Supreme! Or is it?

Abstract

We would like to congratulate Dr Cook et al. on an excellent study [1]. Having a degree of experience in using LMA Supreme™ (SLMA, Intavent Orthofix, Maidenhead, UK), we would like to add some comments. We use the SMLA for selective patient groups and specific surgery, for example, dacrocystorhinostomy where we use total intravenous anaesthesia and ventilate the lungs via the single-use SMLA. Due to the nature of the surgery there is nasopharyngeal bleeding and blood trickles into the oropharynx. In these cases the perceived advantages of the SLMA are better airway protection from nasopharyngeal bleeding, the achievement of higher airway leak pressure during positive pressure ventilation and the option to pass a gastric tube via the drain tube to aspirate blood from the stomach. After reading Cook et al’s paper, however, we feel that we may need to re-assess our practice. Reasons for this include, firstly, their finding that airway leak pressure was no higher that that achieved with i-gel™ (Intersurgical, Wokingham, UK) in a similar study [2] and does not achieve levels seen with Pro-seal™ LMA (PLMA; Intavent Orthofix, Maidenhead, UK) [3]. Importantly, in the i-gel study only size 4 was used in all patients (weight range 42–113 kg), although no data were presented on how many of these were outside the manufacturer’s recommended weight range of 40–90 kg for this size. In this study the SLMA was sized appropriately and despite this, faired no better than the i-gel. As the study mentioned, the other two clinical studies of the SLMA reported a higher airway leak pressure of 28 cmH2O [4] and 37 cmH2O [5], but both were much smaller studies. Consequently, it seems that the SLMA does not confer any advantages over its direct competitors in this respect. Secondly, it is well recognised that an ideal supraglottic airway device provides access to the glottis so that an tracheal tube, Aintree catheter or a bronchoscope with a loaded tracheal tube could be passed into the trachea. Due to its design the SLMA is unable to achieve this and therefore, in our opinion, this gives its direct competitors an advantage. Moreover, it is fairly rigid and anatomically preformed, which possibly facilitates introduction in normal airways, but in fixed flexed neck deformities where one might use a supraglottic airway device, it may be very difficult or impossible to introduce into the mouth. Again, in our opinion, its direct competitors would fair better in this respect. Finally, the ability to pass a gastric tube into the stomach is a useful feature. The SLMA has this ability, with similar success rates to other devices; however even here it fairs no better than the PLMA as the drain tube only allows the passage of a smaller gastric tube (14 Fr vs 16 Fr), but it is larger than the i-gel allows (drain tube size 12 Fr for size 4). Although it seems reasonable to suggest that the drain tube size could play a major role in preventing aspiration in cases of regurgitation, there are no data to confirm it to date. To conclude, after reading this paper we now think that the SLMA falls in between the PLMA and the i-gel as a choice of supraglottic airway device. Which device should we choose? Perhaps now we would choose to use one or the other over the SLMA in most clinical situations, as there are no proven benefits of it over the other two and at least some theoretical drawbacks. Of course, we are happy to be proved wrong by further research.