Post Surgical Pain- The Transition from Acute to Chronic Pain

Preoperative psychological factors influence analgesic consumption and self-reported pain intensity following breast cancer surgery

BACKGROUND

Psychological factors such as anxiety and mood appear to influence acute postoperative pain; however, there is conflicting evidence on the relationship between preoperative psychological parameters and the severity of postoperative pain. In the context of the stressful setting of initial surgery for breast cancer, we conducted a prospective observational study of patients who were scheduled to undergo initial breast cancer surgery.

METHODS

The objectives were to examine the potential associations between predefined preoperative psychological parameters and (i) Self-reported pain scores at discharge from the postoperative acute care unit, (ii) Cumulative perioperative opioid consumption at four hours postoperatively and (iii) Self-reported pain as measured during the first seven days after surgery. Patients completed the following questionnaires during the three hours prior to surgery: the Spielberger State Trait Anxiety Inventory (STAI State and Trait), the Pain Catastrophizing Scale (PCS), the Cohen Stress Questionnaire (CSQ), the Hospital Anxiety and Depression Scale (HADS A and D), and the short-form McGill Pain Questionnaire. Postoperative pain experience was assessed using patient self-reports of pain (SF Magill Pain questionnaire on discharge from the postanaesthesia care unit and a pain diary for seven days postoperatively) and records of analgesic consumption.

RESULTS

Pre- to postoperative self-reported pain was significantly different with respect to the STAI State, Cohen score and PCS for both low and high values (p < 0.001), but only patients categorized as having low STAI Trait, HADS A, and HADS D values achieved significant differences (p < 0.001). A significant positive correlation was demonstrated between preoperative state anxiety (STAI) and the most severe pain reported during the first seven days postoperatively (r = 0.271, p = 0.013). Patients who were categorized preoperatively as having a "high value" for each of the psychological parameters studied (HADS A and D, STAI State and Trait and PCS) tended to have greater perioperative opioid consumption (up to four hours postoperatively); this trend was statistically significant for HADS D and HADS A only. Using a linear regression model, state anxiety was found to be a significant predictor of postoperative pain based on self-reports during the first seven postoperative days (standardized β = 0.271, t = 2.286, p = 0.025).

CONCLUSION

Preoperative state anxiety, in particular, is associated with the severity of postoperative pain experienced by women undergoing initial breast cancer surgery. Formal preoperative assessment of anxiety may be warranted in this setting with a view to optimize perioperative analgesia and wellbeing.

The effect of different regional analgesia methods on chronic pain after thoracic surgery

Introduction

Chronic postsurgical pain (CPSP) is defined as pain persisting for ≥ 3 months after surgery, severely impairing patients' long-term daily activities and quality of life.

Aim

To evaluate the effects of various regional analgesia methods, including thoracic epidural (TE), serratus anterior plane (SAP) block, rhomboid intercostal block (RIB) and paravertebral block (PVB), on the incidence of chronic post-thoracic surgery pain.

Material and methods

A total of 489 patients (240 thoracotomy, 249 VATS) were included in the analysis. The primary outcome measure was the VAS score (postoperative 6th month), while the secondary outcome measures were the LANSS score (postoperative 6th month), the use of analgesic medication and descriptive information.

Results

In thoracotomy patients, VAS scores were statistically significantly lower in patients who underwent RIB and SAP block compared to those who underwent TE and patient-controlled anesthesia (PCA). LANSS scores did not differ between the RIB, SAP and TE groups, while higher scores were found in the PCA group. After VATS, VAS scores were statistically significantly lower in patients who underwent RIB, SAP and PVB block compared to the PCA group. LANSS scores were statistically significantly lower in the RIB and SAP block groups than in the PVB and PCA groups.

Conclusions

This study found that patients who received regional anesthesia had lower LANSS scores and VAS values, indicative of neuropathic pain reduction, following thoracotomy and VATS procedures.

The Analgesic Properties of a Music Intervention in the Postanesthesia Care Unit

PURPOSE

The purpose of this study was to determine whether a combined music pharmacological intervention was an effective multimodal approach to reduce adult pain in the postanesthesia care unit (PACU).

DESIGN

A prospective, randomized control trial study.

METHODS

Participants were recruited in the preoperative holding area on the day of surgery by the principal investigators. Music was selected by the patient following the informed consent process. Participants were randomized either to the intervention group or the control group. Patients in the intervention group received music in addition to standard pharmacological protocol while the control group received only the standard pharmacological protocol. Measured outcomes were change in visual analog pain scores and length of stay.

FINDINGS

In this cohort (N = 134), 68 participants (50.7%) received the intervention, and 66 participants (49.3%) were in the control group. Paired t tests showed that pain scores for the control group worsened by an average of 1.45-points (95% CI: 0.75, 2.15; P < .001) compared to 0.34-points in the intervention group and was not significant (P = .314) as scores went from 1 out of 10 to 1.4 out of 10. Both control and intervention groups experienced pain, with the control group's overall pain scores worsening over time. This finding was statistically significant (P = .023). No statistically significant difference was noted in the average PACU length of stay (LOS).

