The Transition of Acute Postoperative Pain to Chronic Pain: An Integrative Overview of Research on Mechanisms

Genome-wide association study on chronic postsurgical pain after abdominal surgeries in the UK Biobank

INTRODUCTION

Chronic pain is one of the most common and severe complications after surgery, affecting quality of life and overall wellbeing of patients. Several risk factors have been identified but the mechanisms of chronic postsurgical pain development remain unclear. This study aimed to identify single-nucleotide polymorphisms associated with developing chronic postsurgical pain after abdominal surgery, one of the most common types of surgery.

METHODS

A genome-wide association study was performed on 27,603 patients from the UK Biobank who underwent abdominal surgery. The robustness of identified loci was validated by split-half validation analysis. Functionally related top loci were selected for expression validation in clinical samples of adhesions from patients with and without pain.

RESULTS

One locus (rs185545327) reached genome-wide significance for association with chronic postsurgical pain development, and 10 loci surpassed the suggestively significant threshold (p < 1 × 10-6). In the robustness analysis, eight loci had at least nominal significance. The loci passing the suggestively significant threshold were mapped to 15 genes, of which two loci contained pain-related genes (SRPK2, PDE4D). Although marginally approaching statistical significance in the expression validation of clinical samples, the detection rate and expression level of PDE4D were modestly higher in patients with pain compared with those in the control group.

DISCUSSION

This study provides preliminary evidence for genetic risk factors implicated in chronic postsurgical pain following abdominal surgery, particularly the PDE4D gene, which has been associated with pain in previous studies. The findings add to evidence suggesting potential for the future development of a clinically applicable tool for personalised risk prediction, aiding clinicians in stratifying patients and enhancing clinical decision-making through individualised risk assessments.

Changes in spatial bodily pain distribution one year after benign hysterectomy with emphasis on prevalence and risk factors for de novo and persistent pelvic pain- a prospective longitudinal multicenter study

BACKGROUND

The objectives were to determine the prevalence of de novo and persistent pelvic pain after benign hysterectomy and to assess risk factors.

METHODS

A Swedish prospective multicenter study of 440 women undergoing benign hysterectomy was conducted between October 2011 and March 2017. Measures of pain, the spatial extent of bodily pain, and pain sensitivity were assessed using a self-reporting questionnaire, Margolis's patient pain drawing, and quantitative sensory testing of pain thresholds for pressure, heat, and cold, respectively. Quality of life was evaluated by EQ-5D-3L and SF-36. Psychological distress was assessed by the Hospital Anxiety and Depression Scaleand the Stress-Coping Inventory. Logistic regression models were used to assess risk factors, and the outcome was presented as an adjusted odds ratio (aOR) and 95% confidence interval (CI).

RESULTS

Preoperatively, 18.0% of the women reported no bodily pain, 41.5% had pelvic pain, either as the only location (7.0%) or along with pain in other locations (34.5%), and 40.5% had non-pelvic pain only. Postoperatively, 6.2% developed de novo pelvic pain and 16.4% had persistent pelvic pain. De novo pelvic pain developed exclusively in women who preoperatively had non-pelvic pain only. Risk factors for de novo pelvic pain were a long hospital stay (aOR 1.50 (95%CI) 1.02-2.21)), high preoperative pain intensity (aOR 1.25 (95%CI 1.01-1.62)) and a high number of pain areas (aOR 1.15 (95%CI 1.05-1.27)), along with anxiety (aOR 10.61 (95%CI 1.84-61.03)) and low EQ-5D-3L health index (aOR 0.02 (95%CI 0.00-0.31)). Risk factors for persistent pelvic pain were lower age (aOR 0.89 (95%CI 0.81-0.97)), higher number of pain areas (aOR 1.08 (95%CI 1.02-1.14)), and a higher frequency of preoperative pain (aOR 12.75 (95%CI 2.24-72.66)).

CONCLUSION

Although hysterectomy appeared to be reasonably effective in curing pelvic pain, a non-negligible proportion of women developed de novo pelvic pain or had persistent pelvic pain. De novo pelvic pain seemed to affect only those who preoperatively had widespread bodily pain. Women at risk for de novo and persistent pelvic pain after hysterectomy could be identified preoperatively.

TRIAL REGISTRATIONS

The study was retrospectively registered in ClinicalTrial.gov (NCT01526668) on 01/27//2012.

Pain Experiences and Coping Methods of Living Liver Donors Experiencing Chronic Pain After Surgery: Qualitative Study

BACKGROUND

Living liver donors are known to experience many physical symptoms such as pain in the postoperative period.

AIM

This qualitative study was conducted to examine pain experiences and coping methods of living liver donors experiencing postoperative chronic pain.

METHODS

The study sample consisted of 16 living liver donors. Data were collected using a personal information form and a semi-structured questionnaire. Quantitative data were analyzed as number, mean, standard deviation, and percentage. Qualitative data were analyzed within the framework of thematic and content analysis methods.

RESULTS

The mean postoperative chronic pain rate of living liver donors was 4.5. Eight of these people reported experiencing sudden, pinprick-like pain after liver transplantation. Living liver donors stated that the greatest factor that increased their pain was exertion/spontaneous movement. Half of them stated that the pain they experienced after transplantation had no impact on their daily life activities. Most of the living liver donors stated that the pain they experienced had no impact on their social lives; however, it caused sadness and psychological deterioration. The most preferred method to cope with pain was the use of medication.

CONCLUSIONS

Living liver donors experienced moderate postoperative chronic pain, and a significant proportion of them reported psychological symptoms related to the pain they experienced. A multidisciplinary pain team can help with pain management by providing training conducted in transplant centers.

Electroacupuncture Mechanisms in Managing Preoperative Anxiety and Postoperative Pain Chronification: A Review

Introduction

Postoperative hyperalgesic priming, exacerbated by preoperative anxiety, complicates pain management and recovery. Electroacupuncture (EA), a technique that combines traditional acupuncture with electrical stimulation applied through needles to enhance therapeutic effect, offers a potential solution by targeting multiple neurobiological pathways.

Objective

This review investigates how EA addresses preoperative anxiety-induced postoperative hyperalgesic priming ie pain chronification, focusing on its mechanisms in three areas: preoperative anxiety, postoperative hyperalgesic priming, and the interaction between EA and these processes.

Methods

A literature search across PubMed, ScienceDirect, and Google Scholar identified relevant studies on EA's effects on neurobiological pathways related to anxiety and pain. The review synthesized findings to understand EA's role in these contexts.

Results

EA alleviates preoperative anxiety by influencing the body's neurochemical and neurophysiological responses. It reduces inflammation, regulates stress hormones, and improves autonomic function. For postoperative pain chronification, EA modulates pain pathways, reduces inflammation, and affects receptor signaling, gene expression, and neurotransmitter systems.

Conclusion

EA offers a promising approach to managing preoperative anxiety and postoperative pain. By addressing both the physiological and neurochemical pathways that contribute to pain and anxiety, EA has the potential to significantly improve clinical outcomes for patients undergoing surgery. Further research is needed to fully understand its mechanisms and optimize its application in clinical settings.

Is chronic pain caused by central sensitization? A review and critical point of view

Chronic pain causes disability and loss of health worldwide. Yet, a mechanistic explanation for it is still missing. Frequently, neural phenomena, and among them, Central Sensitization (CS), is presented as causing chronic pain. This narrative review explores the evidence substantiating the relationship between CS and chronic pain: four expert researchers were divided in two independent teams that reviewed the available evidence. Three criteria were established for a study to demonstrate a causal relationship: (1) confirm presence of CS, (2) study chronic pain, and (3) test sufficiency or necessity of CS over chronic pain symptoms. No study met those criteria, failing to demonstrate that CS can cause chronic pain. Also, no evidence reporting the occurrence of CS in humans was found. Worryingly, pain assessments are often confounded with CS measures in the literature, omitting that the latter is a neurophysiological and not a perceptual phenomenon. Future research should avoid this misconception to directly interrogate what is the causal contribution of CS to chronic pain to better comprehend this problematic condition.

Efficacy and safety of 4-hydroxy 2-methyl-N-(5-methyl-2-thiazolyl)-2H-1, 2-benzothiazin-3-carboxamide 1,1-dioxide, a fast-acting meloxicam formulation, on moderate-to-severe pain following abdominal surgery: A phase III randomized controlled trial

4-hydroxy 2-methyl-N-(5-methyl-2-thiazolyl)-2H-1, 2-benzothiazin-3-carboxamide 1,1-dioxide (QP001), a novel long-lasting meloxicam formulation, may provide adequate postoperative pain relief with a good safety profile. This study aimed to evaluate the efficacy and safety of QP001 for moderate-to-severe pain following abdominal surgery. This multicenter, randomized, double-blind, placebo-controlled phase III trial recruited patients undergoing abdominal surgery at 23 centers between October 30, 2022, and July 10, 2023. Patients were randomized to a QP001 or placebo group in a 2:1 ratio. Postoperative pain intensity was evaluated using the Numerical Rating Scale. The primary efficacy outcome was the area under curve (AUC) of pain intensity-time 0-24 h after awakening from anesthesia (AUC0-24). Adverse events and drug reactions were recorded to evaluate safety. A total of 258 patients underwent randomization, and 255 patients received at least one trial drug, including 170 in the QP001 group and 85 in the placebo group. Among these patients, 250 completed the study. The AUC0-24 was significantly lower in the QP001 group than in the placebo group (50.5 vs. 85.19, difference of 34.69 [40.7%], p < 0.0001). This was accompanied by a decrease in morphine use and an increase in patient satisfaction. Moreover, the overall adverse events or adverse drug reaction rates were similar between the QP001 and placebo groups. Among patients undergoing abdominal surgery, postoperative pain was significantly lower in the QP001 group than in the placebo group. QP001 has a great analgesic effect of up to 24 h and satisfactory safety in patients with moderate-to-severe abdominal pain.

