Phenytoin Pharmacokinetics During Venoarterial Extracorporeal Membrane Oxygenation and Plasma Exchange

Currently, there is minimal guidance to antiepileptic dose adjustment for a patient requiring either venoarterial (VA) extracorporeal membrane oxygenation (ECMO) or plasma exchange (PLEX) therapy, and to our knowledge, there are rare guidances for a patient requiring both. Given the dangers with non-therapeutic concentrations of phenytoin, it is critical for the intensive care unit (ICU) practitioner to understand how the pharmacokinetic parameters of phenytoin change in critically ill patients requiring extracorporeal support. This case study presents a 41-year-old female transferred to the cardiovascular ICU requiring VA ECMO and PLEX for the treatment of systemic lupus erythematosus (SLE)-induced catastrophic antiphospholipid syndrome (CAPS). Free phenytoin concentrations were measured to assess the removal of phenytoin. There was no significant decrease in the free phenytoin concentrations post-PLEX and while on ECMO. Free phenytoin concentrations are not influenced in the setting of PLEX and while on ECMO.