CONCLUSIONS

The addition of music to the standard postoperative pain protocol demonstrated a lower average pain score on discharge from the PACU. The absence of a difference in LOS may be due to the confounding variables (eg, general versus spinal anesthesia or a difference in voiding time).

Perioperative Indications for Gabapentinoids in Pediatrics: A Narrative Review

In recent years, there has been increased interest in using gabapentinoids (gabapentin and pregabalin) as part of multimodal medication plans or enhanced recovery after surgery protocols to mitigate several perioperative clinical challenges. Outcomes explored in the context of using gabapentinoids perioperatively in children are variable and include acute complications of pain, anxiety, nausea and vomiting, and emergence agitation, as well as the long-term postoperative outcome of chronic postsurgical pain. This narrative review describes the current literature regarding perioperative use of gabapentinoids in pediatric patients and aims to describe the role of gabapentinoids in the perioperative setting for each specific indication.

Risks of refractory chest pain after peroral endoscopic myotomy in achalasia-related esophageal motility disorders: short-term results from a multicenter study in Japan

BACKGROUND AND AIMS

The etiology of chest pain in achalasia-related esophageal motility disorders and the frequency and risk factors of persistent chest pain after peroral endoscopic myotomy (POEM) remain unclear.

METHODS

A multicenter cohort study including 14 hospitals was conducted to elucidate the characteristics of patients with chest pain and the efficacy of POEM.

RESULTS

Consecutive cases of achalasia-related esophageal motility disorders included 2294 (64.2%) and 1280 (35.8%) patients with and without chest pain, respectively. Among the 2107 patients with chest pain who underwent POEM, we observed complete remission in 1464 patients (69.5%) and nonremission in 643 patients (30.5%), including a partial response in 619 patients (29.4%) and resistance in 24 patients (1.1%). Multivariate analysis revealed that advanced age (odds ratio [OR], .28), male sex (OR, .70), prior treatment (OR, 1.39), and sigmoid type (OR, .65) were related to the prevalence of chest pain. Long disease duration (OR, .69) and esophageal dilation (OR, .79) were related to decreased severity. POEM improved patients' quality of life that was hindered by chest pain. Early onset (OR, 1.45), advanced age (OR, .58), male sex (OR, .79), prior treatment (OR, 1.37), and posterior myotomy (OR, 1.42) were associated with nonremission after POEM; high-resolution manometry (HRM) findings and myotomy length showed no statistical significance on pain etiology and persistence after POEM.

CONCLUSIONS

The prevalence and severity of chest pain were dependent on age, sex, disease duration, prior treatment, and esophageal morphology rather than HRM findings. The efficacy of POEM is satisfactory; however, residual pain was often observed. Excessively long myotomy can be avoided, and anterior myotomy may be recommended.

Pain "chronification": what is the problem with this model?

OBJECTIVES

There appears to be an unwarranted focus on all chronic pain being a "chronification" of acute pain. Despite a plethora of studies on mechanisms to prevent this "chronification" following surgery, the positive effects have been minimal. An alternate model to explain chronic pain is presented.

METHODS

Research in PUBMED and accessing data from the HUNTpain examination study.

RESULTS

Data from the HUNT pain examination study reveal that less than 25% of individuals with chronic pain in a general population can relate the onset to an acute event. Another theory explaining the origin of chronic pain is that of priming and the accumulation of events that can be predictors along a continuum before chronic pain is apparent. This theory is presented to refocus for better prevention and treatment of chronic pain.

CONCLUSIONS

"Chronification" cannot explain all cases of chronic/persistent pain. The plastic changes in the pain processing system can be seen as a continuum where at some point where an acute pain event is only one of several possible tipping points on this continuum that changes potential pain to perceived pain.

The effect of motor imagery and action observation in the rehabilitation of lower limb injuries: A scoping review

OBJECTIVE

To synthesize research literature, which has investigated the application of motor imagery and action observation in rehabilitation protocols. Specifically, we aimed to review the implementation of motor imagery and action observation in the rehabilitation of lower limb injuries.

METHODS

This scoping review followed Arksey and O'Malley's framework and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension guidelines for scoping reviews checklist. The Medline (PubMed), Cochrane Library, Scopus, and Web of Science databases were searched for controlled clinical trials published between 2010 and 2021 using key search terms. Primary articles were screened for inclusion based upon applying motor imagery and action observation as a rehabilitation protocol (independently or in combination) after sustaining an injury or undergoing surgery. Data were charted by extracting the exercise duration, frequency, and the number of weeks from the rehabilitative intervention protocols, and the measured clinical outcomes (pain, range of motion, muscle activity, and functional outcomes).

