Hyomental Distance Measured Ultrasonography Versus Weight-based Criteria for Laryngeal Mask Size Selection in Children. A Prospective, Randomised Controlled Study

• The laryngeal mask airway (LMA) is classified as one of the supraglottic devices that have been extensively adopted as an adjunctive or alternative technique to tracheal intubation or mask ventilation for airway management in short-time surgery. Moreover, it is characterized by ease of placement and removal, less injury to the respiratory tract, better tolerability by patients, improved hemodynamic stability, less coughing, less sore throat, avoidance of laryngoscopy, and hands-free airway. However, it is not suitable to overcome functional airway problems and mechanical airway obstruction.
• Although the weight-based method was considered the traditional method for the selection of the optimal LMA size, a clinical practice viewed that this method is not always applicable as there is no linear correlation between the upper airway anatomy and body weight with the presence of usual individual anatomical variation.
• Fortunately, ultrasonography gave high-resolution images of the anatomic structures of the upper airway comparable to computed tomography and magnetic resonance imaging, Ultrasound measurements were applied for the hyomental distance and the hyomental distance ratio. Some studies revealed variable sensitivity and specificity.
• This prospective randomized controlled study will aim to assess the efficacy and safety of ultrasonographic measured hyomental distance in the optimization of the laryngeal mask(LMA)size selection and placement in pediatric patients Operational Design

A) Pre-anaesthetic management:

• Informed written parental consent will be taken from all participants.
• Medical history and complete clinical examination.
• Routine laboratory investigation including :

1. CBC
2. CRP
3. INR, PT & PTT

• Patients will fast for at least 8 hours before surgery.
• Routine Monitoring, including heart rate (HR), oxygen saturation (SpO2) and noninvasive blood pressure (NIBP) in the pre-anaesthesia room (Base Line Data).
• A peripheral intravenous line (24-22G) will be inserted.
• A premedication of 0.01 mg/kg Atropine will be administrated IM 1 hour before surgery.

B) Induction of general anaesthesia: