Hospital-Wide Adherence to Postsurgical Opioid Prescribing Guidelines: A Retrospective Cohort Study

INTRODUCTION

Lowering opioid prescription doses and quantity decreases the risk of chronic opioid usage. A tool was inserted into the brief operative note for the surgeon to assess the severity of pain associated with the procedure. We studied surgeon adherence to current opioid-prescribing recommendations.

METHODS

Retrospective cohort study with 5486 patients were included in the study population. Each patient's prescription was scored yes or no for adherence on total morphine milligram equivalents (MMEs) and days prescribed with the selection in the brief operative note. The entire study population was tested for an increase from the null-hypothesis "benchmark" value of 75% using a one-sided exact binomial test of a single proportion with P < 0.05. This procedure was repeated for subgroups, with P < 0.01.

RESULTS

Adherence to guidelines was higher than the 75% benchmark for "total MMEs prescribed" (79.5%; P < 0.001), but lower for "number of days prescribed" (63.5%; P > 0.999). Surgeries with severe predicted pain showed the highest adherence toward total MMEs prescribed at 87.1%, followed by moderate (80.5%) and mild (74.5%). Severe cases also showed the highest adherence in number of days prescribed (92.4%). Adherence to total MMEs prescribed was highest among attending physicians (88.1%) and lowest among residents/fellows (76.6%).

CONCLUSIONS

Adherence to current guidelines was 79.5% for MMEs prescribed but only 63.5% for days prescribed. Compliance with guidelines was better for severe procedures than mild or moderate. Differences were seen across surgical departments. While an improvement from previous reports, further improvement is needed to reduce the number of days of opioids prescribed and increase compliance with recommended guidelines.

Transitional Pain Service: Optimizing Complex Surgical Patients

PURPOSE OF REVIEW

The care of patients with complex postsurgical pain can be challenging and burdensome for the healthcare system. Transitional pain service (TPS) is a relatively new concept and has not been widely adopted in the USA. This article explores the benefits and barriers of transitional pain services and describes the development of a TPS at our institution.

RECENT FINDINGS

Evidence from a few institutions that have adopted TPS has shown decreased postsurgical opioid consumption for patients on chronic opioids and decreased incidence of chronic postsurgical opioid use for opioid-naïve patients. The development of a transitional pain service may improve outcomes for these complex patients by providing longitudinal and multidisciplinary perioperative pain care. In this article, we describe the implementation of a TPS at a tertiary medical center. Our TPS model involves a multidisciplinary team of anesthesiologists, pain psychologists, surgeons, and advanced practice providers. We provide longitudinal care, including preoperative education and optimization; perioperative multimodal analgesic care; and longitudinal follow-up for 90 days post-procedure. With our TPS service, we aim to reduce long-term opioid use and improve functional outcomes for our patients.

Liposomal bupivacaine versus conventional anesthetic or placebo for hemorrhoidectomy: a systematic review and meta-analysis

BACKGROUND

Liposome bupivacaine (LB) is a long-acting anesthetic to enhance postoperative analgesia. Studies evaluating the efficacy of the LB against an active comparator (bupivacaine or placebo) on acute postoperative pain control in hemorrhoidectomy procedures are few and heterogeneous. Therefore, we performed a systematic review and meta-analysis comparing LB's analgesic efficacy and side effects to conventional/placebo anesthetic in hemorrhoidectomy patients.

METHODS

We performed a systematic review and meta-analysis of randomised controlled trials investigating the use of LB after haemorrhoidectomy. We searched the literature published from the time of inception of the datasets to August 19, 2022. The electronic databases included English publications in Ovid MEDLINE In-Process & Other Non-Indexed Citations, Ovid MEDLINE, Ovid EMBASE, and Scopus.

RESULTS

A total of 338 patients who underwent a hemorrhoidectomy procedure enrolled in three randomized clinical trials were included. The overall mean age was 45.84 years (SD ± 11.43), and there was a male predominance (53.55% male). In total 194 patients (52.2%) received LB and 144 (47.8%) received either bupivacaine or placebo. Pain scores at 72 h in the LB (199, 266, and 300 mg) were significantly lower than in the bupivacaine HCl group (p = 0.002). Compared to the bupivacaine/placebo group, the time to first use of opioids in the LB group was significantly longer at LB 199 mg (11 h vs. 9 h), LB 266 mg (19 h vs. 9 h), and LB 300 mg (19 h vs. 8 h) (p < 0.05). Moreover, compared to the bupivacaine/epinephrine group, it was significantly lower in the LB 266 mg group (3.7 vs. 10.2 mg) and at LB 300 mg (13 vs. 33 mg) (p < 0.05). Finally, regarding adverse effects, the conventional anesthetic/placebo group reported more pain in bowel movement than LB groups (OR 2.60, 95% CI 1.31-5.16).

CONCLUSIONS

Comparing LB to conventional anesthetic/placebo anesthetic for hemorrhoidectomy, we found a statistically significant reduction in pain through 72 h, decreased opioid requirements, and delayed time to first opioid use. Moreover, the conventional anesthetic/placebo group reported more pain in bowel movement than LB groups.

Which ultrasound-guided parasternal intercostal nerve block for post-sternotomy pain? Results from a prospective observational study

BACKGROUND

Parasternal intercostal blocks (PSB) have been proposed for postoperative analgesia in patients undergoing median sternotomy. PSB can be achieved using two different approaches, the superficial parasternal intercostal plane block (SPIP) and deep parasternal intercostal plane block (DPIP) respectively.

METHODS

We designed the present prospective, observational cohort study to compare the analgesic efficacy of the two approaches. Cardiac surgical patients who underwent full sternotomy from January to September 2022 were enrolled and divided into three groups, according to pain control strategy: morphine, SPIP, and DPIP group. Primary outcomes were was postoperative pain evaluated as absolute value of NRS at 12 h. Secondary outcomes were the NRS at 24 and 48 h, the need for salvage analgesia (both opioids and NSAIDs), incidence of postoperative nausea and vomiting, time to extubation, mechanical ventilation duration, and bowel disfunction.