RESULTS

The initial database search resulted in 1367 articles, with 1352 excluded after screening, resulting in a total of 15 articles eligible for inclusion in the review. Six of the included articles included an action observation intervention, eight studies a motor imagery intervention, and a single study included combined motor imagery and action observation approach. The motor imagery and action observation techniques were able to improve clinical outcomes, including daily activity, functional movement, rage of motion, pain, and muscle strength.

CONCLUSION

Motor imagery and action observation interventions may be effective to improve rehabilitative outcomes of lower limb injuries, thus its application should be considered alongside standard treatment protocols.

Reimagining How We Treat Acute Pain: A Narrative Review

Acute pain may be influenced by biopsychosocial factors. Conditioned pain modulation, distraction, peripheral nerve stimulation, and cryoneurolysis may be helpful in its treatment. New developments in opioids, such as opioids with bifunctional targets and oliceridine, may be particularly suited for acute pain care. Allosteric modulators can enhance receptor subtype selectivity, offering analgesia with fewer and/or less severe side effects. Neuroinflammation in acute pain is caused by direct insult to the central nervous system and is distinct from neuroinflammation in degenerative disorders. Pharmacologic agents targeting the neuroinflammatory process are limited at this time. Postoperative pain is a prevalent form of acute pain and must be recognized as a global public health challenge. This type of pain may be severe, impede rehabilitation, and is often under-treated. A subset of surgical patients develops chronic postsurgical pain. Acute pain is not just temporally limited pain that often resolves on its own. It is an important subject for further research as acute pain may transition into more damaging and debilitating chronic pain. Reimagining how we treat acute pain will help us better address this urgent unmet medical need. 

Ilioinguinal and Iliohypogastric Nerve Block for Acute and Chronic Pain Relief After Caesarean Section: A Randomized Controlled Trial

Background

There is an increasing cesarean section (CS) rate in Egypt. Multiple methods are used to manage pain after CS.

Objectives

This study aimed to assess the effect of ultrasound-guided bilateral ilioinguinal and iliohypogastric nerve block on pain reduction after CS.

Methods

We classified 64 cases of elective CS into two equal groups. The block group underwent the nerve block, and the control group did not. Postoperative pain, morphine consumption, time to analgesic request, and complications were compared between the two groups.

Results

No significant difference was detected between the two groups regarding patient characteristics or operation duration. However, pain scores during rest and movement were significantly lower in the block group than in controls, especially within the first 12 hours following the operation. Morphine consumption was significantly lower in the block group (4.53 ± 1.456) in group B vs. (8.87 ± 2.013) in group C with P-value < 0.001. Time to the first rescue analgesia was significantly longer in the intervention group than in the other group (12.25 vs. 3.81 hours). Pruritis and nausea incidence was significantly higher in controls than in the block group. The incidence of chronic postoperative pain was significantly lower in the block group.

Conclusions

The ilioinguinal and iliohypogastric nerve block is efficient and safe for managing postoperative pain following CS. It is associated with significant improvement of acute and chronic pain after such operations.

Serratus Anterior Block for Long-Term Post-Thoracoscopy Pain Management

Purpose

Neuropathic, chronic pain is a common and severe complication following thoracic surgery, known as post-thoracotomy pain syndrome (PTPS). Here we evaluated the efficacy of an ultrasound-guided serratus anterior plane block (SAPB) on pain control compared to traditional pain management with intravenous opioids and nonsteroidal anti-inflammatory drugs (NSAIDs) six months after thoracic surgery.

Patients and Methods

In this retrospective observational study, we analyzed data from a questionnaire survey. We interviewed all patients who underwent elective video-assisted thoracoscopy surgery (VATS) at Soroka University Medical Center between December 2016 and January 2018. The responses of ninety-one patients were included.

Results

Participants reported PTPS in both groups, 43% of patients in the SAPB group and 57% of patients in the standard group, which failed to reach significance. However, we demonstrated that the percentage of pain occurrence trended lower in the SAPB group. There was significantly less burning/stitching or shooting, shocking, pressure-like, and aching pain in SAPB patients compared to the standard protocol group. Patients in the SAPB group had significantly less pain located in the upper and lower posterior thorax anatomical regions compared to the standard protocol group. Moreover, we found a significant difference in occurrence of PTPS depending on the type of thoracic surgery. From both study groups, 69% of patients who underwent lobectomy reported pain, compared with 41.9% of those in the segmental (wedge resection) procedure, and 42.1% of patients in other procedures.

Conclusion

While the present study did not demonstrate a statistically significant reduction of PTPS after SAPB concerning postoperative pain control, there was a trend of a decrease. We also found significance in the type of pain and location of pain after thoracic surgery between the two groups, as well as a significant difference between pain occurrence in types of thoracic surgeries from both groups.

Impact of Ketamine on Opioid Use and Persistent Pain After Cytoreductive Surgery with Hyperthermic Chemotherapy

Background

Persistent pain and opioid use can be devastating after cytoreductive surgery (CRS) and hyperthermic intraoperative chemotherapy (HIPEC).

Methods

We conducted a retrospective study to investigate the impact of ketamine use on postoperative complications and persistent and chronic pain after CRS-HIPEC.

