Abstract
Background and Objectives: Alpha-2 agonists are used as adjuvant with local anaesthetic agents to prolong the duration of spinal, epidural and peripheral nerve blocks as well as to prolong the duration of post operative analgesia. We performed a study to compare clonidine(1ug/kg) and dexmedetomidine (1ug/kg) as an adjuvant to 0.5% bupivacaine in supraclavicular brachial plexus block.
 Methods: Eighty ASA I and II patients scheduled for elective upper limb orthopaedic surgeries under supraclavicular brachial plexus block were divided into two groups(n=25 each) in a randomized, double-blinded fashion. Group C received clonidine 1 μg/kg and Group D received dexmedetomidine 1 μg/kg added to bupivacaine 0.5% (30 cc). Onset and recovery time of sensory and motor block, as well as duration of analgesia were studied in both the groups.
 Results: Duration of sensory block and motor block was 220.12 ±50.3 and 280.1± 20.12 min respectively in group C, while it was 410.34± 60.12 and 460.4 ± 50.56 min respectively in group D and hence both were significantly prolonged in group D. No statistically significant difference was seen in onset of sensory and motor block between the two groups. The duration of analgesia i.e. time to requirement of rescue analgesia was 270.4± 56.7 mins and 452.7 ±64.23 mins in group C and D respectively and this difference was statistically significant (P=0.001).
 Conclusion: Addition of dexmedetomidine to bupivacaine 0.5% in supraclavicular brachial plexus block prolonged the duration of sensory and motor block as well as the duration of analgesia when compared with clonidine.
 Keywords: Clonidine, dexmedetomidine, supraclavicular block
Highlights
Brachial plexus block is most commonly used technique for performing upper limb surgeries
Addition of dexmedetomidine to bupivacaine 0.5% in supraclavicular brachial plexus block prolonged the duration of sensory and motor block as well as the duration of analgesia when compared with clonidine
The current study was designed to test the hypothesis that when compared to clonidine, addition of dexmedetomidine to local anaesthetics in supraclavicular brachial plexus block, show a greater enhancement of the duration of analgesia as well as duration of sensory and motor block
Summary
Brachial plexus block is most commonly used technique for performing upper limb surgeries. Dexmedetomidine is more selective towards the α2 adrenoceptor than clonidine.[5] Previous clinical studies have shown a decrease in inhalational anaesthetic requirements and opioid sparing effects, by the use of intravenous alpha-2 adrenergic receptor agonists.[6] Some previous animal studies have shown dexmedetomidine to cause increase in duration of analgesia in addition to enhancing the sensory and motor blockade.[7,8,9,10] In humans, alpha-2 adrenergic receptor agonists have been shown to prolong the duration of various regional blocks when used as adjunct to local anaesthetic solutions.[11,12,13] The current study was designed to test the hypothesis that when compared to clonidine, addition of dexmedetomidine to local anaesthetics in supraclavicular brachial plexus block, show a greater enhancement of the duration of analgesia as well as duration of sensory and motor block This double-blind randomized prospective study was carried out on 80 patients of American Society of Anaesthesiologist (ASA) Grade I or II, aged 20–50 years, of either sex, undergoing various upper limb orthopaedic surgeries under supraclavicular brachial plexus block. The sensory block duration was considered from the end of local anaesthetic administration till the complete resolution of anaesthesia on all nerves. P-value 0.05 was considered non significant
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