[Vancomycin dosing in hemodialysis patients]

Vancomycin is widely used in haemodialysis (HD) patients for treating infections of vascular access due to St. Aureus. To avoid subtherapeutic levels it is important to know the adequate dosing in patients undergoing haemodialysis with high flux membranes.

The aim of this study was to evaluate whether HD patients treated with 1 g intravenous (IV) vancomycin reached optimum plasma levels.

In a crossover design we studied 28 chronic HD patients, 3 times a week, treated with vancomycin between 15/2/2006 and 14/2/2007. Antibiotic was given at dose of 1 g during the last hour of dialysis session. Plasma levels of vancomycin were measured immediately before next HD (preHD1) and after (postHD1), and prior to the beginning of the second next session (preHD2). We evaluated age, sex, dry height, week Kt/V and the type of membrane used.

Of 28 patients, 5 were analysed 3 times, 2 were analysed twice and 9 were analysed once . There were 43 samples, 19 men (44,2%) and 24 women (55,8%), with a mean age of 70 +/- 8,4 years. 1 g dose is equivalent to > 15 mg/kg in 31 patients (72,1%) and < 15 mg/kg in 12 (27,9%). The type of membrane used was high flux polyetersulfone (PES-AP) (44,2%), eval (7%), medium-low polyetersulfone (PES-BP) (32,5%) and polyacrylonitrile (16,3%). PreHD1 mean concentration results for the total population was 7,06 mg/ml, being 16,3% bellow optimum levels. There were not difference between patients treated with dose > 15 mg/kg (7,5 mg/ml) and < 15 mg/kg (6 m/ml). When the dose administered was > 15 mg/kg, 6,45% results were subtherapeutic, whereas if the dose was < 15 mg/kg, 41,67% values were bellow optimum levels (p<0,05). With regard to the dialyzers used, the lowest concentrations were observed with PES-AP (5,95 mg/ml) and the highest values were observed with PES-BP (7,27 mg/ml) (p no significance). No patient using PES-BP versus 31,58% patients using PES-AP showed suboptimum values (p> or =0,07). All postHD1 and preHD2 results were in subtherapeutic range (mean values, dose > and < 15 mg/kg and all types of membrane).

Based on the above results, the vancomycin dosing schedule of 1 g IV every 5-7 days is not recommended for patients undergoing haemodialysis with high flux membranes. Since there are not guidelines for handling this antibiotic in these patients our findings suggest that it may be necessary to monitorize predialysis plasma levels to avoid subtherapeutic values.