RESULTS

Ninety-six were enrolled. There was no significant difference in terms of median Numeric Pain Rating Scale at 24 h and at 48 h between the study groups. Total postoperative morphine consumption was 1.00 (0.00-3.00), 2.00 (0.00-5.50), and 15.60 mg (9.60-30.00) in the SPIP, DPIP, and morphine group, respectively (SPIP and DPIP vs morphine: p < 0.001). Metoclopramide consumption was lower in SPIP and DPIP group compared with morphine group (p = 0.01). There was no difference in terms of duration of mechanical ventilation and of bowel activity between the study groups. Two pneumothorax occurred in the DPIP group.

CONCLUSIONS

Both SPIP and DPIP seem able to guarantee an effective pain management in the postoperative phase of cardiac surgeries via full median sternotomy while ensuring a reduced consumption of opioids and antiemetic drugs.

Minimally invasive recipient procedure in kidney transplantation

Background

There are several procedural variations for kidney transplant donors, including open, laparoscopic, hand-assisted, and robotic methods, with either an intra- abdominal or retroperitoneal approach. Conversely, fewer options are available for the recipient procedure. We introduce a method that involves a small incision, with the goal of being less invasive for recipients.

Methods

Our current method was introduced in April 2022. As of July 2023, we have completed 27 cases. We analyzed several factors in these 27 cases, including the size of the incision, rewarming time, anastomosis time, graft function, analgesic use, and complications.

Results

The average incision size was 73 mm. The time taken for anastomosis was 24. 1 minutes, while the rewarming time averaged 43.1 minutes. There were no instances of primary nonfunction. One case necessitated postoperative dialysis three times due to heart failure. Following stent removal, one patient developed grade 1 hydronephrosis. There was one instance of bleeding from the drain insertion site. Another case involved a clamp injury to the external iliac artery, which necessitated stent insertion on the fourth postoperative day. Compared to procedures performed using conventional methods, the use of analgesics was less in these cases.

Conclusions

Our minimally invasive technique, which involves a small incision, is a feasible alternative that could potentially be less invasive than traditional methods.

Transitional Pain Medicine; New Era, New Opportunities, and New Journey

Chronic postsurgical pain (CPSP), also known as persistent postsurgical pain (PPSP), is pain that develops or increases in intensity after a surgical procedure and lasts more than 3 months. Transitional pain medicine is the medical field that focuses on understanding the mechanisms of CPSP and defining risk factors and developing preventive treatments. Unfortunately, one significant challenge is the risk of developing opioid use dependence. Multiple risk factors have been discovered, with the most common, and modifiable, being uncontrolled acute postoperative pain; preoperative anxiety and depression; and preoperative site pain, chronic pain, and opioid use.

Prevalence of postoperative pain after hospital discharge: systematic review and meta-analysis

Assessment and management of postoperative pain after hospital discharge is very challenging. We conducted a systematic review to synthesize available evidence on the prevalence of moderate-to-severe postoperative pain within the first 1 to 14 days after hospital discharge. The previously published protocol for this review was registered in PROSPERO. MEDLINE and EMBASE databases were searched until November 2020. We included observational postsurgical pain studies in the posthospital discharge setting. The primary outcome for the review was the proportion of study participants with moderate-to-severe postoperative pain (eg, pain score of 4 or more on a 10-point Numerical Rating Scale) within the first 1 to 14 days after hospital discharge. This review included 27 eligible studies involving a total of 22,108 participants having undergone a wide variety of surgical procedures. The 27 studies included ambulatory surgeries (n = 19), inpatient surgeries (n = 1), both ambulatory and inpatient surgeries (n = 4), or was not specified (n = 3). Meta-analyses of combinable studies provided estimates of pooled prevalence rates of moderate-to-severe postoperative pain ranging from 31% 1 day after discharge to 58% 1 to 2 weeks after discharge. These findings suggest that moderate-to-severe postoperative pain is a common occurrence after hospital discharge and highlight the importance of future efforts to more effectively evaluate, prevent, and treat postsurgical pain in patients discharged from the hospital.

Green Light Exposure Elicits Anti-inflammation, Endogenous Opioid Release and Dampens Synaptic Potentiation to Relieve Post-surgical Pain

Light therapy improves multiple conditions such as seasonal affective disorders, circadian rhythm dysregulations, and neurodegenerative diseases. However, little is known about its potential benefits in pain management. While current pharmacologic methods are effective in many cases, the associated side effects can limit their use. Non-pharmacological methods would minimize drug dependence, facilitating a reduction of the opioid burden. Green light therapy has been shown to be effective in reducing chronic pain in humans and rodents. However, its underlying mechanisms remain incompletely defined. In this study, we demonstrate that green light exposure reduced postsurgical hypersensitivity in rats. Moreover, this therapy potentiated the antinociceptive effects of morphine and ibuprofen on mechanical allodynia in male rats. Importantly, in female rats, GLED potentiated the antinociceptive effects of morphine but did not affect that of ibuprofen. We showed that green light increases endogenous opioid levels while lessening synaptic plasticity and neuroinflammation. Importantly, this study reveals new insights into how light exposure can affect neuroinflammation and plasticity in both genders. Clinical translation of these results could provide patients with improved pain control and decrease opioid consumption. Given the noninvasive nature of green light, this innovative therapy would be readily implementable in hospitals. PERSPECTIVE: This study provides a potential additional therapy to decrease postsurgical pain. Given the safety, availability, and the efficacy of green light therapy, there is a significant potential for advancing the green light therapy to clinical trials and eventual translation to clinical settings.

Acute and subacute postsurgical pain in women with breast cancer: incidence and associations with biopsychosocial predictors-a secondary analysis of a randomized controlled trial

Introduction

Women who undergo breast cancer surgery risk suffering from postsurgical pain long after their surgery. Still, research on postsurgical pain in the subacute phase has been neglected.

