Cardiorespiratory stability of very low birth weight premature neonates following postoperative administration of morphine

Abstract

Abstract The cardiac and respiratory status of mechanically ventilated premature neonates, who received intraoperative fentanyl during thoracotomy for ligation of a patent ductus arteriosus ( n =24), were evaluated before and after administration of the first postoperative dose of morphine. The neonates were 26.1 ± 2.1 (mean ± SD) weeks gestational age and 13.8 ± 8.1 (mean ± SD) days of age at the time of surgery. Changes in heart rate, arterial blood pressure, respiratory rate and oxygen saturation were measured preoperatively and immediately before and 20 and 60 minutes after parenteral administration of the morphine dose. Heart rate values increased (mean increase 6%; p=0.02) and respiratory rate values decreased (mean decrease 23%; p=0.01) postoperatively. There were no significant differences in heart rate, respiratory rate, blood pressure and oxygen saturation following administration of morphine. Mean arterial blood pressure decreased following the administration of morphine in a few neonates already being treated for hypotension. However, given the severity of illness of these neonates during the immediate postoperative period, it is difficult to directly attribute clinically significant hypotension to morphine administration alone. The findings from this study suggest that fears of morphine-induced bradycardia and hypotension in normovolaemic critically ill premature neonates during the immediate postoperative period are not warranted and should not be used as reasons for withholding opioid analgesia from these neonates. Use of a continuous infusion of morphine or fentanyl may be more appropriate methods of postoperative analgesia for hypotensive neonates or those at risk for hypotension.