Effect of pretreatment with intravenous lidocaine and magnesium sulfate on onset and duration of rocuronium

ABSTRACT

Rocuronium is a steroidal non - depolarizing muscle relaxant that provides rapid onset with intermediate duration of action [1-5] Many drugs have been used to make its onset of action as short as that of succinyl choline[7, 8] The aim of this study is to evaluate the relaxant efficacy of low dose rocuronium 0.6 mg/kg either alone or pretreated with lidocaine 1.5 mg/kg or magnesium sulfate 30 mg/kg. Their effects on the time of onset and time of recovery [duration] of rocuronium muscle blockade and on the intubation conditions were assessed. A prospective randomized double blind clinical study was conducted on 75 ASA I and II adults undergoing short elective surgical procedures requiring tracheal intubation. They were divided into three groups 25 in each. In group I rocuronium was pretreated with normal saline. In patients of group II, rocuronium was pretreated with 1.5 mg/kg lidocaine. In group Ill, the patients were given 30mg/kg magnesium sulfate as pretreatment 3 minutes before rocuronium. Rocuronium was given in a dose of 0.6 mg /kg. The response of the adductor pollicis muscle of the non - dominant hand to train of four stimulation of the ulnar nerve at the wrist at 10 watch SX seconds intervals was measured using TOF watch [acceleromyography principle]. The mean onset time to T[1]= 25% and to complete disappearance of TOF trace [T[1]=0%] were measured [seconds]. All patients were intubated when T[1]=25% and intubation conditions were assessed on a four point scale as excellent, good, poor or inadequate according to the method described by Goldberg, et at., [12] [table I]. The mean times to initial recovery T[1]=10% and, clinical recovery, TOF ratio 75% were also measured. The mean onset time of rocuronium to T[1]= 25% and T1-0% were equally reduced by lidocaine in group II and magnesium sulfate in group Ill if compared with group I [control or saline]. Iidocaine pretreatment [group II] gave as excellent acceptable intubation scores as magnesium pretreatment [group III]. Intubation scores in groups II and m were statistically superior to those in group I - As regard recovery the mean times to initial recovery [T[1]=10%] and clinical recovery [TOF ratio 75%] were not affected by lidocaine while they were prolonged by magnesium sulfate. rocuronium [low dose] -lidocaine combination may be a safe alternative in rapid tracheal intubation of patients when succinyl choline is contraindicated especially when the surgery is of short duration. We recommend strict monitoring of neuromuscular block and titration of the dose of non - depolarizing muscle relaxants in patients on magnesium therapy