Objective

This study aims to investigate the incidence, intensity, unpleasantness, and presurgical predictors of acute and subacute postsurgical pain after breast cancer surgery.

Methods

The study used an observational design through secondary analyses of the control group in a randomized controlled trial. Data from 102 women undergoing breast cancer surgery were included. Levels of acute and subacute pain intensity and unpleasantness were measured using 100 mm Visual Analogue Scales on the day of surgery and 4 weeks postsurgery. Linear regression analyses were performed to identify presurgical biopsychosocial predictors of acute and subacute postsurgical pain.

Results

Average levels of postsurgical pain intensity and unpleasantness were as follows: 22.7 mm for acute pain intensity, 19.0 mm for acute pain unpleasantness, 10.3 mm for subacute pain intensity, and 11.7 mm for subacute pain unpleasantness. Pain expectancy predicted acute pain intensity (R² = 0.04, p = 0.047) and acute unpleasantness (R² = 0.06, p = 0.02). Perceived social support inversely predicted acute pain unpleasantness (R² = 0.04, p = 0.014).

Conclusion

Mild and moderate acute pain intensity and unpleasantness are common after breast cancer surgery, whereas levels of subacute pain intensity and unpleasantness are low. Pain expectancy predicts acute postsurgical pain intensity and unpleasantness, whereas expected social support inversely predicts acute postsurgical pain unpleasantness.

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.

The PPARγ agonist pioglitazone produces a female-predominant inhibition of hyperalgesia associated with surgical incision, peripheral nerve injury, and painful diabetic neuropathy

Pioglitazone, an agonist at peroxisome proliferator-activated receptor gamma, is FDA-approved for the treatment of insulin resistance in type 2 diabetes. Numerous studies in male rodents suggest that pioglitazone inhibits inflammatory and neuropathic pain, but few included female subjects. To address this gap, we compared the effects of pioglitazone in both sexes in the intraplantar methylglyoxal model (MG) model of chemical pain and painful diabetic neuropathy (PDN), the plantar incision model (PIM) of postoperative pain, the spared nerve injury (SNI) model of traumatic nerve injury, and the ZDF rat and db/db mouse models of PDN. We administered pioglitazone by one-time intrathecal or intraperitoneal injection or by adding it to chow for 6 weeks, followed by measurement of hypersensitivity to non-noxious mechanical, noxious mechanical, heat, and/or cold stimuli. In all mouse models, injection of pioglitazone decreased pain-like behaviors with greater potency and/or efficacy in females as compared to males: heat and mechanical hypersensitivity in the MG model (0.1-10 mg/kg); mechanical hypersensitivity in the PIM model (10 μg); mechanical and cold hypersensitivity in the SNI model (100 mg/kg); and heat hypersensitivity in the db/db model (100 mg/kg). Furthermore, co-administration of low doses of morphine (1 mg/kg) and pioglitazone (10 mg/kg) decreased SNI-induced mechanical and cold hypersensitivity in female but not male mice. In the ZDF rat, pioglitazone (100 mg/kg) decreased heat and mechanical hypersensitivity with no sex difference. In the db/db model, pioglitazone had no effect when given into chow for 6 weeks at 0.3, 3 or 30 mg/kg doses. We conclude that females exhibit greater anti-hyperalgesic responses to pioglitazone in mouse models of chemical-induced nociception, postsurgical pain, neuropathic pain, and PDN. These findings set the stage for clinical trials to determine whether pioglitazone has analgesic properties across a broad spectrum of chronic pain conditions, particularly in women.

Pain, numbness, or both? Distinguishing the longitudinal course and predictors of positive, painful neuropathic features vs numbness after breast cancer surgery

Supplemental Digital Content is Available in the Text. Examining the divergence of prevalence and predictors of postsurgical numbness vs positive neuropathic symptoms gives insights into variation in clinical postoperative pain experienced by patients.

Introduction:

Both positive (burning, stabbing, and allodynia) and negative (numbness) neuropathic symptoms may arise after surgery but likely contribute differently to patients' postoperative pain experience. Numbness has been identified as divergent from positive neuropathic symptoms and therefore excluded from some neuropathic assessment tools (Neuropathic Pain Scale for PostSurgical patients [NeuPPS]).

Objectives:

In this prospective longitudinal study of patients undergoing breast surgery, we aimed to delineate the time course of numbness and its coincidence with NeuPPS and to contrast the association of surgical, psychosocial, and psychophysical predictors with the development of negative vs positive neuropathic symptoms.

Methods:

Patients reported surgical area sensory disturbances at 2 weeks and 3, 6, and 12 months postoperatively. Association of baseline demographic, surgical, psychosocial, and psychophysical factors with NeuPPS and numbness across time was investigated using generalized estimating equation linear and logistic regression.

Results:

Numbness was consistently reported by 65% of patients; positive neuropathic symptoms were less common, often decreasing over time. Neuropathic Pain scale for PostSurgical patients and numbness co-occurred in half of patients and were both associated with greater clinical pain severity and impact, younger age, axillary surgery, and psychosocial factors. More extensive surgery and chemotherapy were only associated with numbness. Conversely, other chronic pain, lower physical activity, perioperative opioid use, negative affect, and lower baseline pressure pain threshold and tolerance were only associated with NeuPPS. Patients reporting numbness alone did not endorse substantial clinical pain.

Conclusions:

Differentiation of predictors, prevalence, and time course of numbness vs NeuPPS in breast surgical patients revealed important distinctions, suggesting that their independent assessment is worthwhile in future studies of postsurgical pain.

Scoping review of the association between postsurgical pain and heart rate variability parameters

Supplemental Digital Content is Available in the Text. This scoping review provides some evidence of a possible association between heart rate variability and postsurgical pain, although significant variability exists among included studies.

