Day-to-day experience in resolution of pain after surgery

Intravenous Lidocaine for the Management of Chronic Pain: A Narrative Review of Randomized Clinical Trials

Background

Chronic pain remains a serious health problem with significant impact on morbidity and well-being. Available treatments have only resulted in relatively modest efficacy. Thus, novel therapeutic treatments with different mechanisms have recently generated empirical interest. Lidocaine is postulated to provide anti-inflammatory and anti-nociceptive effect through its action at the N-methyl-D-aspartate (NMDA) and voltage gated calcium receptors. Emerging research indicates that lidocaine could be a reasonable alternative for treating chronic pain.

Objective

Considering the evidence surrounding lidocaine's potential as a therapeutic modality for chronic pain, we conducted a narrative review on the evidence of lidocaine's therapeutic effects in chronic pain.

Methods

A review of the PubMed, and Google scholar databases was undertaken in May 2022 to identify completed studies that investigated the effectiveness of lidocaine in the treatment of chronic pain from database inception to June 2022.

Results

A total of 25 studies were included in the narrative review. Findings on available studies suggest that intravenous infusion of lidocaine is an emerging and promising option that may alleviate pain in some clinical populations. Our narrative synthesis showed that evidence for intravenous lidocaine is currently mixed for a variety of chronic pain syndromes. Findings indicate that evidence for efficacy is limited for: CRPS, and cancer pain. However, there is good evidence supporting the efficacy of intravenous lidocaine as augmentation in chronic post-surgical pain.

Conclusion

Lidocaine may be a promising pharmacologic solution for chronic pain. Future investigation is warranted on elucidating the neurobiological mechanisms of lidocaine in attenuating pain signaling pathways.

Pain and Opioid use Following Total Knee Arthroplasty: Psycho-Social Factors are More Predictive Than Pharmacogenomics

BACKGROUND

This prospective, observational study was designed to assess the phenotype variation of the genes associated with pain and opioid use following total knee arthroplasty (TKA) in comparison to psycho-social elements.

METHODS

Preoperative demographic data and Patient-Reported Outcomes Measurement Information System-43 scores were obtained on 305 elective TKA patients. Patient visual analog scale pain scores and opioid use were extracted from the hospital record. Following discharge, participants completed a daily log of visual analog scale pain score, and medications used over 30 days. Pharmacogenomic testing was performed for three genes, CYP2D6, COMT, and OPRM1, which are involved in the opioid pathway and pain modulation.

RESULTS

Other than increased pain seen in the COMT high activity group while in the hospital, none of the phenotype variations of the three genes were significantly associated with the participants' pain or opioid use. The Patient-Reported Outcomes Measurement Information System-43 domains of pain interference and anxiety were significantly associated with pain and opioid use using multiple logistic regression.

CONCLUSIONS

Pharmacogenomic testing in this study was not predictive of pain and opioid use following TKA compared with psycho-social variables.

Optimizing the use of ketamine to reduce chronic postsurgical pain in women undergoing mastectomy for oncologic indication: study protocol for the KALPAS multicenter randomized controlled trial

BACKGROUND

Mastectomies are commonly performed and strongly associated with chronic postsurgical pain (CPSP), more specifically termed postmastectomy pain syndrome (PMPS), with 25-60% of patients reporting pain 3 months after surgery. PMPS interferes with function, recovery, and compliance with adjuvant therapy. Importantly, it is associated with chronic opioid use, as a recent study showed that 1 in 10 patients continue to use opioids at least 3 months after curative surgery. The majority of PMPS patients are women, and, over the past 10 years, women have outpaced men in the rate of growth in opioid dependence. Standard perioperative multimodal analgesia is only modestly effective in prevention of CPSP. Thus, interventions to reduce CPSP and PMPS are urgently needed. Ketamine is well known to improve pain and reduce opioid use in the acute postoperative period. Additionally, ketamine has been shown to control mood in studies of anxiety and depression. By targeting acute pain and improving mood in the perioperative period, ketamine may be able to prevent the development of CPSP.

METHODS

Ketamine analgesia for long-lasting pain relief after surgery (KALPAS) is a phase 3, multicenter, randomized, placebo-controlled, double-blind trial to study the effectiveness of ketamine in reducing PMPS. The study compares continuous perioperative ketamine infusion vs single-dose ketamine in the postanesthesia care unit vs placebo for reducing PMPS. Participants are followed for 1 year after surgery. The primary outcome is pain at the surgical site at 3 months after the index surgery as assessed with the Brief Pain Inventory-short form pain severity subscale.

DISCUSSION

This project is part of the NIH Helping to End Addiction Long-term (HEAL) Initiative, a nationwide effort to address the opioid public health crisis. This study can substantially impact perioperative pain management and can contribute significantly to combatting the opioid epidemic.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05037123. Registered on September 8, 2021.

