve fibers rapidly discharging and signaling the initial sharp fracture pain to the brain. Within minutes to hours, a host of neurotransmitters, cytokines, and nerve growth factor are released by cells at the fracture site. These factors stimulate, sensitize, and induce ectopic nerve sprouting of the sensory and sympathetic nerve fibers which drive the sharp pain upon movement and the dull aching pain at rest. If rapid and effective healing of the fracture occurs, these factors return to baseline and the pain subsides, but if not, these factors can drive chronic bone pain. New mechanism-based therapies have the potential to fundamentally change the way acute and chronic fracture pain is managed.

Hypnosis for Acute Procedural Pain: A Critical Review

Clinical evidence for the effectiveness of hypnosis in the treatment of acute procedural pain was critically evaluated based on reports from randomized controlled clinical trials (RCTs). Results from the 29 RCTs meeting inclusion criteria suggest that hypnosis decreases pain compared to standard care and attention control groups and that it is at least as effective as comparable adjunct psychological or behavioral therapies. In addition, applying hypnosis in multiple sessions prior to the day of the procedure produced the highest percentage of significant results. Hypnosis was most effective in minor surgical procedures. However, interpretations are limited by considerable risk of bias. Further studies using minimally effective control conditions and systematic control of intervention dose and timing are required to strengthen conclusions.

Intraoperative Methadone Reduces Pain and Opioid Consumption in Acute Postoperative Pain: A Systematic Review and Meta-analysis

BACKGROUND

Methadone is a potent opioid exerting an analgesic effect through N-methyl-D-aspartate receptor antagonism and the inhibition of serotonin and noradrenaline reuptake. It has also been used in several procedures to reduce postoperative pain and opioid use. This meta-analysis aimed to determine whether the intraoperative use of methadone lowers postoperative pain scores and opioid consumption in comparison to other opioids.

METHODS

Double-blinded, controlled trials without language restrictions were included from MEDLINE, Embase, LILACS, The Cochrane Central Register of Controlled Trials (CENTRAL), and CINAHL via EBSCOhost. The included studies tracked total opioid consumption, postoperative pain scores, opioid-related side effects, and patient satisfaction until 72 hours postoperatively. Mean difference (MD) was used for effect size.

RESULTS

In total, 476 articles were identified and 13 were considered eligible for inclusion in the meta-analysis. In 486 patients (7 trials), pain at rest (MD, 1.09; 95% confidence interval (CI), 1.47-0.72; P < .00001) and at movement (MD, 2.48; 95% CI, 3.04-1.92; P = .00001) favored methadone 24 hours after surgery. In 374 patients (6 trials), pain at rest (MD, 1.47; 95% CI, 3.04-1.02; P < .00001) and at movement (MD, 2.03; 95% CI, 3.04-1.02; P < .00001) favored methadone 48 hours after surgery. In 320 patients (4 trials), pain at rest (MD, 1.02; 95% CI, 1.65-0.39; P = .001) and at movement (MD, 1.34; 95% CI, 1.82-0.87; P < .00001) favored methadone 72 hours after surgery. A Trial Sequential Analysis was performed and the Z-cumulative curve for methadone crossed the monitoring boundary at all evaluations, additionally crossing Required Information Size at 24 and 48 hours at rest. Methadone group also showed lower postoperative opioid consumption in morphine equivalent dosage (mg) at 24 hours (MD, 8.42; 95% CI, 12.99-3.84 lower; P < .00001), 24-48 hours (MD, 14.33; 95% CI, 26.96-1.91 lower; P < .00001), 48-72 hours (MD, 3.59; 95% CI, 6.18-1.0 lower; P = .007) postoperatively.

CONCLUSIONS

Intraoperative use of methadone reduced postoperative pain scores compared to other opioids, and Trial Sequential Analysis suggested that no more trials are required to confirm pain reduction at rest until 48 hours after surgery. Methadone also reduced postoperative opioid consumption and led to better patient satisfaction scores through 72 hours postoperatively compared to other opioids.