Surgical interventions can elicit neuroendocrine and sympathovagal responses, leading to cardiac autonomic imbalance. Cardiac complications account for approximately 30% of postoperative complications. Altered heart rate variability (HRV) was initially described in the 1970s as a predictor of acute coronary syndromes and has more recently been shown to be an independent predictor of postoperative morbidity and mortality after noncardiac surgery. In general, HRV reflects autonomic balance, and altered HRV measures have been associated with anesthetic use, chronic pain conditions, and experimental pain. Despite the well-documented relationship between altered HRV and postsurgical outcomes and various pain conditions, there has not been a review of available evidence describing the association between postsurgical pain and HRV. We examined the relationship between postsurgical pain and HRV. MEDLINE and EMBASE databases were searched until December 2020 and included all studies with primary data. Two reviewers independently assessed risk of bias for each study using the criteria outlined in the Cochrane Handbook for Systematic Review of Interventions. A total of 8 studies and 1002 participants were included. Studies examined the association of postsurgical pain and HRV or analgesia nociception index derived from HRV. There was a statistically significant association between HRV measures and postsurgical pain in 6 of 8 studies. Heterogeneity of studies precluded meta-analyses. No studies reported cardiovascular outcomes. There is a potential association between postsurgical pain and HRV or analgesia nociception index, although results are likely impacted by confounding variables. Future studies are required to better delineate the relationship between postsurgical pain and HRV and impacts on cardiovascular outcomes.

Myofascial Pain in Hysterectomy Patients

STUDY OBJECTIVE

To assess the prevalence of myofascial pain in women undergoing uncomplicated, minimally invasive hysterectomy for chronic pelvic pain, to identify clinical and demographic factors associated with preoperative myofascial pain, and examine the association between myofascial pain and postoperative pain in hysterectomy patients.

DESIGN

A retrospective cohort study.

SETTING

A tertiary care teaching hospital.

PATIENTS

A total of 353 adult women who underwent uncomplicated, minimally invasive hysterectomy between January 2014 and 2016.

INTERVENTIONS

All women underwent a preoperative pelvic floor examination. Myofascial pain was diagnosed as tenderness and reproduction of pain symptoms in at least 2 of 6 pelvic floor muscles. Demographics, comorbidities, and intraoperative characteristics were compared between women with and without preoperative myofascial pain.

MEASUREMENTS AND MAIN RESULTS

Of the 353 women who underwent hysterectomy, the prevalence of myofascial pain was 42.7% (86.0% in patients with chronic pelvic pain [CPP] compared with 13.7% without CPP). Women with myofascial pain were more likely younger, Caucasian, sexually active, and with comorbid pain conditions. Patients with myofascial pain used a greater number of adjuvant pain medications before surgery including opiates (29.5%) but were only half as likely to use muscle relaxants (12.1%) for preoperative pain control. Contrastingly, in women without myofascial pain before surgery, controlled substances such as opiates (8%, p <.01) and benzodiazepines (3%, p <.01) were used at a three- fold lower frequency. Postoperative pain score was higher in patients with myofascial pain, with 37% reporting a visual analog scale score greater than 5 at the routine postoperative visit compared with only 1% of patients without myofascial pain.

CONCLUSION

Myofascial pelvic pain must be considered in the evaluation of CPP, especially in surgical candidates. Women with myofascial pelvic use a greater amount of pain medication preoperatively and have higher pain scores postoperatively. Identification of these high-risk patients before surgery may improve pre and postoperative pain management with a multimodal therapy approach.

A virtual reality-based intervention for surgical patients: study protocol of a randomized controlled trial

Background

Pain after surgery is normal, and treatments, including both pharmacological and psychological components, are fundamental for proper postoperative care. While several trials have investigated the analgesic effect of traditional non-pharmacological treatments, such as cognitive behavior therapies, the newer ways of delivering psychological interventions for pain after surgery are scarcely investigated. The aim of this randomized controlled trial (RCT) is to determine if delivering the psychological content through virtual reality (VR) along with the standard pharmacological treatment return better pain relief outcomes than standard care in adult patients following surgery.

Methods

This is a protocol of a parallel RCT conducted in one community hospital. In order to test the efficacy of VR environments for reducing pain intensity, in the following day after surgery, adults (18 to 65 years) will be randomly assigned to either (1) standard treatment after surgery (control group) or (2) VR based intervention along with standard treatment. It is intended that a minimum of 30 patients be recruited in each group. For estimating the intensity of pain, both self-report and physiological measures will be used. Repeated measures of pain outcomes will be taken before and after the intervention. Moreover, for allowing an in-depth investigation of the effect of VR environments, the primary outcome will be complemented with measures of the adverse effects, level of immersion, and level of presence in the VR environment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05196-7.

Alpha lipoic acid attenuates evoked and spontaneous pain following surgical skin incision in rats

Our previous studies have implicated Ca_V3.2 isoform of T-type Ca2+ channels (T-channels) in the development of postsurgical pain. We have also previously established that different T-channel antagonists can alleviate in vivo postsurgical pain. Here we investigated the analgesic potential of another T-channel blocker and endogenous antioxidant molecule, α-lipoic acid (ALA), in a postsurgical pain model in rats. Our in vivo results suggest that single and repetitive intraperitoneal injections of ALA after surgery or preemptively, significantly reduced evoked mechanical hyperalgesia following surgical paw incision. Furthermore, repeated preemptive systemic injections of ALA effectively alleviated spontaneous postsurgical pain as determined by dynamic weight-bearing testing. We expect that our preclinical study may lead to further investigation of analgesic properties and mechanisms of analgesic action of ALA in patients undergoing surgery.

Plantar incision with severe muscle injury can be a cause of long-lasting postsurgical pain in the skin

AIMS

Although chronic local inflammation in deeper tissues after skin wound healing might produce chronification of acute postsurgical pain, its mechanisms have not been fully elucidated. We hypothesized that muscle injury and severe inflammation would prolong acute postsurgical pain by its central nervous system mechanisms.

