Study of Serum and Ultrafiltrate Vancomycin Levels in Patients Undergoing Predilution Online Hemodiafiltration

Aim: The aim of the study was to investigate the efficacy of vancomycin, when administered at a specific dose before the end of the dialysis session, in achieving therapeutic serum levels for the treatment of fistula infections or permanent venous catheter exit site infections. Patients-Methods: Sixteen hemodialyzed patients (6 men and 10 women), with a median age of 77 years (range 44 - 89), who were on predilution online hemodiafiltration, were studied. The diagnosis of infections was made using laboratory findings, clinical findings, and local clinical imaging. The dose of vancomycin given depended on the body weight of each patient (grouped). Vancomycin levels were measured both in serum (before and after the end of the dialysis session) and in the ultrafiltrate, which was collected in a specific barrel. In patients with residual renal function, urea and creatinine were determined in serum, as well as in urine from a 44-hour collection (to determine the patients’ urea and creatinine clearances). Total protein and serum albumin levels were also determined (before and after the end of the dialysis session). Results: The patients were divided into 3 groups: Group A with 6 anuric patients, where the ultrafiltrate was collected only during vancomycin administration; Group B with 5 non-anuric patients with residual renal function (renal clearance from 0.865 to 6.45 ml/min), where again the ultrafiltrate was collected only during vancomycin administration; and Group C with 5 anuric patients, where the ultrafiltrate was collected throughout the whole dialysis session. In 34/64 serum samples which were taken before any dialysis session (after 44 or 68 hours of the previous vancomycin infusion), the serum vancomycin levels were subtherapeutic (10 mg/L). The results also showed that the serum levels of vancomycin 44 hours after the infusion did not differ from those on the day after the long interval between dialysis sessions (Wednesday or Thursday) (p = NS). Also, in serum vancomycin levels at the end of any infusion from the second to the fifth, 9 samples were higher and 3 lower than the desired levels. In the patients with residual renal function, after 68 hours, the serum levels of vancomycin were not lower than those in anuric patients (p = NS), except for one with relatively increased renal clearance. The presence of hypoalbuminemia was found to be associated with lower serum levels of vancomycin (χ2, p < 0.05) after its first administration (26/32 serum samples from patients with hypoalbuminemia had pre-session serum vancomycin levels < 10 mg/L, while in the group with normoalbuminemia 8/32 had levels < 10 mg/L). One patient with very low serum albumin levels (mean ± SD = 33.2 ± 0.4 g/L) among all patients had subtherapeutic vancomycin levels in all samples (from 3 to 5 mg/L). Comparing the removed amounts of vancomycin between the groups, a significantly higher amount was found in group C (315 ± 141 mg), compared to group A (212 ± 90 mg) and B (222 ± 118 mg), where the collection was limited only during the vancomycin infusion (p [A-C] < 0.002 and p [B-C] < 0.009). It is concluded that the levels of vancomycin achieved by its administration with a dosage that depends on body weight (not individually, but grouped, in a range of body weights) do not achieve therapeutic serum levels in about half of the samples, despite having a good clinical outcome. Vancomycin is lost throughout the entire course of the infusion (and not just during its infusion). Residual renal function should be considered when administering vancomycin, as should the presence of hypoalbuminemia, while a larger dose is not required at long intervals between the dialysis sessions.