| Summary: | 碩士 === 長庚大學 === 醫療機電工程研究所 === 98 === Postoperative cerebral infarction is one of the most serious complications of aortic surgeries in adult patients. The acute cerebral infarction often causes life-long cerebral dysfunction or death of these patients. Cerebral ischemia resulted from circulatory arrest while repairing the thoracic aorta is thought to be related to this acute cerebral infarction. To attenuate the brain injuries of circulatory arrest, surgeons use deep hypothermia (body temperature less than 20C° ) and cerebral perfusion to reduce the cerebral metabolism and provide cold blood to the brain. Selective antegrade cerebral perfusion (SACP; the perfusion flow is provide through the right axillary artery to the right carotid artery) is the most popular technique of cerebral perfusion nowadays. SACP could provide bilateral cerebral perfusion via the cerebral communicating network, called “Circle of Willis (CoW)”, to pass the right side flow to the left side of brain. Nevertheless, the efficacy of cerebral protection of SACP is close related to the structure of CoW. According to the previous reports, the prevalence of the abnormalities of CoW which may not have bilateral cerebral perfusion during SACP is 12%. The goal of this study was to develop a hydraulic mechanical system to simulate the SACP during circulatory arrest, and get the knowledge of the regional cerebral flow distribution during SACP. Based on the results, an integrated monitor to perform a reliable intra-operative surveillance of the adequacy of the SACP during circulatory arrest could be invented. It should guide surgeons to perform aortic surgeries during an adequate SACP which provides the maximal cerebral protection to the patients.
A 3-staged experiment was designed. The first stage was to create a hydraulic machine which mimics human cardiovascular and cerebral vasculature. The second stage was to validate the performance of the integrated simulator. And the third stage was to simulate the condition of circulatory arrest with SACP in the intergraded simulator. Regression methods were applied to establish the prediction model of the regional cerebral flows to the perfusion flow of SACP, and the prediction model of the ratio of flow velocities in bilateral middle cerebral arteries to the ratio of flow velocities in bilateral distal external carotid arteries. The latter one was important to the future development of the integrated surveillance system, which use the superficial vascular doppler probes to replace the transcranial vascular doppler probes to monitor the corresponding cerebral blood flows during SACP.
The scientific contribution of this study was to develop an integrated cardiovascular simulator with an extension of cerebral vasculature. The integrated simulator could provide a controllable platform, other than animal models, for researches of regional cerebral flow disturbance after cerebral artery occlusion, as circulatory arrest during SACP in this study. The suggested prediction models of regional cerebral flows and intra-cranial flows could be very help to the further studies of the development of the surveillance system, and the impacts of the structures of CoW to the flow distributions of SACP. Both studies are promising to reduce the prevalence of cerebral infarction related to aortic surgery.
|
|---|