MAIN METHODS

After approval of the Animal Care Committee, experiments were performed in Male Sprague-Dawley rats weighing 250-300 g. Plantar incision and plantar incision combined with cryoinjury of the plantar flexor digitorum brevis muscle were made in the plantar incision group and muscle injury group, respectively. Pain-related behaviors were assessed, and inflammatory cells were isolated from injured muscle and analyzed by flow cytometry. Spinal microglial activation was assessed with Iba-1 staining.

KEY FINDINGS

Mechanical hyperalgesia from day 5 to day 8 and spontaneous pain-related behavior from day 3 to day 7 were significantly greater in the muscle injury group than in the plantar incision group (P < 0.05), whereas there was no significant difference between the two groups in thermal hyperalgesia. In the muscle injury group, the number of inflammatory cells on day 4 was significantly larger and spinal Iba-1 expression levels on days 4 and 7 were significantly higher than those in the plantar incision group (P < 0.05).

SIGNIFICANCE

Surgical injury in deep tissues accompanying severe muscle inflammation induced prolonged postsurgical pain in the healing wound of the skin not by the persistence of muscle inflammation but by a central mechanism involving microglial activation at the level of the spinal cord.

Pharmacokinetics and Safety of INL-001 (Bupivacaine HCl) Implants Compared with Bupivacaine HCl Infiltration After Open Unilateral Inguinal Hernioplasty

Introduction

Surgical site infiltration with bupivacaine HCl results in short-lived analgesia for postsurgical pain and carries the risk of systemic bupivacaine toxicity due to accidental intravascular injection. INL-001 is a bupivacaine HCl collagen-matrix implant that provides extended delivery of bupivacaine directly at the site and avoids the risk of accidental injection. Here, we examine the pharmacokinetic (PK) and safety profile of INL-001 placement during unilateral open inguinal hernioplasty.

Methods

This multicenter, single-blind study (NCT03234374) enrolled patients undergoing open inguinal hernioplasty to receive three INL-001 implants, each containing 100 mg bupivacaine HCl (n = 34) or local infiltration of 0.25% bupivacaine HCl 175 mg (n = 16). Acetaminophen was provided in the postsurgical period and supplemented by opioids for breakthrough pain, as needed. PK blood samples were taken before surgery and up to 96 h after drug administration.

Results

INL-001 demonstrated a prolonged rate of absorption and clearance of bupivacaine compared with 0.25% bupivacaine HCl 175 mg, as demonstrated by a longer time to peak plasma concentration and terminal elimination half-life. Peak plasma concentration with INL-001 300 mg was comparable to bupivacaine HCl 175 mg and well below levels associated with systemic bupivacaine toxicity. The most common adverse events (AEs) in both groups were associated with general anesthesia and the postsurgical setting. No AE was related to the implant, including those associated with wound healing.

Conclusions

These findings demonstrate that INL-001 provides immediate and extended delivery of bupivacaine and is well tolerated in patients undergoing open inguinal hernioplasty with no adverse effect on wound healing.

Trial registration

Clinicaltrials.gov identifier, NCT03234374.

Electronic supplementary material

The online version of this article (10.1007/s12325-020-01565-x) contains supplementary material, which is available to authorized users.

A Comprehensive Review of the Diagnosis, Treatment, and Management of Postmastectomy Pain Syndrome

PURPOSE OF REVIEW

Postmastectomy pain syndrome (PMPS) remains poorly defined, although it is applied to chronic neuropathic pain following surgical procedures of the breast, including mastectomy and lumpectomy in breast-conserving surgery. It is characterized by persistent pain affecting the anterior thorax, axilla, and/or medial upper arm following mastectomy or lumpectomy. Though the onset of pain is most likely to occur after surgery, there may also be a new onset of symptoms following adjuvant therapy, including chemotherapy or radiation therapy.

RECENT FINDINGS

The underlying pathophysiology is likely multifactorial, although exact mechanisms have yet to be elucidated. In this regard, neuralgia of the intercostobrachial nerve is currently implicated as the most common cause of PMPS. Numerous pharmacological options are available in the treatment of PMPS, including gabapentinoids, tricyclic antidepressants, selective serotonin reuptake inhibitors, NMDA receptor antagonists, and nefopam (a non-opioid, non-steroidal benzoxazocine analgesic). Minimally invasive interventional treatment including injection therapy, regional anesthesia, botulinum toxin, and neuromodulation has been demonstrated to have some beneficial effect. A comprehensive update highlighting current perspectives on the treatment of postmastectomy pain syndrome is presented with emphasis on treatments currently available and newer therapeutics currently being evaluated to alleviate this complex and multifactorial condition.

CD163 overexpression using a macrophage-directed gene therapy approach improves wound healing in ex vivo and in vivo human skin models

Large tissue damage or wounds cause serious comorbidities and represent a major burden for patients, families, and health systems. Due to the pivotal role of immune cells in the proper resolution of inflammation and tissue repair, we focus our current study on the interaction of macrophages with skin cells, and specifically on the effects of CD163 gene induction in macrophages in wound healing. We hypothesize that the over-expression of the scavenger receptor gene CD163 in human macrophages would result in a more efficient wound healing process. Using 3D human wounded skin organotypic tissues, we observed that CD163 overexpression in THP-1 and human primary macrophages induced a more efficient re-epithelization when compared to control cells. Using human primary skin cells and an in vitro scratch assay we observed that CD163 overexpression in THP-1 macrophages promoted a more rapid and efficient wound healing process through a unique interaction with fibroblasts. The addition of CD163-blocking antibody, but not isotype control, blocked the efficient wound healing process induced by CD163 overexpression in macrophages. We found that the co-culture of skin cells and CD163 overexpressing macrophages reduced monocyte chemoattractant protein (MCP)-1 and enhanced tumor growth factor (TGF)-α, without altering interleukin (IL)-6 or TGF-β. Our findings show that CD163 induces a more efficient wound healing and seems to promote a wound milieu with a pro-resolution molecular profile. Our studies set the foundation to study this approach in in vivo clinically relevant settings to test its effects in wound healing processes such as acute major injuries, large surgeries, or chronic ulcers.