Altered fMRI resting-state connectivity in individuals with fibromyalgia on acute pain stimulation

BACKGROUND

Fibromyalgia is a chronic widespread pain condition, with patients commonly reporting other symptoms such as sleep difficulties, memory complaints and fatigue. The use of magnetic resonance imaging (MRI) in fibromyalgia has allowed for the detection of neural abnormalities, with alterations in brain activation elicited by experimental pain and alterations in resting state connectivity related to clinical pain.

METHODS

In this study, we sought to monitor state changes in resting brain connectivity following experimental pressure pain in fibromyalgia patients and healthy controls. Twelve fibromyalgia patients and 15 healthy controls were studied by applying discrete pressure stimuli to the thumbnail bed during MRI. Resting-state functional MRI scanning was performed before and immediately following experimental pressure pain. We investigated changes in functional connectivity to the thalamus and the insular cortex.

RESULTS

Acute pressure pain increased insula connectivity to the anterior cingulate and the hippocampus. Additionally, we observed increased thalamic connectivity to the precuneus/posterior cingulate cortex, a known part of the default mode network, in patients but not in controls. This connectivity was correlated with changes in clinical pain.

CONCLUSIONS

These data reporting changes in resting-state brain activity following a noxious stimulus suggest that the acute painful stimuli may contribute to the alteration of the neural signature of chronic pain. WHAT DOES THIS STUDY/ADD?: In this study acute pain application shows an echo in functional connectivity and clinical pain changes in chronic pain.

Methoxyflurane Analgesia in Adult Patients in the Emergency Department: A Subgroup Analysis of a Randomized, Double-blind, Placebo-controlled Study (STOP!)

INTRODUCTION

Acute pain remains highly prevalent in the Emergency Department (ED) setting. This double-blind, randomized, placebo-controlled UK study investigated the efficacy and safety of low-dose methoxyflurane analgesia for the treatment of acute pain in the ED in the adult population of the STOP! trial.

METHODS

Patients presenting to the ED requiring analgesia for acute pain (pain score of 4-7 on the Numerical Rating Scale) due to minor trauma were randomized in a 1:1 ratio to receive methoxyflurane (up to 6 mL) or placebo (normal saline), both via a Penthrox® (Medical Developments International Limited, Scoresby, Australia) inhaler. Rescue medication (paracetamol/opioids) was available immediately upon request. Change from baseline in visual analog scale (VAS) pain intensity was the primary endpoint.

RESULTS

300 adult and adolescent patients were randomized; data are presented for the adult subgroup (N = 204). Mean baseline VAS pain score was ~66 mm in both groups. The mean change from baseline to 5, 10, 15 and 20 min was greater for methoxyflurane (-20.7, -27.4, -33.3 and -34.8 mm, respectively) than placebo (-8.0, -11.1, -12.3 and -15.2 mm, respectively). The primary analysis showed a highly significant treatment effect overall across all four time points (-17.4 mm; 95% confidence interval: -22.3 to -12.5 mm; p < 0.0001). Median time to first pain relief was 5 min with methoxyflurane [versus 20 min with placebo; (hazard ratio: 2.32; 95% CI: 1.63, 3.30; p < 0.0001)]; 79.4% of methoxyflurane-treated patients experienced pain relief within 1-10 inhalations. 22.8% of placebo-treated patients requested rescue medication within 20 min compared with 2.0% of methoxyflurane-treated patients (p = 0.0003). Methoxyflurane treatment was rated 'Excellent', 'Very Good' or 'Good' by 77.6% of patients, 74.5% of physicians and 72.5% of nurses. Treatment-related adverse events (mostly dizziness/headache) were reported by 42.2% of patients receiving methoxyflurane and 14.9% of patients receiving placebo; none caused withdrawal and the majority were mild and transient.

CONCLUSION

The results of this study support the evidence from previous trials that low-dose methoxyflurane administered via the Penthrox inhaler is a well-tolerated, efficacious and rapid-acting analgesic.

FUNDING

Medical Developments International (MDI) Limited and Mundipharma Research GmbH & Co.KG.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT01420159, EudraCT number: 2011-000338-12.

