Cite as: Nanda M, Singla P. Literature review: May 2024. ASRA Pain Medicine News 2024;49. https://doi.org/10.52211/asra050124.013.

Acute Pain

A Comparison of the Effects of Thoracolumbar Interfascial Plane (TLIP) Block and Erector Spinae Plane (ESP) Block in Postoperative Acute Pain in Spinal Surgery

Dilsiz P, Sari S, Tan KB, et al. Eur Spine J 2024;33(3):1129-36. https://doi.org/10.1007/s00586-023-08097-2

Summary by Monika Nanda, MBBS, MPH, FASA

Introduction: Spinal surgeries often result in significant postoperative pain, challenging effective pain management strategies. This study investigates the analgesic efficacy of two regional anesthesia techniques, the thoracolumbar interfascial plane (TLIP) block and the erector spinae plane (ESP) block, in patients undergoing lumbar disk surgery.

Methods: A double-blind randomized controlled trial was conducted on 68 patients undergoing elective lumbar disk surgery under general anesthesia, divided into ESP and TLIP block groups. Bilateral blocks were performed in the prone position using a total volume of 40 ml of 0.25% bupivacaine prior to emergence. Pain intensity was measured using the Numerical Rating Scale (NRS) at intervals post-surgery (30 minutes; 1, 6, 12, and 24 hours), and opioid consumption was recorded over the first 24 hours. The primary outcome was total opioid consumption through a patient-controlled analgesia system, and secondary outcomes included NRS pain scores and the incidence of side effects.

Results: The ESP block group showed significantly lower total opioid consumption in morphine equivalents (7.7 ± 7.0 mg) compared to the TLIP block group (13.0 ± 10.1 mg, p=0.015). NRS scores were similar at initial time points but significantly lower in the ESP group at 24 hours. No significant differences in side effects were observed between the groups.

Key Point: The ESP block is modestly more effective than the TLIP block in reducing opioid consumption and pain scores at 24 hours post-lumbar disk surgery.

The Analgesic Effect of Transversalis Fascia Plane Block After Caesarean Section Under Spinal Anaesthesia with Intrathecal Morphine: A Randomised Controlled Trial

Baghirzada L, Walker A, Yu HC, et al. Anaesthesia 2024;79:63-70. https://doi.org/10.1111/anae.16173

Summary by Jeffrey Grzybowski, MD

Introduction: Intrathecal morphine administration before caesarean section is a commonly utilized analgesic strategy. It is unclear if ultrasound-guided interfascial plane blocks reduce pain severity or duration when administered for analgesia after caesarean section after intrathecal morphine administration. This study aims to test whether transversalis fascia plane blocks reduced cumulative opioid dose after spinal anesthesia with intrathecal morphine for caesarean section.

Methods: Eligible women scheduled for caesarean section of a singleton pregnancy were allocated in a 1:1 ratio to bilateral transversalis fascia plane block with 20 mL saline or 20 mL 0.25% bupivacaine (with 2.5 mcg/mL epinephrine) bilaterally. Spinal anesthesia with 1.4-1.6 mL 0.75% hyperbaric bupivacaine, 10 mcg fentanyl, and 100 mcg morphine was performed in each participant. In the post anesthesia care unit, the allocated solution was injected into the transversalis fascia plane under ultrasound-guidance. Oral and intravenous morphine were prescribed for pain as needed, up to every two hours. Mean cumulative opioid dose through 24 hours after fascial block was the primary outcome. 

Results: One hundred and six women were randomly allocated (52 to bilateral saline injection and 54 to bilateral bupivacaine). Intention to treat analysis demonstrated mean cumulative morphine equivalent opioid dose 24 hours after saline injection was 32.3 mg and 18.7 mg after 0.25% bupivacaine injection, a mean difference of 13.7 mg, p=0.006. The median time to first postoperative opioid dose was 3 hours after saline and 8.2 hours after bupivacaine (p=0.054). There were no differences in participant satisfaction, quality of recovery, rates of sedation, pruritis, nausea, or vomiting at 48 hours following intervention.

Key Point: Bilateral transversalis fascia plane blocks with bupivacaine reduced 24-hour opioid consumption as well as 24- and 48-hour pain scores and increased time to first opioid compared to saline injection when performed post-operatively for caesarean section.

Deep Parasternal Intercostal Plane Block for Intraoperative Pain Control in Cardiac Surgical Patients for Sternotomy: A Prospective Randomized Controlled Trial

Wong HMK, Chen PY, Tang GCC, et al. J Cardiothorac Vasc Anesth 2024;38(3):683-90. https://doi.org/10.1053/j.jvca.2023.11.038

Summary by Marcelle Blessing, MD

Introduction: Severe pain is common after cardiac surgery with sternotomy. Optimal regional anesthesia techniques for sternotomy pain are unclear. The deep parasternal intercostal plane block (DPIP) is a fascial plane block hypothesized by the authors to provide intraoperative analgesia for sternotomy.

Methods: This was a single-center, prospective, randomized, double-blinded, placebo-controlled study. Patients were randomly divided into two groups, an intervention DPIP group that received 20 mL 0.25% levobupivacaine for bilateral DPIP or a control group that received a normal saline block. Primary outcomes studied were intraoperative opioid consumption and the percentage change in hemodynamic parameters from baseline during the first 10 minutes after skin incision for sternotomy. Secondary outcomes were postoperative pain scores (at rest and coughing) and morphine consumption within 72 hours of surgery and the time to extubation.

Results: Eighty-four patients were included in the final statistical analysis. Intraoperative opioid consumption in morphine equivalents was significantly lower in the DPIP group (median 9.5, IQR 7.3-11.2 mg) than it was in the control group (median 21.4, IQR 13.8-24.3 mg) (p<0.001). Hemodynamic variables within 10 minutes of skin incision as a percentage increase from baseline were also more stable in the DPIP group than in the control group. No differences were found in any of the secondary outcomes between the groups.

