National review of acute pain service utilization, models of care, and clinical practices within the Veterans Health Administration.

INTRODUCTION: The Veterans Health Administration (VHA) is the largest healthcare network in the USA and has been a national leader in opioid safety for acute pain management. However, detailed information on the availability and characteristics of acute pain services within its facilities is lacking. We designed this project to assess the current state of acute pain services within the VHA. METHODS: A 50-question electronic survey developed by the VHA national acute pain medicine committee was emailed to anesthesiology service chiefs at 140 VHA surgical facilities within the USA. Data collected were analyzed by facility complexity level and service characteristics. RESULTS: Of the 140 VHA surgical facilities contacted, 84 (60%) completed the survey. Thirty-nine (46%) responding facilities had an acute pain service. The presence of an acute pain service was associated with higher facility complexity level designation. The most common staffing model was 2.0 full-time equivalents, which typically included at least one physician. Services performed most by formal acute pain programs included peripheral nerve catheters, inpatient consult services, and ward ketamine infusions. CONCLUSIONS: Despite widespread efforts to promote opioid safety and improve pain management, the availability of dedicated acute pain services within the VHA is not universal. Higher complexity programs are more likely to have acute pain services, which may reflect differential resource distribution, but the barriers to implementation have not yet been fully explored.

Opioid tapering after surgery and its association with patient-reported outcomes and behavioral changes: a mixed-methods analysis.

INTRODUCTION: Opioid tapering after surgery is recommended among patients with chronic opioid use, but it is unclear how this process affects their quality of life. The objective of this study was to evaluate how opioid tapering following surgery was associated with patient-reported outcome measures related to pain control and behavioral changes that affect quality of life. METHODS: We conducted an explanatory sequential mixed-methods study at a VA Medical Center among patients with chronic opioid use who underwent a spectrum of orthopedic, vascular, thoracic, urology, otolaryngology, and general surgery procedures between 2018 and 2020. Patients were stratified based on the extent that opioid tapering was successful (complete, partial, and no-taper) by 90 days after surgery, followed by qualitative interviews of 10 patients in each taper group. Longitudinal patient-reported outcome measures related to pain intensity, interference, and catastrophizing were compared using Kruskal Wallis tests over the 90-day period after surgery. Qualitative interviews were conducted among patients in each taper group to identify themes associated with the impact of opioid tapering after surgery on quality of life. RESULTS: We identified 211 patients with chronic opioid use (92% male, median age 66 years) who underwent surgery during the time period, including 42 (20%) individuals with complete tapering, 48 (23%) patients with partial tapering, and 121 (57%) patients with no taper of opioids following surgery. Patients who did not taper were more likely to have a history of opioid use disorder (10%-partial, 2%-complete vs 17%-no taper, p<0.05) and be discharged on a higher median morphine equivalent daily dose (52-partial, 30-complete vs 60-no taper; p<0.05) than patients in the partial and complete taper groups. Pain interference (-7.2-partial taper and -9.8-complete taper vs -3.5-no taper) and pain catastrophizing (-21.4-partial taper and -16.5-complete taper vs -1.7-no taper) scores for partial and complete taper groups were significantly improved at 90 days relative to baseline when compared with patients in the no-taper group (p<0.05 for both comparisons), while pain intensity was similar between groups. Finally, patients achieving complete and partial opioid tapering were more likely to report improvements in activity, mood, thinking, and sleep following surgery as compared with patients who failed to taper. CONCLUSIONS: Partial and complete opioid tapering within 90 days after surgery among patients with chronic opioid use was associated with improved patient-reported measures of pain control as well as behaviors that impact a patient's quality of life.

Postsurgical Opioid Use Among Veterans Discharged to Skilled Care Facilities Compared to Veterans Discharged to Home After Orthopedic Surgery.

