Cerebral blood flow measurements and electroencephalograms during carotid endarterectomy

TLDR

The study discusses the value and limitations of monitoring techniques and introduces concepts of ischemic tolerance and critical cerebral blood flow. The authors monitored 93 carotid endarterectomies with cerebral blood flow measurements and 113 with both CBF and continuous EEG. Significant CBF increases were seen only with stenosis >90%, and a strong CBF‑EEG correlation showed that maintaining a CBF of 18 ml/100 g/min at PaCO₂ = 40 torr is required for normal EEG, with EEG changes below this threshold reflecting reversible flow deficits.

Abstract

✓ 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 (PaCO 2 ) 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.