Key Point: In this study, DPIP block provided an opioid-sparing intraoperative effect that did not extend to the postoperative period. The optimal dose for block, timing of block, and potential use of adjuvants are areas for further potential study.

Chronic Pain

by Harsha Shanthanna. MD, PhD, FRCPC, Mohammad R. Rasouli, MD, and Bhavana Yalamuru, MBBS

Multicenter, Randomized, Placebo-controlled Crossover Trial Evaluating Topical Lidocaine for Mechanical Cervical Pain

Summary by Harsha Shanthanna. MD, PhD, FRCPC

Cohen SP, Larkin TM, Weitzner AS, et al. Anesthesiology 2024;140(3):513-23. https://doi.org/10.1097/ALN.0000000000004857

Introduction: According to the latest estimates, chronic neck pain is very common with an annual incidence of 8.1% and lifetime prevalence 48.5%. Previous studies have suggested short duration benefit with topical lidocaine patches in nociceptive neck pain.

Methods: This is a randomized, placebo-controlled crossover trial of 76 patients performed at four sites. Patients received patches of either placebo followed by lidocaine (group 1) or lidocaine followed by placebo (group 2) for 4-week intervals. Lidocaine patches were of 1.8% strength with 36 mg total lidocaine with a potential bioavailability close to 50%. The primary outcome was mean reduction in average neck numerical rating scale pain score.

Results: The median reduction in average neck pain score with lidocaine was not significant: −1.0 (interquartile range, −2.0, 0.0) lidocaine, −0.5 (interquartile range, −2.0, 0.0) placebo treatment (P = 0.17). A positive outcome (at least a two-point reduction in average neck pain along with at least a five-point score of seven points on the Patient Global Impression of Change Scale at the four-week endpoint) was reported by 27.7% (lidocaine) and 14.9% (placebo), (P=0.073) with no differences in the secondary outcomes, except a possible carryover effect on pain pressure threshold from the lidocaine phase (P=0.015). Minor reactions, most commonly as pruritis, were observed in both groups, 27.5% (lidocaine) and 20.5% (placebo).

Key Point: Topical lidocaine patches do not reduce pain in patients with chronic neck pain of nociceptive origin. However, there may be a subgroup of patients in whom this might be helpful.

Influence of Intravenous S-Ketamine on the Pharmacokinetics of Oral Morphine in Healthy Volunteers.

Lohela TJ, Poikola S, Backmansson D, et al. Anesth Analg 2024;138:598-606. https://doi.org/10.1213%2FANE.0000000000006640

Summary by Mohammad R. Rasouli, MD

Introduction: Ketamine and morphine are frequently used for perioperative pain management. Experimental studies have suggested that subanesthetic dose of ketamine inhibits UGT2B7, an enzyme that glucuronides morphine and converts morphine to its metabolites morphine-6-glucoronide (M6G) and morphine-3-glucoronide (M3G). However, the pharmacokinetic interaction of morphine and ketamine in human is not well defined. The authors hypothesized that S-ketamine inhibits UGT2B7 and morphine metabolism.

Methods: This randomized, paired, double-blinded crossover study was performed on 12 healthy volunteers. Placebo or S-ketamine (0.57 mg/kg/h) were infused intravenously for 2 hours. A single dose of oral morphine (0.2 mg/kg) was given to the participants 30 minutes after starting the infusion. Blood samples were obtained in various time intervals, and plasma concertation of morphine, morphine metabolites, and ketamine were measured. The area under the concentration-time curve of morphine, M6G, and M3G were determined. Maximum plasma concentration and time to reach maximum concentration were also calculated.

Results: S-ketamine reduced area under the curve of morphine at 1.5 hours by 69% and increased time to reach maximum concentration from 0.5 hour to 1 hour. The effect of S-Ketamine on area under the curve of M6G (morphine analgesic metabolite) was even more profound and reduced area under the curve by 84%, maximum plasma concentration by 43%, and time to reach maximum concentration from 1.5 hours to 4 hours.

Key Point: This study showed that intravenous S-ketamine may delay absorption and reduce efficacy of oral morphine and possibly other opioids.

Cooled Radiofrequency Ablation Versus Standard Medical Management for Chronic Sacroiliac Joint Pain: A Multicenter, Randomized Comparative Effectiveness Study

Cohen SP, Kapural L, Kohen L, et al. Reg Anesth Pain Med 2024;49(3):184-91. https://doi.org/10.1136/rapm-2023-104568

Summary by Bhavana Yalamuru, MBBS

Introduction: Over 30% of the patients with axial low back pain have sacroiliac joint pain. This study is one of the first large multicenter prospective studies comparing cooled radiofrequency ablation (RFA) of lateral branches to standard medical management for sacroiliac joint pain.

Methods: This is a randomized controlled multicenter study in which 210 patients with clinically diagnosed sacroiliac joint pain, who had a positive result to diagnostic sacroiliac joint injections or lateral branch blocks, were randomized to one of two arms- conventional medical management or cooled RFA of S1, 2, 3 and dorsal ramus of L5. The primary outcome was reduction in pain scores at 3 months, and secondary outcomes were quality of life and disability index. 

Results: Of 5,713 patients screened, 210 patients were randomized into cooled RFA (CRFA) and standard medical management groups (SMM). Fifty-three percent of the CRFA group met responder criteria (>30 % pain reduction or two-point decrease in pain score) versus the 4.3% of SMM. The secondary outcome measures of Oswestry Disability Index and quality of life were also improved in the CRFA group.

Key Point: CRFA of lateral branches provides superior outcomes in pain reduction and quality of life compared to conventional medical management.