OBJECTIVES: To compare opioid use patterns among Veterans who were discharged to a skilled care facility vs home after orthopedic surgery at a VA hospital. DESIGN: We conducted a retrospective cohort study of Veterans who had orthopedic surgery at the Salt Lake City VA Medical Center (VAMC) between January 2018 and December 2021 and were followed by a transitional pain service. The principal outcome of interest was the time to stop opioid use after discharge from the hospital. SETTING AND PARTICIPANTS: Veterans not already on chronic opioid therapy who had orthopedic surgery at the Salt Lake City VAMC and were followed by a transitional pain service. METHODS: 448 patients were included in the study, of which 371 (83%) were discharged to home and 77 (17%) were discharged to a skilled care facility. Median days to opioid cessation were estimated using the Kaplan-Meier method with 95% CIs and compared with discharge disposition using a log-rank test. Time to opioid cessation following hospital discharge was compared to baseline characteristics using univariable and multivariable Cox proportional hazards models. RESULTS: Patients who were discharged to a skilled care facility used opioids for twice as long as those who were discharged home [median days (interquartile range)]: 22 (19, 26) vs 11 (10, 12), P < .001, respectively. When controlling for baseline characteristics in the multivariable analysis, discharge to a skilled care facility was significantly associated with continued opioid use at all time points [hazard ratio 0.63 (95% CI 0.44, 0.89), P = .009]. CONCLUSIONS AND IMPLICATIONS: Veterans discharged to a skilled care facility after orthopedic surgery used opioids for twice as long as those who were discharged to home. As postsurgical pain management guidelines change to focus on nonopioid pain modalities and opioid reduction, skilled care providers should adapt those strategies for their facilities.

Complete opioid cessation after surgery improves patient-reported pain measures among chronic opioid users.

BACKGROUND: Preoperative chronic opioid use is common, but it is unclear whether complete opioid tapering can be achieved postoperatively without adversely affecting pain control and quality of life. This study was designed to assess the association between complete opioid tapering after surgery and patient-reported outcomes for pain intensity and pain interference. METHODS: We identified chronic opioid use patients undergoing a spectrum of nonemergency surgical procedures at a single Veterans Affairs medical institution between December 2017 and 2021. All patients were prospectively followed by a transitional pain service that promoted opioid tapering, assessed opioid use (morphine milligram equivalent), and patient-reported outcomes measurement information system for pain intensity (PROMIS-3a) and pain interference (PROMIS-6b). After stratifying based on whether complete versus partial/no opioid tapering was achieved after surgery, longitudinal changes in patient-reported outcomes and morphine milligram equivalents were compared over time. Independent predictors of complete opioid tapering were assessed using logistic regression models. RESULTS: In total, 341 surgical patients (91% male, mean age 64 years) with chronic opioid use underwent surgery during the study period, of which 44 (13%) completely tapered off opioids within 60 days after discharge from the hospital. Patients who completely tapered had significant improvement in the change in patient-reported outcomes for pain intensity and interference with significant differences at 30 and 60 days after discharge for both measures when compared to the partial/no taper group (both P < .05). In risk-adjusted analyses, patients with lower baseline morphine milligram equivalents and those staying longer in the hospital were more likely to achieve complete opioid tapering (both P < .01). CONCLUSION: Complete opioid tapering can be successfully achieved after surgery among patients with chronic opioid use with corresponding improvements in self-reported pain intensity and pain interference. Our results suggest that the highest potential for improving patient-reported outcomes with opioid tapering occurs among patients undergoing orthopedic procedures early after surgical discharge.

A Multidisciplinary Transitional Pain Management Program Is Associated With Reduced Opioid Dependence After Primary Total Joint Arthroplasty.

