CONTINUOUS MEASUREMENT OF BLOOD-FLOW IN THE SUPERIOR SAGITTAL SINUS OF THE LAMB

We assessed the validity of recording blood flow in the superior sagittal sinus (Q(ss)) as a measure of cerebral blood flow (CBF). While anesthetized, 10 lambs were instrumented with a transit-time ultrasonic flow probe around the superior sagittal sinus to measure Q(ss), electrodes to assess sleep state, catheters to measure cerebral perfusion pressure (P-cp), and an occlusive cuff around the common brachiocephalic artery to vary blood pressure. After 72 h recovery, lambs were studied during spontaneous sleep-wake cycles to establish 1) the normal range of Q(ss) and 2) the response rate of Q(ss) to rapid alterations of P-cp. Subsequently, the lambs were reanesthetized, and the measurement of Q(ss) was calibrated and validated. Q(ss) was linearly related to the arterial inflow of 35% of the brain mass (y = 0.5x + 1.6, r = 0.93, n = 4). Q(ss) was greater in active sleep (154.1 +/- 45.7 ml . min(-1) . 100 g(-1), mean +/- SD, n = 5) than in quiet sleep (97.1 +/- 40.8 ml . min(-1) . 100 g(-1)) and quiet wakefulness (107 +/- 44.3 ml . min(-1) . 100 g(-1), P < 0.05). Q(ss) responded rapidly (within one beat) to spontaneous and to induced transient changes in P-cp. We conclude that recording blood flow in the superior sagittal sinus provides a simple, continuous, and quantitative measure of CBF from a defined area of the brain and is appropriate for studying transient changes in the cerebral circulation.