Comparative evaluation of fentanyl and magnesium sulphate as an adjuvant to 0.375% bupivacaine in ultrasound guided supraclavicular brachial plexus block

Abstract

Supraclavicular block helps in achieving good anaesthesia along with complete muscle relaxation while providing hemodynamic stability and excellent post-operative analgesia. The addition of opioids to local anaesthetics injected during brachial plexus block has been shown to decrease the post-operative systemic analgesic requirements. This study was designed to compare the effectiveness of addition of MgSO (150 mg) and Fentanyl (50 micrograms) to 0.375% bupivacaine with placebo in supraclavicular brachial plexus block.A prospective double-blind randomised controlled study was conducted comprising of 75 patients undergoing upper limb surgeries under ultrasound guided supraclavicular brachial plexus block. Patients were randomized into one of the three groups (n=25) and designated as Group P (20ml of 0.375% Bupivacaine only), Group M (150 mg Magnesium sulphate with Bupivacaine) and Group F (50 micrograms Fentanyl with Bupivacaine). The primary purpose of the studywasto compare the onset and quality of sensory as well as motor blockade in all three groups. The onset time (in minutes) of sensory as well as motor blockade was significantly shorter in group P (p<0.001). Mean duration of sensory blockade (7.65±1.05 hours) and motor blockade (8.17±1.17 hours) was longest in group F when compared to group M and group P (p<0.001). Percentage of patients requiring rescue analgesia were significantly less in group F (16%) than group M (32%) and group P (80%) respectively (p<0.001). The mean time prior to administration of rescue analgesia in groups F, M and P were 14.21±4.29, 9.86±1.49 and 8.50 ±2.37 hours respectively (p<0.001).Although the additives delay the onset of action of local anaesthetic agents in brachial plexus block, Fentanyl as an adjuvant provided superior analgesia when compared to Magnesium sulphate as well as placebo with respect to duration of motor and sensory blockade. In addition, patients who received fentanyl as an adjuvant, required lesser rescue analgesia in the post-operative period.