There is evidence that catheter lock solutions containing taurolidine reduce the risk of catheter related infections and improve catheter patency. Lock solutions have a local, but no systemic effect. In this study a taurolidine based lock regimen (TauroLock™-Hep500, Tauropharm, Waldbüttelbrunn, Germany, 2x/week and TauroLock™-U25.000, Tauropharm, Waldbüttelbrunn, Germany, 1x/ week) will be compared to 4% citrate (CitraFlow™ 4%, MedXL, Montreal, Canada, 3x/week) as standard lock solution.