Deep or awake removal of laryngeal mask airway in children at risk of respiratory adverse events undergoing tonsillectomy – a randomised controlled trial

This was a single centre open-label parallel-arm randomised trial performed at Princess Margaret Hospital in Perth. Children undergoing tonsillectomy with a Laryngeal Mask Airway (LMA) and who had at least one risk factor for perioperative respiratory adverse events (PRAE), were randomised to have the LMA removed deep or awake. Their list of risk factors is evidence based from a large retrospective study in their own institution. Deep removal occurred in theatre and was defined as having an end tidal sevoflurane concentration >1 MAC (age-adjusted); awake removal was defined as when the child demonstrated facial grimace, adequate tidal volume and respiratory rate, coughing with open mouth or opening of their eyes and purposeful movements. Awake airway removal could occur in theatre or in the Post Anaesthesia Care Unit (PACU). The hypothesis was that PRAE would be 15% higher in the “awake” group than in the “deep” group. The primary outcome was the rate of occurrence of PRAE. Previous evidence on deep versus awake LMA removal in tonsillectomy is limited, but in children without risk factors, there does not appear to be an association between PRAE and timing of LMA removal.

The rate of PRAE was 10% higher in the awake vs the deep group (45% vs 35%), but this did not reach statistical significance as the study was powered to detect a larger difference of 15%. Length of PACU stay was no different between groups. A secondary outcome of PRAE in the PACU phase of recovery did show a statistically higher rate in the awake group (39% vs 26%). There was also a higher rate in children with OSA and awake removal (56% vs 33% in mild-mod OSA). Coughing and desaturation were the most common events recorded.

Take Home Message and Comments

Deep removal of the LMA in tonsillectomy patients with risk factors for PRAE might lead to a smoother emergence with fewer respiratory events in PACU.  Length of PACU stay is not affected.

This group has produced a wealth of literature on PRAE, and as such has a list of well-defined PRAE. This study looked at a cohort of patients in which the overall rate of PRAE is high, in order to have a good chance of detecting a difference. I have three comments to make:  firstly, 15% was a fairly large difference to power the study on, and it was not very clear to me where this figure came from. The 10% difference that was found could also be considered clinically relevant (NNT=10). Secondly, not all PRAE are equal in severity. Although the overall trend was favouring deep removal of the LMA, the incidence of airway obstruction was higher in the deep group (NS), arguably a more important PRAE and harder to recognise than coughing or desaturation.  Finally, this study is applicable to those using LMA to secure the airway for tonsillectomy under volatile anaesthesia. It is not relevant to those using TIVA or endotracheal intubation.

Reviewed by: Dr Claire Furyk