Response to Kessell and Trapp

Sir, Williamson and colleagues’ description of their successful use of rocuronium for rapid sequence induction with subsequent reversal using sugammadex in an obstetric cohort is interesting for a number of reasons. Firstly, the paper states that the mean duration of action of rocuronium at a dose of 1.2 mg/kg is 60–73 min and that this ‘is significantly longer than most obstetric procedures’. However, the authors’ own results demonstrate a mean time from administration to reversal of rocuronium of 62 min, which although not supporting their assertion regarding duration of obstetric procedures, does seem to provide evidence for an extended duration of action of rocuronium in the obstetric patient. Secondly, in referring to a case series of seven obstetric patients who received rocuronium at a lower dose of 0.6 mg/kg, the authors state that a dose of sugammadex of 3 mg/kg is not supported by the literature. Profound (deep) block has been described as being present when there is a post-tetanic count (PTC) of two or less for which the recommended dose of sugammadex for reversal is 4 mg/kg. Moderate (shallow) block is described as being present when the train-of-four count is two or more responses and the recommended dose of sugammadex for reversal is 2 mg/kg. Very often the block is somewhere between these points, as in Williamson et al. ‘s series where 7/17 patients had a PTC of > 2 but a train-of-four response of < 2. Consideration of dose-response curves suggests a reversal dose of 3 mg/kg may be appropriate particularly when, as in the authors’ hospital, normal practice involves careful monitoring of neuromuscular function and also bearing in mind the current expense of sugammadex. Thirdly, in discussing the use of rocuronium and sugammadex in place of suxamethonium, the authors highlight the fact that with rocuronium, multiple intubation attempts can occur without deterioration of the intubating conditions. Recently published guidelines suggest that multiple attempts at intubation in the obstetric setting are to be avoided and that each attempt should be completed within 1 min. Some authors advise no more than two attempts in the obstetric patient. Our concern is that the use of rocuronium may lead the anaesthetist to lose situational awareness and become fixated upon trying to intubate rather than proceeding along a failed intubation pathway. One could argue that the fact that suxamethonium wears off spontaneously after 7–10 mins is advantageous as this allows plenty of time for two intubation attempts and also gives a visual reminder that it is time to abandon intubation. Finally, we congratulate the authors on their work in moving forward our understanding of the place of rocuronium/ sugammadex in obstetric anaesthesia and we also look forward to further studies in this area. We declare no conflict of interest.