Impact of Obesity on Clinical Outcomes in Patients Receiving Acyclovir for HSV Encephalitis"

• Obese - WHO definition: Body Mass Index > 30 kg/m2
• Ideal Body Weight (IBW) (male) - 50.0 kg + 2.3 kg x (patient height in inches, above 60 inches)
• Ideal Body Weight (female) - 45.5 kg + 2.3 kg x (patient height inches, above 60 inches)
• Adjusted Body Weight - IBW + [0.4 x (ABW - IBW)]
• HSV encephalitis - PCR positive for HSV-1 or HSV-2 in CSF during index admission
• Baseline Serum Creatinine (S Cr) - The SCr value obtained before the start of acyclovir therapy on which the dose of acyclovir should be based upon
• Acute Kidney Injury (AKI) - per RIFLE criteria and while receiving acyclovir: SCr doubles or urine output < 0.5 mL/kg/hour for 12 hours
• End-stage renal disease (ESRD) on admission - mention of a diagnosis of ESRD in electronic medical records prior to receipt of acyclovir
• Guideline-approved, weight-based doses - within 10% of 10 mg/kg dose (to account for rounding due to vial size)
• Adequate hydration - IV fluid order (other than KVO [keep vein open]) within 24 hours before acyclovir start AND either IV fluid order (other than KVO) for majority of acyclovir course or IV fluid + oral diet for majority of acyclovir course
• Appropriately renally dose-adjusted doses - Frequency of acyclovir matches package insert recommendations based on creatinine clearance at baseline
• Interacting medications - Mycophenolate, probenecid, zidovudine, tenofovir, valproic acid, phenytoin

Inclusion criteria

• Patients Admitted to a SSM Health - St. Clare (STL), St. Mary's (STL), Saint Louis University Hospital (STL), St. Anthony's (OKC), St. Mary's Madison (WIS), Rush University Medical Center (RUMC), or Methodist Dallas Medical Center
• > 18 years old
• Positive cerebrospinal fluid (CSF) PCR for HSV-1 or HSV-2
• BMI > 30 kg/m2
• Received guideline-approved, weight-based doses of IV acyclovir for HSV encephalitis for at least 72 hours during the index admission
• Received appropriately renal dose-adjusted doses of IV acyclovir per package insert recommendations

Exclusion criteria

• More than one dosing weight strategy utilized for > 24 hours for IV acyclovir dosing during the index admission
• Patients transferred to the hospital already on IV acyclovir for HSV encephalitis
• ESRD on admission
• Concomitant pathogen causing meningitis or encephalitis
• Oral acyclovir used for treatment