Opioids and rapid-sequence induction
Milwaukee, WI, USA
* E-mail: elorbany2000{at}yahoo.com
Editor—I read with interest the article about the dose of alfentanil needed during the course of rapid-sequence induction (RSI) with thiopentone and rocuronium.1 Obtaining optimal conditions at the time of tracheal intubation is one of the major goals and prerequisites for a successful RSI/intubation technique. The choice of drugs to be used, proper timing of their administration, and proper timing of tracheal intubation are of paramount importance for the technique to be successful. There is no doubt that prior administration of a fast acting opioid such as alfentanil or remifentanil in adequate doses will lead to improved intubation conditions during RSI.2 Although the choice of alfentanil and timing of its administration were successful, the timing of tracheal intubation (40 s after rocuronium administration) was too early for the full effect of rocuronium to be established. Using mechanomyography, the onset of rocuronium neuromuscular block after a 1.2 mg kg–1 dose was found to be 54 s at the laryngeal adductors and 65 s at the adductor pollicis.3 May be what the authors were really testing are the intubation conditions resulting only from opioid and induction drug administration. Tracheal intubation without the use of neuromuscular blocking agent can result in satisfactory intubation conditions in 93% of the patients,4 but this should not be tried for RSI because we should give the technique all the chances to be successfully completed. What was wrong with waiting 20 more seconds for the intubation attempt to be performed? This could have allowed the neuromuscular blocking agent to establish its effects and could have resulted in even better intubation conditions. On the other hand, there is no evidence that there is an increased incidence of aspiration or desaturation as long as tracheal intubation is accomplished within 90 s. Most importantly, waiting this extra 20 s can dramatically decrease the incidence of a failed RSI with all of its potential risks. Had the authors considered intubation at 60 s, could this have changed the dose of alfentanil required to produce optimal conditions at the new time of intubation? and if the new recommended dose was found to be less than the optimal dose that was required for a 40 s intubation, could this have resulted in a decrease in the incidence of hypotension (20%) that was associated with alfentanil/thiopentone administration? This may need further investigation.
1 Oslo, Norway
2 San Francisco, USA
* E-mail: tom.heier{at}medisin.uio.no
Editor—We appreciate Dr El-Orbany's comments on our study,1 and although we agree that the effect of rocuronium was not at its peak when the tracheal intubation was performed, we still think that the effect of this drug contributed significantly to optimizing the intubation conditions. This assumption is based on results from previous studies.3 5 In the latter publication, rocuronium 1.0 mg kg–1 was superior to 0.6 mg kg–1 with respect to intubation conditions.
It is also correctly addressed by Dr El-Orbany that waiting 60 s (instead of 40 s in our study) before laryngoscopy probably would have reduced the need for alfentanil to obtain perfect intubation conditions. However, even if no study has shown that the morbidity or mortality rate is different when intubation is performed 60 or 90 s after commencement of anaesthesia induction, we believe that most anaesthetists prefer to secure the airway as early as possible after the drug administration in a rapid-sequence situation. Waiting more than 40 s after administration of the neuromuscular blocking agent will also require artificial ventilation before tracheal intubation in a significant number of patients. We therefore think that the design used in our study, that is, performing tracheal intubation 40 s post-rocuronium administration, is closely imaging the clinical needs during RSI of anaesthesia.
References
1 Abou-Arab MH, Heier T, Caldwell JE. Dose of alfentanil needed to obtain optimal intubation conditions during rapid-sequence induction of anaesthesia with thiopentone and rocuronium. Br J Anaesth (2007) 98:604–10.
2 Lavazais S, Debaene B. Choice of the hypnotic and the opioid for rapid-sequence induction. Eur J Anaesthesiol (2001) 23:66–70.
3 Wright PM, Caldwell JE, Miller RD. Onset and duration of rocuronium and succinylcholine at the adductor pollicis and laryngeal adductor muscles in anesthetized humans. Anesthesiology (1994) 81:1110–5.[Web of Science][Medline]
4 Klemola UM, Mennander S, Saarnivaara L. Tracheal intubation without the use of muscle relaxants: remifentanil or alfentanil in combination with propofol. Acta Anesthesiol Scand (2000) 44:465–9.[CrossRef][Web of Science][Medline]
5 Andrews JI, Kumar N, Van Don Brom RHG, et al. A large simple randomized trial of rocuronium versus succinylecholine in rapid-sequence induction of anaesthesia along with propofol. Acta Anaesiol Scand (1999) 43:4–8.[CrossRef]
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