The optimal dose of rocuronium for rapid sequence induction

Abstract

To the Editor, In their study using lidocaine, low-dose rocuronium, remifentanil, and propofol for tracheal intubation, SiddikSayyid et al. found tracheal intubation conditions 90 sec after rocuronium 0.3 mg kg to be comparable to those achieved 60 sec following succinylcholine 1.5 mg kg. The onset of neuromuscular block is a function of the dose given. Using electromyography, the onset of rocuronium 0.6 mg kg at the laryngeal adductors was found to be 106 sec in one study and 124 sec in another. The onset of lower doses is further delayed and can be too slow for rapid sequence induction purposes. Higher doses (1 mg kg) are recommended when rapid tracheal intubation is indicated. Low doses will also result in a less intense block at the laryngeal adductors, which are known to be more resistant than skeletal muscles to the action of rocuronium. Using a 0.25 mg kg dose, Meistelman et al. found the maximum block attained at the vocal cords to be only 37 ± 8%. Thus, low doses may only result in a delayed and partial laryngeal block. The authors’ favourable results are due to their strict adherence to the described induction technique. As pointed out in the accompanying editorial, minor deviations from that technique may lead to different results, including failure to achieve tracheal intubation due to poor relaxation and inadequate intubation conditions. This may increase the risk of aspiration during the rapid sequence induction which the technique was originally instituted to guard against. The authors are to be commended for describing a technique that can be advantageous for brief surgical procedures that require muscle relaxation. A Cochrane database review, however, showed that the optimal dose of rocuronium for rapid sequence induction probably should be higher than 1 mg kg.