Analgesic Efficacy, Practicality and Safety of Inhaled Methoxyflurane Versus Standard Analgesic Treatment for Acute Trauma Pain in the Emergency Setting: A Randomised, Open-Label, Active-Controlled, Multicentre Trial in Italy (MEDITA)

INTRODUCTION

Inhaled low-dose methoxyflurane is approved in Europe for emergency relief of moderate-to-severe trauma-related pain in adults, but data versus active comparators are sparse. The phase IIIb Methoxyflurane in Emergency Department in ITAly (MEDITA) trial investigated the analgesic efficacy, practicality and safety of methoxyflurane versus standard analgesic treatment (SAT) for acute trauma pain.

METHODS

This was a randomised, active-controlled, parallel-group, open-label trial conducted in 15 Italian emergency units. Adults with limb trauma and pain score ≥ 4 on numerical rating scale (NRS) were randomised 1:1 to inhaled methoxyflurane 3 mL or SAT [intravenously administered (IV) morphine 0.1 mg/kg for severe pain (NRS ≥ 7); IV paracetamol 1 g or IV ketoprofen 100 mg for moderate pain (NRS 4-6)]. The primary endpoint was overall change in visual analogue scale (VAS) pain intensity from baseline (time of randomisation) to 3, 5 and 10 min. Non-inferiority and superiority of methoxyflurane versus SAT were concluded if the upper 95% confidence interval (CI) for the treatment comparison (methoxyflurane-SAT) was less than 1 and less than 0, respectively.

RESULTS

Between 8 February 2018 and 8 February 2019, 272 patients were randomised (136 per treatment group). A total of 270 patients (mean age 51 years; 49% male; 34% with severe pain; mean baseline VAS 67 mm) were treated and analysed for efficacy and safety. Superiority of methoxyflurane was demonstrated for moderate-to-severe pain (adjusted mean treatment difference - 5.94 mm; 95% CI - 8.83, - 3.06 mm), moderate pain (- 5.97 mm; 95% CI - 9.55, - 2.39 mm) and severe pain (- 5.54 mm; 95% CI - 10.49, - 0.59 mm). Median onset of pain relief was 9 min for methoxyflurane and 15 min for SAT. Practicality of methoxyflurane treatment was rated "Excellent", "Very Good" or "Good" by 90% of clinicians vs. 64% for SAT. Adverse events (all non-serious) were reported by 17% of methoxyflurane-treated patients and 3% of SAT-treated patients.

CONCLUSION

Methoxyflurane provided superior pain relief to SAT in patients with moderate-to-severe trauma pain and may offer a simple, fast, effective non-opioid treatment option.

TRIAL REGISTRATION

Trial registered with EudraCT (2017-001565-25) on 2 March 2018 and ClinicalTrials.gov (NCT03585374) on 13 July 2018.

FUNDING

Mundipharma Pharmaceuticals S.r.l.

The Acute to Chronic Pain Transition: Can Chronic Pain Be Prevented?

Chronic postsurgical pain (CPSP) is a distressing disease process that can lead to long-term disability, reduced quality of life, and increased health care spending. Although the exact mechanism of development of CPSP is unknown, nerve injury and inflammation may lead to peripheral and central sensitization. Given the complexity of the disease process, no novel treatment has been identified. The preoperative use of multimodal analgesia has been shown to decrease acute postoperative pain, but it has no proven efficacy in preventing development of CPSP.

Trends in Any and High-Dose Opioid Analgesic Receipt Among Aging Patients With and Without HIV

Harms of opioid analgesics, especially high-dose therapy among individuals with comorbidities and older age, are increasingly recognized. However, trends in opioid receipt among HIV-infected patients are not well characterized. We examined trends, from 1999 to 2010, in any and high-dose (≥120 mg/day) opioid receipt among patients with and without HIV, by age strata, controlling for demographic and clinical correlates. Of 127,216 patients, 64 % received at least one opioid prescription. Opioid receipt increased substantially among HIV-infected and uninfected patients over the study; high-dose therapy was more prevalent among HIV-infected patients. Trends in high-dose receipt stratified by three age groups revealed an increasing trend in each age strata, higher among HIV-infected patients. Correlates of any opioid receipt included HIV, PTSD and major depression. Correlates of high-dose receipt included HIV, PTSD, major depression and drug use disorders. These findings suggest a need for appropriate balance of risks and benefits, especially as these populations age.

