Effects of needle shape on the integrity of the vascular endothelium.

Lesions generated by the passage of micro-needles through vessel walls are of concern because any lesion may significantly alter hemodynamics of an anastomosis. To study this problem, three different needles were tested on the exposed carotid arteries of 30 rats: the 100 mu taper point, the 100 mu cutting point, and the 75 mu taper point. Trauma generated by the penetration of needles was tested first as the needle and its attached suture was passed through the vessel, then the suture was left in place. One hour after penetration, the arteries were prepared for scanning electron microscopy. Differences between the 100 mu taper point and the 75 mu taper point were significant in terms of size and extent of lesions. An arc of endothelial cells surrounding the wounds showed flattening, tissue destruction and clotting. To minimize endothelial trauma, taper point needles are superior to cutting needles. The 100 mu cutting needle caused damage to the vessel wall in tissue cutting on needle penetration, causing a slit-like incision, and in aggregation of platelets at the puncture site.