Sleep Disturbance Trends in the Short-Term Postoperative Period for Patients Undergoing Total Joint Arthroplasty

BACKGROUND

Patients undergoing total joint arthroplasty (TJA) often experience preoperative/postoperative sleep disturbances. Although sleep quality generally improves > 6 months after surgery, patterns of sleep in the short-term postoperative period are poorly understood. This study sought to (1) characterize sleep disturbance patterns over the 3-month postoperative period and (2) investigate clinical and sociodemographic factors associated with 3-month changes in sleep.

METHODS

This retrospective analysis of prospectively collected data included 104 primary elective TJA patients. Patients were administered the PROMIS Sleep Disturbance questionnaire preoperatively and at 2 weeks, 6 weeks, and 3 months postoperatively. Median sleep scores were compared between time points using Wilcoxon signed-rank tests, stratified by preoperative sleep impairment. A multivariable logistic regression model identified factors associated with 3-month clinically improved sleep.

RESULTS

The percentage of patients reporting sleep within normal limits increased over time: 54.8% preoperatively and 58.0%, 62.5%, and 71.8% at 2 weeks, 6 weeks, and 3 months post-TJA, respectively. Patients with normal preoperative sleep experienced a transient 4.7-point worsening of sleep at 2 weeks ( P = 0.003). For patients with moderate/severe preoperative sleep impairment, sleep significantly improved by 5.4 points at 2 weeks ( P = 0.002), with improvement sustained at 3 months. In multivariable analysis, patients undergoing total hip arthroplasty (versus knee; OR: 3.47, 95% CI: 1.06 to 11.32, P = 0.039) and those with worse preoperative sleep scores (OR: 1.13, 95% CI: 1.04 to 1.23, P = 0.003) were more likely to achieve clinically improved sleep from preoperatively to 3 months postoperatively.

DISCUSSION

Patients experience differing patterns in postoperative sleep changes based on preoperative sleep disturbance. Hip arthroplasty patients are also more likely to experience clinically improved sleep by 3 months compared with knee arthroplasty patients. These results may be used to counsel patients on postoperative expectations and identify patients at greater risk of impaired postoperative sleep.

STUDY DESIGN

Retrospective analysis of prospectively collected data.

Randomized controlled trial of intrathecal oxytocin on speed of recovery after hip arthroplasty

ABSTRACT

Recovery from surgery is quicker in the postpartum period, and this may reflect oxytocin action in the spinal cord. We hypothesized that intrathecal injection of oxytocin would speed recovery from pain and disability after major surgery. Ninety-eight individuals undergoing elective total hip arthroplasty were randomized to receive either intrathecal oxytocin (100 μg) or saline. Participants completed diaries assessing pain and opioid use daily and disability weekly, and they wore an accelerometer beginning 2 weeks before surgery until 8 weeks after. Groups were compared using modelled, adjusted trajectories of these measures. The study was stopped early due to the lack of funding. Ninety patients received intrathecal oxytocin (n = 44) or saline (n = 46) and were included in the analysis. There were no study drug-related adverse effects. Modelled pain trajectory, the primary analysis, did not differ between the groups, either in pain on day of hospital discharge (intercept: -0.1 [95% CI: -0.8 to 0.6], P = 0.746) or in reductions over time (slope: 0.1 pain units per log of time [95% CI: 0-0.2], P = 0.057). In planned secondary analyses, postoperative opioid use ended earlier in the oxytocin group and oxytocin-treated patients walked nearly 1000 more steps daily at 8 weeks ( P < 0.001) and exhibited a clinically meaningful reduction in disability for the first 21 postoperative days ( P = 0.007) compared with saline placebo. Intrathecal oxytocin before hip replacement surgery does not speed recovery from worst daily pain. Secondary analyses suggest that further study of intrathecal oxytocin to speed functional recovery without worsening pain after surgery is warranted.

Following Evidence-Based Recommendations for Perioperative Pain Management after Cesarean Section Is Associated with Better Pain-Related Outcomes: Analysis of Registry Data

Women who have had a Cesarean Section (CS) frequently report severe pain and pain-related interference. One reason for insufficient pain treatment might be inconsistent implementation of evidence-based guidelines. We assessed the association between implementing three elements of care recommended by guidelines for postoperative pain management and pain-related patient-reported outcomes (PROs) in women after CS. The analysis relied on an anonymized dataset of women undergoing CS, retrieved from PAIN OUT. PAIN OUT, an international perioperative pain registry, provides clinicians with treatment assessment methodology and tools for patients to assess multi-dimensional pain-related PROs on the first postoperative day. We examined whether the care included [i] regional anesthesia with a neuraxial opioid OR general anesthesia with wound infiltration or a Transvesus Abdominis Plane block; [ii] at least one non-opioid analgesic at the full daily dose; and [iii] pain assessment and recording. Credit for care was given only if all three elements were administered (= “full”); otherwise, it was “incomplete”. A “Pain Composite Score-total” (PCStotal), evaluating outcomes of pain intensity, pain-related interference with function, and side-effects, was the primary endpoint in the total cohort (women receiving GA and/or RA) or a sub-group of women with RA only. Data from 5182 women was analyzed. “Full” care was administered to 20% of women in the total cohort and to 21% in the RA sub-group. In both groups, the PCStotal was significantly lower compared to “incomplete” care (p < 0.001); this was a small-to-moderate effect size. Administering all three elements of care was associated with better pain-related outcomes after CS. These should be straightforward and inexpensive for integration into routine care after CS. However, even in this group, a high proportion of women reported poor outcomes, indicating that additional work needs to be carried out to close the evidence-practice gap so that women who have undergone CS can be comfortable when caring for themselves and their newborn.