Quercetin Inhibits Peripheral and Spinal Cord Nociceptive Mechanisms to Reduce Intense Acute Swimming-Induced Muscle Pain in Mice

The present study aimed to evaluate the effects of the flavonoid quercetin (3,3´,4´,5,7-pentahydroxyflavone) in a mice model of intense acute swimming-induced muscle pain, which resembles delayed onset muscle soreness. Quercetin intraperitoneal (i.p.) treatment dose-dependently reduced muscle mechanical hyperalgesia. Quercetin inhibited myeloperoxidase (MPO) and N-acetyl-β-D- glucosaminidase (NAG) activities, cytokine production, oxidative stress, cyclooxygenase-2 (COX-2) and gp91^phox mRNA expression and muscle injury (creatinine kinase [CK] blood levels and myoblast determination protein [MyoD] mRNA expression) as well as inhibited NFκB activation and induced Nrf2 and HO-1 mRNA expression in the soleus muscle. Beyond inhibiting those peripheral effects, quercetin also inhibited spinal cord cytokine production, oxidative stress and glial cells activation (glial fibrillary acidic protein [GFAP] and ionized calcium-binding adapter molecule 1 [Iba-1] mRNA expression). Concluding, the present data demonstrate that quercetin is a potential molecule for the treatment of muscle pain conditions related to unaccustomed exercise.

Comparison of Acute and Chronic Pain after Open Nephrectomy versus Laparoscopic Nephrectomy: A Prospective Clinical Trial

We evaluated postoperative pain intensity and the incidence of chronic pain in patients with renal cell carcinoma undergoing laparoscopic or open radical nephrectomy. In this prospective study, 27 laparoscopic nephrectomy (Group LN) and 25 open nephrectomy (Group ON) patients were included. All patients received paracetamol infusion and intramuscular morphine 30 minutes before the end of the operation and intravenous patient controlled analgesia with morphine postoperatively. Data including patients' demographics, visual analog scale (VAS) pain scores at postoperative 0.5, 1, 2, 4, 6, 12, and 24 hours, postoperative morphine consumption, analgesic demand, analgesic delivery, number of patients requiring rescue analgesics, side effects because of analgesic medications, and overall patient satisfaction were recorded and compared between the two groups. Two and 6 months after the operation, patients were evaluated for chronic postsurgical pain (CPSP). Postoperative average VAS pain scores were not different between the two groups. However, only at 2 hours postoperatively, pain score was significantly higher in Group ON than in Group LN. In both groups, the highest pain scores were recorded at 30 minutes and 1 hour after surgery. Ninety-six percent of group ON patients and 88% of group LN patients required additional analgesia in the early postoperative period (P = 0.33). Postoperative morphine consumption and analgesic demand were found to be similar between the two groups. CPSP at 2 months after surgery was observed in 4 out of 25 patients (16%) in the ON group and 3 out of 27 patients (11.1%) in the LN group (P = 0.6). Chronic pain at 6 months after surgery was observed in 1 ON patient (4%) and 1 LN patient (3.7%, P = 0.9). This study demonstrated that postoperative acute pain scores were not different after laparoscopic or open nephrectomy and patients undergoing laparoscopic or open nephrectomy were at equal risk of developing CPSP. Pain control should be carefully planned in order to reduce early postoperative pain and also potentially prevent CPSP.

Comparison of Intraoperative Sedation With Dexmedetomidine Versus Propofol on Acute Postoperative Pain in Total Knee Arthroplasty Under Spinal Anesthesia: A Randomized Trial

BACKGROUND

In patients undergoing total knee arthroplasty under spinal anesthesia, we compared the postoperative analgesic effect of intraoperative sedation with dexmedetomidine versus propofol. We hypothesized that sedation with dexmedetomidine would result in lower postoperative opioid analgesic consumption than with propofol.