BACKGROUND: Overprescription of opioids after total joint arthroplasty (TJA) increases risks of opioid dependence, overdose, and death. The authors hypothesized that a multidisciplinary, perioperative pain management program (the Transitional Pain Service or TPS) for TJA would lead to fewer patients becoming opioid dependent. METHODS: A TPS was implemented at a Veterans Affairs Medical Center focused on nonopioid pain management, cessation support, and prospective data tracking. A historical control, interventional study design was used to assess opioid use at 90 days post-discharge. Secondary analysis of the implementation group included post-operative outcome scores, time to opioid cessation, and median opioid tablets consumed at 90 days. RESULTS: Fewer patients in the TPS group demonstrated persistent opioid use at 90 days post-discharge (0.7% vs 9.9%; P = .004). Independent predictors of total opioid tablet prescriptions included TPS (ß = -19.41; 95% confidence interval [CI] -35.37 to -3.47), number of tablets prescribed at discharge (ß = 1.08; 95% CI 0.86-1.31), and TKA surgery (ß = 16.84; 95% CI 4.58-29.10). Under the TPS, median tablets consumed was 20.5 for THA and 36.5 for TKA; median time to cessation was shorter in THA (7 days; 95% CI 2-10) when compared to TKA (13 days; 95% CI 11-16). CONCLUSION: In opioid-naïve veterans undergoing TJA, the TPS was associated with a 93% reduction in opioid dependence and a 60% reduction in opioid tablet prescriptions at 90 days post-discharge. Under the TPS, median 90-day opioid consumption was 20.5 and 36.5 tablets for THA and TKA, respectively. Widespread adoption of similar programs may greatly reduce opioid use and dependence in orthopedic patients nationally. LEVEL OF EVIDENCE: III.

Relationships between physical therapy intervention and opioid use: A scoping review.

OBJECTIVE: To synthesize available evidence that has examined the relationship between physical therapy (PT) and opioid use. TYPE: Scoping Review LITERATURE SURVEY: Data sources including Google Scholar, Embase, PubMed, Cochrane Library, and CINAHL were searched for English articles up to October 24, 2019 using terms ("physical therapy"[Title/Abstract] OR physiotherapy[Title/Abstract] OR rehabilitation[Title/Abstract]) AND (opiate*[Title/Abstract] OR opioid*[Title/Abstract]). METHODOLOGY: Included studies evaluated a PT intervention and reported an opioid-use outcome. Data were extracted to describe the PT intervention, patient sample, opioid-use measurement, and results of any time or group comparisons. Study quality was evaluated with Joanna Briggs checklists based on study design. SYNTHESIS: Thirty studies were included that evaluated PT in at least one of these seven categories: interdisciplinary program (n = 8), modalities (n = 3), treatment (n = 3), utilization (n = 2), content (n = 3), timing (n = 13), and location (n = 2). Mixed results were reported for reduced opioid-use after interdisciplinary care and after PT modalities. Utilizing PT was associated with lower odds (ranging from 0.2-0.8) of using opioid medication for persons with low back pain (LBP) and injured workers; however, guideline-adherent care did not further reduce opioid use for persons with LBP. Early PT utilization after index visit for spine or joint pain and after orthopedic surgery was also associated with lower odds of using opioid medications (ranging from 0.27-0.93). Emergency department PT care was not associated with fewer opioid prescriptions than standard emergency department care. PT in a rehabilitation center after total knee replacement was not associated with lower opioid use than inpatient PT. CONCLUSIONS: The relationship between timing of PT and opioid use was evaluated in 13 of 30 studies for a variety of patient populations. Eight of these 13 studies reported a relationship between early PT and reduced subsequent opioid use, making the largest sample of studies in this scoping review with supporting evidence. There is limited and inconclusive evidence to establish whether the content and/or location of PT interventions improves outcomes because of heterogeneity between studies.

The effect of audiovisual distraction on patient-controlled sedation under spinal anesthesia: a prospective, randomized trial.

