Evaluation of Intravenous ephedrine's Effect on shortening the onset time of muscle relaxation of induced by atracurium

Delayed onset time of neuromuscular blocking is one of the limitations of using nondepolarizing muscle relaxants for facilitation of endotracheal intubation. This double-blinded randomized clinical trial was designed with the presumption that ephedrine can increase cardiac index and muscle blood flow and therefore it may shorten the onset time of muscle relaxation by atracurium.

Sixty patients, aged 18-60 yr, with ASA physical status I, II, were randomly assigned into two equal groups. Baseline vital signs were recorded and then all patients received intravenous midazolam and fentanyl, as premedication. One minute before induction of anesthesia with propofol and atracurium, the experimental group received intravenous ephedrine 70µg/kg and control group received an equal volume of normal saline. Muscle relaxation was assessed by means of peripheral nerve stimulator, based on TOF pattern of stimulation on ulnar nerve. The time interval between atracurium injection and the absence of TOF response (TOF=0) was recorded in all patients. Using SPSS software, data were analyzed by means of student’s t-test and Chi-square test.

Demographic data and baseline vital signs were similar in both groups (p>0.05). The mean time taken for onset of relaxation, needed for endotracheal intubation (from atracurium administration to the time of TOF=0), was less in study group compared to control group (185.1±21.59 vs. 258.43±20.63 seconds) which was statistically significant (p<0.001).

Intravenous injection of ephedrine shortens the onset time of atracurium induced muscle relaxation which is similar to other nondepolarizing muscle relaxants, such as vecuronium and rocuronium.