METHODS

Forty-eight patients were enrolled and randomly assigned to either a dexmedetomidine group (n = 24), which received a loading dose of 1 μg/kg dexmedetomidine over 10 minutes, followed by a continuous infusion of 0.1-0.5 μg·kg·hour, or a propofol group (n = 24), which received a continuous infusion of propofol via a target-controlled infusion to maintain the effect-site concentration within a range of 0.5-2.0 μg/mL. The drug infusion rate was determined according to the sedation level, targeting a modified observer's assessment of alertness/sedation score of 3 or 4. The cumulative amounts of fentanyl administered via intravenous patient-controlled analgesia were recorded at 24 and 48 hours postoperatively (primary outcome). The postoperative numerical rating scale for pain was assessed at 6, 12, 24, and 48 hours (secondary outcome). The postoperative use of additional rescue analgesic (ketoprofen) and antiemetic drugs was also compared between the 2 groups at 24 and 48 hours.

RESULTS

Dexmedetomidine significantly reduced postoperative fentanyl consumption (median [interquartile range]) during 0-24 hours (45 [30-71] vs 150 [49-248] μg, P = .004; median difference = -105 μg [99.98% CI, 210-7.5]), 24-48 hours (90 [45-143] vs 188 [75-266] μg, P = .005; median difference = -98 μg [99.98% CI, 195-45]), and 0-48 hours (135 [68-195] vs 360 [146-480] μg, P = .003; median difference = -225 μg [99.98% CI, 405-7.5]). The numerical rating scale (median [interquartile range]) was lower at 6 hours (1 [0-2] vs 2 [1-3], P = .003), 12 hours (1 [1-2] vs 3 [2-3], P < .001), 24 hours (1 [1-2] vs 3 [2-3], P < .001), and 48 hours (2 [2-3] vs 3 [3-4], P < .001) after surgery in the dexmedetomidine group compared to the propofol group. No significant intergroup differences were observed in the amount of rescue analgesics and antiemetics at 24 hours (P = .155 and P = .482) and 48 hours (P = .082 and P = .153) after surgery.

CONCLUSIONS

Intraoperative dexmedetomidine sedation was associated with a small but clinically important reduction in postoperative opioid use after total knee arthroplasty.

Preventive Analgesic Efficacy of Nefopam in Acute and Chronic Pain After Breast Cancer Surgery: A Prospective, Double-Blind, and Randomized Trial

Breast cancer surgery is known to cause severe acute postoperative pain, which can persist for a long time. We administered nefopam preventively to patients undergoing lumpectomy with axillary lymph node dissection or sentinel lymph node biopsy, and evaluated its efficacy on acute and chronic postoperative pain.Enrolled patients were assigned to the nefopam (n = 41) or the control (n = 42) group. Before initiating the operation, 20 mg of nefopam was given to the patients of the nefopam group, and normal saline was used in the control group. Ketorolac was given at the end of surgery, and meloxicam was prescribed in the postoperative period to all patients in both groups. Pain was assessed using a numerical rating scale (NRS), and the rescue analgesic drug was given when the NRS was >5. Implementation of postoperative chemotherapy, radiotherapy (RT), or hormone therapy was evaluated.The NRS of postoperative pain was significantly lower in the nefopam than in the control group in the postanesthetic care unit (4.5 ± 2.2 vs 5.7 ± 1.5, respectively; P = 0.01), at postoperative 6 h (3.0 ± 1.6 vs 4.5 ± 1.3, respectively; P < 0.001), and at postoperative 24 h (3.1 ± 1.1 vs 3.8 ± 1.5, respectively; P = 0.01) with reduced use of rescue analgesic drugs. Significantly fewer patients suffered from chronic postoperative pain in the nefopam than in the control group at postoperative 3 months (36.6% vs 59.5%, P = 0.04). Considering only the cohort without postoperative adjuvant RT, the difference in the proportion of patients reporting chronic pain increased (23.5% in the nefopam group vs 61.5% in the control group, P = 0.04).Preventive nefopam was helpful in reducing the acute postoperative pain, with reduced use of rescue analgesic drugs, and it contributed to reduced occurrence of chronic pain at postoperative 3 months after breast cancer surgery.