Audiovisual distraction (AVD) has been used to augment or replace procedural sedation. We investigated whether AVD in patients having total hip (THA) or total knee arthroplasty (TKA) under spinal anesthesia would reduce self-administered propofol consumption during surgery. 50 participants were randomized equally into a patient-controlled sedation (PCS) group or AVD group. All participants were given a spinal block and a propofol PCS device prior to surgery. In addition, Group AVD participants selected and watched a movie or documentary film on a tablet device with noise-cancelling headphones during surgery. The primary outcome of this study was total propofol consumption standardized as mcg/kg/min. Secondary outcomes evaluated increased supplemental oxygen use, rescue airway interventions, hypotension, disruptive movement events during surgery, sedation, and satisfaction with anesthesia scores. Historical clinician-controlled propofol usage at our institution over the previous 2 years were recorded. There was no significant difference in median propofol consumption between Groups PCS and AVD, 8.4 mcg/kg/min (1.6-18.9) vs 4 mcg/kg/min (0-9) (P = 0.29), respectively. Historical clinician-controlled usage of propofol demonstrated a median of 39.3 mcg/kg/min (29.2-51.2). There were few differences in the secondary outcome measures. The use of AVD did not reduce patient-controlled propofol consumption in patients having a THA or TKA surgery under spinal anesthesia.

Perioperative Pain and Addiction Interdisciplinary Network (PAIN): consensus recommendations for perioperative management of cannabis and cannabinoid-based medicine users by a modified Delphi process.

In many countries, liberalisation of the legislation regulating the use of cannabis has outpaced rigorous scientific studies, and a growing number of patients presenting for surgery consume cannabis regularly. Research to date suggests that cannabis can impact perioperative outcomes. We present recommendations obtained using a modified Delphi method for the perioperative care of cannabis-using patients. A steering committee was formed and a review of medical literature with respect to perioperative cannabis use was conducted. This was followed by the recruitment of a panel of 17 experts on the care of cannabis-consuming patients. Panellists were blinded to each other's participation and were provided with rater forms exploring the appropriateness of specific perioperative care elements. The completed rater forms were analysed for consensus. The expert panel was then unblinded and met to discuss the rater form analyses. Draft recommendations were then created and returned to the expert panel for further comment. The draft recommendations were also sent to four independent reviewers (a surgeon, a nurse practitioner, and two patients). The collected feedback was used to finalise the recommendations. The major recommendations obtained included emphasising the importance of eliciting a history of cannabis use, quantifying it, and ensuring contact with a cannabis authoriser (if one exists). Recommendations also included the consideration of perioperative cannabis weaning, additional postoperative nausea and vomiting prophylaxis, and additional attention to monitoring and maintaining anaesthetic depth. Postoperative recommendations included anticipating increased postoperative analgesic requirements and maintaining vigilance for cannabis withdrawal syndrome.

Multidisciplinary Transitional Pain Service for the Veteran Population.

BACKGROUND: For patients with existing chronic opioid use or a history of substance use disorder, often little presurgical planning or postsurgical coordination of care among surgeons, primary care providers, or addiction care providers occurs. METHODS: In 2018, we developed the Transitional Pain Service (TPS) to identify at-risk patients as soon as they were indicated for surgery, to allow time for evaluation, education, and developing an individualized pain plan, and opioid taper prior to surgery if indicated. An electronic dashboard registry of surgical episodes provided data to TPS providers and included baseline history, morphine equivalent daily dose, and patient-reported pain outcomes, using measures from the Patient-Reported Outcome Measurement System for pain intensity, pain interference, and physical function, and a pain-catastrophizing scale score. RESULTS: Two-hundred thirteen patients were enrolled between January and December 2018. Nearly all (99%) patients had ≥ 1 successful follow-up within 14 days after discharge; 96% had ≥ 1 follow-up between 14 and 30 days after surgery; and 72% had completed personal follow-up 90 days after discharge. CONCLUSIONS: In 2018 the overall use of opioids after orthopedic surgery decreased by > 40% from the previous year. Despite this more restricted use of opioids, pain interference and physical function scores indicated that surgical patients do not seem to experience increased pain or reduced physical function.

Opioid use among veterans undergoing major joint surgery managed by a multidisciplinary transitional pain service.

