Bilateral Jugular Venous Blood Flow by Thermal Dilution

Measurements of internal jugular venous flow were made in 12 patients with severe cerebral vascular disease. Flow rates were determined by the thermal dilution method, using room temperature physiological (heparinized) saline as an indicator infused at a constant rate. The major sources of error (indicator mixing) were studied under highly controlled in vitro experiments. Total jugular venous outflow was substantially below mean values of total cerebral flow for normal subjects and somewhat below the mean values for demented patients. Free communication between the two jugular veins via the torcular was observed in all patients. Following unilateral venous compression, the differential shift to the contralateral vein was not always equal to the precompression total flow. This would seem to indicate that this maneuver produces some diversion of flow to other venous channels and suggests that total cerebral blood flow can be obtained reliably only through bilateral measurements.