TITLE: LACK OF EFFECT OF EPHEDRINE ON ONSET TIME OF CISATRACURIUM FOR ENDOTRACHEAL INTUBATION

AUTHORS: Anthony L. Kovac, MD, P Long, SRNA, J Bailey, SRNA
AFFILIATION: University of Kansas Medical Center, Kansas City, KS.

INTRODUCTION: Onset time of a muscle relaxant drug is dependent on the speed with which the muscle relaxant reaches the neuromuscular junction (via muscle blood flow and cardiac output). Ephedrine can help increase cardiac output and muscle blood flow (1). Ephedrine 70mg/kg intravenous (IV) has been shown to decrease the onset time of rocuronium (2). This effect has not been previously reported in combination with cisatracurium.
PURPOSE: To determine the effect of ephedrine administered immediately prior to anesthesia induction on the onset time of cisatracurium for endotracheal intubation.
METHODS: Following IRB approval and written informed consent 46 ASA physical class 1-3 adult patients scheduled for elective surgery under general endotracheal anesthesia were enrolled in this prospective, randomized, double-blind, placebo- controlled study. Patients were excluded if they had previously diagnosed neuromuscular or cardiovascular disease, blood pressure (BP) greater than 160/100, were being treated for hypertension or were taking drugs which would interact with ephedrine or the neuromuscular junction. Patients were premedicated with IV midazolam 1-2 mg and fentanyl 2-3 mg/kg. Patients were randomzied into two equal groups. Immediately prior to anesthesia induction, Group 1 (n=23) received ephedrine 70 mg/kg IV (diluted in 5ml of saline) and Group 2 (n=23) received 5ml IV of saline as placebo control. Anesthesia was induced with propofol 2-2.5mg/kg IV. Cisatracurium 0.3 mg/kg was administered IV after loss of lid reflex. Onset time was determined by Datex NMT 221 neuromuscular twitch monitor and defined as time from end of injection of cisatracurium to maximum depression of neuromuscular twitch. Data was evaluated by t-test followed by Wilcoxon Man Whitney test. A p<0.05 value was considered significant.
RESULTS: There was no significant difference between groups in demographic variables of age, gender, weight, height and ASA class. There was no significant difference in onset time (seconds, mean±SD) between the ephedrine (181.04±39.09) and placebo (170.17±41.37) groups. No adverse effects were noted.
CONCLUSION: Compared to placebo, administration of ephedrine 70 mg/kg IV had no effect on the onset time of cisatracurium 0.3mg/kg IV for endotracheal intubation.
REFERENCES:

1) Circ Res 1965; 16:174-82.

2) Anesth Analg 1997; 85(2):437-40.