Effects of Patient and Surgery Characteristics on Persistent Postoperative Pain: A Mediation Analysis

Intraoperative Methadone in Next-day Discharge Outpatient Surgery: A Randomized, Double-blinded, Dose-finding Pilot Study

BACKGROUND

Contemporary perioperative practice seeks to use less intraoperative opioid, diminish postoperative pain and opioid use, and enable less postdischarge opioid prescribing. For inpatient surgery, anesthesia with intraoperative methadone, compared with short-duration opioids, results in less pain, less postoperative opioid use, and greater patient satisfaction. This pilot investigation aimed to determine single-dose intraoperative methadone feasibility for next-day discharge outpatient surgery, determine an optimally analgesic and well-tolerated dose, and explore whether methadone would result in less postoperative opioid use compared with conventional short-duration opioids.

METHODS

This double-blind, randomized, dose-escalation feasibility and pilot study in next-day discharge surgery compared intraoperative single-dose IV methadone (0.1 then 0.2, 0.25 and 0.3 mg/kg ideal body weight) versus as-needed short-duration opioid (fentanyl, hydromorphone) controls. Perioperative opioid use, pain, and side effects were assessed before discharge. Patients recorded pain, opioid use, and side effects for 30 days postoperatively using take-home diaries. Primary clinical outcome was in-hospital (intraoperative and postoperative) opioid use. Secondary outcomes were 30-day opioid consumption, pain, opioid side effects, and leftover opioid counts.

RESULTS

Median (interquartile range) intraoperative methadone doses were 6 (5 to 7), 11 (10 to 12), 14 (13 to 16), and 18 (15 to 19) mg in 0.1, 0.2, 0.25, and 0.3 mg/kg ideal body weight groups, respectively. Anesthesia with single-dose methadone and propofol or volatile anesthetic was effective. Total in-hospital opioid use (IV milligram morphine equivalents [MME]) was 25 (20 to 37), 20 (13 to 30), 27 (18 to 32), and 25 (20 to 36) mg, respectively, in patients receiving 0.1, 0.2, 0.25 and 0.3 mg/kg methadone, compared to 46 (33 to 59) mg in short-duration opioid controls. Opioid-related side effects were not numerically different. Home pain and opioid use were numerically lower in patients receiving methadone.

CONCLUSIONS

The most effective and well-tolerated single intraoperative induction dose of methadone for next-day discharge surgery was 0.25 mg/kg ideal body weight (median, 14 mg). Single-dose intraoperative methadone was analgesic and opioid-sparing in next-day discharge outpatient surgery.

EDITOR’S PERSPECTIVE

Ultrasound-Triggered On-Demand Insulin Release for Diabetes Mellitus Treatment

Exogenous insulin (INS) is successfully used for controlling glucose in diabetic patients. Although frequent INS injections can overcome hyperglycemia, they are both painful and inconvenient. Herein, we report an ultrasound-regulated INS release platform (INS-PPIX@ER hydrogel) that allows for remotely regulated on-demand INS release and minimizes pain. In this system, protoporphyrin IX (PPIX)-containing erythrocytes (ERs) served as an INS reservoir, an injectable peptide hydrogel provided strong protection for the ERs, and INS release was regulated using ultrasound. This particular INS release behavior was triggered by increased production of reactive oxygen species (ROS) by PPIX from the PPIX-loaded ERs under ultrasound irradiation. The ROS then interacted with the phospholipid bilayer of the ERs, thereby opening the stomata of the INS-PPIX@ER and releasing INS. INS-PPIX@ER hydrogels could control hyperglycemia within 2 h and maintained normal blood glucose levels for up to 3 days. This effective remote approach allowed closed-loop drug release spatiotemporally without causing any pain and injury. Our findings could serve as a powerful tool for constructing a precisely controlled release system.

Risk factors for chronic postsurgical pain in visceral surgery: a matched case–control analysis

Purpose

Chronic postsurgical pain (CPSP) after abdominal visceral surgery is an underestimated long-term complication with relevant impact on health-related quality of life and socioeconomic costs. Early identification of affected patients is important. We aim to identify the incidence and risk factors for CPSP in this patient population.

Methods

Retrospective case–control matched analysis including all patients diagnosed with CPSP after visceral surgery in our institution between 2016 and 2019. One-to-two case–control matching was based on operation category (HPB, upper-GI, colorectal, transplantation, bariatric, hernia and others) and date of surgery. Potential risk factors for CPSP were identified using conditional multivariate logistic regression.

Results

Among a cohort of 3730 patients, 176 (4.7%) were diagnosed with CPSP during the study period and matched to a sample of 352 control patients. Independent risk factors for CPSP were age under 55 years (OR 2.64, CI 1.51–4.61), preexisting chronic pain of any origin (OR 3.42, CI 1.75–6.67), previous abdominal surgery (OR 1.99, CI 1.11–3.57), acute postoperative pain (OR 1.29, CI 1.16–1.44), postoperative use of non-steroidal anti-inflammatory drugs (OR 3.73, OR 1.61–8.65), opioid use on discharge (OR 3.78, CI 2.10–6.80) and length of stay over 3 days (OR 2.60, CI 1.22–5.53). Preoperative Pregabalin intake was protective (OR 0.02, CI 0.002–0.21).

Conclusion

The incidence of CPSP is high and associated with specific risk factors, some of them modifiable. Special attention should be given to sufficient treatment of preexisting chronic pain and acute postoperative pain.

Ultrasound-Triggered on Demand Lidocaine Release Relieves Postoperative Pain

Safe and non-invasive on-demand relief is a crucial and effective treatment for postoperative pain because it considers variable timing and intensity of anesthetics. Ultrasound modulation is a promising technique for this treatment because it allows convenient timed and non-invasive controlled drug release. Here, we created an ultrasound-triggered lidocaine (Lido) release platform using an amino acid hydrogel functioning as three-dimensional (3D) scaffold material (Lido-PPIX@ER hydrogel). It allows control of the timing, intensity and duration of lidocaine (Lido) to relieve postoperative pain. The hydrogel releases Lido due to the elevated reactive oxygen species (ROS) levels generated by PPIX under ultrasound triggering. The Lido-PPIX@ER hydrogel under individualized ultrasound triggering released lidocaine and provided effective analgesia for more than 72 h. The withdrawal threshold was higher than that in the control group at all time points measured. The hydrogel showed repeatable and adjustable ultrasound-triggered nerve blocks in vivo, the duration of which depended on the extent and intensity of insonation. On histopathology, no systemic effect or tissue reaction was observed in the ultrasound-triggered Lido-PPIX@ER hydrogel-treated group. The Lido-PPIX@ER hydrogel with individualized (highly variable) ultrasound triggering is a convenient and effective method that offers timed and spatiotemporally controlled Lido release to manage postoperative pain. This article presents the delivery system for a new effective strategy to reduce pain, remotely control pain, and offer timed and spatiotemporally controlled release of Lido to manage postoperative pain.