In vivo Analyse der Mikrozirkulation im Stromgebiet der A. carotis int. bei gefäßchirurgischen Rekonstruktionen

Abstract

Introduction: Hemodynamically relevant stenosis of the internal carotid artery is predicted to increase the risk of cerebral ischemic stroke significantly. Using non-invasive orthogonal polarized spectral (OPS) imaging, the aim of this study was to visualize and quantitatively assess microcirculation in the terminal vascular bed of the internal carotid artery (ICA) during ICA surgery. Material and Methods: Twenty patients with hemodynamically relevant stenosis (measured from arteriograms by NASCET score) of the ICA undergoing endarterectomy were studied. In all patients application of intraluminal shunts during endarterectomy was used. Intraoperative in vivo microscopy of the ipsiand contralateral bulbar conjunctiva (ICA capillary bed) was sequentially performed using OPS imaging at baseline (I), following clam** of ECA (II), and ICA (III), during intraluminal shunt perfusion (IV), following re-clam** of the ICA for shunt removal (V), after reperfusion of ECA (VI), and ICA (VII), and 15 min following final reperfusion (VIII). Microhemodynamic analysis included determination of capillary diameter (KD), functional capillary density (FCD), and red blood cell velocity (RBCV). Results: During sequential clam** of the ECA and ICA conjunctival capillary perfusion (FCD) was found markedly impaired ( p < 0.05) by 35 and 50% of preis chemic baseline, accompanied by a significant decrease in KD and RBCV. ICA reperfusion through the shunt caused a complete restitution of these microcirculatory deteriorations. Re-clam** of the ICA for shunt removal was associated with a significant reduction in FCD, KD and RBCV, which was significantly less pronounced compared with the first ICA clam** and effectively restored to baseline following final reperfusion. The individual degree of ICA stenosis was inversely correlated with the extent of conjunctival perfusion deficit following the first ICA clam**. Conclusion: Short clam** of the ICA leads directly to ischemic microvascular dysfunction, which is completely restored by intraluminal shunt reperfusion. Inversed correlation of the degree of stenosis with extent of microcirculatory impairment following ICA ischemia appears to result from sufficient compensation of the ipsilateral ICA territory, suggesting stenosis-dependent adaption of capillary perfusion. The finding of less pronounced microcirculatory disturbances during the second ICA clam** may be partly explained by ischemic preconditioning of the ICA vascular bed. Maintenance of ICA perfusion using the shunt leads to reduction of microvascular dysfunction. The use of OPS imaging during carotid-artery reconstruction enables continuous monitoring of both microcirculation in the territory of the ICA and efficient shunt perfusion, thereby allowing corrective therapeutic measures to be taken to reduce the likelihood of intraoperative strokes.