The effect of cisatracurium and rocuronium on cisatracurium precurarization and the priming principle.
OBJECTIVE
To demonstrate the effect of administering a precurarizing dose of cisatracurium or rocuronium on the speed of onset of cisatracurium, and to review the possible mechanisms and value of the priming principle.


METHODS
Double-blind, randomized, controlled trial.


METHODS
Inpatient anesthesia in a university teaching hospital.


METHODS
90 ASA physical status I and II patients undergoing elective surgery requiring endotracheal intubation.


METHODS
Three groups of 30 patients each were investigated. Following induction of anesthesia with fentanyl and propofol, Group 1 received cisatracurium 0.015 mg.k(-1), Group 2 received rocuronium 0.09 mg. kg(-1), and Group 3 (control) received normal saline. Six minutes after priming, Groups 1 and 2 received cisatracurium 0.135 mg. kg(-1) whereas Group 3 received cisatracurium 0.15 mg. kg(-1).


RESULTS
In each group, first twitch height and the train-of-four ratios were recorded every 10 seconds after the initial priming dose. Intubation was attempted after the first twitch height became less than 15% of baseline. The decrease in the train-of-four ratios at 6 minutes was 0.97 for cisatracurium and 0.85 for rocuronium. The onset of muscle relaxation was significantly faster after priming with cisatracurium and rocuronium (71.7 +/- 21.3 and 65 +/- 19.8 sec, respectively) compared with control (148.7 +/- 43.1 sec). Females receiving both muscle relaxants had a faster onset of paralysis than did males (65.9 +/- 20.6 vs. 79.2 +/- 20.6 and 55 +/- 14.5 vs. 71.7 +/- 20.4 sec). Intubation conditions were either excellent or satisfactory in all patients.


CONCLUSIONS
Six minutes after precurarization, there is no significant difference between rocuronium and cisatracurium when used as priming drugs. An even faster onset time with both drugs was demonstrated in females. The use of priming doses of 25% to 30% of ED(95) may cause symptomatic muscle weakness. The mechanisms of the priming principle are discussed.
Mak
Peter H K
PH
Department of Anaesthesiology, Queen Mary Hospital, University of Hong Kong, Pokfulam, Hong Kong, Taiwan ROC. peter.mak@uhn.on.ca
Irwin
Michael G
MG
D000328:Adult; D000732:Androstanols / Q000008:administration & dosage*; D000768:Anesthesia, General; D001279:Atracurium / Q000008:administration & dosage* / Q000031:analogs & derivatives*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007442:Intubation, Intratracheal; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D019148:Neuromuscular Blockade; D009466:Neuromuscular Blocking Agents / Q000008:administration & dosage*; D003473:Neuromuscular Nondepolarizing Agents / Q000008:administration & dosage*; D000077123:Rocuronium; D012727:Sex Characteristics; D013997:Time Factors
D000732:Androstanols; D009466:Neuromuscular Blocking Agents; D003473:Neuromuscular Nondepolarizing Agents; D001279:Atracurium; C101584:cisatracurium; D000077123:Rocuronium