Aim of our study is to evaluate the predictive value of ultrasonographic (USG) measurement of thyrohyoid distance for difficult intubation and determination of optimal endotracheal tube size by using USG in pediatric patients undergoing elective surgery.

After ethics committee approval and parental consent were obtained, 119 patients undergoing genitourinary surgery or inguinal hernia repair under general anesthesia, were included in study. Patients with head or neck anomalies, syndromic patients, patients undergoing emergency surgery and patients with a history of difficult airway were excluded from the study. Patients were grouped according to their ages; Group I (1-2 years,n=38), Group II (3-5 years,n=46) and Group III (6-8 years,n=35). USG measurements were performed following sevoflurane induction in groups I and II. In group III, USG measurements were performed following premedication with intravenous midazolam 0.05 mg/kg . Thyrohyoid distance, glottic and subglottic diameters were measured with ultrasonography. The size of the endotracheal tube according to Bae's formula ( internal diameter of Endotracheal tube = 0.705 x subglottic diameter - 0.091) was calculated and recorded. Before intubation, endotracheal tube (cuffed/uncuffed) was selected using age-related formulas. In group II, anaesthesia induction was achieved with propofol 2 mg/kg. In all groups, endotracheal intubation was achieved with fentanyl 2μg/kg and rocuronium 0.6 mg/kg. Endotracheal tube size was considered as optimal when a leak was detected at 20-30cmH₂O inflation pressures. If a resistance was felt in the subglottic region, the tube was exchanged with a smaller and was exchanged with a larger (0.5 mm) size if a leak occurred at inflation pressures lower than 20cmH₂O. Intubation duration , Cormack-Lehane scores and Intubation Difficulty Scale scores were recorded. For comparison of age related formula and Bae 's formula, only patients who were intubated with un-cuffed endotracheal tube were evaluated.

Inclusion Criteria:

• Aged between 1 and 8 years
• Elective surgery

Exclusion Criteria:

• Patients with head or neck abnormalities
• Syndromic patients
• Emergency surgery and patients with a
• History of difficult airway
• Allergy to ultrasound gel