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We have assessed, in 200 patients, the determinants of the reversal time of competitive neuromuscular block by anticholinesterase when alcuronium and atracurium neuromuscular block were antagonized by neostigmine 0.04 and 0.08 mg kg-1 and edrophonium 0.5 and 1.0 mg kg-1. A biexponential relationship was found between the reversal time (time from injection of anticholinesterase to a train-of-four ratio of 70%) and the degree of neuromuscular block at reversal (all groups; F ratio, P less than 0.05). Reversal time was determined by two processes: direct antagonism by the anticholinesterase and spontaneous recovery of the neuromuscular blocking agent, with the latter becoming the major determinant at profound levels of neuromuscular block (0-10% of control twitch height). Neostigmine, in the doses studied, appeared to have a higher "ceiling" of neuromuscular block which it completely antagonized, although edrophonium had a more rapid onset of action. The reversal time for alcuronium became progressively longer relative to atracurium as neuromuscular block increased because of the slower spontaneous recovery rate. Avoidance of profound neuromuscular block at the completion of surgery is required to ensure reliable antagonism of the block within 5-10 min by an anticholinesterase. Neostigmine 0.08 mg kg-1 was found to be the most effective agent in antagonizing profound neuromuscular block.

We have assessed the effect of i.m. ketorolac or morphine on early postoperative gastric emptying of liquids in patients undergoing orthopaedic surgery with spinal anaesthesia. Liquid gastric emptying was measured by absorption of paracetamol with patients acting as their own controls. There was no delay after ketorolac 30 mg, but morphine 10mg resulted in marked delay. There was no difference in postoperative visual analogue pain scores between treatments. (Br. J. Anaesth. 1995; 74: 257–260).

Fentanyl and bupivacaine were tested for their stability when diluted with 0.9% sodium chloride to 4 micrograms ml-1 and 0.1% respectively, in 100-ml polyvinyl chloride (PVC) bags, alone and in combination, with and without adrenaline 1:200,000. Changes in drug concentration and pH were investigated for 56 days. The combination of fentanyl, bupivacaine and adrenaline was tested under varying environmental conditions of 35 degrees C, 4 degrees C, -18 degrees C, room temperature, darkness and after autoclaving. Fentanyl and bupivacaine were adsorbed onto PVC, resulting in reductions of 12.6% and 9.6% drug mass, respectively, at day 3, but remained stable thereafter. Adrenaline was progressively degraded to a maximum reduction of 37.3% at 35 degrees C by day 56. Solutions containing adrenaline became more acidic over 56 days. Fentanyl and bupivacaine were stable.