Potentiation by Propranolol of the Skeletal Neuromuscular Block Caused by Rocuronium

Lee, Soo il; Lee, Jong Hwan; Lee, Seung Cheol; Lee, Ji Hyeon

Abstract

BACKGROUND: Propranolol potentiates the effect of neuromuscular blocking agents and induces myasthenic syndromes through curare-like and local anesthetic activities.The purpose of this study was to determine if propranolol potentiated the neuromuscular block caused by rocuronium during both single (0.1 Hz) and tetanic stimulation (50 Hz for 1.9 seconds).
METHODS
Left phrenic nerve-hemidiaphragms (Male Sprague-Dawley rats, 150-250 g) were mounted in Krebs solution, and three consecutive single twitches and one tetanic tension were obtained prior to each treatment. Each preparation was exposed to one of 4 propranolol concentrations (0, 1.0, 2.5, 5micrometer), 5micrometer propranolol with 2micrometer norepinephrine or 2micrometer norepinephrine alone and the concentration of rocuronium was then increased cumulatively until a 80% reduction of single twitch occurred.The effects of the drugs used were allowed to reach a steady state by waiting for 20 minutes at each concentration before measuring the tension. Effective concentrations of rocuronium at each treatment were calculated using a probit model.Differences between treatments were tested with student's t-test and Bonferroni's correction with a P < 0.05 being regarded as significant.
RESULTS
The neuromuscular block caused by rocuronium was augmented by propranolol, however the augmentation caused by propranolol was not reversed by norepinephrine.
CONCLUSIONS
The results of this study indicate that the potentiation by propranolol of the neuromuscular block caused by rocuronium is independent of its adrenoceptor blocking action.