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 us ed to achieve sedation and analgesia during pediatric oral procedures, yet there are few, if any, data that illustrate the ventilatory effec ts of N2O in children, especially when used in combination with additi onal central nervous system (CNS) depressants. It was hypothesized tha t the addition of N2O inhalation to oral midazolam premedication would enhance the sedative effects of the midazolam and add analgesia witho ut causing significant respiratory depression. The purpose of this stu dy was to test this hypothesis. Materials and Methods. Thirty-four hea lthy children about to undergo restorative dental treatment. under gen eral 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 p eriod. The effect of adding N2O on SpO(2), respiratory rate, PETCO2, V -T, and V-T/T-1 was examined and the levels of consciousness (consciou s vs deep sedation) before and during N2O inhalation were determined. Results: During the course of the study, no child developed hypoxemia (SpO(2) < 92%) nor clinically significant upper airway obstruction. Fo ur children who did not develop hypoventilation (defined as PETCO2 > 4 5 mm Hg) during the control period did so after initiation of N2O. Ove rall, there were no significant differences in SpO(2), PETCO2, V-T, or V-t/T-1 between the control and study periods. However, respiratory r ates were significantly higher in the first 10 minutes of N2O inhalati on when compared with the control period. Before starting N2O administ ration, 14 children were not clinically sedated, 19 children met the c riteria for conscious sedation, and one child met the criteria for dee p sedation; At the end of 15 minutes of N2O inhalation, 12 children we re 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 d ifferences 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 midazo lam, 0.7 mg/kg, did not result in clinically meaningful respiratory de pression nor upper airway obstruction, but did, in some children, caus e an increase in the level of sedation beyond simple conscious sedatio n.