Regional anaesthesia: Overview

Regional Anesthesia & Pain Medicine, the official publication of the American Society of Regional Anesthesia and Pain Medicine (ASRA Pain Medicine), is a monthly journal that publishes peer-reviewed scientific and clinical studies to advance the understanding and clinical application of regional techniques for surgical anesthesia and postoperative analgesia. Coverage includes intraoperative regional techniques, perioperative pain, chronic pain, obstetric anesthesia, paediatric anesthesia, outcome studies, and complications.

Abstract
Background: Whether regional anesthesia impacts the development of chronic postsurgical pain is currently debateable, and few studies have evaluated an effect on prolonged opioid use. We sought to systematically review the effect of regional anesthesia for adults undergoing noncardiac elective surgery on these outcomes.

Methods: A systematic search was conducted in MEDLINE, EMBASE, CENTRAL, and CINHAL for randomized controlled trials (from inception to April 2022) of adult patients undergoing elective noncardiac surgeries that evaluated any regional technique and included one of our primary outcomes: (1) prolonged opioid use after surgery (continued opioid use ≥2 months postsurgery) and (2) chronic postsurgical pain (pain ≥3 months postsurgery). We conducted a random-effects meta-analysis on the specified outcomes and used the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) approach to rate the quality of evidence.

Results: Thirty-seven studies were included in the review. Pooled estimates indicated that regional anesthesia had a significant effect on reducing prolonged opioid use (relative risk [RR] 0.48, 95% CI, 0.24-0.96, P = .04, I2 0%, 5 trials, n = 348 patients, GRADE low quality). Pooled estimates for chronic pain also indicated a significant effect favoring regional anesthesia at 3 (RR, 0.74, 95% CI, 0.59-0.93, P = .01, I2 77%, 15 trials, n = 1489 patients, GRADE moderate quality) and 6 months (RR, 0.72, 95% CI, 0.61-0.85, P < .001, I2 54%, 19 trials, n = 3457 patients, GRADE moderate quality) after surgery. No effect was found in the pooled analysis at 12 months postsurgery (RR, 0.44, 95% CI, 0.16-1.17, P = .10).

Conclusions: The results of this study suggest that regional anesthesia potentially reduces chronic postsurgical pain up to 6 months after surgery. Our findings also suggest a potential decrease in the development of persistent opioid use.

Abstract
The nociceptive withdrawal reflex (NWR) is a protective limb withdrawal response triggered by painful stimuli, used to assess spinal nociceptive excitability. Conventionally, the NWR is understood as having two reflex responses: a short-latency Aβ-mediated response, considered tactile, and a longer-latency Aδ-mediated response, considered nociceptive. However, nociceptors with conduction velocities similar to Aβ tactile afferents have been identified in human skin. In this study, we investigated the effect of a preferential conduction block of Aβ fibers on pain perception and NWR signaling evoked by intradermal electrical stimulation in healthy participants. We recorded a total of 198 NWR responses in the intact condition, and no dual reflex responses occurred within our latency bandwidth (50-150 ms). The current required to elicit the NWR was higher than the perceptual pain threshold, indicating that NWR did not occur before pain was felt. In the block condition, when the Aβ-mediated tuning fork sensation was lost while Aδ-mediated nonpainful cooling was still detectable (albeit reduced), we observed that the reflex was abolished. Further, short-latency electrical pain intensity at pre-block thresholds was greatly reduced, with any residual pain sensation having a longer latency. Although electrical pain was unaffected at suprathreshold current, the reflex could not be evoked despite a two-fold increase in the pre-block current and a five-fold increase in the pre-block pulse duration. These observations lend support to the possible involvement of Aβ-fiber inputs in pain and reflex signaling.

Abstract
Aim: This study aimed to assess the feasibility and effectiveness of the pectoral nerves (PECS) II block in facilitating cardiac implantable electronic device (CIED) insertion in a sample of 120 patients, with a focus on the percentage of cases completed without additional intraoperative local anesthesia.

Methods: PECS II blocks were performed on the left side using ultrasound guidance in all 120 patients. Feasibility was assessed by the proportion of cases completed without the need for extra intraoperative local anesthetic. Secondary outcomes included the amount of additional local anesthetic used, intraoperative opioid requirements, postoperative pain scores, time to first postoperative analgesia, analgesic consumption, patient satisfaction, and block-related complications.

Results: Of the 120 patients, 78 (65%) required additional intraoperative local anesthetic, with a median volume of 8.2 mL (range 3-13 mL). Fifteen patients (12.5%) needed intraoperative opioid supplementation. Nine patients (7.5%) required postoperative tramadol for pain relief. In total, 98 patients (81.7%) reported high satisfaction levels with the procedure.

Conclusions: The PECS II block, when combined with supplementary local anesthetic, provided effective postoperative analgesia for at least 24 h in 120 patients undergoing CIED insertion. While it did not completely replace surgical anesthesia in most cases, the PECS II block significantly contributed to a smoother intraoperative experience for patients.