Context: Available evidence on efficacy of adjuvants to local anesthetics (LAs) in supraclavicular BPB is of varying strengths and levels. Several studies have been conducted in which Magnesium Sulphate (MgSO4) was administered (with placebos and other drugs) as adjunct to LAs in supraclavicular BPB, and they revealed varying degrees of efficacy with or without side effects

Aim: To study efficacy of 20ml 0.5% ropivacaine with 250mg MgSO4 and 20ml 0.5% Ropivacaine with 500mg of MgSO4 in supraclavicular approach to brachial plexus block under ultrasound guidance

Settings and design: Prospective Randomized Controlled Comparative Interventional study was conducted at KIMS Hospital, Kondapur, Hyderabad.

Methods: 80 patients undergoing upper limb surgeries were included. They were randomly assigned in two groups of 40 each; with one group receiving MgSO4 250mg and the other MgSO4 500mg. two groups were compared for different parameters.

Statistical Analysis: Chi Square Test was applied for categorical data and t test for the continuous data.

Results: Baseline parameters, pre-anesthesia vital parameters were comparable in two groups (p>0.05). Duration of onset of sensory and motor block and completeness of block was similar in two groups (p>0.05). But duration of block was significantly more both for sensory and motor in Mg-500 compared to Mg-250 group (p<0.05). Heart rate, Mean Arterial Pressure (mmHg) were comparable in two group at all durations from pre-operative to 24 hours (p>0.05).

Conclusion: Duration of sensory and motor blockade is prolonged by addition of MgSO4 in two doses (500mg and 250mg) to Ropivacaine in USG-guided supraclavicular BPB. Action of MgSO4 is dependent on the dose, more the dose longer the action.

Key messages: 20ml of 0.5% ropivacaine with 500mg of magnesium sulphate in supraclavicular approach to brachial plexus block under ultrasound guidance can be used instead of 250mg magnesium sulphate.