Monitoring of Cerebral Vasodilatory Capacity With Transcranial Doppler Carbon Dioxide Inhalation in Patients With Severe Carotid Artery Disease

✓ Noninvasive transcranial Doppler recordings were correlated to the angiographic findings in 77 patients with carotid artery disease. Stenoses reducing the luminal area of the internal carotid artery by 75% or more also reduced the pulsatility transmission index (PTI) of the ipsilateral middle cerebral artery (MCA). The PTI is the pulsatility index of the artery under study expressed as a percent of the pulsatility index of another intracranial artery with presumed unimpeded inflow in the same individual. For stenoses in the 75% to 89% category, PTI reduction was significantly greater in patients with bilateral carotid stenosis, indicating an impaired potential for collateral flow in these patients. The PTI reduction probably reflects both the pressure drop across the stenosis and the cerebral autoregulatory response. Two criteria proved useful in demonstrating collateral MCA supply through the circle of Willis. On the recipient side, retrograde flow in the proximal anterior cerebral artery was demonstrated in 29 of the 31 patients when this flow pattern was disclosed angiographically. In 26 of these patients, the anterior cerebral artery on the supplying side also had clearly increased flow velocity. Increased flow velocities in the proximal posterior cerebral artery were present in 26 of the 30 vessels that were acting as a collateral channel to the ipsilateral MCA.

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Cerebrovascular Carbon Dioxide Reactivity in Carotid Artery Disease

Anesthesiology ◽

10.1097/00000542-199503000-00007 ◽

1995 ◽

Vol 82 (3) ◽

pp. 655-661 ◽

Cited By ~ 27

Author(s):

A. Thiel ◽

B. Zickmann ◽

W. A. Stertmann ◽

T. Wyderka ◽

G. Hempelmann

Keyword(s):

Carbon Dioxide ◽

Carotid Artery ◽

Carotid Artery Disease ◽

Transcranial Doppler Sonography ◽

Cerebrovascular Reactivity ◽

Conduction Time ◽

Exact Test ◽

Increased Risk ◽

Artery Disease ◽

Carbon Dioxide Reactivity

Background In patients with carotid artery disease, poor intracerebral collateralization is reflected by impaired cerebrovascular reactivity to carbon dioxide inhalation, which will improve after endarterectomy. The relationship between preoperative reactivity to carbon dioxide using transcranial Doppler sonography (TCD) and intraoperative changes of somatosensory evoked potentials (SEP) and TCD parameters were investigated. Methods In 94 patients, preoperative carbon dioxide reactivity was examined and defined impaired if mean blood flow velocity in the middle cerebral artery (Vm-MCA) increased less than 1.5% mmHg during carbon dioxide challenge. Patients then underwent 100 carotid operations under general anesthesia with both SEP and TCD monitoring. Shunts were placed if SEP amplitude decreased to less then 50% of control or central conduction time increased by 20% after clamping (critical SEP changes). TCD changes were defined as critical in case of a postclamping/preclamping Vm-MCA ratio < or = 0.4. The incidence of critical SEP and TCD changes was compared to preoperative carbon dioxide testing using Fisher's exact test with P < 0.05 considered significant. Postoperatively, neurologic state and carbon dioxide responsiveness were re-examined. Results Twelve patients showed impaired preoperative carbon dioxide reactivity on the side of operation, which improved markedly after surgery. The incidence of critical SEP changes in these cases (8.3%) was not significantly different from that in the remaining patients (14.8%). Critical SEP changes were significantly correlated with critical TCD changes (P < 0.0001). Conclusions Patients with poor carbon dioxide reactivity (preoperative TCD testing) did not have an increased risk of cerebral ischemia during carotid surgery, as assessed by intraoperative SEP recording.

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