Sub-glottic Diameter Measured by Ultrasonography Predicts Outer Diameter of the Clinically Best Fit Endotracheal Tube in Infants Undergoing Pediatric Cardiac Surgery

BACKGROUND: Tracheal intubation with an oversized endotracheal tube (ETT) in a pediatric patient can lead to serious complications following extubation, including stridor, hoarseness, difficulty in breathing, increased work of breathing, respiratory failure, cardiac failure, and reintubation. Whereas undersized ETT may lead to erratic delivery of preset tidal volume during mechanical ventilation and increase the risk of aspiration of gastric contents. This study investigates the correlation between ultrasound measured subglottic airway diameter and ETT size selected by the anesthesiologists in infants undergoing cardiac surgery. MATERIALS AND METHODS: We measured the subglottic airway diameter in sniffing position with a 25 mm linear high frequency hockey stick transducer using ultrasonography machine and compared it to the ETT size selected by the anesthesiologist. We analyzed the agreement between the two methods. RESULTS: One hundred and three infants undergoing cardiac surgery were included. The median age of the infants were 30 days (interquartile range 19-90 days). The anesthesiologist's ETT size choice matched ultrasonography (USG)-measured subglottic diameter in all patients, with 90 receiving 3.5 mm ID and 13 receiving 4.0 mm ID ETTs. Upsizing of the ETT due to air leak was not required in any patient. A significant correlation was found between USG-measured ETT size and the anesthesiologist's choice of clinically best-fit ETT. CONCLUSIONS: Subglottic diameter measured by USG reliably predict outer diameter of the ETT size in infants undergoing cardiac surgery. The finding is particularly valuable in low-volume centers where anesthesiologists may have limited experience with pediatric cardiac surgery.