Status quo of pain-related patient reported outcomes and perioperative pain management in 10 415 patients from 10 countries: analysis of registry data

BACKGROUND

Postoperative pain is common at the global level, despite considerable attempts for improvement, reflecting the complexity of offering effective pain relief. In this study, clinicians from Mexico, China, and eight European countries evaluated perioperative pain practices and patient-reported outcomes (PROs) in their hospitals as a basis for carrying out quality improvement (QI) projects in each country.

METHODS

PAIN OUT, an international perioperative pain registry, provided standardized methodology for assessing management and multi-dimensional PROs on the first postoperative day, in patients undergoing orthopedic, general surgery, obstetric & gynecology or urological procedures.

RESULTS

Between 2017-2019, data obtained from 10,415 adult patients in 105 wards, qualified for analysis. At the ward level: 50% (median) of patients reported worst pain intensities ≥7/10 NRS, 25% spent ≥50% of the time in severe pain and 20-34% reported severe ratings for pain-related functional and emotional interference. Demographic variables, country and surgical discipline explained a small proportion of the variation in the PROs, leaving about 88% unexplained. Most treatment processes varied considerably between wards. Ward effects accounted for about 7% and 32% of variation in PROs and treatment processes, respectively.

CONCLUSIONS

This comprehensive evaluation demonstrates that many patients in this international cohort reported poor pain-related PROs on the first postoperative day. PROs and treatments varied greatly. Most of the variance of the PROs could not be explained. The findings served as a basis for devising and implementing QI programs in participating hospitals.

Psychiatric Comorbidities Associated with Persistent Postoperative Opioid Use

PURPOSE OF REVIEW

This review outlines the psychiatric comorbidities associated with persistent opioid use in the postoperative period. We finish our analysis with evidence-based, patient-centered interventions that can be rendered in the perioperative setting to decrease postoperative opioid requirements.

RECENT FINDINGS

Opioids are overprescribed in the USA, especially in the postoperative setting. Excess opioids can result in diversion and contribute to the ongoing opioid epidemic. Mental health and substance use disorders can contribute to persistent postoperative opioid use. Adequately managing these disorders preoperatively promises to reduce persistent postoperative opioid use. Due to the lack of homogenous, evidence-based recommendations on the appropriate quantity and duration of postoperative opioid therapy, there is wide variability in provider prescribing habits. Further research is needed to establish surgery-specific postoperative opioid therapy protocols. Opioids continue to be a mainstay in the treatment of postoperative pain. Unmonitored postoperative opioid use can lead to opioid use disorder. Mental health disorders increase susceptibility to persistent postoperative opioid use. By managing these psychiatric illnesses preoperatively, clinicians have the ability to decrease opioid consumption postoperatively. Lastly, given the healthcare burden of opioid misuse and abuse, it is important to establish concrete protocols to guide provider-prescribing habits.

Trajectories, Risk Factors, and Impact of Persistent Pain After Major Musculoskeletal Surgery in Adolescents: A Replication Study

Studies have identified high rates of chronic postsurgical pain in adolescents. Characterizing patterns of pain in the transition from acute to chronic following major surgery may pinpoint critical periods of recovery. This observational study modelled pain trajectories over 1-year following surgery to attempt replication of prior work and evaluate baseline psychosocial factors and 12-month health outcomes. Adolescents 10 to 18 years completed electronic daily pain reporting for 7 days and self-reported health outcomes, at 5 assessment timepoints. Group-based trajectory modelling identified two trajectories with similar starting points in-hospital but distinct recovery courses at home. Pain declined steadily in one group across the study period ("Declining Pain"; estimated probability,18.9%), but pain increased after hospital discharge and remained high through 12-months in the other group ("High and Persistent Pain"; estimated probability,81.1%). Pre-surgery pain (Aor = 1.86, P = .001) and sleep quality (Aor = 0.49, P = .029) were associated with the High and Persistent pain trajectory in multivariate regressions. This trajectory was associated with lower total quality of life (B=-9.79, P = .002), physical health (B = -15.93, P < .001), psychosocial health (B = -6.73, P = .06), and greater fatigue (B = -13.61, P = .001). This study replicated prior findings identifying two post-surgical pain trajectories with diverging pain in the first two weeks. Clinical detection of those with increasing pain and early intervention may interrupt persistence of pain. PERSPECTIVE: This article replicates a prior study identifying distinct post-surgical pain trajectories, Declining Pain and High and Persistent Pain. The High and Persistent pain trajectory is associated with pre-surgery pain, pre-surgery sleep quality, and lower quality of life (total, physical, and psychosocial health as well as fatigue) at 12-month follow-up.

