A novel method for laryngeal mask airway size selection in paediatric patients

The successful use of the laryngeal mask airway in children partly depends on the correct selection of size. Most anaesthesiologists rely on the weight-based table which is often difficult to remember. A simple method allowing an adequate choice of the correct size may be highly desirable.

To test the hypothesis that the size of the external ear (pinna) of the child may be used as proxy for the required size of laryngeal mask airway.

A descriptive study.

King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia.

Two hundred and ten paediatric patients aged 6 months to 15 years, of either sex, American Society of Anesthesiologists (ASA) 1-2 and scheduled for routine ophthalmological procedures from 1 March to 31 December 2010. Emergency cases, patients with a full stomach or with a history of any oropharyngeal lesion other than tonsillar hypertrophy were excluded.

The size of the external ear was measured with a ruler in vertical and horizontal dimensions in the first 30 patients, and visually evaluated for the remaining patients. For all, the nearest corresponding size of partially inflated laryngeal mask airway was chosen and inserted after induction. The correct placement was assessed using predefined criteria.

Insertion and good ventilation was achieved in 196 (93.3%) on first attempt. Fourteen patients (6.7%) required a second attempt and the main reason for failure was an audible leak because of smaller size.

Choosing the size of the laryngeal mask airway in children according to the size of the external ear was associated with a success rate of 93% which is comparable with that reported in the literature when the tables are used. This simple method may allow a rapid choice of the correct size of laryngeal mask airway and may eliminate the need to remember different tables or formulae.