Vancomycin is the most important antibiotic in the treatment of resistant G(+) bacteria infections. Close monitor of serum level is important to ensure its safety and effectiveness. So far there is not enough data to support the optimal dose regimen of vancomycin in patients on SLEDD-f. In this study, we draw blood levels between 2 doses of vancomycin to determine the pharmacokinetic parameters of vancomycin and fraction removed by SLEDD-f so as to determine the most appropriate dose regimen.