A Brief Measure Assessing Adolescents' Daily In-Hospital Function Predicts Pain and Health Outcomes at Home After Major Surgery

OBJECTIVE

Pain-related function, an important component of pain assessment, is not systematically assessed in the hospital in part because of a lack of clinically meaningful measures of pain-related function. This prospective cohort study examined whether adolescents' pain-related function during hospitalization, measured daily with the Youth Acute Pain Functional Ability Questionnaire (YAPFAQ) is associated with pain and health-related quality of life (HRQOL) 2 weeks following surgery.

DESIGN

Adolescents undergoing major musculoskeletal surgery (N = 93) completed YAPFAQ (11 items) daily for up to three days in-hospital following surgery. Adolescents self-reported health-related quality of life on the pediatric quality of life inventory and pain intensity on a NRS at baseline (pre-surgery) and two-weeks following surgery. Regression models examined mean YAPFAQ and YAPFAQ rate of change as predictors of two-week outcomes, adjusting for sex, surgery type, and baseline pain/HRQOL.

RESULTS

Higher mean YAPFAQ scores (poorer function) were associated with higher pain intensity (β  =  0.2, p = 0.04) and poorer HRQOL (β = -0.3, p = 0.01) at home 2 weeks following surgery. YAPFAQ rate of change was not associated with 2-week outcomes.

CONCLUSIONS

Implementation of the YAPFAQ with in-hospital assessments to measure pain-related function will allow more comprehensive pain assessment. In-hospital YAPFAQ scores can predict important postsurgical outcomes at home and inform post-hospital care.

PERSPECTIVE

This article provides validation of a measure of pediatric pain-related function, the Youth Acute Pain Functional Ability Questionnaire (YAPFAQ) to predict important post-hospital outcomes after surgery.

Balanced Opioid Prescribing via a Clinical Trade-Off: Pain Relief vs. Adverse Effects of Discomfort, Dependence, and Tolerance/Hypersensitivity

In the backdrop of the opioid epidemic, opioid prescribing has distinct medical and social challenges. Overprescribing contributes to the ongoing opioid epidemic, whereas underprescribing yields inadequate pain relief. Moreover, opioids have serious adverse effects including tolerance and increased sensitivity to pain, paradoxically inducing more pain. Prescribing trade-offs are recognized but not modeled in the literature. We study the prescribing decisions for chronic, acute, and persistent pain types to minimize the cumulative pain that incorporates opioid adverse effects (discomfort and dependence) and the risk of tolerance or hypersensitivity (THS) developed with opioid use. After finding closed-form solutions for each pain type, we analytically investigate the sensitivity of acute pain prescriptions and examine policies on incorporation of THS, patient handover, and adaptive treatments. Our analyses show that the role of adverse effects in prescribing decisions is as critical as that of the pain level. Interestingly, we find that the optimal prescription duration is not necessarily increasing with the recovery time. We show that not incorporating THS or information curtailment at patient handovers leads to overprescribing that can be mitigated by adaptive treatments. Last, using real-life pain and opioid use data from two sources, we estimate THS parameters and discuss the proximity of our model to clinical practice. This paper has a pain management framework that leads to tractable models. These models can potentially support balanced opioid prescribing after their validation in a clinical setting. Then, they can be helpful to policy makers in assessment of prescription policies and of the controversy around over- and underprescribing.

Multidimensional Perioperative Recovery Trajectories in a Mixed Surgical Cohort: A Longitudinal Cluster Analysis Utilizing National Institutes of Health Patient-Reported Outcome Measurement Information System Measures

BACKGROUND

Pain trajectories have been described in numerous surgical settings where preoperative characteristics have been used to predict trajectory membership. Suboptimal pain intensity trajectories have been linked to poor longitudinal outcomes. However, numerous biopsychosocial modulators of postoperative pain may also have distinct longitudinal trajectories that may inform additional targets to improve postoperative recovery.

METHODS

Patients undergoing total joint arthroplasty, thoracic surgery, spine surgery, major abdominal surgery, or mastectomy completed Patient Reported Outcome Measurement Information System (PROMIS) measures and additional scales preoperatively and at 1 week, 2 weeks, 1 month, 3 months, and 6 months postoperatively. A k-means clustering for longitudinal data was utilized to explore and describe distinct pain impact (PROMIS Pain Interference and Physical Function) trajectories and associated changes in additional biopsychosocial measures. Follow-up analyses examined participant demographics and clinical characteristics associated with trajectory memberships.

