Background: We investigated the hypothesis that manipulation of cardiac output (CO) with esmolol (Es) or ephedrine (E) affects the onset time of rocuronium. Methods: Following anesthesia induction, 33 patients received E (70 μg kg-1), Es (500 μg kg-1) or placebo (P) 30 s before rocuronium (0.6 mg kg-1) administration. Cardiac output was measured non-invasively after intubation every 3 min. The interval from the end of rocuronium administration to the disappearance of all twitches was considered to be the onset time. Results: Onset time was shorter after E (52.2±16.5 s) and longer after Es (114.3±11.1s) compared with P (87.4±7.3 s) (P < 0.0001). Cardiac output increased (P < 0.05) in group E for 15 min after rocuronium. In group Es, CO decreased (P < 0.05) at 3 and 6 min. Cardiac output was higher in group E vs. group Es, 3-6 min post administration of rocuronium (P=0.015). Conclusion: Pretreatment with E or Es appears to affect the onset time of rocuronium by altering CO as measured with the NICO™ (Non-Invasive Cardiac Output) monitor (Novametrix Medical Systems Inc., Willingford, CO).
- Onset time