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纤维蛋白鞘是血管内插管的感染来源，它通常在中央静脉导管放置3天后形成。但只有大约50%的纤维蛋白鞘培养结果呈阳性。在那些培养结果阳性的病例中，细菌开始繁殖的时间因导管不同部位各不相同：皮下平均5.1天，导管尖端平均8.6天，导管腔内平均13.1天。导管上的细菌越多，就越可能发生炎症或血液感染。因导管导致血液感染的危险从小于2/1000器械使用天数(外周静脉留置针，外周穿刺中央静脉导管PICC，隧道式中央静脉导管，皮下输液装置)，10/1000器械使用天数(动脉导管和Swan-Ganz导管)，30～50/1000k器械使用天数(多通路中央静脉导管和肾透析插管)。影响血管内插管感染发生的内源性因素包括：宿主情况，细菌类型，导管材料以及制造工艺。人类非常容易感染葡萄球菌，兔子却不这样。表面葡萄球菌需要粘多糖才能引起导管感染。硅胶材料的导管比聚氨酯、聚氯乙烯及特氟隆材料更容易发生感染，这可能与它的过度活化作用有关。影响血管内插管感染发生的外源性因素包括：无菌屏障的范围，皮肤消毒剂种类，穿刺人员是否经过专业培训，整个输液系统被外物介入的次数，高营养输液(酵母菌最易繁殖)，5%葡萄糖溶液(革兰氏阴性菌最易繁殖)以及脂质乳液(糠疹癣菌最易繁殖)。“,”Biofilms are the source of vascular catheter infections and arefound uniformly on central venous catheters after 3 days.Only about half of these biofilms are culture positive.Of those that are culture positive the timing of initial colonization varies by catheter site:subcutaneous segment (average:5.1 days),tip segment (8.6d),and lumen (13.1d).The more organisms that come to reside on a catheter,the greater the likelihood that the catheter will have associated purulence or bloodstream infection.The risk of catheter-related bloodstream infection ranges considerably from≤2/1 000 patient days (peripheral venous catheters,peripherally inserted central catheters (PICC)),cuffed central venous catheters,ports,10/1 000 patient days (arterial and Wwan-Ganz catheters)to 30-50/1 000 patient days (multilumen,hemodialysis).Intrinsic factors that affect the risk of vascular catheter infection include host factors,type of organism,catheter material,and the manufacturing process.Humans are quite susceptible to Saureus,rabbits are not.S.epidermidis requires a polysaccharide adhesin to produce catheter infections.Silicone catheters have a greater risk of infection than polyurethane,polyvinylchloride,or teflon,and this increased risk is related to excess complement activation.Extrinsic factors that can affect the risk of infection include the use of maximal sterile barriers,chlorhexidine skin preparation,insertion by inadequately trained personnel,the number of line breaks,hyperalimentation fluid (favors yeasts),5% dextrose (favors gram-negative organisms),and lipid emulsions (favors Malassezia).