Objective: To examine the short-term cardiorespiratory effects of intravenous morphine infusion in ventilated preterm infants.
Methodology: A randomized double-blind placebo-controlled trial in a neonatal intensive care unit. Twenty-six preterm infants (29-36 weeks gestation) with hyaline membrane disease requiring ventilatory assistance on the first day after birth were included in the study. A loading dose of morphine 100 micrograms/kg over 30 min followed by a continuous intravenous infusion at 10 micrograms/kg per hour was given. Primary measures were heart rate, blood pressure, respiratory rate and interaction of spontaneous respiration with mechanical ventilation. Secondary measures were durations of oxygen therapy, ventilator therapy and hospitalization as well as incidence of bronchopulmonary dysplasia, periventricular haemorrhage and pneumothorax.
Results: Morphine-treated infants spent a significantly greater percentage of total ventilated time breathing in synchrony with their ventilators (median [IQ] = 72[58-87] vs 31[17-51]%; P = 0.0008). Heart rate and respiratory rate, but not blood pressure, were reduced in morphine-treated infants. Duration of oxygen therapy was reduced (median [IQ] = 4.5[3-7] vs 8[4.75-12.5] days; P = 0.046).
Conclusions: Intravenous morphine infusion increases synchronicity of spontaneous and ventilator-delivered breaths in preterm infants. Morphine reduces heart rate and respiratory rate without reducing blood pressure, and may help to reduce duration of oxygen therapy in preterm infants with hyaline membrane disease.