Diagnosis and Management of Neuropathic Breast Pain

Chronic postoperative pain after breast surgery is a significant concern, with studies indicating varying rates depending on the type of surgical procedure. The risk of developing neuropathic pain is notably increased with axillary lymph node dissection due to potential nerve injuries. Additionally, the method of breast reconstruction may influence postsurgical pain rates, with conflicting findings on the impact of reconstruction type. Recent advancements in techniques such as targeted muscle reinnervation, among others, show promise in addressing postoperative pain in these patients. As the prevalence of these procedures rises, future research is likely to focus on assessing and managing pain in this patient population. The development of patient-reported outcome measures specific to breast surgery pain can aid in clinical assessment and treatment planning. This review emphasizes the importance of gaining a deeper understanding of risk factors, nerve anatomy, and treatment options to enhance outcomes and quality of life for individuals undergoing breast surgery.

Chronic post-surgical pain after total knee arthroplasty: a narrative review

Total knee arthroplasty (TKA) is an efficacious treatment for end-stage knee osteoarthritis, often accompanied by severe postoperative pain. In certain patients, this pain can persist for over 3 months and is referred to as chronic post-surgical pain (CPSP). Postoperative persistent pain has emerged as a significant and noteworthy issue impacting patient quality of life following TKA. The etiology of CPSP after TKA is multifaceted. Peripheral or central sensitizations resulting from inflammatory reactions, nerve injury, and neurobiological mechanisms are the primary mechanisms contributing to chronic persistent pain after TKA. Preoperative, intraoperative, and postoperative factors can induce pain sensitization. Once CPSP occurs after TKA, it significantly hampers patient recovery with challenging treatment options. Currently, among the preventive and therapeutic strategies for chronic pain after TKA, it is widely believed that early comprehensive preventive treatment to prevent acute to chronic pain transition can substantially reduce the incidence of CPSP following TKA. In recent years, studies have investigated perioperative strategies aimed at reducing the occurrence of persistent pain after TKA. This article provides an overview of advancements in understanding the pathogenesis, high-risk factors, and preventive measures for chronic pain following TKA. We hope that this review will guide future research directions on CPSP after TKA while contributing to clinical perioperative pain management.

A neural circuit from thalamic paraventricular nucleus via zona incerta to periaqueductal gray for the facilitation of neuropathic pain

Top-down projections transmit a series of signals encoding pain sensation to the ventrolateral periaqueductal gray (vlPAG), where they converge with various incoming projections to regulate pain. Clarifying the upstream regulatory hierarchy of vlPAG can enhance our understanding of the neural circuitry involved in pain modulation. Here, we show that a in a mouse model of spared nerve injury (SNI), activation of a circuit arising from posterior paraventricular thalamic nucleus CaMKIIα-positive neurons (PVPCaMKIIα) projects to gamma-aminobutyric acid neurons in the rostral zona incerta (ZIrGABA) to facilitate the development of pain hypersensitivity behaviors. In turn, these ZIrGABA neurons project to CaMKIIα-positive neurons in the vlPAG (vlPAGCaMKIIα), a well-known neuronal population involved in pain descending modulation. In vivo calcium signal recording and whole-cell electrophysiological recordings reveal that the PVPCaMKIIα→ZIrGABA→vlPAGCaMKIIα circuit is activated in SNI models of persistent pain. Inhibition of this circuit using chemogenetics or optogenetics can alleviate the mechanical pain behaviors. Our study indicates that the PVPCaMKIIα→ZIrGABA→vlPAGCaMKIIα circuit is involved in the facilitation of neuropathic pain. This previously unrecognized circuit could be explored as a potential target for neuropathic pain treatment.

Smart Response Biomaterials for Pain Management

The intricate nature of pain classification and mechanism constantly affects the recovery of diseases and the well-being of patients. Key medical challenges persist in devising effective pain management strategies. Therefore, a comprehensive review of relevant methods and research advancements in pain management is conducted. This overview covers the main categorization of pain and its developmental mechanism, followed by a review of pertinent research and techniques for managing pain. These techniques include commonly prescribed medications, invasive procedures, and noninvasive physical therapy methods used in rehabilitation medicine. Additionally, for the first time, a systematic summary of the utilization of responsive biomaterials in pain management is provided, encompassing their response to physical stimuli such as ultrasound, magnetic fields, electric fields, light, and temperature, as well as changes in the physiological environment like reactive oxygen species (ROS) and pH. Even though the application of responsive biomaterials in pain management remains limited and at a fundamental level, recent years have seen the examination and debate of relevant research findings. These profound discussions aim to provide trends and directions for future research in pain management.

Efficacy of gabapentin and pregabalin for treatment of post refractive surgery pain: a systematic review and meta-analysis

INTRODUCTION

For ophthalmic patients, eye discomfort is a major problem that requires efficient pain treatment techniques. Pregabalin and gabapentin have surfaced as viable treatments for post-refractive surgery pain. To manage pain after refractive surgery, gabapentin and pregabalin were evaluated in this systematic review and meta-analysis.

METHODOLOGY

A thorough search of databases including PubMed, Embase, Cochrane Library, and CINAHL was performed until March 2024. Inclusion criteria were randomized controlled trials assessing pregabalin and/or gabapentin's effectiveness in treating pain post-PRK, LASIK, and LASEK surgeries.

RESULTS

Six studies met inclusion criteria, comprising a total of 391 patients undergoing various corneal surgeries. The meta-analysis revealed that pregabalin was significantly more effective than placebo in reducing pain on the first and second postoperative days (SMD day 1: -0.32, 95% CI -0.54, -0.09; SMD day 2: -0.55, 95% CI -0.85, -0.25), while gabapentin showed significant pain reduction on the second day only (SMD day 2: -0.42, 95% CI -0.71, -0.13). Combined analysis for both medications showed significant pain reduction on the first- and second-days post-surgery. No significant increase in adverse events was associated with either medication. Publication bias was minimal except for a slight asymmetry noted on day 1 effectiveness.

CONCLUSION

Pregabalin and gabapentin are effective in reducing postoperative pain following refractive surgeries, with pregabalin showing a greater effect. Both medications are safe, with no significant increase in adverse events. Further research with standardized methodologies and long-term follow-up is recommended to optimize postoperative pain management in ocular surgeries.

Widespread hyperexcitability of nociceptor somata outlasts enhanced avoidance behavior after incision injury

ABSTRACT

Nociceptors with somata in dorsal root ganglia (DRGs) readily switch from an electrically silent state to a hyperactive state of tonic, nonaccommodating, low-frequency, irregular discharge of action potentials (APs). Spontaneous activity (SA) during this state is present in vivo in rats months after spinal cord injury (SCI) and has been causally linked to SCI pain. Intrinsically generated SA and, more generally, ongoing activity (OA) are induced by various neuropathic conditions in rats, mice, and humans and are retained in nociceptor somata after dissociation and culturing, providing a powerful tool for investigating its mechanisms and functions. The present study shows that long-lasting hyperexcitability that can generate OA during modest depolarization in probable nociceptors dissociated from DRGs of male and female rats is induced by plantar incision injury. OA occurred when the soma was artificially depolarized to a level within the normal range of membrane potentials where large, transient depolarizing spontaneous fluctuations (DSFs) can approach AP threshold. This hyperexcitability persisted for at least 3 weeks, whereas behavioral indicators of affective pain-hind paw guarding and increased avoidance of a noxious substrate in an operant conflict test-persisted for 1 week or less. The most consistent electrophysiological alteration associated with OA was enhancement of DSFs. An unexpected discovery after plantar incisions was hyperexcitability in neurons from thoracic DRGs that innervate dermatomes distant from the injured tissue. Potential in vivo functions of widespread, low-frequency nociceptor OA consistent with these and other findings are to contribute to hyperalgesic priming and to drive anxiety-related hypervigilance.

Effects of training on Feline Grimace Scale scoring for acute pain assessment in cats

OBJECTIVES

The aim of the study was to determine the effects of training on inter-rater reliability and agreement of Feline Grimace Scale (FGS) scoring by small animal practitioners.

METHODS

Seven small animal veterinarians were asked to score a total of 50 images of cats in varying degrees of pain before and after training in FGS scoring. Participant scores were compared with those of an expert rater. Inter-rater reliability was analyzed using the intraclass correlation coefficient (ICC) before and after training (ICC <0.50 = poor reliability, 0.50-0.75 = moderate reliability, 0.76-0.90 = good reliability and >0.90 = excellent reliability). The Bland-Altman method was used to analyze the limits of agreement (LoAs) and bias between participants and the expert rater.

RESULTS

After training, the ICC classification improved for each action unit (ear position, orbital tightening, muzzle tension, whiskers change and head position). The inter-rater reliability for the total FGS ratio scores before and after the FGS training session was moderate (ICC = 0.75; 95% confidence interval [CI] 0.66-0.83) and good (ICC = 0.80; 95% CI 0.73-0.87), respectively. Before training, LoAs were -0.277 to 0.310 with a bias of 0.016. After training, LoAs were -0.237 to 0.255 with a bias of 0.008. The bias was low (<0.1) both before and after training and LoAs did not span the FGS analgesic threshold (0.39).

CONCLUSIONS AND RELEVANCE

Training in FGS scoring improved inter-rater reliability and agreement among seven small animal veterinarians and the veterinarians' skills in pain assessment.

