Rapid sequence intubation – how?

RAPID sequence intubation or rapid sequence induction (RSI) is used when general anaesthesia must be given in spite of a significant risk of pulmonary aspiration of gastric contents. Typically, this is relevant in emergency situations in which the patient has not been fasting or in patients with gastrointestinal disease. In addition, RSI is recommended in other patients, such as women presenting for surgery in the last trimester of pregnancy. Classic RSI consists of careful pre-oxygenation, cricoid pressure and a rapid injection of an intravenous hypnotic followed by succinylcholine. Tracheal intubation is performed after the onset of neuromuscular blockade, detected either by fasciculations following the injection of succinylcholine or by monitoring neuromuscular function by a nerve stimulator. RSI is associated with a high risk of complications. This is related to the period of apnoea between induction and tracheal intubation and to the fact that a neuromuscular blocking agent (NMBA) is given before it has been ensured that mask ventilation is possible. In infants and obese patients, apnoea for even less than 1 min may lead to hypoxaemia and, in a worst case scenario, neither mask ventilation nor tracheal intubation is possible. This is lifethreatening, even in patients with normal metabolism of succinylcholine. In the case of a prolonged duration of action of succinylcholine caused by abnormal plasma cholinesterase, this may be disastrous (1–3). Other problems with RSI are circulatory depression and complications caused by the use of succinylcholine, such as hyperkalaemia and malignant hyperthermia. Over the years, propofol has replaced thiopental as the most commonly used intravenous hypnotic, and rocuronium has been shown to be useful during RSI as it has a short onset time that may be reduced even further when the dose is increased to 0.9–1.2 mg/kg. The problem is, however, that the duration of action of rocuronium is much longer than that of succinylcholine, especially when given in high doses. This problemmay, however, soon be solved. Sugammadex, representing a revolutionary new approach (the chelating principle) to the antagonism of even deep block caused by steroidal-based NMBAs, is presently undergoing phase III trials all over the world, and may be commercially available within the next few years (4–6). In this issue of Acta Anaesthesiologica Scandinavica, Lysakowski et al. (7) present an interesting analysis of RSI, comparing different RSI models with tracheal intubation conditions as the end point. They conclude that rocuronium and succinylcholine provide good or excellent conditions after 60 s, but the dose of rocuronium should be 0.9– 1.2 mg/kg if thiopental is used. In contrast, a dose of 0.6–0.7 mg/kg rocuronium will suffice if propofol is given. In their analysis, no significant relationship was found between the use of opioid and intubation conditions. It is no major surprise that propofol may provide better intubation conditions than thiopental, but it should be noted that the significance of the doses of hypnotics and opioids was not analysed separately, and it is difficult to imagine that the given doses of these drugs do not influence the intubation conditions (8, 9). Moreover, remifentanil was not included in the analysis. It is well known that tracheal intubation is possible without the use of an NMBA using relatively high doses of propofol and remifentanil (10, 11). However, this technique, which may cause profound circulatory depression, especially in elderly patients, and may result in more laryngeal damage (12), has not yet been satisfactorily evaluated for RSI. The review by Lysakowski et al. (7) includes an evaluation of a ‘modified RSI’, in which a variable delay between the administration of the hypnotic and NMBA was allowed. No significant difference was found between propofol and thiopental in this