title: Ephedrine fails to accelerate the onset of neuromuscular block by vecuronium.
abstract: The onset time of neuromuscular blocking drugs is partially determined by circulatory factors, including muscle blood flow and cardiac output. We thus tested the hypothesis that a bolus of ephedrine accelerates the onset of vecuronium neuromuscular block by increasing cardiac output. A prospective, randomized study was conducted in 53 patients scheduled for elective surgery. After the induction of anesthesia, the ulnar nerve was stimulated supramaximally every 10 s, and the evoked twitch response of the adductor pollicis was recorded with accelerometry. Patients were maintained under anesthesia with continuous infusion of propofol for 10 min and then randomly assigned to ephedrine 210 microg/kg (n = 27) or an equivalent volume of saline (n = 26). The test solution was given 1 min before the administration of 0.1 mg/kg of vecuronium. Cardiac output was monitored with impedance cardiography. Ephedrine, but not saline, increased cardiac index (17%; P = 0.003). Nonetheless, the onset of 90% neuromuscular block was virtually identical in the patients given ephedrine (183 +/- 41 s) and saline (181 +/- 47 s). There was no correlation between cardiac index and onset of the blockade. We conclude that the onset of the vecuronium-induced neuromuscular block is primarily determined by factors other than cardiac output. The combination of ephedrine and vecuronium thus cannot be substituted for rapid-acting nondepolarizing muscle relaxants.
  
  
  CONCLUSIONS
  Ephedrine increased cardiac index but failed to speed onset of neuromuscular block with vecuronium. We conclude that ephedrine administration does not shorten the onset time of vecuronium.
authors.affiliation: *Department of Anesthesiology, Tokyo Women's Medical University, Tokyo, Japan; and †Outcomes Research™ Institute and Departments of Anesthesiology and Pharmacology & Toxicology, University of Louisville, Louisville, Kentucky.
authors.forename: Ryu
authors.initials: R
authors.lastname: Komatsu
authors.forename: Osamu
authors.initials: O
authors.lastname: Nagata
authors.forename: Makoto
authors.initials: M
authors.lastname: Ozaki
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Sessler
mesh_terms: D000328:Adult; D000368:Aged; D000768:Anesthesia, General; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D004558:Electric Stimulation; D004809:Ephedrine / Q000494:pharmacology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D009126:Muscle Relaxation / Q000187:drug effects; D019148:Neuromuscular Blockade; D003473:Neuromuscular Nondepolarizing Agents; D011446:Prospective Studies; D014673:Vecuronium Bromide
chemical_list: D003473:Neuromuscular Nondepolarizing Agents; D014673:Vecuronium Bromide; D004809:Ephedrine