Comparative Efficacy of Spinal Cord Stimulation in the Management of Acute Pain and Chronic Pain Related to Failed Back Surgery Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Spinal cord stimulation (SCS) is a well-established treatment for chronic pain. However, its potential in acute pain management requires further investigation. The goal of this review is to assess and compare the effectiveness of SCS for managing acute postoperative pain against chronic pain associated with failed back surgery syndrome (FBSS). A comprehensive search of databases identified randomized controlled trials (RCTs) that examined SCS for both acute and chronic pain associated with FBSS. Pain relief was measured using the Visual Analog Scale (VAS) and Numeric Rating Scale (NRS). Study quality was evaluated using the Jadad score and Cochrane risk of bias tool. Evidence suggests that SCS significantly reduces acute pain, achieving over a 50% reduction in VAS scores. For chronic pain associated with FBSS, SCS demonstrated substantial efficacy, with a mean reduction of -2.45 on pain scales compared to baseline. When compared to optimal medical management (OMM), SCS was more effective, showing a mean reduction of -1.17 in pain scores for FBSS. Overall, SCS offers significant benefits in managing chronic pain, particularly in FBSS, by reducing pain intensity and opioid use. While the initial findings for acute pain relief are promising, further high-quality RCTs are needed to better understand SCS's role in preventing the transition from acute to chronic pain. Continued research into optimizing patient selection and stimulation parameters will be essential to improve therapeutic outcomes in both acute and chronic pain management.

Current concepts and targets for preventing the transition of acute to chronic postsurgical pain

PURPOSE OF REVIEW

It is estimated that approximately a third of patients undergoing certain surgeries may report some degree of persistent pain postoperatively. Chronic postsurgical pain (CPSP) reduces quality of life, is challenging to treat, and has significant socio-economic impact.

RECENT FINDINGS

From an epidemiological perspective, factors that predispose patients to the development of CPSP may be considered in relation to the patient, the procedure or, the care environment. Prevention or management of transition from acute to chronic pain often need a multidisciplinary approach beginning early in the preoperative period and continuing beyond surgical admission. The current concepts regarding the role of central and peripheral nervous systems in chronification of pain may provide targets for future therapies but, the current evidence seems to suggest that a multimodal analgesic approach of preventive analgesia along with a continued follow-up and treatment after hospital discharge may hold the key to identify and manage the transitioning of acute to chronic pain.

SUMMARY

A comprehensive multidisciplinary approach with prior identification of risk factors, minimizing the surgical insult and a culture of utilizing multimodal analgesia and continued surveillance beyond the period of hospitalization is an important step towards reducing the development of chronic pain. A transitional pain service model may accomplish many of these goals.

Effect of adductor canal block combined with infiltration between the popliteal artery and posterior capsular of the knee on chronic pain after total knee arthroplasty: a prospective, randomized, double-blind, placebo-controlled trial

INTRODUCTION

Total knee arthroplasty (TKA) is accompanied by severe postoperative pain, which is reported to be an important cause of chronic pain. Ultrasound-guided adductor canal block (ACB) combined with infiltration between the popliteal artery and posterior capsular of the knee (IPACK) has been proven to have a better effect on relieving acute pain after TKA. However, whether it has a significant effect on the incidence of chronic pain after TKA has not been reported. This trial was designed to investigate the effect of ultrasound-guided ACB combined with IPACK on the incidence and intensity of chronic pain after TKA.

METHODS

In this prospective, randomized, double-blind, placebo-controlled study, 100 subjects scheduled for TKA were randomly (1:1) divided into two groups: the ropivacaine group and the placebo group. Patients in each group received ultrasound-guided ACB + IPACK procedures with 0.25% ropivacaine or equal volume normal saline. All patients received multimodal analgesia. Pain intensity was assessed using the Numerical Rating Scale (NRS). The primary outcome was the incidence of chronic pain at 3 months after TKA by telephone follow-up. In addition, pain intensity in early resting and mobilized states, chronic pain intensity, the time to first rescue analgesia; opioid consumption; CRP and IL-6 after the operation; length of postoperative hospital stay; and cost of hospitalization and postoperative complications; as well as the function of the knee in the early stage after the operation, were recorded.

RESULTS

Ninety-one participants were included in the final analysis. At 3 months, the incidence of chronic pain was 30.4% in the ropivacaine group, significantly lower than 51.1% in the placebo group. Compared with the placebo group, the ACB + IPACK with ropivacaine group had significantly lower pain scores at 4 hours, 8 hours, 16 hours, and 24 hours after the operation; increased the knee range of motion at 8 hours and 24 hours after the operation; and a significantly decreased incidence of chronic pain at 3 months after the operation. During the follow-up period, there were no nerve block-related complications in either group.

CONCLUSION

In the context of multimodal analgesia protocols, ACB combined with IPACK before surgery decreases the incidence and intensity of chronic pain 3 months after TKA compared with placebo injection. In addition, it reduces the NRS scores, whether at rest or during mobilization, and improves knee function within 24 hours after TKA.

TRIAL REGISTRATION

This trial was registered in the China Clinical Trial Center (registration number ChiCTR2200065300) on November 1, 2022.

Drugs used for pain management in gastrointestinal surgery and their implications

Pain is the predominant symptom troubling patients. Pain management is one of the most important aspects in the management of surgical patients leading to early recovery from surgical procedures or in patients with chronic diseases or malignancy. Various groups of drugs are used for dealing with this; however, they have their own implications in the form of adverse effects and dependence. In this article, we review the concerns of different pain-relieving medicines used postoperatively in gastrointestinal surgery and for malignant and chronic diseases.

Evaluation of Oral Pregabalin as a Preemptive Adjuvant for Postoperative Pain in Patients Undergoing Coronary Artery Bypass Grafting With General Anesthesia and High Thoracic Epidural: A Randomized Controlled Study

Aim This study aimed to evaluate the effectiveness of oral pregabalin as a preventive supplement in managing postoperative pain in patients undergoing coronary artery bypass grafting (CABG) with a combination of general anesthesia and high thoracic epidural anesthesia. Material and methods This 18-month randomized controlled study at a tertiary hospital's anesthesiology department included 62 American Society of Anesthesiologists (ASA) II or III patients aged 35-75 with left ventricular ejection fraction >35%. Placebo (Group B, n = 31) or pregabalin (Group A, n = 31) was randomly allocated. Group A got 150 mg of pregabalin the night before surgery and 75 mg on postoperative days 0 and 1, whereas Group B received a placebo. Postoperative pain was evaluated using the Verbal Numerical Scale and Visual Analogue Scale, while sedation was assessed with the Ramsay Sedation Scale. Statistical analysis was performed using SPSS for Windows, Version 16.0 (Released 2007; SPSS Inc., Chicago). Results In this study, pregabalin significantly reduced postoperative pain on Day 0 and Day 1 (p < 0.001) compared to the placebo. The pregabalin group exhibited higher sedation scores on Day 0 (p < 0.001), but there were no significant differences on Day 1. Inotrope requirements were similar between both groups. Conclusions CABG patients' postoperative pain was greatly reduced by pregabalin without impacting sedation or inotrope needs. These data imply that pregabalin was a useful supplementary analgesic for CABG patients' multimodal pain treatment.

Advanced statistical approaches for predicting pain after pediatric thoracotomy: a cross-sectional study using zero-inflated and Poisson models

BACKGROUND

Thoracotomy is one of the surgical procedures most burdened by chronic post-operative pain. There is poor evidence regarding the possibility that even in pediatric patients, thoracotomy can be followed by post-operative pain. The primary objective of this analysis is to identify associations with home pain therapy, pain intensity, and possible protective factors acting on chronic pain in this population.

METHODS

A retrospective cross-sectional study was conducted at Ospedale Pediatrico Bambino Gesù IRCCS. The study included pediatric patients undergoing thoracotomy. For statistical analyses, a logistic model and a zero-inflated strategy were implemented to explore associations and predict factors related to home-based analgesic therapy and pain intensity.

RESULTS

Gender and age were identified as significant factors in the assignment of home therapy, with males having over seven times the risk compared to females (OR = 7.06, 95% CI = [2.11, 29.7]). At the last measurement, pain intensity was positively associated with age and the number of pain events during the week.

CONCLUSIONS

The study highlights significant factors influencing post-thoracotomy pain management in pediatric patients. These findings underscore the importance of tailored pain management strategies that consider gender and age to improve post-operative care and outcomes in pediatric thoracotomy patients.

Integrating mechanistic-based and classification-based concepts into perioperative pain management: an educational guide for acute pain physicians

Chronic pain begins with acute pain. Physicians tend to classify pain by duration (acute vs chronic) and mechanism (nociceptive, neuropathic and nociplastic). Although this taxonomy may facilitate diagnosis and documentation, such categories are to some degree arbitrary constructs, with significant overlap in terms of mechanisms and treatments. In clinical practice, there are myriad different definitions for chronic pain and a substantial portion of chronic pain involves mixed phenotypes. Classification of pain based on acuity and mechanisms informs management at all levels and constitutes a critical part of guidelines and treatment for chronic pain care. Yet specialty care is often siloed, with advances in understanding lagging years behind in some areas in which these developments should be at the forefront of clinical practice. For example, in perioperative pain management, enhanced recovery protocols are not standardized and tend to drive treatment without consideration of mechanisms, which in many cases may be incongruent with personalized medicine and mechanism-based treatment. In this educational document, we discuss mechanisms and classification of pain as it pertains to commonly performed surgical procedures. Our goal is to provide a clinical reference for the acute pain physician to facilitate pain management decision-making (both diagnosis and therapy) in the perioperative period.

Pain Predictors in Patients in the Postanesthesia Care Unit

PURPOSE

To analyze the effects of pain-predicting factors on patients in the postanesthesia care unit (PACU).

