Acute cardiopulmonary effects of pancuronium bromide in mechanically ventilated newborn infants

The short-term effects of muscle relaxation with pancuronium bromide on arterial blood gas values, heart rate, and arterial blood pressure were studied in 49 neonates receiving mechanical ventilation. After pancuronium administration, mean PaO₂ increased from 61.9±30.0 to 80.9±52.8 mm Hg (P=0.006), mean PaCO₂ decreased from 40.1±13.0 to 37.5±13.3 mm Hg (P=0.03), and mean heart rate rose from 146.2±24.9 to 161.0±20.5 beats/min (P<0.001). Arterial blood pressure did not change significantly. When results were analyzed by diagnosis (meconium aspiration syndrome, hyaline membrane disease, pneumonia), only infants with meconium aspiration syndrome had a significant improvement in oxygenation (P=0.008). Six of 18 patients with hyaline membrane disease responded to muscle relaxation, with a decrease in PaO₂ of 10mm Hg or more. No significant correlation was found between change in PaO₂ and birth weight, gestational age, postnatal age, or change in heart rate. A weak correlation (r=-0.37, P<0.006) was observed between change in PaO₂ and change in PaCO₂. Although the reasons for the divergence in response in different groups of patients are not entirely clear, the risk of deterioration with pancuronium therapy should be kept in mind, particularly if treatment in an infant with hyaline membrane disease is being considered.