Results

Ketamine reduced perioperative opioid use before and after implementation of recovery after surgery programs. Ketamine did not impact the formation of persistent and chronic pain formation and long-term opioid use. Postoperative complications and postoperative re-operations were independent predictors of persistent pain. Interestingly, the risk of having a complication was increased by 1% for every doubling in opioids used intraoperatively.

Conclusion

Ketamine use reduces perioperative opioid consumption in patients undergoing CRS-HIPEC, but it is not associated with improvements in long-term opioid use and chronic pain.

Postoperative pain and the gut microbiome

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Poorly controlled postoperative pain remains a major unresolved challenge globally.

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The gut microbiome impacts on inflammatory pain and neuropathic pain.

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Microbiota metabolites can regulate peripheral and central sensitisation.

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Stress is linked to both postoperative pain and an altered gut microbiome.

In excess of 300 million surgical procedures are undertaken worldwide each year. Despite recognition of the prevalence of postoperative pain, and improvements in pain management techniques, poorly controlled postoperative pain remains a major unresolved challenge globally. An estimated 71% and 51% of patients experience moderate to severe pain after surgery in in-patient and outpatient settings, respectively. Inadequately controlled pain after surgery is associated with significant perioperative morbidity including myocardial infarction and pulmonary complications.

As many as 20–56% of patients develop chronic pain after commonly performed procedures such as hernia repair, hysterectomy, and thoracotomy. Traditional analgesics and interventions are often ineffective or partially effective in the treatment of postoperative pain, resulting in a chronic pain condition with related socio-economic impacts and reduced quality of life for the patient. Such chronic pain which occurs after surgery is referred to as Persistent Post-Surgical Pain (PPSP). The complex ecosystem that is the gastrointestinal microbiota (including bacteria, fungi, viruses, phage) plays essential roles in the maintenance of the healthy state of the host. A disruption to the balance of this microbiome has been implicated not only in gastrointestinal disease but also neurological disorders including chronic pain. The influence of the gut microbiome is well documented in the context of visceral pain from the gastrointestinal tract while a greater understanding is emerging of the impact on inflammatory pain and neuropathic pain (both of which can occur during the perioperative period). The gut microbiome is an essential source for driving immune maturation and maintaining appropriate immune response. Given that inflammatory processes have been implicated in postoperative pain, aberrant microbiome profiles may play a role in the development of this type of pain. Furthermore, the microorganisms in our gut produce metabolites, neurotransmitters, and neuromodulators which interact with their receptors to regulate peripheral and central sensitisation associated with chronic pain. Microbiota-derived mediators can also regulate neuroinflammation, which is associated with activation of microglia as well as infiltration by immune cells, known to modulate the development and maintenance of central sensitisation. Moreover, risk factors for developing postoperative pain include anxiety, depression, and increased stress response. These central nervous system-related disorders have been associated with an altered gut microbiome and microbiome targeted intervention studies indicate improvements. Females are more likely to suffer from postoperative pain. As gonadal hormones are associated with a differential microbiome and pre-clinical studies show that male microbiome confers protection from inflammatory pain, it is possible that the composition of the microbiome and its by-products contribute to the increased risk for the development of postoperative pain. Very little evidence exists relating the microbiome to somatic pain. Here we discuss the potential role of the gut microbiome in the aetiology and pathophysiology of postoperative pain in the context of other somatic pain syndromes and what is known about microbe-neuron interactions. Investigations are needed to determine the specific role of the gut microbiome in this type of pain which may help inform the development of preventative interventions as well as management strategies to improve patient outcome.

Assessment of Antimicrobial Agents, Analgesics, and Epidermal Growth Factors-Embedded Anti-Adhesive Poly(Lactic-Co-Glycolic Acid) Nanofibrous Membranes: In vitro and in vivo Studies

Background

Postoperative tissue adhesion is a major concern for most surgeons and is a nearly unpreventable complication after abdominal or pelvic surgeries. This study explored the use of sandwich-structured antimicrobial agents, analgesics, and human epidermal growth factor (hEGF)-incorporated anti-adhesive poly(lactic-co-glycolic acid) nanofibrous membranes for surgical wounds.

Materials and Methods

Electrospinning and co-axial electrospinning techniques were utilized in fabricating the membranes. After spinning, the properties of the prepared membranes were assessed. Additionally, high-performance liquid chromatography and enzyme-linked immunosorbent assays were utilized in assessing the in vitro and in vivo liberation profiles of the pharmaceuticals and the hEGF from the membranes.

Results

The measured data suggest that the degradable anti-adhesive membranes discharged high levels of vancomycin/ceftazidime, ketorolac, and hEGF in vitro for more than 30, 24, and 27 days, respectively. The in vivo assessment in a rat laparotomy model indicated no adhesion in the peritoneal cavity at 14 days post-operation, demonstrating the anti-adhesive capability of the sandwich-structured nanofibrous membranes. The nanofibers also released effective levels of vancomycin, ceftazidime, and ketorolac for more than 28 days in vivo. Histological examination revealed no adverse effects.

