Effect of ultra-low-dose naloxone during supraclavicular brachial plexus block on the antinociceptive criteria of postoperative opioid in orthopedic upper limb surgeries

Abstract

Background Brachial plexus block is a popular and widely used regional nerve block technique for perioperative anesthesia and analgesia for upper extremity surgeries. Many drugs such as morphine and midazolam have been used as an adjuvant with local anesthetics to achieve quick, dense, and prolonged block. Drugs with minimal side effects are always looked for. Naloxone as opioid antagonists could selectively block excitatory effects of opioids, stimulate release and displace endorphins from receptor sites, and reduce the side effects of opioids. An ultra-low-dose naloxone, added as an adjuvant to local anesthetic, may prolong sensory and motor blockades with enhanced opioid effect or direct antagonism of its excitatory receptors. Patients and methods After approval by Institutional Research Board, clinical trial registration, and obtaining informed consents, 64 patients scheduled for orthopedic upper limb surgeries under supraclavicular brachial plexus block were enrolled into two equal groups: group B (bupivacaine 0.5%) and group BN (bupivacaine 0.5% plus 100 ng naloxone). Results There was significant decrease in fentanyl consumption in GBN (216.6±76.10) versus group B (507.5±117.50). Also, the number of fentanyl requests was lesser in group BN (3.0±1.11) than in group B (7.3±1.73). The onset time for sensory and motor blocks showed no significant difference among groups; the duration of sensory and motor blocks was prolonged in GBN (17.2±2.96–7.7±1.93 h) versus GB (7.3±1.22–4.7±.79 h). The time to first rescue fentanyl was prolonged in GBN (18.3±3.21 h) than in GB (8.0±1.41 h). There was significant reduction in visual analog scale score at 8, 12, and 18 h postoperatively in GBN versus GB. There were no significant changes in Ramsay sedation scale or complications within 48 h postoperatively. Conclusion Ultra-low dose of naloxone (100 ng) added to 20 ml bupivacaine 0.5% for supraclavicular brachial plexus block enhanced the postoperative opioid analgesia by reducing the total postoperative opioid consumption, prolonging the interval between opioid doses and the duration of sensory and motor block.