Comparative evaluation of adding different opiates (morphine, meperidine, buprenorphine, or fentanyl) to lidocaine in duration and quality of axillary brachial plexus block

Background: There is no agreement about the effect of adding opioids to local anesthetics in peripheral nerve blocks. The aim of this study was to investigate the effect of adding different opioids with equipotent doses of lidocaine in axillary brachial plexus block using ultrasonography and nerve locator guidance.
Materials and Methods: In a prospective, randomized, double-blind clinical trial study, 72 adult patients aged 18-65 years old scheduled for orthopedic surgery of the forearm and hand with axillary brachial plexus block were selected and randomly allocated to four groups. Meperidine (pethidine), buprenorphine, morphine, and fentanyl with equipotent doses were added in 40cc of 1% lidocaine in P, B, M, and F groups, respectively. The onset and duration of sensory and motor blocks, severity of patients' pain, duration of analgesia, hemodynamic and respiratory parameters, and adverse events (such as nausea and pruritus) during perioperative period were recorded.
Results: The onset time for the sensory block was similar in the four groups. The onset time for the motor block was significantly faster in morphine and pethidine groups (P = 0.006). The duration of sensory and motor blocks was not statistically different among the four groups. The quality of motor blockade was complete in 100% of patients receiving pethidine or morphine and 77.8% of patients receiving buprenorphine or fentanyl (P = 0.021).
Conclusion: In the upper extremity surgeries performed under axillary brachial plexus block addition of morphine or pethidine to lidocaine may be superior to other opioids (i.e. fentanyl and buprenorphine) due to better quality and quantity of motor blockade and faster onset of the block.