Conclusion

The outcomes of this study implied that the anti-adhesive nanofibers with sustained release of antimicrobial agents, analgesics, and growth factors might offer postoperative pain relief and infection control, as well as promote postoperative healing of surgical wounds.

Comparison of local and regional anesthesia modalities in breast surgery: A systematic review and network meta-analysis

STUDY OBJECTIVE

Moderate to severe postoperative pain occurs in up to 60% of women following breast operations. Our aim was to perform a network meta-analysis and systematic review to compare the efficacy and side effects of different analgesic strategies in breast surgery.

DESIGN

Systematic review and network meta-analysis.

SETTING

Operating room, postoperative recovery room and ward.

PATIENTS

Patients scheduled for breast surgery under general anesthesia.

INTERVENTIONS

Following an extensive search of electronic databases, those who received any of the following interventions, control, local anesthetic (LA) infiltration, erector spinae plane (ESP) block, pectoralis nerve (PECS) block, paravertebral block (PVB) or serratus plane block (SPB), were included. Exclusion criteria were met if the regional anesthesia modality was not ultrasound-guided. Network plots were constructed and network league tables were produced.

MEASUREMENTS

Co-primary outcomes were the pain at rest at 0-2 h and 8-12 h. Secondary outcomes were those related to analgesia, side effects and functional status.

MAIN RESULTS

In all, 66 trials met our inclusion criteria. No differences were demonstrated between control and LA infiltration in regard to the co-primary outcomes, pain at rest at 0-2 and 8-12 h. The quality of evidence was moderate in view of the serious imprecision. With respect to pain at rest at 8-12 h, ESP block, PECS block and PVB were found to be superior to control or LA infiltration. No differences were revealed between control and LA infiltration for outcomes related to analgesia and side effects, and few differences were shown between the various regional anesthesia techniques.

CONCLUSIONS

In breast surgery, regional anesthesia modalities were preferable from an analgesic perspective to control or LA infiltration, with a clinically significant decrease in pain score and cumulative opioid consumption, and limited differences were present between regional anesthetic techniques themselves.

Efficacy, Treatment Characteristics, and Biopsychological Mechanisms of Music-Listening Interventions in Reducing Pain (MINTREP): Study Protocol of a Three-Armed Pilot Randomized Controlled Trial

Background: Pain can severely compromise a person's overall health and well-being. Music-listening interventions have been shown to alleviate perceived pain and to modulate the body's stress-sensitive systems. Despite the growing evidence of pain- and stress-reducing effects of music-listening interventions from experimental and clinical research, current findings on music-induced analgesia are inconclusive regarding the role of specific treatment characteristics and the biopsychological mechanisms underlying these effects. Objective: The overall aim of this pilot randomized controlled trial is to test and compare the differential effects of frequency-modulated and unmodulated music (both researcher-selected) on experimentally induced perception of acute pain and to test the efficacy of the interventions in reducing biological and subjective stress levels. Moreover, these two interventions will be compared to a third condition, in which participants listen to self-selected unmodulated music. Methods and Analysis: A total of 90 healthy participants will be randomly allocated to one of the three music-listening intervention groups. Each intervention encompasses 10 sessions of music listening in our laboratory. Frequency-modulation will involve stepwise filtering of frequencies in the audible range of 50-4,000 Hz. Acute pain will be induced via the cold pressor test. Primary (i.e., pain tolerance, perceived pain intensity) and secondary (i.e., heart rate variability, electrodermal activity, hair cortisol, subjective stress) outcomes will be measured at baseline, post, and follow-up. In addition, intermittent measurements as well as a follow-up assessment and a range of tertiary measures (e.g., music-induced emotions) are included. Discussion: This is the first study to systematically test and compare the effects of music frequencies along with the control over music selection, both of which qualify as central treatment characteristics of music-listening interventions. Results will be highly informative for the design of subsequent large-scale clinical trials and provide valuable conclusions for the implementation of music-listening interventions for the reduction of perceived pain. Clinical Trial Registration: Clinical Trials Database of the U.S. National Library of Medicine: Identifier NCT02991014.

Local infiltration of tramadol as an effective strategy to reduce post-operative pain: a systematic review protocol and meta-analysis

OBJECTIVE

The purpose of this review is to evaluate the use and effectiveness of the local administration of tramadol in reducing post-operative pain during surgical interventions.

METHODS

The PubMed, EMBASE and Cochrane Central Register of Controlled Trials (CENTRAL) databases will be searched for this review. This systematic review will include studies evaluating the clinical efficacy of the local infiltration of tramadol, with no study design restrictions. Only studies that present clear descriptions of local tramadol administration are published in peer-reviewed journals in the English, Italian, Spanish, French, Portuguese or German language and are published in full will be taken into consideration. A meta-analysis will be performed when there is sufficient clinical homogeneity among the retrieved studies, and only randomized controlled studies and quasi-randomized controlled studies will be included. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach will be used to assess the certainty in the evidence. If a quantitative analysis cannot be conducted, a qualitative description of the results of the retrieved studies will be provided.

