title: Variability of duration of action of neuromuscular-blocking drugs in elderly patients.
abstract: BACKGROUND
  Steroid-based, non-depolarizing neuromuscular-blocking (NMB) drugs (e.g. rocuronium, vecuronium) are characterized by organ-dependent elimination and significantly longer durations of action in elderly compared to young patients. Cisatracurium is a benzylisoquinolinium NMB drug with a duration of action not altered by ageing. The objective of the study was to determine if elderly patients had less variability in duration of action with 2 x ED95 of cisatracurium compared to equipotent doses of rocuronium or vecuronium.
  
  
  METHODS
  Informed consent was obtained from 66 elderly patients with normal renal and liver function. Preoperative midazolam (1 mg) was given IV. The anaesthestic induction was with 5 mg kg(-1) thiopental and 2 microg kg(-1) fentanyl. The patients received 0.6 mg kg(-1) rocuronium, 0.1 mg kg(-1) vecuronium or 0.1 mg kg(-1) cisatracurium. Anaesthetic maintenance was with sevoflurane in oxygen/nitrous oxide. Neuromuscular-blocking duration of action was defined as the return of T1 twitch height to 25% of control. Variability was determined by subtracting the actual duration of action from the mean duration of action for each drug.
  
  
  RESULTS
  The durations of action (range, min) were: cisatracurium, 37-81; vecuronium, 35-137; and rocuronium, 33-119. The median of the variability of duration was significantly less with cisatracurium (7 min) compared to vecuronium (18 min) and rocuronium (18 min) (P < 0.05).
  
  
  CONCLUSIONS
  When used with sevoflurane/N(2)O, there was a two-fold greater variability of duration of neuromuscular blockade in elderly patients receiving rocuronium or vecuronium compared with cisatracurium.
authors.affiliation: Department of Anaesthesiology, Medical College of Wisconsin, Zablocki VA Medical Center, Milwaukee, WI, USA.
authors.forename: S R
authors.initials: SR
authors.lastname: Arain
authors.forename: S
authors.initials: S
authors.lastname: Kern
authors.forename: D J
authors.initials: DJ
authors.lastname: Ficke
authors.forename: T J
authors.initials: TJ
authors.lastname: Ebert
mesh_terms: D000368:Aged; D000375:Aging / Q000378:metabolism; D000704:Analysis of Variance; D000732:Androstanols / Q000494:pharmacology*; D001279:Atracurium / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D009466:Neuromuscular Blocking Agents / Q000494:pharmacology*; D003473:Neuromuscular Nondepolarizing Agents / Q000494:pharmacology*; D000077123:Rocuronium; D013997:Time Factors; D014673:Vecuronium Bromide / Q000494:pharmacology*
chemical_list: D000732:Androstanols; D009466:Neuromuscular Blocking Agents; D003473:Neuromuscular Nondepolarizing Agents; D001279:Atracurium; D014673:Vecuronium Bromide; C101584:cisatracurium; D000077123:Rocuronium