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Significant knowledge gaps exist in the perioperative pain management of patients with a history of chronic pain, substance use disorder, and/or opioid tolerance as highlighted in the US Health and Human Services Pain Management Best Practices Inter-Agency Task Force 2019 report. The report emphasized the challenges of caring for these populations and the need for multidisciplinary care and a comprehensive approach. Such care requires stakeholder alignment across multiple specialties and care settings. With the intention of codifying this alignment into a reliable and efficient processes, a consortium of 15 professional healthcare societies was convened in a year-long modified Delphi consensus process and summit. This process produced seven guiding principles for the perioperative care of patients with chronic pain, substance use disorder, and/or preoperative opioid tolerance. These principles provide a framework and direction for future improvement in the optimization and care of 'complex' patients as they undergo surgical procedures., Competing Interests: Competing interests: DMD receives research support from Abbott and SPR therapeutics; speaker and/or consulting fees from Abbott, SPR Therapeutics, Vertos, Pfizer, Myovant, Nalu, and Biotronik; NME receives consulting fees for legal case review and from Pacira; SS receives consulting fees from SPR Therapeutics, Masimo Corp, and Allergan. GS receives consulting fees from Pacira and holds minor stake equity (stock options) in Dorsal Health; MS receives consulting fees and research support from Saluda Medical, consulting fees from Patch technologies, Witness, etc and iVitalie, and holds stock and/or receives consulting fees from Cellarian, Spark Biomedical, Nanomedical Systems, Full Spectrum Healthcare Management, MedAnswers, Reveliance solutions, and Assurance Med Management, (© American Society of Regional Anesthesia & Pain Medicine 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Introduction: We previously reported that a 6-day continuous peripheral nerve block reduces established postamputation phantom pain. To provide patients and providers with the information to best inform treatment decisions, here we reanalyze the data and present the results in a more patient-centered format. We also provide information on patient-defined clinically relevant benefits to facilitate evaluation of available studies and guide future trial design., Methods: The original trial enrolled participants with a limb amputation and phantom pain who were randomized to receive a 6-day continuous peripheral nerve block(s) of either ropivacaine (n=71) or saline (n=73) in a double-masked fashion. Here we calculate the percentage of each treatment group that experienced a clinically relevant improvement as defined by previous studies as well as present what the participants of our study defined as small, medium, and large analgesic improvements using the 7-point ordinal Patient Global Impression of Change scale., Results: Among patients who were given a 6-day ropivacaine infusion, 57% experienced at least a 2-point improvement on the 11-point numeric rating scale in their average and worst phantom pain 4 weeks postbaseline as compared with 26% (p<0.001) for average and 25% (p<0.001) for worst pain in patients given a placebo infusion. At 4 weeks, the percentage of participants rating their pain as improved was 53% for the active vs 30% for the placebo groups (95% CI 1.7 (1.1, 2.7), p = 0.008). For all patients combined, the median (IQR) phantom pain Numeric Rating Scale improvements at 4 weeks considered small, medium, and large were 2 (0-2), 3 (2-5), and 5 (3-7), respectively. The median improvements in the Brief Pain Inventory interference subscale (0-70) associated with small, medium, and large analgesic changes were 8 (1-18), 22 (14-31), and 39 (26-47)., Conclusions: Among patients with postamputation phantom pain, a continuous peripheral nerve block more than doubles the chance of a clinically relevant improvement in pain intensity. Amputees with phantom and/or residual limb pain rate analgesic improvements as clinically relevant similarly to other chronic pain etiologies, although their smallest relevant improvement in the Brief Pain Inventory was significantly larger than previously published values., Trial Registration Number: NCT01824082., Competing Interests: Competing interests: BMI and BK: The University of California has received funding and/or equipment for other research projects from Epimed International (Dallas, TX), Infutronics (Natick, MA), Avanos (Irvine, CA), and SPR Therapeutics (Cleveland, OH). DIS: Chair Data and Safety Monitoring Board, Neuros Medical QUEST trial. Consultant for Pacira Pharmaceuticals (Parsippany, NJ), and this company funds trials in the Department of Outcomes Research. SPC: receives research funding (paid to the institution) from Avanos (Irvine, CA), and research funding (paid to the institution) from Scilex (San Diego, CA). He serves as a consultant for SPR Therapeutics (Cleveland, OH). AT: Pacira Pharmaceuticals (Parsippany, NJ) funds trials in the Department of Outcomes Research., (© American Society of Regional Anesthesia & Pain Medicine 2023. Re-use permitted under CC BY-NC. No commercial re-use. Published by BMJ.)

