Removal of vancomycin in sustained low-efficiency dialysis (SLED): a need for better surveillance and dosing.

Aims: This study was designed to evaluate the extent of vancomycin removal from the blood compartment during sustained low-efficiency dialysis (SLED) and the efficacy of our current vancomycin dosing practice.

Material: 10 ICU patients were selected. They all had oliguric renal failure requiring SLED and were on vancomycin therapy. SLED was provided with the Fresenius 2000K machine and used an AV400 polysulfone dialyzer (sieving coefficient for vitamin B12 = 1, and surface area = 0.7 m2).

Method: SLED prescriptions were individualized for each patient but the duration for all was at least 8 hours. The blood flow rate (Qb) and dialysate flow rate (Qd) did not vary between patients by greater than 100 cc per minute. Blood samples were drawn at 0, 2, 4, and 8 hours to determine the extent of reduction in vancomycin level.

Results: The total reduction of vancomycin was about 36% with an 8-hour treatment, when following a typical SLED prescription. Serum vancomycin levels dropped below the therapeutic window (< 15 mcg/ml) at the end of an 8-hour SLED session in almost half of the patients. Drug removal was greatest during the first 4 hours (29.5 +/- 6.5%) compared to the last 4 hours (9.1 +/- 7.4%) of SLED.

Conclusions: Vancomycin removal during a typical 8-hour SLED treatment approaches 36%. SLED patients are at risk for undertreatment of their infections. A redosing strategy should be considered if the estimated or measured predialysis level is 20 - 30 mcg/ml. Vancomycin should be redosed with at least 500 mg in most patients at the completion of the SLED. Therapeutic drug monitoring (TDM) is an essential part of any dosing scheme, until further studies are done.