The effect of increasing clamping forces on endothelial and arterial wall damage: an experimental study in the sheep

This study aimed to relate the level of physical force applied to the arterial wall by atraumatic clamps to the degree of endothelial and wall damage.

Sixteen sheep carotid and femoral arteries were each demarcated into four segments 1 cm apart (total 64 segments). Each segment was clamped for 15 min with a standard angled DeBakey vascular clamp. Four levels of force were generated by closing the clamp at three, four, five and six notches of closure. The extent of endothelial injury was assessed by using a dedicated computer assisted image acquisition program to measure the area stained by Evan's blue dye. The extent of damage to the layers of the arterial wall was analyzed and compared by scanning electron microscopy and light microscopy.

For femoral arteries, the area of endothelial injury was considerably less for three notch (3.76 +/- 0.28 newtons) and four notch (5.68 +/- 0.29 newtons) closure compared with that for five notch (6.19 +/- 0.31 newtons) and six notch (6.61 +/- 0.16 Newtons) closure (p = 0.01). For carotid arteries, three notch (5.68 +/- 0.28 newtons) closure caused less damage than did four notch (7.98 +/- 0.29 newtons), five notch (9.17 +/- 0.40 newtons) and six notch (9.57 +/- 0.64 newtons) closure (P = 0.02). Scanning electron microscopy confirmed the extent and depth of arterial injury corresponded directly to the forces generated by the vascular clamps.

The closing forces generated by arterial clamps correlated positively with the extent of artery wall injury. Vascular clamps should be applied at the minimum level of force that will arrest blood flow.