Background: We recently reported that a 6-day continuous peripheral nerve block reduced established postamputation phantom pain 3 weeks after treatment ended. However, the immediate effects of perineural infusion (secondary outcomes) have yet to be reported., Methods: Participants from 5 enrolling academic centers with an upper or lower limb amputation and established phantom pain received a single-injection ropivacaine peripheral nerve block(s) and perineural catheter insertion(s). They were subsequently randomized to receive a 6-day ambulatory perineural infusion of either ropivacaine 0.5% or normal saline in a double-masked fashion. Participants were contacted by telephone 1, 7, 14, 21, and 28 days after the infusion started, with pain measured using the Numeric Rating Scale. Treatment effects were assessed using the Wilcoxon rank-sum test at each time point. Adjusting for 4 time points (days 1, 7, 14, and 21), P < .0125 was deemed statistically significant. Significance at 28 days was reported using methods from the original, previously published article., Results: Pretreatment average phantom and residual pain scores were balanced between the groups. The day after infusion initiation (day 1), average phantom, and residual limb pain intensity was lower in patients receiving local anesthetic (n = 71) versus placebo (n = 73): median [quartiles] of 0 [0-2.5] vs 3.3 [0-5.0], median difference (98.75% confidence interval [CI]) of -1.0 (-3.0 to 0) for phantom pain (P = .001) and 0 [0-0] vs 0 [0-4.3], and median difference 0.0 (-2.0 to 0.0) for residual limb pain (P < .001). Pain's interference with physical and emotional functioning as measured with the interference domain of the Brief Pain Inventory improved during the infusion on day 1 for patients receiving local anesthetic versus placebo: 0 [0-10] vs 10 [0-40], median difference (98.75% CI) of 0.0 (-16.0 to 0.0), P = .002. Following infusion discontinuation (day 6), a few differences were found between the active and placebo treatment groups between days 7 and 21. In general, sample medians for average phantom and residual limb pain scores gradually increased after catheter removal for both treatments, but to a greater degree in the control group until day 28, at which time the differences between the groups returned to statistical significance., Conclusions: This secondary analysis suggests that a continuous peripheral nerve block decreases phantom and residual limb pain during the infusion, although few improvements were again detected until day 28, 3 weeks following catheter removal., Competing Interests: Conflicts of Interest: See Disclosures at the end of the article., (Copyright © 2021 International Anesthesia Research Society.)

Importance: Opioid-induced ventilatory depression and hypoxemia is common, severe, and often unrecognized in postoperative patients. To the extent that nonopioid analgesics reduce opioid consumption, they may decrease postoperative hypoxemia., Objective: To test the hypothesis that duration of hypoxemia is less in patients given intravenous acetaminophen than those given placebo., Design, Setting, and Participants: Randomized, placebo-controlled, double-blind trial conducted at 2 US academic hospitals among 570 patients who were undergoing abdominal surgery, enrolled from February 2015 through October 2018 and followed up until February 2019., Interventions: Participants were randomized to receive either intravenous acetaminophen, 1 g (n = 289), or normal saline placebo (n = 291) starting at the beginning of surgery and repeated every 6 hours until 48 postoperative hours or hospital discharge, whichever occurred first., Main Outcomes and Measures: The primary outcome was the total duration of hypoxemia (hemoglobin oxygen saturation [Spo2] <90%) per hour, with oxygen saturation measured continuously for 48 postoperative hours. Secondary outcomes were postoperative opioid consumption, pain (0- 10-point scale; 0: no pain; 10: the most pain imaginable), nausea and vomiting, sedation, minimal alveolar concentration of volatile anesthetic, fatigue, active time, and respiratory function., Results: Among 580 patients randomized (mean age, 49 years; 48% women), 570 (98%) completed the trial. The primary outcome, median duration with Spo2 of less than 90%, was 0.7 (interquartile range [IQR], 0.1-5.1) minutes per hour among patients in the acetaminophen group and 1.1 (IQR, 0.1-6.6) minutes per hour among patients in the placebo group (P = .29), with an estimated median difference of -0.04 (95% CI,-0.18 to 0.11) minutes per hour. None of the 8 secondary end points differed significantly between the acetaminophen and placebo groups. Mean pain scores within initial 48 postoperative hours were 4.2 (SD, 1.8) in the acetaminophen group and 4.4 (SD, 1.8) in the placebo group (difference, -0.28; 95% CI, -0.71 to 0.15); median opioid use in morphine equivalents was 50 mg (IQR, 18-122 mg) and 58 mg (IQR, 24-151 mg) , respectively, with a ratio of geometric means of 0.86 (95% CI, 0.61-1.21)., Conclusions and Relevance: Among patients who underwent abdominal surgery, use of postoperative intravenous acetaminophen, compared with placebo, did not significantly reduce the duration of postoperative hypoxemia over 48 hours. The study findings do not support the use of intravenous acetaminophen for this purpose., Trial Registration: ClinicalTrials.gov Identifier: NCT02156154.

