Respiratory depression at birth-value of Apgar score and ventilatory measurements in its detection

The purpose of this investigation was to determine the value of ventilatory measurements and Apgar score in the diagnosis of respiratory depression in the newborn infant. The following were the results of the determinations made in 24 neonates whose mothers had received meperidine in a total dose up to 3 mg/kg within three hours prior to delivery: Respiratory rate, 51±3.7/minute; tidal volume, 21.4±1.5 ml; minute ventilation, 339±24 ml/kg×minute; end tidal CO₂, 40.8±1.3 mm Hg; ventilatory response to CO₂, 21.8±2.7 ml/kg×minute×mm Hg Pa_CO2. The mean Apgar score was 7.1 and 9.0 at 1 and 5 minutes, respectively. None of the determinations were indicative of respiratory depression with the exception of the slope of the CO₂ response curve; it was considered to be below the normal range. No correlations existed between the CO₂ response curve and any of the other values. It is concluded that meperidine administered to mothers in labor in the described dose will not significantly alter Apgar score, V_E, V_T, RR, and Pa_CO2 in the newborn infant. The extent of respiratory center depression could be determined only by the decreased ventilatory response to CO₂.