DESIGN

This is an observational and prospective study.

METHODS

This study was conducted at a University Hospital in the state of Minas Gerais (Brazil). To collect data on demographic, clinical, and surgical factors, a collection instrument was devised. The verbal numerical scale was employed to measure pain levels before and after surgery in the PACU. A path analysis was used to assess a predictive model.

FINDINGS

A total of 226 patients were included in this study. The incidence of pain in the PACU was 31.9%. A model with demographic, clinical, and surgical variables was tested. The final model, after including modification indices, obtained results that indicated an acceptable data fit (comparative fit index = 0.996; root mean square error of approximation = 0.08). Age (being young), sex (being a woman), oncological diagnosis as an indication for the surgical procedure, type of surgery (surgery of the digestive system), duration of surgery (longer surgeries), and high intraoperative doses of opioids were predictive variables for pain in the PACU.

CONCLUSIONS

This study's findings provide support for pain management in the PACU. Furthermore, the results of this research can be used to anticipate the occurrence of acute postoperative pain and personalized perioperative analgesia needs.

Elevated circulating soluble interleukin-2 receptor (sCD25) level is associated with prefrontal excitatory-inhibitory imbalance in individuals with chronic pain: A proton MRS study

Aberrant neuronal excitability in the anterior cingulate cortex (ACC) is implicated in cognitive and affective pain processing. Such excitability may be amplified by activated circulating immune cells, including T lymphocytes, that interact with the central nervous system. Here, we conducted a study of individuals with chronic pain using magnetic resonance spectroscopy (MRS) to investigate the clinical evidence for the interaction between peripheral immune activation and prefrontal excitatory-inhibitory imbalance. In thirty individuals with chronic musculoskeletal pain, we assessed markers of peripheral immune activation, including soluble interleukin-2 receptor alpha chain (sCD25) levels, as well as brain metabolites, including Glx (glutamate + glutamine) to GABA+ (γ-aminobutyric acid + macromolecules/homocarnosine) ratio in the ACC. We found that the circulating level of sCD25 was associated with prefrontal Glx/GABA+. Greater prefrontal Glx/GABA+ was associated with higher pain catastrophizing, evaluative pain ratings, and anxiodepressive symptoms. Further, the interaction effect of sCD25 and prefrontal Glx/GABA+ on pain catastrophizing was significant, indicating the joint association of these two markers with pain catastrophizing. Our results provide the first evidence suggesting that peripheral T cellular activation, as reflected by elevated circulating sCD25 levels, may be linked to prefrontal excitatory-inhibitory imbalance in individuals with chronic pain. The interaction between these two systems may play a role as a potential mechanism underlying pain catastrophizing. Further prospective and treatment studies are needed to elucidate the specific role of the immune and brain interaction in pain catastrophizing.

The use of healthcare services and disabling chronic pain: results from the cross-sectional population-based Andalusian Health Survey

BACKGROUND

Several factors seem to be related to the use of healthcare services, and chronic pain (CP) is among these characteristics. The objective is to describe the number of visits to a doctor's surgery or emergency rooms, and the periods of hospitalization; to identify characteristics associated with frequent healthcare use, including disabling chronic pain (DCP) and non-disabling chronic pain (n-DCP).

METHODS

Representative population-based cross-sectional study of 6569 people older than 16 years from southern Spain was collected. The frequency of visits to a doctor's surgery or emergency rooms and periods of hospitalization were defined as at or above the 90th percentile. Binary logistic regression analyses were conducted separately on women and men to identify characteristics associated with being frequent visitors.

RESULTS

People with DCP are more frequent visitors to a doctor's surgery and emergency rooms and endure longer periods of hospitalization compared to people with n-DCP and without pain. In logistic regression models, people with DCP are twice as likely to over-visit a doctor's surgery; to endure longer periods of hospitalization and more visits to an emergency room service. No relationship was found in n-DCP.

CONCLUSIONS

Disability seems to modulate a greater use of health services among the population with CP, doubling it when compared to n-DCP and n-CP, both in women and men. Understanding the role of disability in the use of healthcare services for individuals with CP allows for the identification of needs and strategies to optimize resources.

Bibliometric analysis of functional magnetic resonance imaging studies on chronic pain over the past 20 years

PURPOSE

The utilization of functional magnetic resonance imaging (fMRI) in studying the mechanisms and treatment of chronic pain has gained significant popularity. However, there is currently a dearth of literature conducting bibliometric analysis on fMRI studies focused on chronic pain.

METHODS

All the literature included in this study was obtained from the Science Citation Index Expanded of Web of Science Core Collection. We used CiteSpace and VOSviewer to analyze publications, authors, countries or regions, institutions, journals, references and keywords. Additionally, we evaluated the timeline and burst analysis of keywords, as well as the timeline and burst analysis of references. The search was conducted from 2004 to 2023 and completed within a single day on October 4th, 2023.

RESULTS

A total of 1,327 articles were retrieved. The annual publication shows an overall increasing trend. The United States has the highest number of publications and the main contributing institution is Harvard University. The journal PAIN produces the most articles. In recent years, resting-state fMRI, the prefrontal cortex, nucleus accumbens, thalamus, and migraines have been researched hotspots of fMRI studies on chronic pain.

CONCLUSIONS

This study provides an in-depth perspective on fMRI for chronic pain research, revealing key points, research hotspots and research trends, which offers valuable ideas for future research activities. It concludes with a summary of advances in clinical practice in this area, pointing out the need for critical evaluation of these findings in the light of guidelines and expert recommendations. It is anticipated that further high-quality research outputs will be generated in the future, which will facilitate the utilization of fMRI in clinical decision-making for chronic pain.

Postoperative pain at Landspitali: A prospective study

BACKGROUND

Moderate or severe postoperative pain is common despite advances in surgical technique and perioperative analgesia. This study aimed to assess the prevalence and severity of postoperative pain following procedures requiring anaesthesia and identify factors associated with increased risk of postoperative pain.

METHODS

Surgical patients ≥18 years of age were prospectively questioned on level of current pain on a numerical rating scale (NRS) from 0 to 10 in the post-anaesthesia care unit (PACU) and on resting, active and worst pain experienced in the first 24 h postoperatively. Clinical data was obtained from medical records. Descriptive statistics were applied, and predictors of worst pain assessed as moderate/severe (NRS ≥ 5) on postoperative day one were assessed using multivariable logistic regression.

RESULTS

Of 438 included participants, moderate/severe pain occurred in 29% on the day of surgery and 70% described their worst pain as moderate/severe on postoperative day one. Procedures with the highest incidence of moderate/severe pain on the day of surgery were gynaecology-, plastic-, abdominal-, breast-, and orthopaedic procedures. On postoperative day one, patients undergoing vascular-, orthopaedic-, and abdominal operations most commonly rated their worst pain as moderate/severe. Female sex (OR = 2.15, 95% Cl 1.21-3.88, p = .010), chronic preoperative pain (OR = 4.20, 95% Cl 2.41-7.51, p < .001), undergoing a major procedure (OR = 2.07, 95% Cl 1.15-3.80, p = .017), and any intraoperative remifentanil administration (OR = 2.16, 95% Cl 1.20-3.94, p = .01) had increased odds of rating the worst pain as moderate/severe. Increased age (OR = 0.66 per 10 years (95% Cl 0.55-0.78, p < .001)) and undergoing breast-, gynaecology-, otolaryngology-, and neurosurgery (OR = 0.15-0.34, p < .038) was associated with lower odds of moderate/severe pain on postoperative day one.

DISCUSSION

In our cohort, patients rated their current pain in the PACU similarly to other studies. However, the ratio of patients rating the worst pain experienced as moderate/severe on postoperative day one was relatively high. The identified patient- and procedural-related factors associated with higher odds of postoperative pain highlight a subgroup of patients who may benefit from enhanced perioperative monitoring and pain management strategies.

PENG for chronic pain: the clinical effectiveness of pericapsular nerve group block in chronic hip pain

OBJECTIVES

To evaluate the efficiency and tolerability of pericapsular nerve group block (PENG) for the treatment of chronic hip pain.

METHODS

This is a retrospective, single-centre, 4-group study conducted over a 3-month period to find out the most typical cause of chronic hip pain. A total of 112 patients with symptomatic hip osteoarthritis (OA), Stage 2-3, greater trochanteric pain (GTPS) and chronic pain after total hip arthroplasty (cTHA), who had an ultrasound-guided PENG block, were selected. To assess the effectiveness of the treatment, the Western Ontario and McMaster Universities osteoarthritis index (WOMAC) and visual analogue scale (VAS) scores of the patients prior to treatment were compared with their scores after the 1st week, 1st month, and 3rd month of treatment. The study also aimed to analyse the patients' initial feelings of alleviation following the block (1st VAS/2) and problems experienced both during and after the block.

RESULTS

The parameters studied included pain, stiffness, and results of physical activity in the 1st week, 1st month, and 3rd month following PENG block application. At the beginning of the 1st week, of the 112 patients who were administered a PENG block for hip pain, we reported a 62% improvement in pain, a 52% reduction in stiffness, and a 53% increase in physical activity. Even though these results slightly declined in the 1st and 3rd months, the rates were still higher than 45%.

CONCLUSIONS

Overall, the PENG block was well-tolerated by the patients in our study. No treatment-related infections or any other serious complications were observed.