We report the rare complication of a retained peripheral nerve block catheter (PNBC). A 45-year-old man with intractable postamputation phantom limb pain was treated with continuous infusions via femoral and sciatic peripheral nerve catheters. The catheters were removed by an emergency department physician 2 days after placement. Five months later, the patient presented with a discharging sinus from the sciatic nerve catheter site. Magnetic resonance imaging (MRI) was inconclusive. Surgical exploration showed 15 cm of retained peripheral nerve catheter, which was removed.

Background: Postoperative pain is common and promotes opioid use. Surgical wounds are hypoxic because normal perfusion is impaired. Local wound ischemia and acidosis promote incisional pain. Some evidence suggests that improving oxygen supply to surgical wounds might reduce pain. We therefore tested the hypothesis that supplemental (80% inspired) intraoperative oxygen reduces postoperative pain and opioid consumption., Methods: We conducted a post hoc analysis of a large, single-center alternating cohort trial allocating surgical patients having general anesthesia for colorectal surgery to either 30% or 80% intraoperative oxygen concentration in 2-week blocks for a total of 39 months. Irrespective of allocation, patients were given sufficient oxygen to maintain saturation ≥95%. Patients who had regional anesthesia or nerve blocks were excluded. The primary outcome was pain and opioid consumption during the initial 2 postoperative hours, analyzed jointly. The secondary outcome was pain and opioid consumption over the subsequent 24 postoperative hours. Subgroup analyses of the primary outcome were conducted for open versus laparoscopic procedures and for patients with versus without chronic pain., Results: A total of 4702 cases were eligible for analysis: 2415 were assigned to 80% oxygen and 2287 to 30% oxygen. The groups were well balanced on potential confounding factors. Average pain scores and opioid consumption were similar between the groups (mean difference in pain scores, -0.01 [97.5% CI, -0.16 to 0.14; P = .45], median difference in opioid consumption, 0.0 [97.5% CI, 0 to 0] mg morphine equivalents; P = .82). There were also no significant differences in the secondary outcome or subgroup analyses., Conclusions: Supplemental intraoperative oxygen does not reduce acute postoperative pain or reduce opioid consumption.

Background: Neuraxial anesthesia improves components of the Virchow's triad (hypercoagulability, venous stasis, and endothelial injury) which are key pathogenic contributors to venous thrombosis in surgical patients. However, whether neuraxial anesthesia reduces the incidence of venous thromboembolism (VTE) remain unclear. We therefore tested the primary hypothesis that neuraxial anesthesia reduces the incidence of 30-day VTE in adults recovering from orthopedic surgery. Secondarily, we tested the hypotheses that neuraxial anesthesia reduces 30-day readmission, 30-day mortality, and the duration of postoperative hospitalization., Methods: Inpatient orthopedic surgeries from American College of Surgeons National Surgical Quality Improvement Program database (2011-2015) in adults lasting more than 1 hour with either neuraxial or general anesthesia were included. Groups were matched 1:1 by propensity score matching for appropriate confounders. Logistic regression model was used to assess the effect of neuraxial anesthesia on 30-day VTE, 30-day mortality, and readmission, while Cox proportional hazard regression model was used to assess its effect on length of stay., Results: Neuraxial anesthesia decreased odds of 30-day VTE (odds ratio 0.85, 95% confidence interval, 0.78-0.95; P = .002) corresponding to number-needed-to-treat of 500. Although there was no difference in 30-day mortality, neuraxial anesthesia reduced 30-day readmission (odds ratio 0.90, 98.3% confidence interval, 0.85-0.95; P < .001) corresponding to number-needed-to-treat of 250 and had a shortened hospitalization (2.87 vs 3.11; P < .001)., Conclusions: Neuraxial anesthesia appears to provide only weak VTE prophylaxis, but can be offered as an adjuvant to current thromboprophylaxis in high-risk patients.

Background: Various methods for peripheral nerve and epidural catheter location assessment exist, with varying degrees of ease of use, utility, and accuracy. Pulsed wave Doppler (PWD) evaluates the presence of fluid flow and is possible modality to assess the location of a percutaneously inserted perineural catheter., Methods: A retrospective chart review was conducted in which PWD ultrasonography was used to confirm the position of nerve catheters for regional anesthesia. Data was collected to assess 24-hour postoperative pain scores, opioid consumption, complications, and the incidence of catheter replacement., Results: Eighty-six patients were included; average age was 58 years and a 27% incidence of chronic pain. These catheters were left in place based on the PWD images. Three catheters failed and a total of 16 catheters were repositioned. In the first 24 hours average pain scores ranges between 3.5 to 5.9 and median postoperative opioid consumption range was 11.3 mg to 60.8 mg. For epidural catheters, PWD changes were more obvious with air injection and there was only one episode of hemodynamic instability., Conclusions: Our preliminary experience with PWD ultrasonography suggests that they may offer the ability to selectively assess flow at different locations to identify the proper location of epidural and perineural catheters. Future randomized, controlled investigations are warranted to further evaluate the effectiveness and safety of this modality.

