9Bern MM, Lokieh J J, Wallach SR,et al. Very low doses of warfarin Can prevent thrombosis in central venous catheters:A randomized prospective trial[J]. Ann Intern Med, 1990,112 : 423 - 428.
10Hu KK,Lipsky BA,Veenstra DL,et al. Using maximal ster-ile barriers to prevent central venous catheter - related in-fection :a systematic evidence - based review[ J]. Am J In-fect Control,2004,32(3) : 142 - 146.