EARLY PHASE ALTERATIONS IN ENDOTHELIUM-DEPENDENT VASORELAXATION RESPONSES DUE TO ANEURYSM CLIP APPLICATION AND RELATED MANIPULATIONS

Mechanically induced vasoconstriction observed throughout surgery and in the immediate postoperative period was investigated to assess the e ffects of various microsurgical manipulations. Factors such as the typ e of aneurysm clip, duration of temporary clipping and peri-adventitia l tissue stripping were the variables in this study. Microsurgical cli ps were applied on guinea pig ''cervical carotid arteries'' in which p eri-adventitia had been removed microsurgically. Arterial rings were r emoved immediately after surgery. Endothelium dependent relaxations we re measured and morphological investigations were performed using ligh t microscopy. It was observed that as the clip application period incr eased, relaxation responses decreased. Peri-adventitial tissue strippi ng caused a marked decrease in the relaxation responses in all types o f the clips. Microvascular clips, in spite of their lower closing forc es, had the greatest deleterious effect on relaxation responses of the vessel, in both normal and peri-adventitial tissue stripped. When the peri-adventitial tissue of the vessel had been stripped, convolutions of the lamina elastica interna were found to be lost in parallel with the decreased tonus of the artery. In the vessels subjected to clippi ng endothelial denudation and cracking took place. As a conclusion it can be stared that both peri-adventitial tissue stripping and microvas cular clip application have deleterious effects in the early postopera tive period. While choosing clips from minimal occlusion force tables, care must be taken to choose clips with less width; and while perform ing microvascular anastomosis, temporary clips with a lesser width mus t be used in place of microvascular clips. Adventitial stripping must not be unnecessarily generous during microvascular anastomosis.