1996 Volume 9 Issue 3 Pages 74-79
A study was conducted to evaluate the severity of reduction of middle cerebral artery flow velocity (FVmca) during cross-clamping of the cervical carotid artery using transcranial Doppler ultrasound (TCD), and to compare the reduction rate of FVmca with internal carotid artery back-pressure (BPica) during carotid endarterectomy (CEA) .
Subjects and methods: Among 56 patients (46 men, 10 women) who underwent CEA during a period of 2.5 years, 43 (38 men, 5 women) were evaluable for FVmca measurement during CEA (detection rate: 78%) . The internal carotid artery (ICA) was occluded for 70 sec, and four measurements of FVmca were taken: 1) prior to ICA occlusion, 2) 10 sec after occlusion, 3) 60 sec after occlusion, and 4) immediately following the restoration of ICA flow. The rate of reduction in FVmca and the blood flow pattern during occlusion as well as the rate of increase in FVmca following the restoration of ICA were examined. Then the correlation of these factors with BPica was studied by inserting a three-way shunt tube.
Results: The degrees of FVmca resulting from ICA occlusion were classified as a percentage of the preocclusion value: 1) severe (FVmca≤15%; 10 patients), 2) moderate (FVmca=16-40%; 12 patients), and 3) mild or no ischemia (FVmca ≥ 41%; 21 patients) . The BPica (mmHg) in each of the groups was 6.9±2.3, 20.1±5.6, and 51.1±18.3, respectively. Nearly all the patients with severe or moderate ischemia showed a blood flow pattern of the plateau type in FVmca during ICA occlusion (i.e., flow velocity was unchanged), whereas most patients in the mild or no ischemia group showed a gradual increase of blood flow velocity (i.e., an increasing pattern) .
Conclusion: A high correlation was shown between the rate of reduction in FVmca and BPica during ICA occlusion. The reduction rate of FVmca and the flow pattern observed with ICA occlusion provided useful information for deciding on the use of the shunt procedure intraoperatively.
