The effect of midazolam after intranasal administration on spontaneous respiration and respiratory control in young children

Abstract

The aim of this study was to investigate the influence of intranasally administered midazolam in different doses on spontaneous respiration in children. 40 children received in randomised order 0.2, 0.4 or 0.6 mg/kg b.w. midazolam intranasally or NaCl 0.9% as control. 10 minutes later, anaesthesia was induced by inhalation of halothane, nitrous oxide and oxygen. The children were breathing spontaneously at a PEEP of 5 cm H2O on a circle system with a fresh gas flow of 61/min (FIO2 = 0.33). Intubation was performed in deep anaesthesia without muscle relaxant. Halothane concentration was reduced to an endtidal concentration of 0.4 Vol%. With a baby pneumotachograph, minute ventilation, tidal volume, peak inspiratory and expiratory flow and respiratory rate were recorded during quiet breathing. Endtidal pCO2 was measured. Ventilation was then stimulated with 0.2 and 0.41/min CO2 and the same parameters were recorded. Regression analysis was performed for minute ventilation and endtidal pCO2 to obtain the slope which is a parameter for the sensitivity of the chemoreceptor mediated control of ventilation. The tidal volume and peak inspiratory flow were significantly reduced for a dose of 0.6 mg/kg compared to the control group. No statistical difference could be found for any other parameter between the control and study groups. We conclude that nasally administered midazolam reduces tidal volume and inspiratory peak flow in spontaneously breathing children at a dose of 0.6 mg/kg b.w. compared to control during halothane--nitrous oxide--oxygen anaesthesia. The CO2 mediated control of respiration under this condition is preserved.