Cannabinoid Analgesia in Postoperative Pain Management: From Molecular Mechanisms to Clinical Reality

Postoperative pain (POP) is a challenging clinical phenomenon that affects the majority of surgical patients and demands effective management to mitigate adverse outcomes such as persistent pain. The primary goal of POP management is to alleviate suffering and facilitate a seamless return to normal function for the patient. Despite compelling evidence of its drawbacks, opioid analgesia remains the basis of POP treatment. Novel therapeutic approaches rely on multimodal analgesia, integrating different pharmacological strategies to optimize efficacy while minimizing adverse effects. The recognition of the imperative role of the endocannabinoid system in pain regulation has prompted the investigation of cannabinoid compounds as a new therapeutic avenue. Cannabinoids may serve as adjuvants, enhancing the analgesic effects of other drugs and potentially replacing or at least reducing the dependence on other long-term analgesics in pain management. This narrative review succinctly summarizes pertinent information on the molecular mechanisms, clinical therapeutic benefits, and considerations associated with the plausible use of various cannabinoid compounds in treating POP. According to the available evidence, cannabinoid compounds modulate specific molecular mechanisms intimately involved in POP. However, only two of the eleven clinical trials that evaluated the efficacy of different cannabinoid interventions showed positive results.

Increased risk of persistent neuropathic pain after traumatic nerve injury and surgery for carriers of a human leukocyte antigen haplotype

ABSTRACT

It is not known why some patients develop persistent pain after nerve trauma while others do not. Among multiple risk factors for the development of persistent posttrauma and postsurgical pain, a neuropathic mechanism due to iatrogenic nerve lesion has been proposed as the major cause of these conditions. Because there is some evidence that the human leukocyte antigen (HLA) system plays a role in persistent postsurgical pain, this study aimed to identify the genetic risk factors, specifically among HLA loci, associated with chronic neuropathic pain after traumatic nerve injuries and surgery in the upper extremities. Blood samples were taken to investigate the contribution of HLA alleles (ie, HLA-A, HLA-B, HLA-DRB1, HLA-DQB1, and HLA-DPB1) in a group of patients with persistent neuropathic pain (n = 70) and a group of patients with neuropathy without pain (n = 61). All subjects had intraoperatively verified nerve damage in the upper extremity. They underwent bedside clinical neurological examination to identify the neuropathic pain component according to the present grading system of neuropathic pain. Statistical analyses on the allele and haplotype were conducted using the BIGDAWG package. We found that the HLA haplotype A*02:01-B*15:01-C*03:04-DRB1*04:01-DQB1*03:02 was associated with an increased risk of developing persistent neuropathic pain in the upper extremity (OR = 9.31 [95% CI 1.28-406.45], P < 0.05). No significant associations were found on an allele level when correcting for multiple testing. Further studies are needed to investigate whether this association is on a haplotypic level or if certain alleles may be causing the association.

Long-term pain outcomes after serial lidocaine infusion in participants with recent onset of peripheral neuropathic pain: A pilot double-blind, randomized, placebo-controlled trial

BACKGROUND

This study investigated the outcomes up to 12 weeks after serial lidocaine infusion for early-onset peripheral neuropathic pain.

METHODS

This pilot double-blind, randomized, 2-arm placebo-controlled trial recruited 50 participants with onset of peripheral neuropathic pain within the past 6 months and randomized them to either receive lidocaine (3 mg/kg) in normal saline (50 mL) intravenous infusion over 1 hour (lidocaine group) once a week for 4 weeks or 50 mL of normal saline infusion (placebo group) once a week for 4 weeks. Twenty-nine participants completed the protocol; 15 participants were assigned to the lidocaine group and 14 to the placebo group. The outcomes were pain intensity assessed using a numerical rating scale (NRS), quality of life assessed using EuroQol-Five Dimensions-Five Levels questionnaire (EQ-5D-5L), psychological function using the Thai version of the 21-item Depression Anxiety Stress Scales (DASS-21), pain medication use, and adverse effects, all assessed at baseline (BL) and again at 4, 8, and 12 weeks following randomization.

RESULTS

The reported tramadol use at 8 and 12 weeks following the first infusion was significantly lower in the lidocaine group (P = .023). No other significant between-group differences were observed at any time point or for any other outcome, and no serious adverse events were observed.

CONCLUSION

Multiple lidocaine infusions of 3 mg/kg once a week for 4 weeks in participants with recent onset of peripheral neuropathic pain demonstrated no significant benefits in pain intensity, quality of life, or psychological outcomes. At most, this treatment may result in less tramadol use.

Duration of the preemptive analgesic effects of low- and high-frequency transcutaneous electrical nerve stimulation in rats with acute inflammatory pain

Transcutaneous electrical nerve stimulation (TENS) activates various pathways to induce antinociceptive effects, based on the frequencies used. This study evaluates the preemptive analgesic effects and their duration of low- (LT: 4 Hz) and high-frequency TENS (HT: 100 Hz) using a rat model of acute inflammatory pain. Acute inflammation was induced by injecting 1% formalin into the hind paws of rats. LT or HT was applied for 30 min before formalin injection. Pain-related behaviors, such as licking, flinching, and lifting, were recorded for 60 min postinjection. Immunohistochemistry was used to assess the number of phosphorylated extracellular signal-regulated kinase (pERK)- and c-fos-positive cells in the spinal cord. Naloxone, a μ-opioid receptors (MORs) antagonist, and naltrindole, a δ-opioid receptors (DORs) antagonist, were administered before TENS application. Pain behavior duration and pERK- and c-fos-positive cell expression were then measured. LT and HT pretreatment significantly reduced both pain behaviors and the number of pERK- and c-fos-positive cells postformalin injection. Naloxone and naltrindole partially reversed the effects of LT and HT, respectively. Notably, HT's analgesic effect lasted up to 120 min whereas that of LT persisted for 90 min. LT and HT effectively exerted their preemptive analgesic effects on acute inflammatory pain by inhibiting pERK and c-fos expression in the spinal cord. HT presented a longer-lasting effect compared to LT. MOR and DOR activation may contribute to LT and HT's analgesic mechanisms, respectively.

Risk Factors for Chronic Abdominal Pain After RYGB: Are Patients Adequately Selected Beforehand?

PURPOSE

Chronic abdominal pain after RYGB is a known issue. Identifying the potential patient-related and modifiable risk factors might contribute to diminish the risk for this undesirable outcome.

METHODS

A single-center retrospective cohort study with prospective data collection was conducted with inclusion of all patients who underwent RYGB surgery between 2015 and 2021. Data from the NBSR and medical records were used. Patients with chronic abdominal pain were defined when pain lasting or recurring for more than 3 to 6 months.

RESULTS

Six hundred sixty-four patients who underwent RYGB surgery were included with a median follow-up of 60.5 months. Forty-nine patients (7.3%) presented with chronic abdominal pain. Postoperative complications (OR 13.376, p = 0.020) and diagnosis of depression (OR 1.971, p = 0.037) were associated with developing abdominal pain. On the other hand, ex-smokers (OR 0.222, p = 0.040) and older age (0.959, p = 0.004) presented as protective factors.

CONCLUSION

Postoperative complications and diagnosis of depression are risk factors for chronic pain after RYGB. The role of the bariatric MDT remains crucial to select these patients adequately beforehand.

Acute Effects of In-Hospital Resistance Training on Clinical Outcomes in Patients Undergoing Total Knee Arthroplasty: A Randomized Controlled Trial

OBJECTIVE

The aim of the study is to evaluate the acute responses, in the in-hospital setting, of intensive elastic resistance training on physical function, pain, psychosocial variables, and inflammatory markers in patients undergoing total knee arthroplasty.

DESIGN

In a randomized controlled trial, 40 patients with total knee arthroplasty (≥55 yrs) were assigned to either (1) the intervention group (elastic resistance strengthening) or (2) a control group (conventional protocol). Patients performed three sessions in the hospital at 24, 48, and 72 hrs after total knee arthroplasty. Outcome measures included: self-administered physical function, pain intensity, kinesiophobia, catastrophizing, self-efficacy, range of motion, perceived change, test timed up and go, knee joint effusion, isometric strength, pressure pain thresholds, and inflammatory markers (levels of procalcitonin and C-reactive protein).

RESULTS

The mixed analysis of variance model showed a significant group*time interaction in favor of the intervention group with a large effect size for kinesiophobia (ηp 2 = 0.308, P < 0.001), catastrophizing (ηp 2 = 0.242, P < 0.001), and passive range of motion flexion (ηp 2 = 0.167, P < 0.001) and a moderate effect size for physical function (ηp 2 = 0.103, P = 0.004), pain intensity (ηp 2 = 0.139, P < 0.001), timed up and go (ηp 2 = 0.132, P = 0.001), self-efficacy (ηp 2 = 0.074, P = 0.016), active range of motion flexion (ηp 2 = 0.121, P = 0.002), levels of procalcitonin (ηp 2 = 0.099, P = 0.005), and C-reactive protein (ηp 2 = 0.106, P = 0.004).

CONCLUSIONS

Three sessions of intensive elastic resistance training improve physical function, perceived pain, psychosocial variables, and inflammatory markers during the hospitalization period after total knee arthroplasty.

Update on Musculoskeletal Pain Management

Pain is the most common complaint reported to orthopedists in the outpatient clinic, emergency room, or booth. Numerous publications report the inadequate management of both acute and chronic pain by health professionals. This updated article aims to provide information about musculoskeletal pain, its classification, evaluation, diagnosis, and the multimodal therapeutic approach for each case. For acute pain, adequate control allows for earlier rehabilitation to work and reduces the rates of pain chronification. For chronic pain, the goal is to reduce its intensity and improve the quality of life. Currently, some procedures are increasingly used and aided by imaging tests for diagnostic and therapeutic purposes.

