Clinical Research Of Transcranial Doppler Monitoring In Aortic Surgery

BackgroundThe way to establish cardiopulmonary bypass (CPB) in aortic surgery is various from each other. Moreover, profound hypothermia and selective cerebral perfusion will be applied in aortic arch operations. These will greatly affect the hemodynamics of the brain. As a result, neurological complications were common after aortic operations. This study tries to estimate the follows by monitoring the hemodynamic changes of middle cerebral artery (MCA) through transcranial Doppler (TCD) in cardiac and aortic surgery: 1. The hemodynamic effection to the brain when the artery cannulas were inserted in different sites during CPB. 2. The changes of hemodynamics of MCA when cardiopulmonary bypass was administered by different CPB strategies. 3. The effection to the hemodynamics of the brain in single antegrade selective cerebral perfusion (ASCP ). 4. To record the time and quality of microembolic signals (MESs) during operations. This study also tries to analyze the relationship between the hemodynamic changes of the brain and neurological complications after cardiac and aortic surgery. The patho-physiological significance of the MESs which was recorded by TCD during operations was also explored. And this study is a preparation for further exploration of more reasonable neurological protective methods for aortic surgery.Patients and methodsThis is a prospective clinical study. The final research point of this study is neurological complications and early death after surgery. In partⅠ, 27 patients were included in the study. Among them, 13 patients were got aortic dissection (group 1). And the rest of them were heart valve diseases patients (group 2, control group). In group 1, right axillary artery cannulation was performed and one pump with two perfusion lines was administered in CPB. In group 2, the CPB was established and administered in a regular way. The hemodynamic signals of bilateral MCA in different times and different CPB ways were monitored via TCD throughout the operations in both groups. The MESs were also recorded in a real-time way through TCD and analyzed off-line by the TCD operator.In partⅡ, totally 36 patients were included in the study. Twenty seven of them were aortic dissection and complicated aortic aneurysm patients (group 1, control group). The others underwent aortic root aneurysm (group 2). In group 1, the method of establishment and administration of CPB was the same as the method which was described in part I . In group 2, right femoral artery cannulation was performed and CPB was administered in regular way. Hemodynamic data and MESs were recorded as described in partⅠ. The pulsatility index (PI) and resistivity index (RI) of bilateral MCA were also recorded in both groups. All the perioperative mortality and morbidity was recorded by an experienced doctor of the intensive care unit, who was blinded to this study.ResultIn partⅠ, no early death was observed in both groups, nor was the permanent neurological dysfunction (PND). Temporary neurological dysfunction (TND) was observed in 23. 08% (3/13) patient in group 1, but none was found in group 2. In partⅡ, the early mortality after surgery was 4. 76%(1/21), and 1 patient was found underwent PND in group 1. Whereas none was found in group 2. About 35% (7/20) patients were found underwent TND in group 1 vs 6.67% (1/15) in group 2 (p=0.048).In partⅠ, during the full flow of CPB, blood flow velocities of MCA were found similar between both sides (p=0. 592) and also there were no differences between groups (p>0. 05). During the selective cerebral perfusion time, the flow velocity of left MCA was low (13. 00±3. 72cm/s). When one pump with two perfusion began, the flow velocity of right MCA was obviously high (55. 77±22. 24cm/s), and this high level of velocity maintained until aortic clamp was released. The blood flow velocities of MCA were found always similar between both sides in group 2 during CPB time.In partⅡ, the hemodynamic changes of MCA in group 1 was similar with which in partⅠgroup 1. The level of flow velocities of MCA in group 2 were kept similar between both sides and smoothly during CPB time. After CPB was ended, PI and RI was found much higher in the patients of group 1 (p<0. 05) and returned to normal level after 7 days of operations. Lots of MESs were recorded during CPB time in both groups in the two parts of the study.Conclusion1. Right axillary artery cannulation and right femoral artery cannulation can fit the requirement of full flow CPB and will offer the same blood supply to both hemisphere of the brain. 2. Luxury perfusion was observed in right brain hemisphere during the CPB under the controlment of one pump with two perfusion lines. This luxury perfusion to the brain may be the reason of TND after surgery. 3. The resistance of brain arteries was increased after CPB which was administered by one pump with two perfusion lines. It implies that the proper temperature and flow administration of this CPB strategy still needs to be explored. 4. The blood supply to the non-perfusion hemisphere of the brain was reduced during single ASCP. But it would not cause ischemia in that brain area. This implies that single ASCP is safe during DHCA. 5. The pathological significance of MESs which were recorded by TCD during CPB needs further research.