BACKGROUND: Chronic postsurgical pain and opioid use is a problem among patients undergoing many types of surgical procedures. A multidisciplinary approach to perioperative pain management known as a transitional pain service (TPS) may lower these risks. METHODS: This retrospective cohort study was conducted at the Salt Lake City VA Medical Center to compare patients undergoing elective primary or revision total knee, hip, or shoulder replacement or rotator cuff repair in the year before (2017) and after (2018) implementation of a TPS. The primary outcome is the proportion of patients taking opioids 90 days after surgery. Secondary outcomes include new chronic opioid use (COU) after surgery as well as the proportion of previous chronic opioid users who stopped or decreased opioid use after surgery. RESULTS: At 90 days after surgery, patients enrolled in TPS were significantly less likely to be taking opioids (13.4% TPS vs 27.3% pre-TPS; p=0.002). This relationship remained statistically significant in a multivariable logistic regression analysis, where the TPS group had 69% lower odds of postoperative COU compared with the preintervention group (OR: 0.31; 95% CI: 0.14 to 0.66; p=0.03). Opioid-naive patients enrolled in TPS were less likely to have new COU after surgery (0.7% TPS vs 8.4% pre-TPS; p=0.004). Further, patients enrolled in TPS with existing COU prior to surgery were more likely to reduce or completely stop opioid use after surgery (67.5% TPS vs 45.3% pre-TPS; p=0.037) as compared with pre-TPS. CONCLUSIONS: These data suggest that a TPS is an effective strategy for preventing new COU and reducing overall opioid use following orthopedic joint procedures in a Veterans Affairs hospital.

The muscle reflex and chemoreflex interaction: ventilatory implications for the exercising human.

We examined the interactive influence of the muscle reflex (MR) and the chemoreflex (CR) on the ventilatory response to exercise. Eleven healthy subjects (5 women/6 men) completed three bouts of constant-load single-leg knee-extension exercise in a control trial and an identical trial conducted with lumbar intrathecal fentanyl to attenuate neural feedback from lower-limb group III/IV muscle afferents. The exercise during the two trials was performed while breathing ambient air ([Formula: see text] ~97%, [Formula: see text]~84 mmHg, [Formula: see text] ~32 mmHg, pH ~7.39), or under normocapnic hypoxia ([Formula: see text] ~79%, [Formula: see text] ~43 mmHg, [Formula: see text] ~33 mmHg, pH ~7.39) or normoxic hypercapnia ([Formula: see text] ~98%, [Formula: see text] ~105 mmHg, [Formula: see text] ~50 mmHg, pH ~7.26). During coactivation of the MR and the hypoxia-induced CR (O2-CR), minute ventilation (V̇e) and tidal volume (VT) were significantly greater compared with the sum of the responses to the activation of each reflex alone; there was no difference between the observed and summated responses in terms of breathing frequency (fB; P = 0.4). During coactivation of the MR and the hypercapnia-induced CR (CO2-CR), the observed ventilatory responses were similar to the summated responses of the reflexes (P ≥ 0.1). Therefore, the interaction between the MR and the O2-CR exerts a hyperadditive effect on V̇e and VT and an additive effect on fB, whereas the interaction between the MR and the CO2-CR is simply additive for all ventilatory parameters. These findings reveal that the MR:CR interaction further augments the ventilatory response to exercise in hypoxia.NEW & NOTEWORTHY Although the muscle reflex and the chemoreflex are recognized as independent feedback mechanisms regulating breathing during exercise, the ventilatory implications resulting from their interaction remain unclear. We quantified the individual and interactive effects of these reflexes during exercise and revealed differential modes of interaction. Importantly, the reflex interaction further amplifies the ventilatory response to exercise under hypoxemic conditions, highlighting a potential mechanism for optimizing arterial oxygenation in physically active humans at high altitude.

The exercise pressor reflex and chemoreflex interaction: cardiovascular implications for the exercising human.

