Regional Cerebral Blood Flow Measured by the Gamma Camera After Direct Injection of 133 Xe into the Distal Stump of the Occluded Middle Cerebral Artery

Abstract

Regional cerebral blood flow (rCBF) was measured after intracarotid injection of ¹³³ Xe concurrently with measurements of local cerebral blood flow (LCBF) after injection of ¹³³ Xe directly into the distal stump of the occluded middle cerebral artery (MCA) by the use of the gamma camera after producing experimental ischemia in baboons by occluding the MCA. Regional MCA stump pressure (rMCAP) was also measured. Regions of ischemia assessed by intracarotid injection of ¹³³ Xe correlated well with the territory of infarct defined by injection of ¹³³ Xe into the distal MCA stump. Flow values in ischemic regions obtained by direct injection of ¹³³ Xe into the MCA were 15% to 20% lower than those obtained by intracarotid injection of ¹³³ Xe. Possible explanations for these differences are discussed. During induced hypertension autoregulation in ischemic areas was abolished and paradoxical responses of LCBF and rMCAP to changes in arterial carbon dioxide tension (Pa _{co co2 ) were confirmed.}