Upper airway obstruction during midazolam/nitrous oxide sedation in children with enlarged tonsils

The purpose of this nonrandomized, case-control study was to examine the incidence and severity of upper airway obstruction (UAO) in children with enlarged tonsils during inhalation of nitrous oxide (N2O).

Following premedication with oral midazolam, 0.5 mg/kg, measurements were collected during a 3-minute control period followed by 3 minutes of breathing 50% N2O in oxygen. An unblinded anesthesiologist held a facemask over the child's mouth and nose without supporting the head or neck, or attempting to maintain airway patency. Every 20 seconds, the degree of airway obstruction was graded as none, partial, or complete. Twenty-five children presenting for tonsillectomy and 25 controls without enlarged tonsils participated.

During 50% N2O inhalation, 14 children (56%) in the tonsillectomy group, and four children (16%) in the control group demonstrated partial UAO. One child in the tonsillectomy group with partial UAO developed hypoxemia (SpO2 72%). One child in the tonsil group developed complete UAO during inhalation of 50% N2O.

Children who receive sedation with oral midazolam and 50% N2O inhalation may exhibit significant UAO, especially in the presence of enlarged tonsils. Presedation physical exams should evaluate the presence of tonsil size during examination of the mouth and airway.