Maki et al randomized 407 patients at 25 dialysis units to have their catheters "locked" for up to 6 months with either heparin, or "C-MB-P solution" (citric acid, methylene blue, and propylparaben). The patients getting the antimicrobial potion had a 0.29 relative risk for bloodstream infection (BSI) without loss of catheter patency.