Percutaneous Peripheral Nerve Stimulation to Control Postoperative Pain, Decrease Opioid Use, and Accelerate Functional Recovery Following Orthopedic Trauma

Orthopedic trauma is a significant military problem, causing several of the most disabling conditions with high rates of separation from duty and erosion of military readiness. The objective of this report is to summarize the findings of case series of a non-opioid therapy-percutaneous peripheral nerve stimulation (PNS) - and describe its potential for postoperative analgesia, early opioid cessation, and improved function following orthopedic trauma. Percutaneous PNS has been evaluated for the treatment of multiple types of pain, including two case series on postoperative pain following total knee replacement (n = 10 and 8, respectively) and a case series on postamputation pain (n = 9). The orthopedic trauma induced during TKR is highly representative of multiple types of orthopedic trauma sustained by Service members and frequently produces intense, prolonged postoperative pain and extended opioid use following surgery. Collectively, the results of these three clinical studies demonstrated that percutaneous PNS can provide substantial pain relief, reduce opioid use, and improve function. These outcomes suggest that there is substantial potential for the use of percutaneous PNS following orthopedic trauma.

Perioperative activation of spinal α7 nAChR promotes recovery from preoperative stress-induced prolongation of postsurgical pain

Preoperative stress could delay the recovery of postoperative pain and has been reported to be a risk factor for chronic postsurgical pain. As stress could facilitate the proinflammatory activation of microglia, we hypothesized that these cells may play a vital role in the development of preoperative stress-induced pain chronification after surgery. Our experiments were conducted in a rat model that consists of a single prolonged stress (SPS) procedure and plantar incision. A previous SPS exposure induced anxiety-like behaviors, prolonged incision-induced mechanical allodynia, and potentiated the activation of spinal microglia. Based on the results from ex vivo experiments, spinal microglia isolated from SPS-exposed rats secreted more proinflammatory cytokines upon challenge with LPS. Our results also demonstrated that microglia played a more important role than astrocytes in the initiation of SPS-induced prolongation of postsurgical pain. We further explored the therapeutic potential of agonism of α7 nAChR, an emerging anti-inflammatory target, for SPS-induced prolongation of postsurgical pain. Multiple intrathecal (i.t.) injections of PHA-543613 (an α7 nAChR agonist) or PNU-120596 (a type II positive allosteric modulator) during the perioperative period shortened the duration of postsurgical pain after SPS and suppressed SPS-potentiated microglia activation, but their effects were abolished by pretreatment with methyllycaconitine (an α7 nAChR antagonist; i.t.). Based on the results from ex vivo experiments, the anti-inflammatory effects of PHA-543613 and PNU-120596 may have been achieved by the direct modulation of microglia. In conclusion, stress-induced priming of spinal microglia played a key role in the initiation of preoperative stress-induced prolongation of postsurgical pain, and PHA-543613 and PNU-120596 may be potential candidates for preventing pain chronification after surgery.

Persistent postsurgical pain in children and young people: prediction, prevention, and management

Ensuring optimum preoperative and postoperative pain management should always be a priority in children.

Spinal AMPA Receptor GluA1 Ser831 Phosphorylation Controls Chronic Alcohol Consumption-Produced Prolongation of Postsurgical Pain

Previous studies have shown that excessive alcohol drinking is associated with chronic pain development; however, the molecular mechanism underlying this association is poorly understood. In this study, we investigated the effect of chronic alcohol consumption on plantar incision-induced postsurgical pain. We observed that 4-week ethanol drinking significantly prolonged plantar incision-induced mechanical pain, but not thermal pain. The chronic alcohol consumption enhanced plantar incision-produced α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor GluA1 phosphorylation at the Ser831 site in the spinal cord. The targeted mutation of the GluA1 phosphorylation site in GluA1 S831A mutant mice significantly inhibited the incisional pain prolongation produced by chronic alcohol consumption. Moreover, chronic alcohol consumption combined with plantar incision markedly increased AMPA receptor-mediated miniature excitatory postsynaptic currents in the spinal dorsal horn neurons, and this effect was diminished significantly in the GluA1 S831A mutant mice. Our results suggest that chronic alcohol consumption may promote the development of persistent postsurgical pain by enhancing AMPA receptor GluA1 Ser831 phosphorylation. We identified chronic alcohol consumption as a risk factor for pain chronification after surgery.

Validation of the Youth Acute Pain Functional Ability Questionnaire in Children and Adolescents Undergoing Inpatient Surgery

Half of children admitted after surgery experience intense pain in hospital, and many experience continued pain and delayed functional recovery at home. However, there is a gap in tools available to measure acute functional ability in pediatric postsurgical settings. We aimed to validate the Youth Acute Pain Functional Ability Questionnaire (YAPFAQ) in a large inpatient pediatric surgical population, evaluate its responsiveness to expected functional recovery, and develop a short form for broad clinical implementation. The YAPFAQ is a self-report measure assessing acute functional ability, developed in children admitted for acute sickle cell pain. We evaluated psychometric properties of the measure in 564 children ages 8 to 18 years admitted after surgery. A sample of 54 participants completed the YAPFAQ daily for 3 days after major surgery to assess responsiveness. The measure showed good reliability (Cronbach α = .96) and construct validity, with expected relationships with physical health-related quality of life (r = -.53, P < .001) and pain intensity (r = .42, P < .001). YAPFAQ scores decreased over time showing good responsiveness to expected recovery. A 3-item short form of the YAPFAQ showed promising psychometric properties. Early assessment of functioning after surgery may identify children at risk for poor functional outcomes and allow targeting of therapies to improve postsurgical recovery.

PERSPECTIVE

The YAPFAQ showed promising psychometric properties in a pediatric postsurgical population. This study addresses a gap in tools available to monitor functional recovery during hospitalization after pediatric surgery. Early detection of problems with recovery may enable targeted therapies to improve postsurgical outcomes.

