Appropriate Use and Monitoring of Vancomycin (vanc) for the Treatment of Staphylococcus aureus (SA) Bacteremia

Background: SA bacteremia, both methicillin-sensitive (MSSA) and methicillin-resistant (MRSA), remains a major clinical problem among general medical and surgical services.  Infectious Diseases Society of America guidelines published in 2009 recommend significant changes in the dosing and monitoring of vanc.  These include consideration of a loading dose, and maintenance vanc dosing of 15-20 mg/kg/dose every 8 to 12 hours in patients (pts) with normal renal function to attain trough (TR) levels of 15-20 mcg/mL for the treatment of invasive SA infections. They also recommend maintaining minimum steady state TR levels above 10 mcg/mL.

Objective: Our goal is to determine whether clinical practice at Stony Brook University Medical Center (SBUMC) is consistent with these guidelines.

Methods: We conducted a one-year retrospective chart review on admitted pts 18 years and older.  Pts with renal dysfunction (GFR <60) and pregnant women were excluded. Age, sex, weight, allergies, blood cultures (BC), antibiotic history, frequency of Infectious Diseases consultation (IDC), and vanc levels were recorded.  SPSS v.19 was used for statistical analyses. 

Results: Forty one patients met inclusion criteria.  Twenty-six (63%) pts reviewed had MSSA bacteremia; 15 (37%) had MRSA.  Sixty-eight percent were males and 32% females with mean age and weight of 51 years and 79 kg, respectively.  Sixty three percent of pts had an IDC. 

Eighty-eight percent of the pts were initially treated with vanc; only 1 patient received a loading dose of 25-30 mg/kg.  Only 12 patients (29%) received an appropriate initial dose of 15-20 mg/kg.  Trough levels were drawn at the correct time 20% of the time.  The target TR was only achieved in 7% of pts.  Of all vanc levels drawn, 58% were unnecessary, and only 43% of clinicians’ responses to vanc levels were appropriate.  The above parameters were not significantly different among pts with MSSA vs. MRSA bacteremia.

Thirty-nine% of pts had daily BC drawn, and mean time to bacteremia clearance was 5.63 days (5.2 for MSSA, 6.3 for MRSA).  The mean percent of positive BC was high in both groups: (73% MSSA, 66% MRSA).  

Conclusions: The use and monitoring of vanc at SBUMC is not consistent with current guidelines.  We believe that the above data warrant development and implementation of hospital-wide algorithms to help guide clinicians in the appropriate dosing and monitoring of vanc for invasive infections.