RESULTS

Three postoperative biopsychosocial symptom clusters were identified across all patients (n = 402): low (35%), average (47%), and high (18%) performance cluster trajectories. Participants undergoing total knee arthroplasty (TKA), spinal surgery, reporting presurgical opioid use, and higher pain catastrophizing scale scores were found to be associated with the low performance trajectory. Patients within the low performance trajectory, while demonstrating small improvements by 6 months, remained mild to moderately impaired in both pain impact and physical health outcomes. Alternatively, participants in the average performance trajectory demonstrated improvement in pain impact to population norms compared to baseline and demonstrated continued improvement across physical and psychological outcomes. Patients within the high performance cluster started within population norms across all measures at baseline and returned to baseline or exceeded baseline values by 6 months postoperatively. Self-reported opioid utilization was significantly higher in the low performance cluster across all time points. While a larger proportion of average performance patients reported opioid utilization during the first postoperative month compared to the high performance cluster, no differences were detected at 6 months postoperatively between these 2 clusters.

CONCLUSIONS

These pain impact trajectories build upon previous unidimensional pain intensity trajectories and suggest that additional distinct biopsychosocial measures may have unique trajectories related to cluster assignment. Additionally, these findings highlight the importance of continued pain impact surveillance through the perioperative recovery period to detect patients at risk of experiencing a poor trajectory and subsequently poor longitudinal health outcomes.

To be mindful of the breath or pain: Comparing two brief preoperative mindfulness techniques for total joint arthroplasty patients

OBJECTIVE

Total joint arthroplasty (TJA) often reduces pain and improves function, but it is also a risk factor for the development of chronic pain and postoperative opioid use. To protect against these untoward postsurgical outcomes, TJA patients need better, non-pharmacological pain management strategies. This study compared two, promising, mindfulness-based pain management techniques.

METHOD

We conducted a single-site, three-arm, parallel-group randomized controlled study conducted at an orthopedic clinic among patients undergoing TJA of the knee or hip. TJA patients (N = 118, M age = 65, female = 73, Caucasian = 110) were randomized to either a preoperative mindfulness of breath (MoB), mindfulness of pain (MoP), or cognitive-behavioral pain psychoeducation (CB) intervention, approximately 3 weeks before surgery. Each intervention was delivered in a single, 20-min session during a 2-hr, preoperative education program. Change in pain intensity was the sole preoperative outcome. The postoperative outcomes, pain intensity, pain interference, and opioid use were assessed on the 2nd, 3rd, 7th, 14th, 21st, and 28th postoperative days.

RESULTS

MoB was found to most effectively decrease preoperative pain scores, F(2, 89) = 5.28, p = .007, while MoP resulted in the least amount of postoperative pain intensity, F(8, 94) = 3.21, p = .003, and interference, F(8, 94) = 2.52, p = .016). Both MoB and MoP decreased postoperative opioid use relative to CB, F(8, 83) = 16.66, p < .001.

CONCLUSION

A brief preoperative MBI may be able to prevent both postoperative pain and opioid use. Moreover, the MBIs used in this study are highly feasible, capable of being delivered by nearly any healthcare provider, and requiring minimal clinic time given their brevity. As such, embedding MBIs in surgical care pathways has considerable potential. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

AAAPT: Assessment of the Acute Pain Trajectory

OBJECTIVE

Define and contrast acute pain trajectories vs. the aggregate pain measurements, summarize appropriate linear and nonlinear statistical analyses for pain trajectories at the patient level, and present methods to classify individual pain trajectories. Clinical applications of acute pain trajectories are also discussed.

SETTING

In 2016, an expert panel involving the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION), American Pain Society (APS), and American Academy of Pain Medicine (AAPM) established an initiative to create a pain taxonomy, named the ACTTION-APS-AAPM Pain Taxonomy (AAAPT), for the multidimensional classification of acute pain. The AAAPT panel commissioned the present report to provide further details on analysis of the individual acute pain trajectory as an important component of comprehensive pain assessment.

METHODS

Linear mixed models and nonlinear models (e.g., regression splines and polynomial models) can be applied to analyze the acute pain trajectory. Alternatively, methods for classifying individual pain trajectories (e.g., using the 50% confidence interval of the random slope approach or using latent class analyses) can be applied in the clinical context to identify different trajectories of resolving pain (e.g., rapid reduction or slow reduction) or persisting pain. Each approach has advantages and disadvantages that may guide selection. Assessment of the acute pain trajectory may guide treatment and tailoring to anticipated symptom recovery. The acute pain trajectory can also serve as a treatment outcome measure, informing further management.

CONCLUSIONS

Application of trajectory approaches to acute pain assessments enables more comprehensive measurement of acute pain, which forms the cornerstone of accurate classification and treatment of pain.