PKMζ Is Not Required for Development of Postsurgical Pain

Previous studies have shown that protein kinase M zeta (PKMζ), a brain-specific isoform of protein kinase C, is involved in the central processing of nociception in several pain models by using a synthetic zeta inhibitory peptide. In the present study, we investigated whether PKMζ contributes to the pathogenesis of postsurgical pain using both conditional and conventional PKMζ knockout mice. Our results showed that the expression of PKMζ in anterior cingulate cortex, but not spinal cord, of the conditional PKMζ knockout mice was inhibited following tamoxifen injection. And the conditional PKMζ knockout mice displayed similar plantar incision-produced postsurgical pain responses as those in wild-type mice. Moreover, the expression of PKMζ was inhibited in both anterior cingulate cortex and spinal cord of the conventional PKMζ knockout mice. And there were no significant differences in the development of postsurgical pain among wild-type, heterozygous, and homozygous conventional PKMζ knockout mice. These data suggest that PKMζ is not required for the development of postsurgical pain after plantar incision.

Methylprednisolone reduces pain and decreases knee swelling in the first 24 h after fast-track unicompartmental knee arthroplasty

PURPOSE

Unicompartmental knee arthroplasty (UKA) results in less operative trauma and faster patient recovery than after a conventional total knee arthroplasty. Despite an increased focus on multimodal analgesic strategies, there is still a substantial level of patient-reported pain in the early postsurgical period after UKA. The purpose of the study was to evaluate the effect of a single preoperative dose of systemic methylprednisolone on postsurgical pain after fast-track UKA.

METHODS

Seventy-two patients in two consecutive series undergoing unilateral UKA were included in a prospective cohort study. The patients (n = 35) in the treatment group received a single preoperative dose of systemic methylprednisolone 125 mg, whereas the control group (n = 37) did not. Outcome measures were postsurgical pain at rest and during walking, consumption of opioids for pain rescue, knee swelling and knee range of motion, and complications.

RESULTS

In the first 24 h after surgery, the treatment group had less pain at rest (p < 0.001) and during walking (p < 0.001) and less consumption of opioids (p = 0.01) in comparison with the control group. Furthermore, the treatment group had 2.2 cm less knee swelling (p = 0.02) in the first post-operative day, and better knee extension (p = 0.004), whereas knee flexion was similar (n.s.) between groups. No serious complications were associated with the treatment.

CONCLUSION

Addition of a single preoperative dose of 125 mg systemic methylprednisolone to a multimodal analgesic regime significantly reduced postsurgical pain and opioid consumption and decreased knee swelling in the first 24 h after fast-track UKA.

LEVEL OF EVIDENCE

Therapeutic study, Level II.

Best Practices for Medication Utilization Evaluations in Postsurgical Pain Management

Purpose

The purpose of this review is to provide guidance that aids in the practical design, implementation, and analysis of medication use evaluations (MUEs) for postsurgical pain management.

Summary

Clinicians have long employed drug use evaluations or drug utilization reviews to ensure the safe and appropriate use of medications in a hospital, medical practice, or other healthcare setting. Although these approaches are valuable, there is a growing trend toward replacing these methods with the MUE, a performance improvement tool that focuses on assessing and improving medication use processes or medication treatment response with the goal of optimizing patient outcomes. Utilizing MUEs to assess patient outcomes and quality of life can be challenging in certain therapeutic areas such as pain management, where measurements of pain can be quantitative but are inherently subjective. Currently, there is little guidance on the development of MUEs that balance subjective and objective outcomes.

Conclusion

MUEs continue to become the standard for quality improvement for optimizing care and ensuring optimal outcomes. This review of the literature provides guidance in post-surgical pain management, an area that requires measurement of both subjective and objective outcomes.

Targeting AMPK for the Alleviation of Pathological Pain

Chronic pain is a major clinical problem that is poorly treated with available therapeutics. Adenosine monophosphate-activated protein kinase (AMPK) has recently emerged as a novel target for the treatment of pain with the exciting potential for disease modification. AMPK activators inhibit signaling pathways that are known to promote changes in the function and phenotype of peripheral nociceptive neurons and promote chronic pain. AMPK activators also reduce the excitability of these cells suggesting that AMPK activators may be efficacious for the treatment of chronic pain disorders, like neuropathic pain, where changes in the excitability of nociceptors is thought to be an underlying cause. In agreement with this, AMPK activators have now been shown to alleviate pain in a broad variety of preclinical pain models indicating that this mechanism might be engaged for the treatment of many types of pain in the clinic. A key feature of the effect of AMPK activators in these models is that they can lead to a long-lasting reversal of pain hypersensitivity even long after treatment cessation, indicative of disease modification. Here, we review the evidence supporting AMPK as a novel pain target pointing out opportunities for further discovery that are likely to have an impact on drug discovery efforts centered around potent and specific allosteric activators of AMPK for chronic pain treatment.

Characterization of the Affective Component of Acute Postoperative Pain Associated with a Novel Rat Model of Inguinal Hernia Repair Pain

AIMS

Acute postoperative pain remains a significant healthcare issue. Historically, the assessment of postoperative pain in rodents has relied on evoked withdrawal or reflexive measures. Using a recently developed, anatomically relevant rat model of acute postoperative pain (J Pain, 16, 2015, 421), the present experiments sought to investigate the affective component of acute postoperative pain associated with inguinal hernia repair.

METHODS

Male Lister hooded rats underwent surgery to model Lichtenstein inguinal hernia repair (without hernia induction), or a sham procedure. Postsurgical characterization involved a modified place escape/avoidance paradigm (mPEAP), as well as home cage and open field locomotor activity monitoring. In pharmacological validation studies, rats received either morphine or carprofen prior to mPEAP testing.

RESULTS

Surgery was associated with a significantly increased proportion of the trial duration in the light compartment of the mPEAP arena, in avoidance of the noxious stimulus, compared with sham animals. When retested in the mPEAP at day 7 postsurgery, there was no difference between sham and surgery animals for time spent in either compartment, but surgery animals displayed a persistent increase in the percentage response to noxious stimulation. Morphine and carprofen treatment in surgery animals reduced escape/avoidance behavior at discrete time points over the trial. Surgery-induced reductions in home cage and open field locomotor activity were also observed.

