title: Suxamethonium administration prolongs the duration of action of subsequent rocuronium.
abstract: OBJECTIVE
  Rocuronium may be given to patients for intubation and also after they have received suxamethonium for intubation. The neuromuscular profile of rocuronium given after recovery from suxamethonium may not be identical to that when rocuronium has been given alone. The neuromuscular effects of suxamethonium and rocuronium, and their effects on intraocular pressure (IOP), heart rate (HR) and arterial pressure were also recorded.
  
  
  METHODS
  Thirty patients were randomly allocated to receive either 0.6mg kg(-1) rocuronium (n = 15) or 1 mg kg(-1) suxamethonium (n = 15) for intubation. Anaesthesia was first induced using propofol 2.5 mg kg(-1) and fentanyl 2 microg kg(-1) and maintained with propofol 6-12 mg kg(-1) h(-1). The response of the thumb to supramaximal train-of-four (TOF) ulnar nerve stimulation at the wrist was measured using a mechanomyograph. In the suxamethonium group, when the first twitch of the TOF had recovered to 90%, rocuronium 0.6 mg kg(-1) was administered. Before administration of relaxant, baseline readings of HR, arterial pressure and IOP were measured until stable, then the appropriate relaxant administered. Thereafter, all readings were repeated at 30, 90, 150, 210 and 270 s. Tracheal intubation was performed 300 s after the intubating dose and all recordings repeated 30 s later. Mechanomyographic monitoring was continued until 70% TOF recovery.
  
  
  RESULTS
  Suxamethonium had a more rapid onset than rocuronium (49s vs. 74s, P < 0.0001). The onset time of rocuronium after suxamethonium was significantly reduced (56 s) and the time to recover to a TOF of 70% following rocuronium was increased by previous suxamethonium administration (47 vs. 58 min, P < 0.05). Suxamethonium caused a marked rise in IOP (>30%) and HR (>10%) while rocuronium had little effect on either.
  
  
  CONCLUSIONS
  Previous suxamethonium administration decreases the onset time and increases the duration of action of rocuronium. Unlike suxamethonium, rocuronium has few cardiovascular effects and causes little change in IOP.
authors.affiliation: University Medical Center, Department of Anesthesiology, Nijmegen, The Netherlands. e.robertson@anes.umcn.nl
authors.forename: E N
authors.initials: EN
authors.lastname: Robertson
authors.forename: J J
authors.initials: JJ
authors.lastname: Driessen
authors.forename: L H D J
authors.initials: LH
authors.lastname: Booij
mesh_terms: D000328:Adult; D000732:Androstanols / Q000008:administration & dosage / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000627:therapeutic use; D001794:Blood Pressure / Q000187:drug effects; D004357:Drug Synergism; D004558:Electric Stimulation / Q000379:methods; D005283:Fentanyl / Q000627:therapeutic use; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects; D007442:Intubation, Intratracheal / Q000379:methods; D009467:Neuromuscular Depolarizing Agents / Q000008:administration & dosage / Q000494:pharmacology*; D003473:Neuromuscular Nondepolarizing Agents / Q000008:administration & dosage / Q000494:pharmacology*; D013508:Ophthalmologic Surgical Procedures / Q000379:methods; D015742:Propofol / Q000627:therapeutic use; D000077123:Rocuronium; D013390:Succinylcholine / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D000732:Androstanols; D018686:Anesthetics, Intravenous; D009467:Neuromuscular Depolarizing Agents; D003473:Neuromuscular Nondepolarizing Agents; D013390:Succinylcholine; D005283:Fentanyl; D000077123:Rocuronium; D015742:Propofol