JUGULAR VENOUS BULB OXYGEN-SATURATION DEPENDS ON BLOOD-PRESSURE DURING CARDIOPULMONARY BYPASS

Background. Central nervous system dysfunction after cardiopulmonary b ypass is frequent and can be caused by inadequate cerebral perfusion a nd oxygenation. Methods. To test the effectiveness of cerebral autoreg ulation during cardiopulmonary bypass, we induced changes in the cereb ral perfusion pressure by administering phenylephrine during moderate (29 degrees C) hypothermia. Using the Fick principle, we calculated re lative changes in cerebral blood flow from changes in the jugular veno us bulb oxygen saturation. Results. Increasing the cerebral perfusion pressure (from 47 +/- 8.2 to 93 +/- 16 mm Hg) induced increases in the jugular venous bulb oxygen saturation by 4.9% and a calculated increa se in the cerebral blood now by 19.9%, strongly suggesting impaired ce rebral autoregulation. Conclusions. Because cerebral autoregulation is impaired during cardiopulmonary bypass, phenylephrine is effective in increasing the cerebral blood flow and may contribute to the preventi on of postoperative neurologic dysfunction, especially in patients who have a low jugular venous bulb oxygen saturation. (C) 1998 by The Soc iety of Thoracic Surgeons.