Breathing patterns and levels of consciousness in children during administration of nitrous oxide after oral midazolam premedication.

PURPOSE

The combination of midazolam and nitrous oxide is commonly used to achieve sedation and analgesia during pediatric oral procedures, yet there are few, if any, data that illustrate the ventilatory effects of N2O in children, especially when used in combination with additional central nervous system (CNS) depressants. It was hypothesized that the addition of N2O inhalation to oral midazolam premedication would enhance the sedative effects of the midazolam and add analgesia without causing significant respiratory depression. The purpose of this study was to test this hypothesis.

MATERIALS AND METHODS

Thirty-four healthy children about to undergo restorative dental treatment under general anesthesia were premedicated with oral midazolam, 0.7 mg/kg, and were then exposed to 40% N2O for 15 minutes after a 5-minute control period. The effect of adding N2O on SpO2, respiratory rate, PETCO2, VT, and VT/TI was examined and the levels of consciousness (conscious vs deep sedation) before and during N2O inhalation were determined.

RESULTS

During the course of the study, no child developed hypoxemia (SpO2 < 92%) nor clinically significant upper airway obstruction. Four children who did not develop hypoventilation (defined as PETCO2 > 45 mm Hg) during the control period did so after initiation of N2O. Overall, there were no significant differences in SpO2, PETCO2, VT, or VT/TI between the control and study periods. However, respiratory rates were significantly higher in the first 10 minutes of N2O inhalation when compared with the control period. Before starting N2O administration, 14 children were not clinically sedated, 19 children met the criteria for conscious sedation, and one child met the criteria for deep sedation. At the end of 15 minutes of N2O inhalation, 12 children were not clinically sedated, 17 children met the definition of conscious sedation, three were deeply sedated, and one child had no response to IV insertion, implying a state of general anesthesia. There were no differences in sedation scores between the control and study periods (P = .6). Overall, seven children had an increase in their sedation score while breathing N2O, four had a decrease in their sedation score, and 22 had no change.

CONCLUSIONS

The addition of 40% N2O to oral midazolam, 0.7 mg/kg, did not result in clinically meaningful respiratory depression nor upper airway obstruction, but did, in some children, cause an increase in the level of sedation beyond simple conscious sedation.