Induction of antiviral interferon-stimulated genes by neuronal STING promotes the resolution of pain in mice

Inflammation and pain are intertwined responses to injury, infection, or chronic diseases. While acute inflammation is essential in determining pain resolution and opioid analgesia, maladaptive processes occurring during resolution can lead to the transition to chronic pain. Here we found that inflammation activates the cytosolic DNA-sensing protein stimulator of IFN genes (STING) in dorsal root ganglion nociceptors. Neuronal activation of STING promotes signaling through TANK-binding kinase 1 (TBK1) and triggers an IFN-β response that mediates pain resolution. Notably, we found that mice expressing a nociceptor-specific gain-of-function mutation in STING exhibited an IFN gene signature that reduced nociceptor excitability and inflammatory hyperalgesia through a KChIP1-Kv4.3 regulation. Our findings reveal a role of IFN-regulated genes and KChIP1 downstream of STING in the resolution of inflammatory pain.

Are There Any Advantages of the Low Opioid Anaesthesia and Non-Opioid Postoperative Analgesia Protocol: A Clinical Observational Study

Purpose

The methods of perioperative analgesia and pain control have changed. The principle of opioid-based analgesia has been modified to multimodal analgesia, followed by LOA (low opioid anaesthesia) and OFA (opioid-free anaesthesia). The aim was to describe the effects of LOA on nausea, vomiting, and pain control during general anaesthesia and postoperative period after laparoscopic cholecystectomy.

Patients and Methods

The protocol included the study group-40 patients received low-opioid anaesthesia (LOA), and the control group-40 patients received general anaesthesia with opioid analgesia (OA). The scheme of LOA was based on ketamine, lidocaine, magnesium sulfate, paracetamol, and metamizole. The OA was based on standard opioid (fentanyl) administration in induction and maintenance phase due to clinical observation. Postoperative analgesia included 1g of paracetamol and 1g of metamizol intravenously, with a 6-hour interval between doses.

Results

Significant differences in the pain score in the periods of 2-6, 6-12, and 12-24 hours after anaesthesia between the groups were noticed (p < 0.001). Moreover, a significant difference in the frequency of nausea (p = 0.005) and vomiting (p = 0.04) between groups were presented. Nausea occurred in 54.05% of OA group, while in the LOA group, it occurred in a 23.08%. Vomiting occurred in 32.43% of control group, while in the study group, it occurred in 12.82% of patients.

Conclusion

The LOA protocol was more beneficial in reducing nausea and vomiting than the opioid-based method of anaesthesia. The LOA protocol of general anaesthesia during laparoscopic cholecystectomy and non-opioid postoperative analgesia have better outcomes in pain control, as well as nausea and vomiting, and improve postoperative patient comfort. The LOA protocol during anaesthesia and non-opioid postoperative analgesia should be considered in routine practice.

Prevalence and Risk Factors for Chronic Postsurgical Pain After Thoracic Surgery: A Prospective Cohort Study

OBJECTIVE

Thoracic surgery is associated with one of the highest rates of chronic postsurgical pain (CPSP) among all surgical subtypes. Chronic postsurgical pain carries significant medical, psychological, and economic consequences, and further interventions are needed to prevent its development. This study aimed to determine the prevalence, characteristics, and risk factors associated with CPSP after thoracic surgery.

DESIGN

A prospective cohort study.

SETTING

Single-center tertiary care hospital.

PARTICIPANTS

This study included 285 adult patients who underwent thoracic surgery at Toronto General Hospital in Toronto, Canada, between 2012 and 2020.

MEASUREMENTS AND MAIN RESULTS

Demographic, psychological, and clinical data were collected perioperatively, and follow-up evaluations were administered at 3, 6, and 12 months after surgery to assess CPSP. Chronic postsurgical pain was reported in 32.4%, 25.4%, and 18.2% of patients at 3, 6, and 12 months postoperatively, respectively. Average CPSP pain intensity was rated to be 3.37 (SD 1.82) at 3 months. Features of neuropathic pain were present in 48.7% of patients with CPSP at 3 months and 71% at 1 year. Multivariate logistic regression models indicated that independent predictors for CPSP at 3 months were scores on the Hospital Anxiety and Depression Scale (adjusted odds ratio [aOR] of 1.07, 95% CI of 1.02 to 1.14, p = 0.012) and acute postoperative pain (aOR of 2.75, 95% CI of 1.19 to 6.36, p = 0.018).

INTERVENTIONS

None.

CONCLUSIONS

Approximately 1 in 3 patients will continue to have pain at 3 months after surgery, with a large proportion reporting neuropathic features. Risk factors for pain at 3 months may include preoperative anxiety and depression and acute postoperative pain.

Characterization of Common Genetic Variants in P2RX7 and Their Contribution to Chronic Pain Conditions

The adenosine triphosphate (ATP)-gated channel P2X7 is encoded by a gene enriched for common nonsynonymous variants. Many of these variants have functional cellular effects, and some have been implicated in chronic pain. In this study, we first systematically characterized all 17 common nonsynonymous variants using whole-cell patch clamp electrophysiology. Then, we analyzed these variants for statistical association with chronic pain phenotypes using both individual P2RX7 variants as predictors and cumulative allele counts of same-direction cellular effect in univariate models. Association and validation analyses were conducted in the Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA) cohort (N = 3260) and in the Complex Persistent Pain Conditions (CPPC) cohort (N = 900), respectively. Our results showed an association between allele A of rs7958311 and an increased risk of chronic pelvic pain, with convergent evidence for contribution to fibromyalgia and irritable bowel syndrome, confirmed in a meta-analysis. This allelic variant produced a unique cellular phenotype: a gain-of-function in channel opening, and a loss-of-function in pore opening. A computational study using a 12-state Markov model of ATP binding to the P2X7 receptor suggested that this cellular phenotype arises from an increased ATP binding affinity and an increased open channel conductance combined with a loss of sensitization. Cumulative allele count analysis did not provide additional insights. In conclusion, our results go beyond reproducing association for rs7958311 with chronic pain and suggest that its unique combination of gain-of-function in channel and loss-of-function in pore activity may explain why it is likely the only common P2RX7 variant with contribution to chronic pain. PERSPECTIVE: This study characterizes all common P2RX7 variants using cellular assays and statistical association analyses with chronic pain, with Markov state modeling of the most robustly associated variant.

Quantitative somatosensory assessments in patients with persistent pain following groin hernia repair: A systematic review with a meta-analytical approach

OBJECTIVES

Quantitative sensory testing (QST) provides an assessment of cutaneous and deep tissue sensitivity and pain perception under normal and pathological settings. Approximately 2-4% of individuals undergoing groin hernia repair (GHR) develop severe persistent postsurgical pain (PPSP). The aims of this systematic review of PPSP-patients were (1) to retrieve and methodologically characterize the available QST literature and (2) to explore the role of QST in understanding mechanisms underlying PPSP following GHR.

METHODS

A systematic literature search was conducted from JAN-1992 to SEP-2022 in PubMed, EMBASE, and Google Scholar. For inclusion, studies had to report at least one QST-modality in patients with PPSP. Risk of bias assessment of the studies was conducted utilizing the Newcastle Ottawa Scale and Cochrane's Risk of Bias assessment tool 2.0. The review provided both a qualitative and quantitative analysis of the results. A random effects model was used for meta-analysis.

RESULTS

Twenty-five studies were included (5 randomized controlled trials, 20 non-randomized controlled trials). Overall, risk of bias was low. Compared with the contralateral side or controls, there were significant alterations in somatosensory function of the surgical site in PPSP-patients. Following thresholds were significantly increased: mechanical detection thresholds for punctate stimuli (mean difference (95% CI) 3.3 (1.6, 6.9) mN (P = 0.002)), warmth detection thresholds (3.2 (1.6, 4.7) °C (P = 0.0001)), cool detection thresholds (-3.2 (-4.9, -1.6) °C (P = 0.0001)), and heat pain thresholds (1.9 (1.1, 2.7) °C (P = 0.00001)). However, the pressure pain thresholds were significantly decreased (-76 (-123, -30) kPa (P = 0.001)).

CONCLUSION

Our review demonstrates a plethora of methods used regarding outcome assessments, data processing, and data interpretation. From a pathophysiological perspective, the most consistent findings were postsurgical cutaneous deafferentation and development of a pain generator in deeper connective tissues.

TRIAL REGISTRATION

CRD42022331750.

The oral administration of Lotus corniculatus L. attenuates acute and chronic pain models in male rats

ETHNOPHARMACOLOGICAL RELEVANCE

Lotus corniculatus L. (Fabaceae) traditionally used in Persian folk medicine to heal peritoneal inflammation and back pain.

AIM OF THE STUDY

To explore the antinociceptive (acute pain) and anti-neuropathic (chronic pain) activities of Lotus corniculatus leaves essential oil (LCEO) in addition to uncovering the possible mechanisms of antinociception.

MATERIALS AND METHODS

LCEO as well as the pure oleanolic acid (OA) compound, were assayed for their effects on acute (formalin induced paw licking test or FIPT) and chronic (cervical contusion injury models on the fifth cervical vertebra or CCS; 14-day intervals) pain. The possible involvements of NO-cGMP-K+ channel, TRPV, dopamine, cannabinoid, PPAR, adrenergic, and opioid mechanisms in the antinociceptive activity of LCEO have studied by formalin test. The levels of p53 and inflammatory markers were measured using a streptavidin biotin immune peroxidase complex and ELISA methods, respectively.

RESULTS

The LCEO and OA exerted antinociceptive activity in the first-phase of FIPT. Pretreatment with antagonists of TRPV1, dopamine D2, cannabinoid type1 and 2, and NO-cGMP-K+ channel blockers (glibenclamide, L-NAME and methylene blue) attenuated the antinociceptive effect of LCEO in FIPT. In addition, LCEO and OA meaningfully reduced hyperalgesia (days 6-14) and mechanical allodynia (days 2-14) in the CCS model. LCEO suppressed the apoptotic marker (p53) in CCS model and also ameliorated IL-2, TNF-α, and IL-1 in the spinal cord.

