Different additives have been used to prolong brachial plexus block. We performed a prospective, randomised, double-blind study to evaluate the effect of dexamethasone added to lidocaine on the onset and duration of supraclavicular brachial plexus block as this is the most common type of brachial block performed in our institute.
Sixty American Society of Anaesthesiologist's physical status I and II patients undergoing elective hand, forearm and elbow surgery under brachial plexus block were randomly allocated to receive either 1.5% lidocaine (7 mg/kg) with adrenaline (1:200,000) and 2 ml of normal saline (group C, n=30) or 1.5% lidocaine (7 mg/kg) with adrenaline (1:200,000) and 2 ml of dexamethasone (8 mg) (group D, n=30). The block was performed using a nerve stimulator. Onset and duration of sensory and motor blockade were assessed. The sensory and motor blockade of radial, median, ulnar and musculocutaneous nerves were evaluated and recorded at 5, 10, 20, 120 min, and at every 30 min thereafter.
Two patients were excluded from the study because of block failure. The onset of sensory and motor blockade (13.4±2.8 vs. 16.0±2.3 min and 16.0±2.7 vs. 18.7±2.8 min, respectively) were significantly more rapid in the dexamethasone group than in the control group ( P=0.001). The duration of sensory and motor blockade (326±58.6 vs. 159±20.1 and 290.6±52.7 vs. 135.5±20.3 min, respectively) were significantly longer in the dexamethasone group than in the control group ( P=0.001).