Endotracheal tube intubation carries with it a number of disadvantages. The laryngeal mask airway [LMA (LMA is a registered trade mark of The Laryngeal Mask Company Ltd, an affiliate of Teleflex Incorporated, Pennsylvania, USA)] is a safe and efficient alternative. A retrospective review published in 2013 reported a 14.2% complication rate and a 6.8% failure rate, requiring conversion to endotracheal tube, using the flexible LMA in paediatric adenotonsillectomy.1
We have used the flexible LMA successfully for many years and wished to prospectively measure the performance of this airway in elective day case paediatric ear, nose and throat (ENT) surgery for adenoidectomy and (adeno) tonsillectomy (all requiring the insertion of a gag), recording the conversion from flexible LMA to endotracheal tube rate during anaesthesia, with reasons for failure.
Over a 2-year period, 366 children were admitted to a dedicated children's ambulatory care ward for elective day case ENT surgery. Only children with American Society of Anesthesiologists (ASA) physical status grades 1 and 2 were included. Eighteen exclusions included 10 children less than 16 kg, as below this the oropharynx is typically too small to give an adequate view with a flexible LMA and gag in situ, and three children with a predicted poor view because of the presence of grade 4 tonsils. General anaesthesia was induced with propofol and fentanyl by consultant anaesthetists experienced in paediatric anaesthesia. A single-use Ambu AuraFlex reinforced flexible LMA (Ambu, Ballerup, Denmark) was inserted. Size of flexible LMA and cuff volume was based on patient weight and manufacturer's instructions. The children breathed spontaneously, with anaesthesia maintained with sevoflurane in oxygen and air via a circle breathing system. The same consultant ENT surgeon performed all the surgical operations. As the flexible LMA is used for paediatric ENT general anaesthesia as part of our routine clinical practice, local ethical committee approval was not sought prior to conducting this prospective audit.
A total of 348 children were included in the prospective data collection. 303 children were ASA physical status grade 1. 54% were male, mean age was 6.9 years and mean weight was 26.9 kg. 45.7% of procedures were for adenoidectomy (± grommets), 35% tonsillectomy (± grommets) and 19.3% adenotonsillectomy (± grommets). In 15 children the flexible LMA failed, requiring conversion to an endotracheal tube during the anaesthetic. The overall conversion rate was 4.3%. Indications for conversion are summarised in Table 1. Seven conversions occurred before gag insertion, with eight after gag insertion. In these eight cases, the conversion was carried out prior to surgery. The three cases converted because of poor surgical view; all had grade 4 tonsils and in retrospect should have been excluded from flexible LMA use. Other than transitory desaturation (caused by the stated indication for conversion), no child requiring conversion experienced complications during the conversion or surgical procedure, nor did any suffer postoperative anaesthetic complications. There were no urgent re-operations for primary haemorrhage after (adeno) tonsillectomy.
There are numerous benefits of the LMA over the endotracheal tube for paediatric day case ENT surgery.2 Muscle relaxants and laryngoscopy are avoided, reducing airway instrumentation and cardiovascular stimulation. Case duration is shortened and the child may be recovered by experienced recovery staff with the LMA in situ, leading to increased theatre utilisation. Patients have a smoother emergence with LMAs, with reduced incidence of bronchospasm, desaturation, coughing, straining, hoarse voice1 and sore throat.3 A recent meta-analysis comparing LMA and endotracheal tube perioperative respiratory complications in children, showed a significant reduction in the incidence of postoperative desaturation, laryngospasm, cough and breath holding, and in recovery stay duration with LMA use.4 An additional consideration is that upper respiratory tract infections are common in children requiring ENT surgery. Von Ungern-Sternberg et al.5 showed a two-fold increase in respiratory complications with LMA use in the presence of an upper respiratory tract infection, compared with an 11-fold increase in complications using an endotracheal tube.
Concerns regarding the use of LMAs for ENT surgery have included difficulty in flexible LMA placement, protection of the airway from blood and debris soiling, surgical view and obstruction of the flexible LMA after application of the Boyle–Davis gag. With the digital insertion technique and experience, we believe that difficulty in flexible LMA placement is not an issue. In paediatric adenotonsillectomy, the flexible LMA has been shown equivalent to cuffed endotracheal tubes and superior to uncuffed endotracheal tubes at protecting from blood aspiration.6 Inadequate view for adenoidectomy and tonsillectomy, surgery can be an issue in patients with a small oropharynx or large tonsils. Reviewing obstruction of the flexible LMA after gag insertion, recent studies have shown that this does not seem to be a major issue. In a randomised study of 117 patients for paediatric adenotonsillectomy, there were only two cases of obstruction, which resolved after gag adjustment, with no conversions from flexible LMA to endotracheal tube.6
A UK 2009 questionnaire to members of the Association of Paediatric Anaesthetists of Great Britain and Ireland showed that 79% routinely used an endotracheal tube for paediatric tonsillectomy patients.7 However, in this prospective audit of flexible LMA use in paediatric day case ENT surgery, excluding children less than 16 kg, ASA physical status grades 3/4 and those with grade 4 tonsils, we found the flexible LMA safe to use with an overall conversion rate to endotracheal tube of 4.3%. The pre-gag failures caused by excess airway secretions, hypoxia, laryngospasm and inadequate ventilation may have been a reflection of the increased likelihood of the presence of recent or undiagnosed, concurrent upper respiratory tract infection in this sub-group of children. From experience, we recommend using the smaller sized flexible LMA when the child's weight is borderline for manufacturer's guidance and suggest that un-taping the flexible LMA from the face before gag insertion avoids the gag lifting the flexible LMA off the larynx on a fulcrum formed by the tape. We also believe that a tonsil gag blade one size larger than anticipated allows the flexible LMA to sit more anatomically in the pharynx. Looking at the open mouth in a draped child, it is not possible to tell if the airway is a flexible LMA or endotracheal tube (Fig. 1).
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