Background: Clonidine is an α2-adrenoceptor agonist, which has analgesic properties. However, the analgesic efficacy of perioperative clonidine remains unclear. We, therefore, tested the hypothesis that clonidine reduces both pain scores and cumulative opioid consumption during the initial 72 hours after noncardiac surgery., Methods: Six hundred twenty-four patients undergoing elective noncardiac surgery under general and spinal anesthesia were included in this substudy of the PeriOperative ISchemia Evaluation-2 trial. Patients were randomly assigned to 0.2 mg oral clonidine or placebo 2 to 4 hours before surgery, followed by 0.2 mg/d transdermal clonidine patch or placebo patch, which was maintained until 72 hours after surgery. Postoperative pain scores and opioid consumption were assessed for 72 hours after surgery., Results: Clonidine had no effect on opioid consumption compared with placebo, with an estimated ratio of means of 0.98 (95% confidence interval, 0.70-1.38); P = 0.92. Median (Q1, Q3) opioid consumption was 63 (30, 154) mg morphine equivalents in the clonidine group, which was similar to 60 (30, 128) mg morphine equivalents in the placebo group. Furthermore, there was no significant effect on pain scores, with an estimated difference in means of 0.12 (95% confidence interval, -0.02 to 0.26); 11-point scale; P = 0.10. Mean pain scores per patient were 3.6 ± 1.8 for clonidine patients and 3.6 ± 1.8 for placebo patients., Conclusions: Clonidine does not reduce opioid consumption or pain scores in patients recovering from noncardiac surgery.

Background: Ultrasound guidance for continuous femoral perineural catheters may be supplemented by electrical stimulation through a needle or through a stimulating catheter. The authors tested the primary hypothesis that ultrasound guidance alone is noninferior on both postoperative pain scores and opioid requirement and superior on at least one of the two. Second, the authors compared all interventions on insertion time and incremental cost., Methods: Patients having knee arthroplasty with femoral nerve catheters were randomly assigned to catheter insertion guided by: (1) ultrasound alone (n = 147); (2) ultrasound and electrical stimulation through the needle (n = 152); or (3) ultrasound and electrical stimulation through both the needle and catheter (n = 138). Noninferiority between any two interventions was defined for pain as not more than 0.5 points worse on a 0 to 10 verbal response scale and for opioid consumption as not more than 25% greater than the mean., Results: The stimulating needle group was significantly noninferior to the stimulating catheter group (difference [95% CI] in mean verbal response scale pain score [stimulating needle vs. stimulating catheter] of -0.16 [-0.61 to 0.29], P < 0.001; percentage difference in mean IV morphine equivalent dose of -5% [-25 to 21%], P = 0.002) and to ultrasound-only group (difference in mean verbal response scale pain score of -0.28 [-0.72 to 0.16], P < 0.001; percentage difference in mean IV morphine equivalent dose of -2% [-22 to 25%], P = 0.006). In addition, the use of ultrasound alone for femoral nerve catheter insertion was faster and cheaper than the other two methods., Conclusion: Ultrasound guidance alone without adding either stimulating needle or needle/catheter combination thus seems to be the best approach to femoral perineural catheters.

Continuous peripheral nerve blocks (CPNB) are commonly used for intraoperative and postoperative analgesia. Our study aimed at describing our experience with ambulatory peripheral nerve catheters. After Institutional Review Board approval, records for all patients discharged with supraclavicular or popliteal catheters between January 1, 2009 and December 31, 2011 were reviewed. A licensed practitioner provided verbal and written instructions to the patients prior to discharge. Daily follow-up phone calls were conducted. Patients either removed their catheters at home with real-time simultaneous telephone guidance by a member of the Acute Pain Service or had them removed by the surgeon during a regular office visit. The primary outcome of this analysis was the incidence of complications, categorized as pharmacologic, infectious, or other. The secondary outcome measure was the average daily pain score. Our study included a total of 1059 patients with ambulatory catheters (769 supraclavicular, 290 popliteal). The median infusion duration was 5 days for both groups. Forty-two possible complications were identified: 13 infectious, 23 pharmacologic, and 6 labeled as other. Two patients had retained catheters, 2 had catheter leakage, and 2 had shortness of breath. Our study showed that prolonged use of ambulatory catheters for a median period of 5 days did not lead to an increased incidence of complications.