Perioperative Opioid Administration

Opioids form an important component of general anesthesia and perioperative analgesia. Discharge opioid prescriptions are identified as a contributor for persistent opioid use and diversion. In parallel, there is increased enthusiasm to advocate opioid-free strategies, which include a combination of known analgesics and adjuvants, many of which are in the form of continuous infusions. This article critically reviews perioperative opioid use, especially in view of opioid-sparing versus opioid-free strategies. The data indicate that opioid-free strategies, however noble in their cause, do not fully acknowledge the limitations and gaps within the existing evidence and clinical practice considerations. Moreover, they do not allow analgesic titration based on patient needs; are unclear about optimal components and their role in different surgical settings and perioperative phases; and do not serve to decrease the risk of persistent opioid use, thereby distracting us from optimizing pain and minimizing realistic long-term harms.

Subacute Pain Trajectories following major musculoskeletal surgery in adolescents: A Pilot Study

Background: Adolescents who undergo major surgery experience high rates of disabling acute and chronic postsurgical pain (CPSP). However, little is known about the subacute period when acute to chronic pain transition occurs.

Aims: The aims of this study were to examine feasibility of electronic daily monitoring of pain and opioid use in adolescents during the first 30 days at home following major surgery and identify target features of subacute pain curves associated with CPSP at 4 months.

Methods: Twenty-five youth (10–18 years) undergoing major musculoskeletal surgery reported daily pain severity, interference, and opioid use on the Brief Pain Inventory each evening for 30 days after hospital discharge to form short time series trajectories. At 4 months, youth reported on pain intensity and health-related quality of life. Characteristics of subacute pain severity and interference curves were compared by 4-month CPSP status.

Results: At 4 months, 20.8% of youth met criteria for CPSP. During the 30-day monitoring period, youth who went on to develop CPSP reported high pain severity on 45.9% of days compared to 2.9% of days in youth who recovered (P = 0.005) and high pain interference on 49.4% of days vs. 9.7% in youth who recovered (P = 0.01). Pain variability and rate of change were not significantly associated with CPSP in our pilot sample.

Conclusions: We found it feasible to collect daily pain data in youth recovering at home after major surgery. Pilot findings suggest that daily electronic monitoring may identify early recovery problems at home after surgery. Larger studies are needed to validate subacute pain trajectory features to identify risk for CPSP.

Influential factors of postoperative pain trajectories in patients receiving intravenous patient-controlled analgesia: a single-centre cohort study in Taiwan

OBJECTIVES

We aimed to investigate the factors associated with variations in postoperative pain trajectories over time in patients using intravenous patient-controlled analgesia (IV-PCA) for postoperative pain.

DESIGN

Retrospective cohort study.

SETTING

A single medical centre in Taiwan.

PARTICIPANTS

Patients receiving IV-PCA after surgery.

PRIMARY AND SECONDARY OUTCOME MEASURES

Primary outcome was the postoperative pain scores.

RESULTS

A total of 3376 patients and 20 838 pain score observations were analysed using latent curve models. Female and longer anaesthesia time increased the baseline level of pain (p=0.004 and 0.003, respectively), but abdominal surgery and body weight decreased it (both p<0.001). Regarding the trend of pain resolution, lower abdominal surgery steepened the slope (p<0.001); older age, American Society of Anesthesiologists (ASA) class ≥3 and longer anaesthesia time tended to flatten the slope (p<0.001, =0.019 and <0.001, respectively). PCA settings did not affect the variations in postoperative pain trajectories.

CONCLUSIONS

Patient demographics, ASA class, anaesthesia time and surgical sites worked together to affect postoperative pain trajectories in patients receiving IV-PCA. Latent curve models provided valuable information about the dynamic and complex relationships between the pain trajectories and their influential factors.

Recovery of physical activity after cesarean delivery and its relationship with pain

Pain and physical activity are tightly intertwined. Although their relationship has been explored in chronic pain conditions, we know little about the pattern of recovery in activity and its short- and long-term relationship with pain after surgery. We recruited 103 women undergoing elective cesarean delivery and acquired daily pain assessments and hourly steps in 98 of them for 2 months after surgery. Compliance was good, with 78% of subjects missing less than 7 days of activity. Study personnel required daily checking for compliance and 20 minutes per subject per week in study. Activity increased over the first 2 postoperative months in a log(time) manner. The slope of each modeled individual curve for activity was inversely correlated (r = -0.54; P < 0.0001) with worst daily pain. After removing these 2-month trends, pain and activity within an individual day were negatively associated with each point increase in pain being inversely associated with -119 steps (95% confidence interval [CI] = -214 to -25; P = 0.013). A patient's previous experience of pain was not associated with current activity as well as current activity was not associated with future pain scores. These data, although limited by the study of a single operation in a unique social circumstance with low risk of chronic postsurgical pain, demonstrate feasibility of measuring hourly activity for 2 months after surgery. Recovery from pain and inactivity are tightly correlated, and the negative relationship between within-day pain and activity without interday carryover relationships is in stark contrast to findings in chronic pain conditions.

