The Effect of Defasciculating Doses of Pancuronium and Atracurium on Succinylcholine Neuromuscular Blockade

Background: a defasciculating dose of non-depolarizing muscle relaxant administered prior succinylcholine decrease its side effects including fasciculations and postoperative myalgias; however it is believed that the dosage of succinylcholine should be increased when such a pre-treatment is used. objectives: we hypothesized that a defasciculating dose of pancuronium as a pre-treatment could prolong its duration of effect. patients and methods: forty patients scheduled for elective orthopaedic surgery were consecutively assigned into 5 groups, a first group without pre-treatment (succinylcholine 1 mg/kg) and 4 subsequent groups of pretreatment with atracurium 0.05 mg/kg + succinylcholine 1 or 1.5 mg/kg and pancuronium 7.5 μg/kg + succinylcholine 1 and 1.5 mg/kg. the muscle relaxant effect of succinylcholine was assessed with a force transducer using train of four stimulations every 12 seconds. kruskall wallis anova test was used to compare results. results: the duration of succinylcholine induced paralysis (1 and 1.5 mg/kg) was significantly prolonged with pre-treatment with pancuronium but succinylcholine 1mg/kg did not reached maximum blockade after pre-treatment with atracurium. after pancuronium, full recovery after succinylcholine 1.5 and 1 mg/kg occurred respectively after 18 and 15 minutes. p < 0.05 vs. 12 minutes for succinylcholine 1mg/kg alone. conclusions: this study highlights potentiation effect of a defasciculating dose of pancuronium on succinylcholine paralysis suggesting the lack of justification to increase succinylcholine dosage.