WAITING TIME AFTER NONDEPOLARIZING RELAXANTS ALTER MUSCLE FASCICULATION RESPONSE TO SUCCINYLCHOLINE

The purpose of the study was to determine the effect of nondepolarizin g muscle relaxants and waiting time on muscle fasciculations after suc cinylcholine in anaesthetized patients. Adult men and women, 60-80 kg, received pretreatment doses of atracurium 5 mg (n = 160), pancuronium 1 mg (n = 123), d-tubocurarine 3 mg (n = 97), or vecuronium 1 mg (n 6 2). Waiting times between pretreatment and succinylcholine, 100 mg, ra nged between 0.6 and 5 min Data points (presence or absence of fascicu lations and waiting time) were entered for each patient. Waiting time response curves were obtained between the legit transformation of the probability of no fasciculations and the log waiting time for each dru g. Statistical differences between wait time response curves were dete rmined by non-overlapping of the associated 95% confidence interval. T he frequency of muscle fasciculations was reduced with increased waiti ng time for all nondepolarizers tested. Following wait times of three, four and five minutes, the probability of not fasciculating was great est with d-tubocurarine (90, 97 and 99% respectively) and atracurium ( 89, 93 and 96%). Corresponding values for pancuronium were 70, 82 and 88% and for vecuronium were 74, 82 and 86%. Waiting times to prevent f asciculations in 80% and 90% of patients were shorter with d-tubocurar ine (2.46 and 3.02 min, respectively) or atracurium (2.16 and 3.24 min ) than pancuronium (3.77 and 5.35 min) or vecuronium (3.73 and 6.36 mi n). In a subgroup of 107 patients who did not fasciculate after succin ylcholine, patients receiving d-tubocurarine pretreatment had the lowe st frequency of coughing/bucking responses during tracheal intubation (22%), whereas patients receiving atracurium had the highest frequency (58%). The data suggest that pretreatment with d-tubocurarine 3 mg, u sing a 3.5 to 4 min wait lime interval is the optimal method to preven t succinylcholine-induced fasciculations.