RESULTS

A high-quality synthesis of the current evidence on the local administration of tramadol for managing post-surgical pain will be illustrated using subjective reports and objective measures of performance. The primary outcomes will include the magnitude of post-operative pain intensity improvement, with improvement being as defined by a reduction by at least 2 points in the visual analogue scale (VAS) score or numerical rating scale (NRS) score. The secondary outcomes will be the magnitude of reduction in tramadol rescue doses and in other analgesic drug doses.

CONCLUSION

This protocol will present evidence on the efficacy of tramadol in relieving post-surgical pain.

SYSTEMIC REVIEW REGISTRATION

PROSPERO CRD42018087381.

Evaluation of the preclinical analgesic efficacy of naturally derived, orally administered oil forms of Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD), and their 1:1 combination

Chronic neuropathic pain (NP) is a growing clinical problem for which effective treatments, aside from non-steroidal anti-inflammatory drugs and opioids, are lacking. Cannabinoids are emerging as potentially promising agents to manage neuroimmune effects associated with nociception. In particular, Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD), and their combination are being considered as therapeutic alternatives for treatment of NP. This study aimed to examine whether sex affects long-term outcomes on persistent mechanical hypersensitivity 7 weeks after ceasing cannabinoid administration. Clinically relevant low doses of THC, CBD, and a 1:1 combination of THC:CBD extracts, in medium chain triglyceride (MCT) oil, were orally gavaged for 14 consecutive days to age-matched groups of male and female sexually mature Sprague Dawley rats. Treatments commenced one day after surgically inducing a pro-nociceptive state using a peripheral sciatic nerve cuff. The analgesic efficacy of each phytocannabinoid was assessed relative to MCT oil using hind paw mechanical behavioural testing once a week for 9 weeks. In vivo intracellular electrophysiology was recorded at endpoint to characterize soma threshold changes in primary afferent sensory neurons within dorsal root ganglia (DRG) innervated by the affected sciatic nerve. The thymus, spleen, and DRG were collected post-sacrifice and analyzed for long-term effects on markers associated with T lymphocytes at the RNA level using qPCR. Administration of cannabinoids, particularly the 1:1 combination of THC, elicited a sustained mechanical anti-hypersensitive effect in males with persistent peripheral NP, which corresponded to beneficial changes in myelinated Aβ mechanoreceptive fibers. Specific immune cell markers associated with T cell differentiation and pro-inflammatory cytokines, previously implicated in repair processes, were differentially up-regulated by cannabinoids in males treated with cannabinoids, but not in females, warranting further investigation into sexual dimorphisms that may underlie treatment outcomes.

The effectiveness of physiotherapy interventions on pain and quality of life in adults with persistent post-surgical pain compared to usual care: A systematic review

Background

Persistent post-surgical pain (PPSP) is a common condition following surgery, resulting in persistent pain and reduced quality of life (QoL). While pharmacological management is common, its effectiveness remains equivocal. This systematic review investigated the effectiveness of physiotherapy management in adults with PPSP in comparison to usual care.

Methods

A systematic search of six electronic databases was conducted. Studies of human adults (>18 years) with PPSP localised or directly referred from the surgical site, pain persisting for at least two months post-surgery and with physiotherapy as the intervention were included. This review was conducted and reported in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The McMaster critical review form for quantitative studies was utilised to assess the methodological quality. A descriptive synthesis was undertaken due to the heterogeneity of the included studies.

Results

Of the 1395 articles that were screened, eight studies met the inclusion criteria. A diverse range of physiotherapy interventions were utilised, and effectiveness was measured through diverse outcomes and measures. Summarised findings from the heterogenous evidence base indicated that physiotherapy interventions for PPSP has a positive impact across a range of outcomes, including pain, quality of life (QoL), physical function and depression. While these are encouraging findings, the current evidence base lacks uniformity with regards to participant characteristics, time periods since diagnosis, interventions delivered, and its parameters, and outcomes measured.

Conclusion

Due to ongoing challenges in the management of PPSP, alternate treatment strategies such as physiotherapy are being trialled. Despite a number of methodological constraints, current evidence indicates that physiotherapy could play a role in the management of PPSP.

PROSPERO registration

CRD42019129580

Chronic pain among the hospitalized patients after the 22 July 2011 terror attacks in Oslo and at Utøya Island

BACKGROUND

On 22 July 2011, 48 people were hospitalized due to physical injuries from gun shots or explosion, following 2 terror attacks in the Oslo area, Norway. In this study, we have investigated the occurrence of chronic pain, the severity and consequences of chronic pain in these patients, 3 to 4 years after the incidents.

METHODS

Totally 43 eligible terror trauma patients were invited to participate in the study, 30 patients were included. They underwent a consultation with a psychologist and a physician; containing psychological assessment, neuropsychological screening, a standardized clinical interview, medical examination, and a pain protocol.

