• Maarja Hallik, Mari-Liis Ilmoja, Tõnis Tasa, Joseph F Standing, Kalev Takkis, Rūta Veigure, Karin Kipper, Tiiu Jalas, Maila Raidmäe, Karin Uibo, Joel Starkopf, and Tuuli Metsvaht.
• Department of Anesthesiology and Intensive Care, Institute of Clinical Medicine, University of Tartu, Tartu, Estonia.
• Pediatr Crit Care Me. 2019 Jul 1; 20 (7): 621-629.

ObjectivesThe postoperative course of patent ductus arteriosus ligation is often complicated by postligation cardiac syndrome, occurring in 10-45% of operated infants. Milrinone might prevent profound hemodynamic instability and improve the recovery of cardiac function in this setting. The present study aimed to describe the population pharmacokinetics of milrinone in premature neonates at risk of postligation cardiac syndrome and give dosing recommendations.DesignA prospective single group open-label pharmacokinetics study.SettingsTwo tertiary care neonatal ICUs: Tallinn Children's Hospital and Tartu University Hospital, Estonia.PatientsTen neonates with postmenstrual age of 24.6-30.1 weeks and postnatal age of 5-27 days undergoing patent ductus arteriosus ligation and at risk of postligation cardiac syndrome, based on echocardiographic assessment of left ventricular output of less than 200 mL/kg/min 1 hour after the surgery.InterventionsMilrinone at a dose of 0.73 μg/kg/min for 3 hours followed by 0.16 μg/kg/min for 21 hours. Four blood samples from each patient for milrinone plasma concentration measurements were collected.Measurements And Main ResultsConcentration-time data of milrinone were analyzed with nonlinear mixed-effects modeling software (NONMEM Version 7.3 [ICON Development Solutions, Ellicott City, MD]). Probability of target attainment simulations gave a dosing schedule that maximally attains concentration targets of 150-250 μg/L. Milrinone pharmacokinetics was described by a one-compartmental linear model with allometric scaling to bodyweight and an age maturation function of glomerular filtration rate. Parameter estimates for a patient with the median weight were 0.350 (L/hr) for clearance and 0.329 (L) for volume of distribution. The best probability of target attainment was achieved with a loading dose of 0.50 μg/kg/min for 3 hours followed by 0.15 μg/kg/min (postmenstrual age < 27 wk) or 0.20 μg/kg/min (postmenstrual age ≥ 27 wk).ConclusionsPopulation pharmacokinetic modeling and simulations suggest a slow loading dose followed by maintenance infusion to reach therapeutic milrinone plasma concentrations within the timeframe of the postligation cardiac syndrome.

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