RESUMEN
In order to substantiate the "priming principle" discussion, 44 patients admitted for elective gynecological surgery under modified neurolept anesthesia were randomized into two groups. In group I, atracurium was administered by a priming technique in which 0.1 mg/kg was given i.v. and, after 6 min, 0.5 mg/kg. In group II was given an atracurium bolus injection of 0.6 mg/kg. In group I onset time (median 61 sec, range 44-160 sec) was significantly more rapid than in group II (median 83 sec, range 60-128 sec). The median train-of-four ratio in group I was 0.80 (range 0.43-1.00, n = 23), 6 min after the priming dose, in 30% of these patients the TOF ratio was above 0.90 and in 22% below 0.70. It is impossible to determine a fixed pretreatment dose per kg body weight owing to the large individual variation in neuromuscular depression. Modification of the priming principle using incremental small doses of non-depolarizing neuromuscular blocking agents, with anesthetic induction, when the train-of-four ratio is between 0.90 and 0.70 or when there is clinical signs of neuromuscular block, might be an alternative in situations where rapid induction is required and where the use of suxamethonium is contraindicated.