RESULTS

In 18 (60%) the injury was severe, as defined by New Injury Severity Score > 15. Twenty-four patients (80%) reported injury-related chronic pain after the trauma, in 22 with consequences on daily life. Analgesics were used by 20 patients, including 5 in need of opioids. Ten patients had unmet needs of further specialist pain care. In 12 patients, the average pain score last week was above three on a 0-10 Numeric Rating Scale. In these patients, clinical signs of neuropathic pain were evident in 10, as tested by the Douleur Neuropathique score. There were significant correlations (P < 0.05) between severity of chronic pain and presence of post-traumatic stress symptoms, reduced quality of life, reduced psychosocial and physical function; but no correlation with pre-injury patient characteristics or the degree of physical injury.

CONCLUSION

Chronic pain was frequent and significant, irrespective of injury severity, in these patients who obtained their physical injuries under extreme psychological conditions.

Anesthetics and human epidermal growth factor incorporated into anti-adhesive nanofibers provide sustained pain relief and promote healing of surgical wounds

Background: This study exploited sheath-core-structured lidocaine/human EGF (hEGF)-loaded anti-adhesive poly[(d,l)-lactide-co-glycolide] (PLGA) nanofibrous films for surgical wounds via a co-axial electrospinning technique. Materials and methods: After spinning, the properties of the co-axially spun membranes were characterized by scanning electron microscopy, laser-scanning confocal microscopy, Fourier Transform Infrared spectrometry, water contact angle measurements, and tensile tests. Furthermore, a HPLC analysis and an ELISA evaluated the in vitro and in vivo release curves of lidocaine and hEGF from the films. Results: PLGA anti-adhesion nanofibers eluted high levels of lidocaine and hEGF for over 32 and 27 days, respectively, in vitro. The in vivo evaluation of post-surgery recovery in a rat model demonstrated that no adhesion was noticed in tissues at 2 weeks after surgery illustrating the anti-adhesive performance of the sheath-core-structured nanofibers. Nanofibrous films effectively released lidocaine and hEGF for >2 weeks in vivo. In addition, rats implanted with the lidocaine/hEGF nanofibrous membranes exhibited greater activities than the control demonstrating the pain relief efficacy of the films. Conclusion: The empirical outcomes suggested that the anti-adhesive nanofibrous films with extended release of lidocaine and hEGF offer post-operative pain relief and wound healing.

High-fat diet exacerbates postoperative pain and inflammation in a sex-dependent manner

Obesity is often associated with increased pain, but little is known about the effects of obesity and diet on postoperative pain. In this study, effects of diet and obesity were examined in the paw incision model, a preclinical model of postoperative pain. Long-Evans rats were fed high-fat diet (40% calories from butter fat) or low-fat normal chow. Male rats fed high-fat diet starting 6 weeks before incision (a diet previously shown to induce markers of obesity) had prolonged mechanical hypersensitivity and an overall increase in spontaneous pain in response to paw incision, compared with normal chow controls. Diet effects in females were minor. Removing high-fat diet for 2 weeks before incision reversed the diet effects on pain behaviors, although this was not enough time to reverse high-fat diet-induced weight gain. A shorter (1 week) exposure to high-fat diet before incision also increased pain behaviors in males, albeit to a lesser degree. The 6-week high-fat diet increased macrophage density as examined immunohistochemically in lumbar dorsal root ganglion even before paw incision, especially in males, and sensitized responses of peritoneal macrophages to lipopolysaccharide stimuli in vitro. The nerve regeneration marker growth-associated protein 43 (GAP43) in skin near the incision (day 4) was higher in the high-fat diet group, and wound healing was delayed. In summary, high-fat diet increased postoperative pain particularly in males, but some diet effects did not depend on weight gain. Even short-term dietary manipulations, that do not affect obesity, may enhance postoperative pain.

Psychosocial predictors in the transition from acute to chronic pain: a systematic review

Chronic non-cancer pain (CNCP) is a major health problem which psychosocial factors have significant implications in. There is a gap in regards to evidence for the prevention of chronicity specifically addressing psychological and social domains. Four databases were searched with terms related to "psychosocial", "acute pain", and "chronic pain". A total of 1,389 studies were identified in which titles, abstracts, and full texts were assessed for inclusion criteria. A data template was used to capture pertinent details, and overall themes and patterns were organized according to type of pain examined and psychosocial variables measured. Of the 18 articles that met inclusion criteria, fifteen (83%) of the articles reported an association between psychosocial factors and chronicity. A total of 5 of the studies (29%) demonstrated that depression was a possible predictor and 6 (35%) of the studies found fear-avoidance to be associated with chronicity. This review provides evidence that psychosocial factors are associated with chronicity within CNCP. These results suggest a need for targeting psychosocial predictors in prevention and early intervention through clinical guidelines and a national strategy to support a cultural change in pain care.

