Hemodynamic effects of elevated cerebrospinal fluid pressure: alterations with adrenergic blockade.

The cardiovascular effects of elevated cerebrospinal fluid (CSF) pressure were studied in 18 dogs, 6 in a control group, 6 after alpha adrenergic blockade, and 6 after beta adrenergic blockade. Vascular pressures did not change until CSF pressure was increased from 100 mm Hg to 200 mm Hg. In the control group, the aortic, pulmonary arterial, wedge, and right atrial pressures increased significantly. Cardiac output, heart rate, and stroke volume increased but systemic and pulmonary vascular resistances did not change. In the alpha adrenergic blockade group, vascular pressures did not increase after elevation of CSF pressure. Cardiac output increased or did not change, stroke volume increased, systemic resistance decreased, and pumonary resistance did not change. In the beta adrenergic blockade group, the vascular pressures all increased significantly when CSF pressure was elevated, but cardiac output did not change. Systemic resistance increased and pulmonary resistance decreased. Central blood volume increased in all three groups when CSF pressure was 200 mm Hg. The data suggest that a large and distinct alpha and beta adrenergic stimulus occurred when CSF pressure was increased to 200 mm Hg.