CONCLUSION

The present studies report for the first time the characterization of the affective component of acute postoperative pain using the mPEAP in a rodent model, which may facilitate development of improved understanding and treatment of postoperative pain.

p38 and interleukin-1 beta pathway via toll-like receptor 4 contributed to the skin and muscle incision and retraction-induced allodynia

BACKGROUND

Persistent postsurgical pain, as an important clinical problem, seriously affects the quality of life in patients. However, the mechanism underlying persistent postsurgical pain remains largely unclear. The present study aims to elucidate the involvement of toll-like receptor 4 (TLR4) and its interaction with p38 and interleukin [IL]-1β signaling in dorsal root ganglion (DRG) in the persistent postsurgical pain.

METHODS

Skin and muscle incision and retraction (SMIR) surgery-induced paw withdrawal threshold (PWT) change was determined by applying mechanical stimuli to the plantar surface of the hind paw using von Frey hairs. The PE-10 catheter intrathecal placement was used to deliver LPS-RS, interleukin-1 receptor antagonist, or SB203580. Western blot analysis was performed to measure the expression of the TLR4, mitogen-activated protein kinases family, and IL-1β in ipsilateral L3 and L4 DRG. Immunofluorescence staining was performed to further investigate the cell type of TLR4 expression. All data were expressed as means ± standard error of the mean and analyzed using SPSS 13.0.

RESULTS

The results showed that the SMIR surgery, a rat model of persistent postoperative pain, decreased the ipsilateral 50% PWT, and the decrease lasted for at least 20 d. The expression of TLR4 and phosphorylation of p38 were upregulated in ipsilateral L3 and L4 DRG neurons after SMIR surgery. Pretreatment with LPS-RS, an established TLR4 antagonist, prevented p38 activation and attenuated mechanical allodynia induced by SMIR surgery. In addition, the expression of IL-1β was significantly increased after SMIR surgery. Blocking IL-1β by interleukin-1 receptor antagonist significantly improved the decreased PWT evoked by SMIR. Moreover, inhibition of TLR4 or p38 pathway prevented the IL-1β upregulation and mechanical allodynia induced by SMIR.

CONCLUSIONS

These findings suggest that the activation of p38 and IL-1β signaling pathway via TLR4 mediate mechanical allodynia after SMIR surgery.

Development and characterization of a novel, anatomically relevant rat model of acute postoperative pain

Acute postoperative pain remains a significant health care issue. Development of anatomically relevant animal models of postoperative pain, with improved predictive validity, would advance understanding of postoperative pain mechanisms and improve treatment outcomes. This study aimed to develop, characterize, and validate a rat model of acute postoperative pain associated with inguinal hernia repair based on the Lichtenstein inguinal hernia repair procedure (without hernia induction). We hypothesized that the surgery would result in reduced spontaneous locomotor activity, which would represent a pain-related phenotype. Postsurgical characterization involved extensive monitoring of home cage and open field locomotor activity, as well as mechanical hypersensitivity and assessment of c-Fos expression in the dorsal horn of the spinal cord. In pharmacologic validation studies, rats received morphine, carprofen, or paracetamol 1 hour before, and/or immediately after, surgery. Rats that underwent hernia repair surgery exhibited significantly lower horizontal and vertical activities in the home cage and open field in the early postsurgical period, compared with sham rats or rats that underwent skin incision only. Morphine, carprofen, and paracetamol attenuated the surgery-induced reductions in locomotor activity, to varying degrees. Surgery was associated with significantly increased c-Fos expression in the ipsilateral dorsal horn of the spinal cord, an effect attenuated by carprofen treatment. These results support the development and characterization of a novel, anatomically relevant animal model of acute postoperative pain that may facilitate development of improved treatment regimens.

PERSPECTIVE

Acute pain following inguinal hernia repair can be difficult to treat. Here we report, for the first time, the development of a novel, anatomically relevant rat model to facilitate improved understanding and treatment of acute postoperative pain following inguinal hernia repair.

Are psychological predictors of chronic postsurgical pain dependent on the surgical model? A comparison of total knee arthroplasty and breast surgery for cancer

Anxiety, depression, and catastrophizing are generally considered to be predictive of chronic postoperative pain, but this may not be the case after all types of surgery, raising the possibility that the results depend on the surgical model. We assessed the predictive value of these factors for chronic postsurgical pain in 2 different surgical models: total knee arthroplasty for osteoarthritis (89 patients, 65% women, age = 69 ± 9 years, baseline pain intensity = 4.7 ± 2.1) and breast surgery for cancer (100 patients, 100% women, age = 55 ± 12 years, no preoperative pain). Data were collected before surgery, then 2 days and 3 months after surgery. Anxiety, depression, and catastrophizing were measured with the Spielberger State-Trait Anxiety Inventory, Beck Depression Inventory, and Pain Catastrophizing Scale, respectively. Pain was assessed with the Brief Pain Inventory. Neuropathic pain was detected with the DN4 questionnaire. Multivariate logistic regression analyses for the total knee arthroplasty and breast surgery models considered together indicated that the presence of clinically meaningful chronic pain at 3 months (pain intensity ≥3/10) was predicted independently by age (P = .04), pain intensity on day 2 (P = .009), and state anxiety (P = .001). Linear regression models also showed that pain magnification, one of the dimensions of catastrophizing, independently predicted chronic pain intensity (P = .04). These results were not affected by the surgical model or by the neuropathic characteristics of the pain. Thus, state anxiety and pain magnification seem to constitute psychological risk factors for chronic postsurgical pain relevant in all surgical models.

PERSPECTIVE

This prospective study performed in patients with total knee arthroplasty or breast surgery for cancer shows that state anxiety, amplification of pain, and acute postoperative pain independently predict postsurgical pain at 3 months and that this does not depend on the surgical model.