gms | German Medical Science

Objective: The outcome in the treatment of aneurysms by the surgical approach can be impaired by local ischemia or infarction caused by inadvertent occlusion of the parent artery. Aneurysm occlusion and clipping of supplying vessels can be reliable and practically avoided with the help of intraoperative microvascular Doppler sonography. We used aneurysm models in rats for micro Doppler sonography training before and after clipping to introduce young surgeons in application and interpretation of the resulting Doppler curves.

Methods: A total number of 39 microaneurysms were created at three different anatomic regions of the rat: the femoral (13) and the proximal iliac vessels (12) and the bifurcation of the common carotid artery (14). Clipping of the created aneurysms was performed through a human skull cast model made of plaster. A DWL Smart Dop^® microvascular Doppler system with an operating transmission frequency of 20 MHz (Compumedics GmbH, Singen, Germany) was used to record and analyze routine measurements. After performing clipping of the created aneurysms every specimen consisting of the parent artery and their corresponding aneurysm were fixed and stained in toluidine blue following a standardized protocol. Results were analyzed by using a photo microscope by Zeiss (type II, Göttingen, Germany) and electron microscopy.

Results: Clipping maneuvers had been repeated in 4/14 carotid, 2/13 femoral and 4/12 iliac microaneurysms due to local stenosis which were immediately detected using the micro Doppler. The patency, flow velocity and resistance index were analyzed in all aneurysms. Local hemodynamics were demonstrated and insonated. During histologic examination cases the aneurysm sac was nearly totally thrombosed (85 – 100%, depending aneurysm type) with a central excepting ejection zone of the bloodstream. The proportion of endothelial cells showed a high reduction of amount related to the total number per cross-section in all aneurysm types. The highest reduction of endothelial cells was observed in both venous pouch aneurysms. At the arterial wand-flap aneurysm the proportion of endothelial cells found was much higher.

Conclusions: New methods are investigated for intraoperative monitoring but the microvascular Doppler system is our standard approach for testing patency of microvessels. The needed time and costs are low and the application of microrovascular Doppler is easy to learn in combination with intense microsugical laboratory training.

Due to reduction of regulative cells an increase of thrombotic disposition follows as the granula of the endothelial cells promotes thrombotic formation inside of the aneurysm and secretion of antithrombotic substances are no longer carried out. In recent studies creating experimental aneurysms the role and function of endothelial cells were disregarded and histological results were described only after completed treatment.