Rapid tracheal intubation with atracurium: the timing principle

The "Timing Principle" utilises a single bolus of non-depolarising neuromuscular blocking drug followed by thiopentone given at the onset of clinical weakness. The purpose of this study was to compare the intubating conditions after succinylcholine and after atracurium used according to the "timing principle." Eighty patients were randomly assigned to four groups of 20. Three study groups were given atracurium 0.5, 0.75 or 1 mg.kg-1 (Groups I, II and III respectively) and the control group (Group IV) received succinylcholine 1.5 mg.kg-1. The study groups received fentanyl 1 microgram.kg-1, atracurium three minutes later, followed by thiopentone 4-6 mg.kg-1 at the onset of ptosis. The control group had a defasciculating dose of atracurium (0.025 mg.kg-1) and fentanyl (1 microgram.kg-1) followed by thiopentone (4-6 mg.kg-1) and succinylcholine three minutes later. The trachea was intubated one minute after thiopentone was given. The intubating conditions were then graded by a laryngoscopist who was unaware of the induction sequence. All patients were interviewed on the day after surgery. Intubation scores of patients in Group I were worse than in Groups II, III and IV (P < 0.005) but there were no differences between Groups II, III and IV. The technique was not associated with severe haemodynamic changes. All patients, except one were able to cough well after administration of atracurium, before induction of anaesthesia with thiopentone. Patients were generally satisfied with this method of induction. It is concluded that atracurium, when used according to the timing principle, can be an alternative to succinylcholine during rapid-sequence induction.