Purpose: To evaluate the development and histologic features of jugular vein catheter-related (fibrin) sheaths in a swine model.
Materials and methods: The proposal was approved by the University Committee on the Use and Care of Animals. Tunneled silicone 7-F catheters were placed via a jugular vein in eight swine. The animals were separated into four groups of two pigs each according to catheter indwelling times of 7, 14, 30, and 45 days. After the animals were sacrificed, the catheter, access vein, and cranial vena cava were dissected, removed en bloc, and fixed in formalin. Histologic evaluation was performed by using standard light microscopy on hematoxylin-eosin stained specimens; immunohistochemistry was also performed to confirm specific cell populations.
Results: Catheter-related sheaths that covered 33%-100% of the intravascular catheter length were identified in all eight catheter specimens. After 7 days, catheters had a partial or circumferential mixed cellular and noncellular covering consisting of smooth muscle cells, thrombus, and areas with endothelial cell populations. Sheaths from catheters excised at 14 days were characterized by prominent endothelial cell and smooth muscle cell proliferation. Catheters excised at 30 and 45 days showed less prominent cellularity and more prominent collagen content, in a well-developed sheath, than did those excised at 7 and 14 days. With longer catheter indwelling times, an endothelial layer, indistinguishable from the adjacent vein wall, covered the catheter surface.
Conclusion: The sheath that develops around central venous catheters in the swine model consists of cellular and noncellular components. A substantial proportion of the sheath is made up of a smooth muscle cell and collagen layer with overlying endothelial cells.