KEY POINTS: Although the exercise pressor reflex (EPR) and the chemoreflex (CR) are recognized for their sympathoexcitatory effect, the cardiovascular implication of their interaction remains elusive. We quantified the individual and interactive cardiovascular consequences of these reflexes during exercise and revealed various modes of interaction. The EPR and hypoxia-induced CR interaction is hyper-additive for blood pressure and heart rate (responses during co-activation of the two reflexes are greater than the summation of the responses evoked by each reflex) and hypo-additive for peripheral haemodynamics (responses during co-activation of the reflexes are smaller than the summated responses). The EPR and hypercapnia-induced CR interaction results in a simple addition of the individual responses to each reflex (i.e. additive interaction). Collectively, EPR:CR co-activation results in significant cardiovascular interactions with restriction in peripheral haemodynamics, resulting from the EPR:CR interaction in hypoxia, likely having the most crucial impact on the functional capacity of an exercising human. ABSTRACT: We investigated the interactive effect of the exercise pressor reflex (EPR) and the chemoreflex (CR) on the cardiovascular response to exercise. Eleven healthy participants (5 females) completed a total of six bouts of single-leg knee-extension exercise (60% peak work rate, 4 min each) either with or without lumbar intrathecal fentanyl to attenuate group III/IV afferent feedback from lower limbs to modify the EPR, while breathing either ambient air, normocapnic hypoxia (Sa O2 ∼79%, Pa O2 ∼43 mmHg, Pa CO2 ∼33 mmHg, pH ∼7.39), or normoxic hypercapnia (Sa O2 ∼98%, Pa O2 ∼105 mmHg, Pa CO2 ∼50 mmHg, pH ∼7.26) to modify the CR. During co-activation of the EPR and the hypoxia-induced CR (O2 -CR), mean arterial pressure and heart rate were significantly greater, whereas leg blood flow and leg vascular conductance were significantly lower than the summation of the responses evoked by each reflex alone. During co-activation of the EPR and the hypercapnia-induced CR (CO2 -CR), the haemodynamic responses were not different from the summated responses to each reflex response alone (P ≥ 0.1). Therefore, while the interaction resulting from the EPR:O2 -CR co-activation is hyper-additive for blood pressure and heart rate, and hypo-additive for peripheral haemodynamics, the interaction resulting from the EPR:CO2 -CR co-activation is simply additive for all cardiovascular parameters. Thus, EPR:CR co-activation results in significant interactions between cardiovascular reflexes, with the impact differing when the CR activation is achieved by hypoxia or hypercapnia. Since the EPR:CR co-activation with hypoxia potentiates the pressor response and restricts blood flow to contracting muscles, this interaction entails the most functional impact on an exercising human.

Exercise Pressor Reflex Contributes to the Cardiovascular Abnormalities Characterizing: Hypertensive Humans During Exercise.

We investigated the impact of hypertension on circulatory responses to exercise and the role of the exercise pressor reflex in determining the cardiovascular abnormalities characterizing patients with hypertension. After a 7-day drug washout, 8 hypertensive (mean arterial pressure [MAP] 130±4 mm Hg; 65±3 years) and 8 normotensive (MAP 117±2 mm Hg; 65±2 years) individuals performed single-leg knee-extensor exercise (7 W, 15 W, 50%, 80%-Wpeak) under control conditions and with lumbar intrathecal fentanyl impairing feedback from µ-opioid receptor-sensitive leg muscle afferents. Femoral artery blood flow (QL), MAP (femoral artery), leg vascular conductance, and changes in cardiac output were continuously measured. While the increase in MAP from rest to control exercise was significantly greater in hypertension compared with normotension, the exercise-induced increase in cardiac output was comparable between groups, and QL and leg vascular conductance responses were ≈18% and ≈32% lower in the hypertensive patients (P<0.05). The blockade-induced decreases in MAP were significantly larger during exercise in hypertensive (≈11 mm Hg) compared with normotensive (≈6 mm Hg). Afferent blockade attenuated the central hemodynamic response to exercise similarly in both groups resulting in a ≈15% lower cardiac output at each workload. With no effect in normotensive, afferent blockade significantly raised the peripheral hemodynamic response to exercise in hypertensive, resulting in ≈14% and ≈23% higher QL and leg vascular conductance during exercise. Finally, QL and MAP during fentanyl-exercise in hypertensive were comparable to that of normotensive under control conditions (P>0.2). These findings suggest that exercise pressor reflex abnormalities largely account for the exaggerated MAP response and the impaired peripheral hemodynamics during exercise in hypertension.

