Efficacy of Phenylephrine As An Adjuvant To BupivacaineIn Supraclavicular Brachial Plexus Block – A Prospective, Randomised Study

ABSTRACT

Background: Several adjuncts have been studied to potentiate the efficacy of local anaesthetic agents that increase the duration of analgesia, in peripheral nerve blocks, but the results have often been debated and counter debated. Phenylephrine has been studied intrathecally as an adjuvant and has been found to potentiate the effect of local anaesthetic agents. The present study was undertaken with a purpose to assess the efficacy of phenylephrine as an adjuvant to bupivacaine in supraclavicular brachial plexus block. Methods: A prospective, randomised, double blinded study was undertaken which included 40 ASA I or II patients, aged 18-60 years, ≥60 kg, scheduled for upper limb surgery under supraclavicular brachial plexus block. Patients were randomly divided into two groups of 20 each. Group S patients received 30 ml, 0.5% bupivacaine with 0.15 ml of saline and Group P patients received 30 ml, 0.5% bupivacaine with 0.15 ml (equivalent to 150 μg) of phenylephrine. Onset and duration of sensory and motor block, haemodynamic parameters, pain score, analgesia requirement and complications, if any, were recorded. Results: The total duration of sensory and motor block was significantly increased in group P, as compared to group S (p≤0.05). Pain scores were significantly lower and rescue analgesia demand was also significantly low in group P, in comparison to group S (p≤0.05). Demographic variables and haemodynamic parameters were comparable in both the groups. No major complications were seen. Conclusion: Phenylephrine (150 μg) when used as an adjuvant to 30 ml, 0.5% bupivacaine, in supraclavicular brachial plexus block, prolongs the duration of both the sensory and motor block thus enhances analgesia, decreases the rescue analgesic requirement and does not cause any adverse effects.