Patterns of recovery from pain after cesarean delivery

We know very little about the change in pain in the first 2 months after surgery. To address this gap, we studied 530 women scheduled for elective cesarean delivery who completed daily pain diaries for 2 months after surgery through text messaging. Over 82% of subjects missed fewer than 10 diary entries and were included in the analysis. Completers were more likely to be Caucasian, nonsmokers, and with fewer previous pregnancies than noncompleters. Daily worst pain intensity ratings for the previous 24 hours were fit to a log(time) function and allowed to change to a different function up to 3 times according to a Bayesian criterion. All women had at least one change point, occurring 22 ± 9 days postoperatively, and 81% of women had only one change, most commonly to a linear function at 0 pain. Approximately 9% of women were predicted to have pain 2 months after surgery, similar to previous observations. Cluster analysis revealed 6 trajectories of recovery from pain. Predictors of cluster membership included severity of acute pain, perceived stress, surgical factors, and smoking status. These data demonstrate feasibility but considerable challenges to this approach to data acquisition. The form of the initial process of recovery from pain is common to all women, with divergence of patterns at 2 to 4 weeks after cesarean delivery. The change-point model accurately predicts recovery from pain; its parameters can be used to assess predictors of speed of recovery; and it may be useful for future observational, forecasting, and interventional trials.

Capsaicin-induced pain and sensitisation in the postpartum period

BACKGROUND

Recovery from Caesarean delivery in women and surgical nerve injury in animals after delivery is more rapid than expected, an effect reversed in animals by spinal injection of an oxytocin receptor antagonist. We hypothesised that endogenous modulation of acute pain is altered postpartum.

METHODS

Endogenous inhibition of acute pain in a conditioned pain modulation paradigm or endogenous sensitisation by topical capsaicin was tested in women who were breastfeeding 10-14 days after Caesarean delivery and age-matched controls (n=80 total: 20 per group and 20 per test). The study was powered to detect a difference in area of hyperalgesia after capsaicin of 33%. Capsaicin-evoked pain was recorded in women, and capsaicin-evoked mechanical hypersensitivity was measured in rats 48 h after delivery and in age-matched female and male animals.

RESULTS

There was no effect of the postpartum period in the endogenous sensitisation assay in women, and the conditioned pain modulation assay failed to produce analgesia in either group. Postpartum women, however, reported less intense pain than controls at the end of topical capsaicin exposure (1.3 [1.4] vs 2.0 [2.0] on 0-10 verbal scale), and acute hypersensitivity after capsaicin was less in postpartum than control rats (withdrawal threshold 25 [15] vs 3.6 [1] g).

CONCLUSIONS

These results agree with a recent report that oxytocin may desensitise the transient receptor potential for vanilloid-1 channel, although other explanations, including hormone effects, are possible. These results do not, however, support the inhibition of capsaicin-evoked spinal sensitisation in the postpartum period.

CLINICAL TRIAL REGISTRATION

NCT01843517.

Preoperative Psychosocial and Psychophysical Phenotypes as Predictors of Acute Pain Outcomes After Breast Surgery

The severity and impact of acute pain after breast surgery varies markedly among individuals, underlining the importance of comprehensively identifying specific risk factors, including psychosocial and psychophysical traits. In this prospective observational study, women (n = 234) undergoing breast-conserving surgery, mastectomy, or mastectomy with reconstruction completed a brief bedside quantitative sensory testing battery, along with measures of psychosocial characteristics. Postoperative pain severity, impact, and opioid use at 2 weeks were assessed using Brief Pain Inventory and procedure-specific breast cancer pain questionnaires. Moderate-severe average pain (>3/10) was reported by 29% of patients at 2 weeks. Regression analysis of pain outcomes revealed that pain severity was independently predicted by axillary dissection, pre-surgical pain, temporal summation of pain (TSP), (-)positive affect, and behavioral coping style. Pain impact was predicted by age, education, axillary dissection, reconstruction, but also by negative affect and depression scores. Lastly, opioid use was predicted by age, education, axillary dissection, reconstruction, TSP, and reinterpreting coping style. Our findings suggest that, individuals with certain phenotypic characteristics, including high TSP and negative affect, may be at greater risk of significant pain and continued opioid use at 2 weeks after surgery, independent of known surgical risk factors. PERSPECTIVE: We measured differences in the psychosocial and psychophysical processing of pain amongst patients before breast surgery using simple validated questionnaires and brief quantitative sensory testing. Independent of younger age and procedural extent (axillary surgery and reconstruction), affect and greater temporal summation of pain predicted acute postoperative pain and opioid use.

Temporal and sex differences in the role of BDNF/TrkB signaling in hyperalgesic priming in mice and rats

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The effect of TrkB-Fc on hyperalgesic priming is sexually dimorphic in mice.

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The effect of TrkB-Fc on hyperalgesic priming is equivalent in male and female rats.

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Microglial BDNF does not contribute to hyperalgesic priming in mice.