Oleaginous extract from the fruits Pterodon pubescens Benth induces antinociception in animal models of acute and chronic pain

ETHNOPHARMACOLOGICAL RELEVANCE

Pterodon pubescens Benth is a medicinal plant commonly used for therapeutic purposes in folk medicine for rheumatic diseases' treatment. In the present work we analyzed the chemical composition of the oleaginous extract of P. pubescens Benth (OEPp) and extended the antinociceptive effect of OEPp evaluating its role on animal models of acute and chronic pain.

MATERIALS AND METHODS

The antinociceptive and antiedematogenic effects of OEPp (3-100mg/kg, i.g.) were evaluated in the formalin test; mechanical allodynia in the postoperative pain and complex regional pain syndrome type-I (CRPS-I) animal models; and thermal hyperalgesia was induced by plantar incision. Finally, we performed a phytochemical analysis of OEPp.

RESULTS

The chemical composition of OEPp was analyzed by mass spectrometry (GC/MS) and eight sesquiterpene compounds were identified, i.e. three major sesquiterpene (E-cariofilene, γ-muurolene, biciclogermacrene), and nine vouacapane diterpenes, four of which showed in major concentration (6α-acetoxyvouacapane, 6α,7β-dimetoxivouacapan-17-ene, 6α-acetoxy,7β-hidroxyvouacapane, 6α,7β-diacetoxycouacapane). Furthermore, the results of the present study demonstrate, for the first time, that the OEPp reduced mechanical allodynia in the postoperative pain and CRPS-I animal models. OEPp also increased the paw withdrawal latency in hot- and cold-plate tests in the postoperative pain model. In addition, the present work confirms and extends previous data from literature showing that systemic administration of OEPp caused significant inhibition against both phases of pain response to formalin intraplantar injection and edema formation.

CONCLUSIONS

Together, present and previous findings show that OEPp given intra-gastrically caused significant inhibition against both phases of formalin intraplantar injection and effectively inhibited mechanical and thermal hyperalgesia in the postoperative pain and CRPS-I animal models.

Preoperative Pain, Symptoms, and Psychological Factors related to Higher Acute Pain Trajectories during Hospitalization for Total Knee Arthroplasty

OBJECTIVES

Unrelieved postoperative pain after total knee arthroplasty (TKA) is a significant problem. This longitudinal study investigated how preoperative pain intensity, as well as a comprehensive list of preoperative and perioperative factors, influenced the severity of acute average and worst pain after TKA.

METHODS

Prior to surgery, 203 patients completed a demographic questionnaire, Lee Fatigue Scale, Fatigue Severity Scale, Hospital Anxiety and Depression Scale, and Brief Illness Perception Questionnaire. Brief Pain Inventory was completed prior to surgery as well as through postoperative days (POD) 0 to 4. Clinical data were extracted from medical records.

RESULTS

Several factors were associated with higher levels of preoperative and postoperative pain. Lower preoperative average and worst pain intensity scores were associated with increases in average and worst postoperative pain from POD1 to POD4. A higher number of comorbidities, higher C-reactive protein values, and higher pain interference with function were associated with higher preoperative levels of average pain. Older age, higher fatigue levels, and higher scores on identity and emotional responses to osteoarthritis (OA) were associated with higher preoperative levels of worst pain. Lower perceived consequences of OA were associated with higher pain from POD1 to POD4. Males and patients with lower preoperative scores for average pain had higher worst pain following surgery.

DISCUSSION

Patients at higher risk for more severe postoperative pain can be identified through an assessment of pain and other risk factors identified in this study. Future research needs to test the efficacy of interventions that modify patients' perceptions of living with OA and pain intensity before surgery on short and long term postoperative outcomes.