CONCLUSION

Finally, LCEO inhibited acute (possibly via the modulation of opioid, TRPV, dopamine, cannabinoid mechanisms as well as NO-cGMP-K+ channel) and chronic pain (via suppressing apoptotic and inflammatory markers) in male rats. The results also suggest that OA has analgesic activity against acute and chronic pain conditions.

Overlap of pain-related and general measures of disability among adults with chronic pain

PURPOSE

Chronic pain is known to be correlated with disability. We aimed to determine the overlap between a general self-reported measure of disability and a measure of disability due to pain problems among adults with chronic pain.

MATERIALS AND METHODS

We used data from the National Health Interview Survey (NHIS) and analyzed respondents with chronic pain in the past 3 months. General disability was defined as being limited in the kind or amount of work one can do due to any physical, mental, or emotional problem. Pain-related disability was defined as pain limiting one's activity on "most days" or "every day."

RESULTS

Based on a sample of 6874 respondents with chronic pain, 58% had either kind of disability, including 9% who reported only pain-related, but not general disability; and 27% who reported both types of disability. Respondents reporting only pain-related, but not general disability tended to be younger and had lower rates of obesity, smoking, diabetes, and hypertension than respondents reporting both pain-related and general disability.

DISCUSSION

Among people with chronic pain, most people with disability are experiencing limitations related to pain problems. Assessment of disability without addressing pain interference has likely underestimated the disability burden in this population.

[Chronic eye pain]

Numerous conditions in the field of ophthalmology are associated with pain in or around the eye. Chronic pain associated with the eye is a common finding in the daily routine of ophthalmologists and can be associated with primary ocular or extraocular diseases as well as with other conditions. Appropriate diagnostic assessment and management of people with chronic pain requires an understanding of the condition based on the biopsychosocial model in which the interactions of biological/somatic, psychological and social factors are determining pain and suffering. Beyond the ophthalmological findings,  close interdisciplinary cooperation and assessment are required. Therefore, if eye pain is insufficiently responsive to treatment or if symptoms of chronic pain are evident, pain medicine expertise should be involved. The management of chronic ocular pain is based on interdisciplinary multimodal approaches, in addition to the ophthalmologist-specific approaches. These focus on self-efficacy, patient competence and acceptance of pain as central goals of treatment rather than pain relief. Patient information, education and the development of a suitable concept by the interdisciplinary team are essential therapeutic aspects in this context.

Effect of nociception level index-guided intra-operative analgesia on early postoperative pain and opioid consumption: a systematic review and meta-analysis

Acute postoperative pain remains a critical treatment priority and has prompted a search for technologies and techniques to assist with intra-operative analgesic monitoring and management. Anaesthetists traditionally rely on clinical judgement to guide intra-operative analgesia, but several emerging technologies such as the nociception level index herald the possibility of routine intra-operative analgesia monitoring. However, the impact of devices like nociception level index on postoperative outcomes has not been proven. We undertook a systematic review and meta-analysis of articles which compared nociception level index-guided analgesia to standard care. The primary outcomes were pain intensity and opioid consumption during the first 60-120 min after surgery. Secondary outcomes were the incidence of postoperative nausea and vomiting and duration of stay in the post-anaesthesia care unit. Ten studies, collectively including 662 patients and published between 2019 and 2023, met inclusion criteria for both the qualitative systematic review and quantitative meta-analysis. Risk of methodological bias was generally low or unclear, and six studies reported a significant conflict of interest relevant to their findings. Our meta-analysis was performed using a random-effects model. It found statistically significant benefits of nociception level index-guided analgesia for early postoperative pain (mean (95%CI) difference -0.46 (-0.88 to -0.03) on an 11-point scale, p = 0.03), and opioid requirement (mean (95%CI) difference -1.04 (-1.94 to -0.15) mg intravenous morphine equivalent, p = 0.02). Our meta-analysis of the current literature finds that nociception level index-guided analgesia statistically significantly reduces reported postoperative pain intensity and opioid consumption but fails to show clinically relevant outcomes. We found no evidence that nociception level index-guided analgesia affected postoperative nausea and vomiting nor duration of stay in the post-anaesthesia care unit.

Does Immediate Long-Span Nerve Allograft Reconstruction Affect the Incidence of Chronic Postsurgical and Neuropathic Pain in the Reconstructed Mandible Following Resection for Benign and Malignant Disease

BACKGROUND

Peripheral nerve injury can lead to chronic postsurgical pain (CPSP) and neuropathic pain following major surgery.

PURPOSE

Determine in patients undergoing ablative mandibular operations with transection of the trigeminal nerve: do those who undergo immediate repair, when compared to those whose nerves are not repaired, have a decreased or increased risk for CPSP or post-traumatic trigeminal neuropathic pain (PTTNp)?

STUDY DESIGN, SETTING, SAMPLE

A multisite, retrospective cohort of patients who underwent resection of the mandible for benign or malignant disease with either no repair or immediate repair of the intentionally transected trigeminal nerve with a long-span nerve allograft were analyzed for the presence or absence of CPSP and PTTNp at 6 months.

PREDICTOR VARIABLE

The primary predictor was the immediate repair or no repair of the trigeminal nerve.

MAIN OUTCOME VARIABLE

The primary outcome was the presence or absence of CPSP and PTTNp at 6 months postsurgery.

COVARIATES

There were 13 covariate variables, including age, sex, ethnicity, nerve injury, type of PTTNp, malignant or benign pathology and subtypes of each, use of radiation or chemotherapy, treatment of transected nerve end, longest follow-up time, pain scale, and onset of pain.

ANALYSES

Two-tailed Student's t test and Welch's t test were performed on mean scores and post hoc logistics and linear regression modeling were performed when indicated. The confidence level for statistical significance was P value <.05.

RESULTS

There were 103 and 94 subjects in the immediate and no-repair groups, respectively. The incidence of CPSP in the no-repair group was 22.3% and PTTNp was 2.12%, while there was 3.8% CPSP and 0% PTTNp in the repair group, which was statistically significant (P = <.001). Logistic regression modeling showed a statistically significant inverse relationship between the immediate repair and the incidence of CPSP/PTTNp with an odds ratio of 0.43, 95% confidence interval 0.18 to 1.01, P = .05. Greater age, malignant pathology, and chemo/radiation treatments were covariates found more frequently in the no repair group.

CONCLUSION AND RELEVANCE

Immediate repair of an intentionally transected trigeminal nerve with a long-span nerve allograft during resection of the mandible for both benign and malignant disease appears to reduce CPSP and possibly eliminate the development of PTTNp.

Chronic Pain and Functional Outcome 3 years After Total Knee Arthroplasty and Perioperative Dexamethasone: A Follow-Up of the Randomized, Clinical DEX-2-TKA Trial

BACKGROUND

Perioperative dexamethasone as an adjunct to multimodal analgesia, has an opioid-sparing and pain alleviating effect after total knee arthroplasty (TKA), however, the 3-year effects are unknown. We aimed to investigate the 3-year effect of 1 (DX1) or 2 (DX2) intravenous doses of 24 mg dexamethasone or placebo on pain, physical function, and health-related quality of life after TKA.

METHODS

Patients who participated in the Dexamethasone Twice for Pain Treatment after TKA (DEX-2-TKA) were invited to physical tests and questionnaires (self-reported characteristics, Oxford Knee Score, EuroQol-5Dimensions-5Levels (EQ5D5L), and PainDetect). The tests were 40-meter Fast Paced Walk (40FPW) test, Timed Up and Go (TUG), 30 Second Chair Stand test (30CST), Stair Climb Test (SCT), bilateral knee Range of Motion, and knee extension torque. For each test the peak pain intensity was registered on a 0 to 100 mm Visual Analogue Scale. Primary outcome was average peak pain intensity during the 40FPW, TUG, 30CST and SCT. Secondary outcomes were the tests and questionnaires. Out of 252 eligible patients, 133 (52.8%) underwent the tests and 160 (63.5%) answered the questionnaires. Mean follow-up time was 33 months (range, 23 to 40).

RESULTS

Median (interquartile range) peak pain intensity was 0 (0 to 65) for the DX2 group, 0 (0 to 51) for DX1 group and 0 (0 to 70) for the placebo group (P = .72). No differences in secondary outcomes were identified.

CONCLUSION

One or 2 intravenous doses of 24 mg dexamethasone did not impact chronic pain development or physical function 3 years after TKA.

Can Ultrasound-Guided Continuous Paravertebral Block Reduce the Incidence of Chronic Postsurgical Pain in Patients with Thoracoscopic Lung Cancer Surgery? A Randomized Controlled Trial

Background

Thoracoscopic lung cancer surgery is accompanied by severe pain. Both continuous paravertebral block (CPVB) and continuous wound infiltration (CWI) are widely used for perioperative analgesia in thoracoscopic surgery. However, the effects of these different methods on chronic postsurgical pain (CPSP) are still unknown. Patients and Methods. This prospective randomized controlled trial assessed the eligibility of 113 patients. Ninety-seven patients who met the inclusion criteria were randomly divided into a CPVB group and a CWI group, and 80 patients were analyzed in the final study. The primary outcome measures were the incidence and intensity of chronic postsurgical pain (CPSP) at 3, 6, and 9 months after surgery. The secondary outcome measures were the numerical rating scale (NRS) score of rest and activity at 12, 18, and 24 hours and on the 2nd, 3rd, and 7th days postoperatively; the Barthel Activities of Daily Living (ADL) score of activity levels on the 1st, 2nd, 3rd, and 7th days postoperatively; and the long-term quality of the life score at 3, 6, and 9 months postoperatively.

