Evaluation of the Effects of Extracorporeal Membrane Oxygenation on Antiepileptic Drug Serum Concentrations in Pediatric Patients

Patients supported on extracorporeal membrane oxygenation (ECMO) have an increased incidence of seizures. Phenobarbital (PB) and fosphenytoin (fos-PHT) are common antiepileptic drugs (AEDs) used to manage seizures in the pediatric population; however, it is unknown what effect ECMO has on the serum concentrations of AEDs. The purpose of this study is to evaluate the effect of ECMO on AED serum concentrations. A retrospective, matched-cohort study was performed in patients younger than 18 years who received ECMO and were treated with intravenous (IV) PB or fos-PHT at Texas Children's Hospital between 2004 and 2014. Patients receiving IV AED therapy and ECMO were matched, based on age, sex, and weight, with patients receiving IV AED therapy without ECMO. The 24-hour cumulative AED dose, serum concentrations, number of doses per serum concentration drawn ratio, volume of distribution, therapeutic serum concentrations, and time to therapeutic serum concentration were compared between both groups. The fos-PHT and PB groups were analyzed in all patients and in neonates only. Fourteen patients met inclusion criteria. The fos-PHT neonatal (20.1 vs 11.3 mg/kg/day, p = 0.044), PB composite (33.9 vs 21.6 mg/kg/day, p = 0.012), and PB neonatal (40.3 vs 20 mg/kg/day, p = 0.04) had larger 24-hour cumulative doses compared with non-ECMO patients. Lower serum concentrations were observed in the PB composite ECMO group (19.1 vs 35.4 mg/L, p < 0.001) and the PB neonatal ECMO group (20.5 vs 27.8 mg/L, p = 0.01) compared with non-ECMO patients. Pediatric patients receiving PB on ECMO and neonatal patients receiving fos-PHT on ECMO required larger doses, and in pediatric patients achieved lower serum concentrations, suggesting the necessity for alternative dosing strategies in these populations.