Pharmacological attenuation of group III/IV muscle afferents improves endurance performance when oxygen delivery to locomotor muscles is preserved.

We sought to investigate the role of group III/IV muscle afferents in limiting endurance exercise performance, independently of their role in optimizing locomotor muscle O2 delivery. While breathing 100% O2 to ensure a similar arterial O2 content ([Formula: see text]) in both trials, eight male cyclists performed 5-km time trials under control conditions (HCTRL) and with lumbar intrathecal fentanyl (HFENT) impairing neural feedback from the lower limbs. After each time trial, common femoral artery blood flow (FBF) was quantified (Doppler ultrasound) during constant-load cycling performed at the average power of the preceding time trial. The assessment of end-tidal gases, hemoglobin content and saturation, and FBF facilitated the calculation of leg O2 delivery. Locomotor muscle activation during cycling was estimated from vastus lateralis EMG. With electrical femoral nerve stimulation, peripheral and central fatigue were quantified by pre- to postexercise decreases in quadriceps twitch torque (ΔQtw) and voluntary activation (ΔVA), respectively. FBF (~16 mL·min-1·W-1; P = 0.6), [Formula: see text] (~24 mL O2/dL; P = 0.9), and leg O2 delivery (~0.38 mL O2·min-1·W-1; P = 0.9) were not different during HCTRL and HFENT. Mean power output and time to completion were significantly improved by 9% (~310 W vs. ~288 W) and 3% (~479 s vs. ~463 s), respectively, during HFENT compared with HCTRL. Quadriceps muscle activation was 9 ± 7% higher during HFENT compared with HCTRL (P < 0.05). ΔQtw was significantly greater in HFENT compared with HCTRL (54 ± 8% vs. 39 ± 9%), whereas ΔVA was not different (~5%; P = 0.3) in both trials. These findings reveal that group III/IV muscle afferent feedback limits whole body endurance exercise performance and peripheral fatigue by restricting neural activation of locomotor muscle.NEW & NOTEWORTHY Group III/IV muscle afferent feedback facilitates endurance performance by optimizing locomotor muscle O2 delivery but also limits performance by restricting neural drive to locomotor muscle. To isolate the performance-limiting effect of these sensory neurons, we pharmacologically attenuated their central projection during a cycling time trial while controlling for locomotor muscle O2 delivery. With no difference in leg O2 delivery, afferent blockade attenuated the centrally mediated restriction in motoneuronal output and improved cycling performance.

Case Report of a Massive Thigh Hematoma after Adductor Canal Block in a Morbidly Obese Woman Anticoagulated with Apixaban.

Hematoma formation after peripheral nerve block placement is a rare event. We report a case of a morbidly obese patient who was anticoagulated with apixaban and developed a massive thigh hematoma after an ultrasound-guided adductor canal block. Despite continuous visualization of the block needle, an unrecognized vascular injury occurred leading to a 14-cm hematoma in the anterolateral thigh. Morbid obesity warrants additional risk consideration when placing nerve blocks in an anticoagulated patient. In addition, early recognition and expert consultation are both important in the management of block-related hematomas.

Serum Bupivacaine Concentration After Periarticular Injection With a Mixture of Liposomal Bupivacaine and Bupivacaine HCl During Total Knee Arthroplasty.