Results

The incidence of chronic postsurgical pain in the CWI group was significantly higher than that in the CPVB group at 3, 6, and 9 months after surgery (all P < 0.05). The intensity of chronic postsurgical pain was significantly decreased in the CPVB group at 3, 6, and 9 months after surgery (P < 0.05). NRS-R and NRS-A scores were significantly decreased in the CPVB group within the first week after thoracoscopic surgery (P < 0.001). ADL scores were increased in the CPVB group within 3 days postoperatively. However, there were no differences in the ADL score on the 7th postoperative day or the long-term quality of the life score at 3, 6, and 9 months postoperatively.

Conclusion

Continuous ultrasound-guided paravertebral block reduced the intensity of acute pain within 7 days postoperatively and reduced the incidence of chronic pain at 3, 6, and 9 months after surgery, but there was no significant advantage in long-term quality of life. This trial is registered with ChiCTR2000038505.

Electroacupuncture for Pain Relief After Endoscopic Sinus Surgery: A Randomized Controlled Trial

Postoperative pain is a common problem after endoscopic sinus surgery (ESS). Electroacupuncture (EA) is proven to be effective in relieving postoperative pain. However, EA has not been studied in patients undergoing ESS. This study was designed to evaluate the efficacy and safety of EA compared to a sham control in relieving pain after ESS. A total of 62 patients were randomly allocated to receive either EA (n = 31) or sham EA (n = 31) for 5 sessions, 30 minutes per session for 4 days (2 hours before and 2 hours after surgery, and 3 sessions daily for the following 3 days). There were no significant differences between the 2 groups with regard to demographic characteristics. Compared to the sham EA group, the EA group showed a significantly greater reduction in the pain intensity of single daily scoring with a numerical rating scale at the day following surgery (postoperative day 1, POD1) (-1.35; 95% confidence interval [CI], -1.74 to -0.97; P < .001) and POD2 (-1.16; 95% CI, -1.55 to -0.77; P < .001), whereas no significant between-group difference was detected at the day of surgery (POD0), POD3 or POD6. Intraoperative heart rate and mean blood pressure in the EA group showed a more stable trend. A significant improvement was found for an actigraphy-measured average time of night wakings, recovery time from anesthesia, and quality of recovery-15 in the EA group. No severe adverse events occurred during the trial. Our results demonstrate that EA can serve as an effective adjuvant therapeutic tool for pain relief after ESS. PERSPECTIVE: This randomized sham-controlled, patient-and-assessor blinded trial provided evidence for the first time that EA can relieve postoperative pain and other symptom management in patients after ESS. TRIAL REGISTRATION NUMBER: Chinese Clinical Trial Registry, ChiCTR1900024183, http://www.chictr.org.cn/showproj.aspx?proj=40573.

Descending Control of Nociception Poorly Predicts the Development of Persistent Postsurgical Pain-like Behavior in Consomic Dahl S Rat Strains

BACKGROUND

Chronic postsurgical pain is a poorly recognized outcome of surgery where patients experience pain long after healing from the surgical insult. Descending control of nociception, a phenomenon whereby application of a strong nociceptive stimulus to one part of the body of animals inhibits pain in remote body regions, offers one strategy to identify a propensity to develop chronic postsurgical pain-like behavior. Here, consomic rat panel was used to test the hypothesis that pain persistence is mechanistically linked to ineffective descending control of nociception.

METHODS

Male and female Brown Norway, Dahl S, and eight consomic strains (SS-xBN) were used to determine the presence of chronic postsurgical pain-like behaviors by using paw-withdrawal threshold evaluation (von Frey method) in the area adjacent to a hind paw plantar incision. Descending control of nociception was assessed by measuring hind paw-withdrawal thresholds (Randall-Selitto method) after capsaicin (125 µg) injection into a forepaw. Consomic rats were developed by introgressing individual Brown Norway chromosomes on the Dahl S rat genetic background, as Dahl S rats lack preoperative descending control of nociception.

RESULTS

Substitution of several chromosomes from the "pain-resistant" Brown Norway to the "pain-prone" Dahl S/Medical College of Wisconsin reduced mechanical nociceptive sensitivity and increased endogenous pain modulation capacity by differing degrees. Statistical modeling of these data revealed that descending control of nociception is a poor general predictor of the propensity to develop chronic postsurgical pain-like behavior (poor fit for model 1). However, a significant strain-by-descending control of nociception interaction was revealed (model 3, -2*log likelihood; 550.668, -2ll change; 18.093, P = 0.034) with SS-13BN and SS-15BN strains showing a negative descending control of nociception relationship with chronic postsurgical pain-like behavior.

CONCLUSIONS

Descending control of nociception poorly predicted which rat strains developed chronic postsurgical pain-like behavior despite controlling for genetic, environmental, and sex differences. Two consomic strains that mimic clinical chronic postsurgical pain criteria and display a strong negative correlation with descending control of nociception were identified, offering novel candidates for future experiments exploring mechanisms that lead to chronic postsurgical pain.

EDITOR’S PERSPECTIVE

Fasting-mimicking diet alleviates inflammatory pain by inhibiting neutrophil extracellular traps formation and neuroinflammation in the spinal cord

BACKGROUND

Neutrophil extracellular traps (NETs) promote neuroinflammation and, thus, central nervous system (CNS) disease progression. However, it remains unclear whether CNS-associated NETs affect pain outcomes. A fasting-mimicking diet (FMD) alleviates neurological disorders by attenuating neuroinflammation and promoting nerve regeneration. Hence, in this study, we explore the role of NETs in the CNS during acute pain and investigate the role of FMD in inhibiting NETs and relieving pain.

METHODS

The inflammatory pain model was established by injecting complete Freund's adjuvant (CFA) into the hind paw of mice. The FMD diet regimen was performed during the perioperative period. PAD4 siRNA or CI-amidine (PAD4 inhibitor) was used to inhibit the formation of NETs. Monoamine oxidase-B (MAO-B) knockdown occurred by AAV-GFAP-shRNA or AAV-hSyn-shRNA or was inhibited by selegiline (an MAO-B inhibitor). The changes in NETs, neuroinflammation, and related signaling pathways were examined by western blot, immunofluorescence, ELISA, and flow cytometry.

RESULTS

In the acute phase of inflammatory pain, NETs accumulate in the spinal cords of mice. This is associated with exacerbated neuroinflammation. Meanwhile, inhibition of NETs formation alleviates allodynia and neuroinflammation in CFA mice. FMD inhibits NETs production and alleviates inflammatory pain, which is enhanced by treatment with the NETs inhibitor CI-amidine, and reversed by treatment with the NETs inducer phorbol 12-myristate 13-acetate (PMA). Mechanistically, the neutrophil-recruiting pathway MAO-B/5-hydroxyindoleacetic acid (5-HIAA) / G-protein-coupled receptor 35 (GPR35) and NETs-inducing pathway MAO-B/ Reactive oxygen species (ROS) are significantly upregulated during the development of inflammatory pain. MAO-B is largely expressed in astrocytes and neurons in the spinal cords of CFA mice. However, knockdown or inhibition of MAO-B effectively attenuates CFA-induced inflammatory pain, NETs formation, and neuroinflammation in the spinal cord. Moreover, within rescue experiments, MAO-B inhibitors synergistically enhance FMD-induced pain relief, NETs inhibition, and neuroinflammation attenuation, whereas supplementation with MAO-B downstream molecules (i.e., 5-HIAA and PMA) abolished this effect.

CONCLUSIONS

Neutrophil-released NETs in the spinal cord contribute to pain development. FMD inhibits NETs formation and NETs-induced neuroinflammation by inhibiting the MAO-B/5-HIAA/GPR35 and MAO-B/ROS pathways in astrocytes and neurons, thereby relieving pain progression. Video Abstract.

Content and Quality of Mobile Apps for the Monitoring of Musculoskeletal or Neuropathic Pain in Australia: Systematic Evaluation

Background

Mobile apps offer a potential mechanism for people with persistent pain to monitor pain levels conveniently within their own environment and for clinicians to remotely monitor their patients' pain. However, the quality of currently available apps and the usefulness of included features from a clinical perspective are not known.

Objective

The aim of this study was to examine the content and quality of currently available smartphone apps designed for monitoring the intensity or presence of musculoskeletal or neuropathic pain.

Methods

A systematic search was performed in the Australian Apple and Google Play stores. Apps were included if they were designed to monitor the intensity or presence of musculoskeletal or neuropathic pain and were available in the English language within the Australian app stores. Data pertaining to the intended use of the app and clinical population were extracted by using a custom-designed data extraction form, and app quality was assessed by using the 23-item Mobile App Rating Scale.

Results

Of the 2190 apps screened, 49 met the inclusion criteria. Apps were primarily designed for adult users (36/49, 73%) with nonspecific musculoskeletal or neuropathic pain conditions, arthritis, and joint pain. All apps monitored pain intensity, with almost half (23/49, 47%) also specifying pain location. Overall, the mean quality scores from the Mobile App Rating Scale ranged from 1.5 to 4.4 (out of 5.0). Between 20% (10/49) and 22% (11/49) of apps involved clinicians, consumers, or both in their development, and 20% (10/49) had published literature related to the development or use of the app in clinical scenarios. Although 71% (35/49) had data sharing features, only 5 apps enabled client-clinician communication through the app.

Conclusions

The overall quality of mobile apps that are currently available for monitoring pain intensity is acceptable. Presently, mobile apps for remote pain monitoring lack functionality for clinicians to view data between consults. Both users and clinicians should be aware of the limitations of these apps and make informed choices in using or recommending apps that best suit the clinical need.