Alfentanil in infants and children with congenital heart defects

The use of an alfentanil infusion as a supplement to a nitrous oxide-halothane anesthetic and the pharmacokinetics of alfentanil were evaluated in infants and children undergoing surgery for correction of congenital heart defects. Eleven patients, six infants and five children, were studied. Anesthesia was induced with nitrous oxide-halothane and pancuronium, 0.15 mg/kg. After intubation, anesthesia was maintained with nitrous oxide-oxygen and halothane to a maximum inspired concentration of 0.6%. After administration of atropine, 20 tag/kg, alfentanil, 20 μg/kg, was given, followed by a continuous infusion of 1 μgkg/min, which was stopped after closure of the sternum. Supplemental boluses of alfentanil, 5 μ/kg, were given when, during surgery, blood pressure and/or heart rate increased more than 20% above control values. At the end of surgery, after antagonism of residual neuromuscular blockade, the patients were extubated. Arterial blood samples were collected at regular intervals during surgery and for six hours thereafter for determination of alfentanil plasma concentrations by gas chromatography. Pharmacokinetic data were calculated using the method of residuals and noncompartments moment analysis. Although atropine was administered, heart rate decreased significantly (2.5% to 15%) in all infants after administration of alfentanil. In the older children, blood pressure decreased 10% to 35%. In the period before bypass, three infants and four children needed supplemental boluses of alfentanil. During and after bypass, anesthesia was adequate. All patients could be extubed within 34 minutes of stopping the alfentanil infusion. Naloxone was not required in any patient, and postoperative respiratory depression did not occur. In the infants and children, total plasma clearance was 8.2 ± 2. mL/kg/min and 6.3 ± 0.8 mL/kg/min, respectively. Distribution volume was 0.48 ± 0.12 L/kg and 0.31 ± 0.08 L/kg, and elimination half-life was 69 ± 25 min and 62 ± 9 min, respectively. It is concluded that a continuous infusion of alfentanil as a supplement to nitrous oxide-halothane anesthetic is a feasibly method of anesthesia in infants and children undergoing surgery for correction of congenital heart defects.