Effect of Continuous Venovenous Hemodialysis (CVVHD) on the Time to Reach Therapeutic Vancomycin Levels

Background: Vancomycin is a commonly used antibiotic in the intensive care unit (ICU). Early attainment of therapeutic vancomycin levels is associated with lower rates of antimicrobial resistance and improved outcomes. Several studies have tried to identify the optimal dosing of vancomycin during the receipt of continuous veno-venous hemodialysis (CVVHD), but few have identified its impact on time to achieving therapeutic vancomycin levels. We sought to determine the impact of CVVHD on time to achievement of a therapeutic vancomycin level. Methods: A retrospective chart review identified 843 patients admitted to University of Chicago Medicine between May 2016 and April 2020 who received both vancomycin and CVVHD during an ICU admission. Patients were classified based on initiation of vancomycin while on or off CVVHD. The time from initial vancomycin administration to first vancomycin level ≥ 10 mg/L was calculated. Patients were excluded if they received vancomycin within 10 days prior to starting treatment. Results: Two hundred (23.7%) patients started vancomycin on CVVHD, while 470(55.8%) started outside the CVVHD window. Vancomycin levels were not measured in 173(20.5%) patients. Thirty patients failed to achieve a therapeutic level 17(8.5%) vs 13(2.8%) in the on- and off-CVVHD groups respectively. The median time to reach a therapeutic level was 48.9 h (IQR 26.7-78.9 h) vs 28.5h (IQR 23.4-48.3 h) for individuals on and off CVVHD respectively, see Figure 1 (p < 0.0001). Additionally, the incidence of vancomycin levels ≥40 mg/L is higher in patients who are not receiving CRRT (7.5% vs 17.2%, p = 0.009). Conclusion: The time to reach a therapeutic vancomycin level in patients on CVVHD is significantly longer than those who are not receiving CVVHD. Supratherapeutic levels occur more often in patients who are not receiving CVVHD.