LEVELS OF CONSCIOUSNESS AND VENTILATORY PARAMETERS IN YOUNG-CHILDREN DURING SEDATION WITH ORAL MIDAZOLAM AND NITROUS-OXIDE

Objective: To determine the ventilatory effects and levels of consciou sness achieved during sedation with the combination of oral midazolam and inhaled nitrous oxide. Design: Case series. Setting: Surgical suit e. Patients: Twenty-two consecutive children, aged 1 to 3 years, were seen for elective, ambulatory surgery. Interventions: Patients were pr emedicated with oral midazolam hydrochloride, 0.5 mg/kg, and then brea thed 4 concentrations of nitrous oxide (N2O) in oxygen (15%, 30%, 45%, and 60%) for 4 minutes at each concentration prior to induction of ge neral anesthesia. Main Outcome Measures: Levels of consciousness (cons cious vs deep sedation) and ventilatory parameters: respiratory rate, end-tidal carbon dioxide tension (PETCO(2)), and oxyhemoglobin saturat ion (SPO2). Upper airway obstruction was diagnosed by clinical assessm ent by an experienced pediatric anesthesiologist (R.S.L.) and respirat ory impedance plethysmography. Results: During inhalation of N2O, 12 o f the 20 children demonstrated a mild degree of ventilatory depression ; PETCO(2) values were equal to or greater than 45 mm Hg during at lea st 2 concentrations of N2O studied. There were no significant changes in SPO2 or PETCO(2) with increasing concentrations of N2O (P>.05). Res piratory rates tended to be lower during inhalation of 15% N2O than at higher concentrations (P=.05). No child developed upper airway obstru ction or hypoxemia (SPO2 <92%) at any level of N2O inhalation. Sedatio n scores were significantly higher at 60% N2O than at all other concen trations of N2O (P<.02). At 15% N2O, 12 children were not clinically s edated, 8 children met the American Academy of Pediatrics definition o f conscious sedation, and no child met the definition of deep sedation . At 30% N2O, 10 children were not clinically sedated, 9 met the defin ition of conscious sedation, and 1 child met the definition of deep se dation. At 45% N2O, 9 children were not clinically sedated, 9 met the definition of conscious sedation, and 2 met the definition of deep sed ation. At 60% N2O, 6 children were not clinically sedated, 6 met the d efinition of conscious sedation, 6 met the definition of deep sedation , and 1 child progressed to a deeper level of sedation in that there w as no response to a painful stimulus. One child was withdrawn from the study during inhalation of 45% N2O because of emesis. Conclusions: Th e combination of oral midazolam, 0.5 mg/kg, and up to 60% inhaled N2O caused mild ventilatory depression in some children and resulted in a progression from conscious to deep sedation beginning at 30% N2O. When using this particular combination of sedatives, practitioners should monitor each child's mental status continuously and adhere to the appr opriate published guidelines for the monitoring and management of such patients.