Brain-derived neurotrophic factor (BDNF) signaling through its cognate receptor, TrkB, is a well-known promoter of synaptic plasticity at nociceptive synapses in the dorsal horn of the spinal cord. Existing evidence suggests that BDNF/TrkB signaling in neuropathic pain is sex dependent. We tested the hypothesis that the effects of BDNF/TrkB signaling in hyperalgesic priming might also be sexually dimorphic. Using the incision postsurgical pain model in male mice, we show that BDNF sequestration with TrkB-Fc administered at the time of surgery blocks the initiation and maintenance of hyperalgesic priming. However, when BDNF signaling was blocked prior to the precipitation of hyperalgesic priming with prostaglandin E₂ (PGE₂), priming was not reversed. This result is in contrast to our findings in male mice with interleukin-6 (IL6) as the priming stimulus where TrkB-Fc was effective in reversing the maintenance of hyperalgesic priming. Furthermore, in IL6-induced hyperalgesic priming, the BDNF sequestering agent, TrkB-fc, was effective in reversing the maintenance of hyperalgesic priming in male mice; however, when this experiment was conducted in female mice, we did not observe any effect of TrkB-fc. This markedly sexual dimorphic effect in mice is consistent with recent studies showing a similar effect in neuropathic pain models. We tested whether the sexual dimorphic role for BDNF was consistent across species. Importantly, we find that this sexual dimorphism does not occur in rats where TrkB-fc reverses hyperalgesic priming fully in both sexes. Finally, to determine the source of BDNF in hyperalgesic priming in mice, we used transgenic mice (Cx3cr1^CreER × Bdnf^flx/flx mice) with BDNF eliminated from microglia. From these experiments we conclude that BDNF from microglia does not contribute to hyperalgesic priming and that the key source of BDNF for hyperalgesic priming is likely nociceptors in the dorsal root ganglion. These experiments demonstrate the importance of testing mechanistic hypotheses in both sexes in multiple species to gain insight into complex biology underlying chronic pain.

Classification of acute pain trajectory after breast cancer surgery identifies patients at risk for persistent pain: a prospective observational study

Purpose

Predictive value and accuracy of the acute pain trajectory were compared with those of pain intensity at 1 day after the surgery for pain prevalence at 6 months after the surgery.

Materials and methods

Female patients scheduled for breast cancer surgery were eligible for this study. Patients were questioned about pain intensity daily during the 7 days after surgery. Presence of pain, its location, and intensity as well as the Japanese version of the quality of the recovery-40 (QOR-40) were determined in an interview prior to and at 6 months after the surgery. Acute pain trajectory was determined by a group-based trajectory modeling analysis that was based on the pain intensity at 1–7 days after surgery. Predictive value of the acute pain trajectory for the presence of pain at 6 months after the surgery was assessed by a logistic regression model. The predictive value was compared with pain intensity at 1 day after the surgery.

Results

A total of 123 participants completed the 6-month follow-up. The three-cluster model (mild, moderate, and severe pain) was considered to be the most statistically appropriate model for the acute pain trajectory. After 6 months, 51.2% and 8.9% of participants reported pain and severe pain, respectively. Presence of pain at 6 months after the surgery was associated with poor recovery. The severe pain cluster was significantly associated with the presence of pain at 6 months after the surgery (adjusted odds ratio, 9.40; P<0.001 vs mild pain cluster).

Conclusion

Classification of patients according to the acute pain trajectory, when compared with the classification according to pain intensity at 1 day after the surgery, made it possible to predict with better precision those patients who will develop persistent postsurgical pain.

Pain Adaptability in Individuals With Chronic Musculoskeletal Pain Is Not Associated With Conditioned Pain Modulation

Healthy humans can be divided into the pain adaptive (PA) and the pain nonadaptive (PNA) groups; PA showed a greater decrease in pain rating to a cold pressor test (CPT) than PNA. This study examined if the dichotomy of pain adaptability existed in individuals with chronic musculoskeletal pain. CPTs at 2°C and 7°C were used to assess the status of pain adaptability in participants with either chronic nonspecific low back pain or knee osteoarthritis. The participants' potency of conditioned pain modulation (CPM) and local inhibition were measured. The strengths of pain adaptability at both CPTs were highly correlated. PA and PNA did not differ in their demographic characteristics, pain thresholds from thermal and pressure stimuli, or potency of local inhibition or CPM. PA reached their maximum pain faster than PNA (t₄₁ = -2.76, P < .01), and had a gradual reduction of pain unpleasantness over 7 days whereas PNA did not (F_6,246 = 3.01, P = .01). The dichotomy of pain adaptability exists in musculoskeletal pain patients. Consistent with the healthy human study, the strength of pain adaptability and potency of CPM are not related. Pain adaptability could be another form of endogenous pain inhibition of which clinical implication is yet to be understood.

PERSPECTIVE

The dichotomy of pain adaptability was identified in healthy humans. The current study confirms that this dichotomy also exists in individuals with chronic musculoskeletal pain, and could be reliably assessed with CPTs at 2°C and 7°C. Similar to the healthy human study, pain adaptability is not associated with CPM, and may reflect the temporal aspect of pain inhibition.