Internal Jugular Venous Oxygen Tension as an Index of Cerebral Blood Flow During Carotid Endarterectomy

Abstract

From published data which related cerebral blood flow (CBF) to arterial carbon dioxide tension (Pa co _co2 ) and related CBF to internal jugular venous oxygen tension (Pv o _o2 ), the relationship Pv o _o2 =1.20 Pa co _co2 -4.9 was derived. This relationship was based on the documented changes in CBF induced by alterations in Pa co _co2 in normal man anesthetized with halothane. The validity of using Pv o _o2 as a measure of CBF in clinical situations was tested in 29 anesthetized patients from whom 90 paired values of Pa co _co2 and Pv o _o2 were obtained during reconstructive carotid artery surgery. A significant relationship, Pv o _o2 =1.08 Pa co _co2 +3.6 was obtained over a wide range of Pa co _co2 values, indicating that Pv o _o2 was a reliable measure of CBF under these circumstances. No significant differences were found to result from the various anesthetic agents used, the age of patients, and the period of sampling. Samples obtained during the use of a temporary internal carotid artery shunt indicate that the shunt provides blood flow sufficient to maintain cerebral circulation normally responsive to hypercarbia.