BACKGROUND AND OBJECTIVES: A relatively new technique to reduce postoperative pain for total knee arthroplasty is to inject a mixture of 266 mg of liposomal bupivacaine and 125 mg of 0.25% bupivacaine HCl with epinephrine 1:300,000 around the knee joint at the time of surgery. Currently, no publications report serum bupivacaine concentrations over time after periarticular injection of liposomal mixed with free bupivacaine. This information is important to ensure safe serum bupivacaine concentrations are maintained especially when considering supplemental or rescue peripheral nerve blocks. METHODS: A total of 40 subjects scheduled for primary unilateral total knee arthroplasty with intraoperative periarticular injection of the liposomal bupivacaine and bupivacaine HCl mixture were included. Total serum bupivacaine concentrations were measured after the last injection at selected time points and calculated by gas chromatography. Quantile regression techniques were used to analyze the data over time. This study is registered with ClinicalTrials.gov (ID NCT02626559). RESULTS: Peak serum concentration ranged from 0.17 to 1.2 µg/mL and occurred from 10 minutes to 48 hours. Across all time points, the 48-hour interval had the highest mean concentration of total serum bupivacaine at 0.55 µg/mL (SD, 0.27). Quantile regression showed total serum bupivacaine concentrations increased over the 48 hours measured. None of the participants demonstrated signs or symptoms of local anesthetic toxicity. CONCLUSIONS: Total serum concentrations of bupivacaine after periarticular administration of liposomal bupivacaine mixed with bupivacaine HCl remained below the described toxicity threshold (2.5 µg/mL) within the first 48 hours, and no patients demonstrated signs or symptoms of toxicity. However, peak serum concentration time was not achieved within the 48-hour interval. Additional studies are needed to describe the course of serum bupivacaine levels after 48 hours and to ascertain the risk of toxicity when combining this method of periarticular injection with peripheral nerve blocks.

Novel use of perineural pregabalin infusion for analgesia in a rat neuropathic pain model.

BACKGROUND: The anticonvulsant drugs pregabalin and gabapentin are often used systemically to treat some forms of chronic neuropathic pain. However, many patients report side effects serious enough to cause discontinuation of the drug. Here we present evidence that pregabalin may block neuropathic pain when applied to the site of nerve injury in a rat neuropathic pain model. METHODS: Forty male Sprague Dawley rats were randomized into 4 groups: sciatic nerve crush injury with perineural pregabalin treatment (treatment), crush injury with perineural saline treatment (saline control), crush injury with subcutaneous pregabalin treatment (systemic drug control), and sham surgery (sham surgery control). Animals received either continuous infusions of 1% pregabalin for 7 days (treatment and systemic control) or saline (saline control) and were tested for pain behaviors using incapacitance meter, guarding scores, and radiant heat withdrawal latency (Hargreaves method). Nerves were studied using histology and immunohistochemistry for α(2)δ-1 receptors thought to mediate the central analgesic action of pregabalin. RESULTS: Treatment rats had significantly better guarding scores than systemic drug controls or saline controls (P < 0.0001) and had significantly better incapacitance scores than systemic drug controls and saline controls (P ≤ 0.001). Hargreaves method data showed hypoalgesia in all injured animals with no difference among injured groups (P = 0.80). Qualitatively, immunohistochemistry likely showed equivalent expression of the α(2)δ-1 calcium channel at the injured nerve site in all nerve-injured animals. CONCLUSIONS: Perineural pregabalin administration produced superior analgesia compared with that of systemic pregabalin in this neuropathic pain model. Perineural pregabalin treatment may provide a useful alternative to systemic pregabalin treatment for neuropathic pain.

Ultrasound-guided sciatic nerve block in the popliteal fossa using a lateral approach: onset time comparing separate tibial and common peroneal nerve injections versus injecting proximal to the bifurcation.

BACKGROUND: We hypothesized that blocking the tibial and common peroneal nerves individually using ultrasound distal to sciatic bifurcation would decrease time to complete block compared with a block proximal to the bifurcation. METHODS: Seventy-six patients undergoing foot or ankle surgery received a sciatic nerve block either proximal or distal to the point of bifurcation. A mixture of 28 mL 1.5% mepivacaine with 100 microg clonidine and 1 mL 8.4% sodium bicarbonate for a total of 30 mL was used. Ultrasound was used to guide needle adjustments to achieve circumferential spread. Block success was defined as a loss of sensation to pinprick in both nerve distributions within 46 minutes. RESULTS: Patients in the tibial-peroneal group had significantly faster time to complete block than the sciatic group (19.2 vs 26.1 minutes; P = 0.006). CONCLUSIONS: Blocking the tibial and common peroneal nerves in the popliteal fossa separately provides for a faster onset than a prebifurcation sciatic block.