Comparison of clonidine and dexmedetomidine as adjuncts to intravenous regional anaesthesia

Intravenous regional anaesthesia (IVRA) provides reliable and rapid analgesia with good muscular relaxation of the extremity distal to the tourniquet, but tourniquet pain and absence of post-operative analgesia are major drawbacks. α2 agonists, clonidine and dexmedetomidine are known to potentiate peripheral nerve blocks. The aim of this study was to compare clonidine and dexmedetomidine as adjuvants to IVRA with respect to block characteristics, tourniquet pain and post-operative analgesia.

A prospective, randomised, double-blind study was conducted on 60 adult patients of American Society of Anesthesiologists physical status grades I and II, in two groups of 30 each, to receive either clonidine 1 μg/kg or dexmedetomidine 1 μg/kg added to 40 ml 0.5% preservative-free lignocaine. Independent samples t-test was used for analysing demographic data, haemodynamic data and block characteristics and Mann-Whitney U-test for skewed data.

Sensorimotor block onset was significantly faster and recovery delayed with dexmedetomidine as compared to clonidine. Intra-operative visual analogue scale (VAS) at 10 min, 15 min and 40 min and post-operative VAS at 30 min and 2 h were significantly higher with clonidine. Fentanyl consumption and sedation were comparable. Duration of analgesia was significantly longer with dexmedetomidine. Haemodynamic parameters were comparable.

Dexmedetomidine significantly facilitates onset, prolongs recovery of sensory as well as motor block and also prolongs duration of analgesia as compared to clonidine.   Both decrease tourniquet pain satisfactorily and have comparable intra-operative fentanyl requirement . Patient satisfaction is better with dexmedetomidine.