Effect of increasing depth of propofol anesthesia on upper airway configuration in children.

BACKGROUND The upper airway tends to be obstructed during anesthesia in spontaneously breathing patients. The purpose of the current study was to determine the effect of increasing depth of propofol anesthesia on airway size and configuration in children. METHODS Magnetic resonance images of the upper airway were obtained in 15 children, aged 2-6 yr. Cross-sectional area, anteroposterior dimension, and transverse dimension were measured at the level of the soft palate, dorsum of the tongue, and tip of the epiglottis. Images were obtained during infusion of propofol at a rate of 50-80 microg.kg-1.min-1 and after increasing the depth of anesthesia by administering a bolus dose of propofol and increasing the infusion rate to 240 microg.kg-1.min-1. RESULTS Overall, the cross-sectional area of the entire pharyngeal airway decreased with increasing depth of anesthesia. The reduction in cross-sectional area was greatest at the level of the epiglottis (24.5 mm2, 95% confidence interval = 16.9-32.2 mm2; P < 0.0001), intermediate at the level of the tongue (19.3 mm2, 95% confidence interval = 9.2-29.3 mm2; P < 0.0001), and least at the level of the soft palate (12.6 mm2, 95% confidence interval = 2.7-22.6 mm2; P < 0.005) in expiration and resulted predominantly from a reduction in anteroposterior dimension. The airway cross-sectional area decreased further in inspiration at the level of the epiglottis. The narrowest portion of the airway resided at the level of the soft palate or epiglottis in the majority of children. CONCLUSION Increasing depth of propofol anesthesia in children is associated with upper airway narrowing that occurs throughout the entire upper airway and is most pronounced in the hypopharynx at the level of the epiglottis.