Predictors of chronic neuropathic pain after scoliosis surgery in children

Background

Numerous publications describe chronic pain following surgery in both adults and children. However, data in the paediatric population are still sparse and both prevalence of chronic pain after surgery and risk factors of this complication still undetermined.

Methods

We prospectively evaluated the prevalence of chronic pain and its neuropathic pain component at 1 year following correction of idiopathic scoliosis in children less than 18 years of age. Pain was defined as the presence of pain (numerical rating scale – NRS ≥4), the presence of signs of neurologic damage within the area of surgery and the presence of the neuropathic symptoms as a DN4 (Douleur Neuropathique 4) questionnaire ≥4. Factors investigated as potentially associated with the presence of a persistent neuropathic pain were: age, weight, the presence of continuous preoperative pain over the 3 months before surgery, surgical characteristics, pain scores during the first five postoperative days, and DN4 at day 3. Statistical analysis employed univariate analysis and a multivariate logistic regression model.

Results

Thirty six patients were included in the study. Nineteen (52.8%) had pain at one year after surgery. Among them 17 (48.2%) had neuropathic pain. Logistic regression found continuous pain over the 3 months preceding surgery and day 1 morphine consumption ≥0.5 mg kg-1 as independent predictors of persistent chronic pain with a neuropathic component. The overall model accuracy was 80.6 and the area under the curve of the model was 0.89 (95% confidence interval 0.78–0.99).

Conclusions

The present study found a high proportion of paediatric patients developing chronic persistent pain after surgical correction of scoliosis diformity. It allows identifying two factors associated with the occurrence of persistent chronic pain with a neuropathic component: the presence of persistent preoperative pain during the 3 months preceeding surgery and postoperative opioid consumption at day 1 –;0.5 mg kg-1

Implication

Patients scheduled for spine surgery and presenting with preoperative pain should be considered at risk of chronic pain after surgery and managed accordingly by the chronic and/or acute pain team. Postoperative opioid consumption should be lowered as possible by using multimodal analgesia and regional analgesia such as postoperative epidural analgesia.

The Cold Pressor Test as a Predictor of Prolonged Postoperative Pain, a Prospective Cohort Study

INTRODUCTION

Presently, it is difficult to predict which patients are at increased risk of ongoing pain problems postoperatively. This study followed a group of patients from the week before their operation until 3 months after it, to identify potential risk variables.

METHODS

Fifty-four patients undergoing moderate-major gynaecological surgery at Christchurch Women's Hospital were recruited and assessed preoperatively over an 11-week period. At this initial assessment, participants were subjected to a cold pressor test (CPT). Telephonic follow-up was conducted at 6 weeks and 3 months postoperatively, to determine pain status. Information regarding the type of operation and surgical approach was collected from hospital records.

RESULTS

Pain threshold (time taken to report the onset of pain), as measured by the CPT, was significantly predictive of prolonged pain outcomes (area under the curve = 0.80, 95 % CI 0.66, 0.95). Pain tolerance (total time taken to end the CPT voluntarily) was similarly predictive but non-significant (area under the curve = 0.69, 95 % CI 0.47, 0.90).

CONCLUSION

The preoperative cold pressor test shows some promise for predicting ongoing postoperative pain. However, more research is needed to determine the clinical significance of these findings in larger samples and how they could be incorporated into clinical practice.

Perioperative Pain Correlates and Prolonged Postoperative Pain Predictors: Demographic and Psychometric Questionnaires

Introduction

Perioperatively, patients are near-guaranteed to experience acute pain by virtue of the surgical tissue insult. The transition of acute pain to pathological chronic pain is a complex and poorly understood process. To study this, the prevalence of pain was examined preoperatively, and at 6 weeks and 3 months postoperatively.

Methods

Fifty-four patients undergoing moderate-major gynaecological surgery at Christchurch Women’s Hospital (Christchurch, New Zealand) were recruited over a period of 11 weeks. Follow-up by telephone was conducted at 6 weeks and 3 months following surgery. Demographic information including age, gender, ethnicity, work, and education status were collected, as well as aspects of medical history. Participants were subjected to psychometric questionnaires at each time-point.

Results

Of the participants, 15.7% experienced significant pain at 6 weeks postoperatively; 8.2% of participants experienced significant pain at 3 months postoperatively. The psychometric questionnaires used found differences between those experiencing pain and those not experiencing pain at given observation points. Only the Brief Illness Perception Questionnaire (BIPQ) appeared predictive of developing prolonged postoperative pain. The mean difference (7.4 on a 0–50) scale should assist in clinical decision-making regarding analgesia.

Conclusion

Only the BIPQ was predictive of developing prolonged postoperative pain. While none of the demographic factors observed significantly predicted the development of ‘prolonged pain’, the not significant data followed expected trends. Several relationships were detected in this study that should further efforts in developing preoperative predictors to promote the secondary prevention of postoperative pain states.

Electronic supplementary material

The online version of this article (doi:10.1007/s40122-015-0037-7) contains supplementary material, which is available to authorized users.