Abstracts

Rationale: Phenytoin(PHT)is one of the most commonly used antiepileptic drugs (AEDs) in the intensive care unit (ICU) for treatment of seizures in critically ill patients. Therapeutic drug monitoring of PHT is necessary to ensure therapeutic and nontoxic levels. Hypoalbuminemia, renal failure, and interactions with other highly protein-bound drugs alter protein binding of PHT. In critically ill patients, doses of PHT are poorly correlated with serum drug concentrations because of altered drug metabolism and albumin concentrations Therefore, maintaining therapeutic serum concentrations of PHT in this patient population is reported to be difficult. APACHEII and SAPS II are two of the most commonly used scales to assess the severity of underlying medical conditions and predict the mortality rate in critically ill patients. The aim of this study is to determine the fluctuation in free and total PHT levels in critically ill patients and to find out the relation of PHT level fluctuations to severity of underlying medical condition using APACHE II and SAPS II scale scores. In patients with more severe illness and complicated hospital course, PHT levels may be harder to predict. Methods: We conducted a retrospective (chart review) analysis. The approval from institutional review board (IRB) was obtained before this study was conducted. The charts of 42 critically ill patients admitted to Cooper university medical center intensive care unit who received intravenous PHT to treat or prevent seizures were reviewed. The following information was obtained; age, gender, concomitant medical conditions, loading and maintenance doses of PHT, total and free PHT levels, critical care mortality scales APACHIE II and SPAPS II. Patients older than 18 years old were included for chart review. For this study the necessary information was retrieved using Cooper University medical center project IMPACT database and Cooper University Medical Center Epic electronic medical records from 2008 to 2010. Multivariable logistic regression models were used to determine association between PHT levels, loading dose, maintenance dose and APACHE II and SAPS II scores. Results: The range of free PHT level was between 0.3 and 3.2 while it was from 0.6 to 19.9 for total PHT level. SAPS II scores ranged from 9 to 75. Patients with increased mortality scale rates tended to higher free PHT levels. It was confirmed by strong positive correlation between SAPS II scores and free PHT levels (p<0.01). Age and free PHT levels were found to have positive correlation. (p<0.05) as well. No significant correlation with APACHE II score and PHT levels was demonstrated.Conclusions: Critically ill patients with higher SAPS II score have increased risk of having unpredictable PHT levels. Also elderly patients have increased risk of elevated PHT levels. It is recommended to follow up PHT levels in critically ill patients especially those with higher mortality scale rates and old age.