Cerebral blood flow measurements and electroencephalograms during carotid endarterectomy

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✓ Ninety-three endarterectomies for carotid stenosis were monitored with cerebral blood flow (CBF) measurements, and 113 with both CBF measurements and a continuous electroencephalogram (EEG). Significant CBF increase occurred only when carotid endarterectomy was for a stenosis greater than 90%. A high correlation between CBF and EEG indicated when a shunt was required. To sustain a normal EEG, the CBF ascertained by the initial slope technique must be 18 ml/100 gm/min at an arterial carbon dioxide tension (PaCO2) of 40 torr. The degree of EEG change below this level during occlusion reflected the severity of reduced blood flow and was reversible with replacement of a shunt. The value and limitations of these monitoring techniques and a concept of ischemic tolerance and critical CBF are discussed.

Article Information

Address reprint requests to: Thoralf M. Sundt, Jr., M.D., Department of Neurologic Surgery, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55901.

© AANS, except where prohibited by US copyright law.

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    Typical symmetrical EEG pattern in a 51-year-old man during halothane and nitrous anesthesia. Left: Slow paper speed (15 mm/sec). Right: Routine paper speed (30 mm/sec).

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    Left: EEG recording before left carotid clamping (77-year-old woman) shows lower amplitude fast activity over left hemisphere. Middle: EEG recording 40 seconds after clamping shows major EEG changes on left side when the blood flow was reduced to 5 ml/100 gm/min. Right: EEG recording 4 minutes after internal shunting has returned to baseline levels. (R = midline electrode 4 cm below inion.)

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