THE IMPACT OF CARDIAC INDEX ON CEREBRAL HEMODYNAMICS

Background and Purpose: Current noninvasive testing allows accurate as sessment of cerebrovascular hemodynamics. The cardiovascular influence on the noninvasive assessment of cerebrovascular studies has not been defined. This study was designed to determine the effect of cardiac i ndex (CI) on cerebral blood flow velocities, ocular pulse amplitude, o phthalmic systolic pressure, and ocular blood flow (OBF) as currently estimated by noninvasive laboratories. Methods: Based on a retrospecti ve study of 181 patients, we prospectively evaluated 45 patients under going right heart catheterization for hemodynamic monitoring to correl ate the relation between CI, transcranial Doppler sonography, and ocul ar pneumoplethysmography. Patients with hemodynamic instability, sever e carotid stenoses, massive cerebral infarct, or sepsis were ineligibl e for the study. Simultaneous recordings of systemic blood pressure, o phthalmic systolic pressure, heart rate, ocular pulse amplitude, middl e cerebral artery blood flow velocities, and cardiac output were obtai ned on all patients. OBF was calculated from the heart rate and ocular pulse amplitude. Results: The relation between OBF and CI is expresse d by the equation CI=2.36+0.61xOBF (r=.47, P=.0010). The middle cerebr al artery peak systolic velocities and CI had a correlation of .36 (P= .0181). The equation, derived from the linear relation between OBF and CI, was then validated on a sample of 15 patients. With the apparent linear relation between OBF and CI, we used the derived equation to pr edict CI from OBF. The OBF determination predicted CI within 30% in al l patients and within 20% in 53.3% of the patients. Conclusions: We de monstrated that OBF and middle cerebral artery systolic velocity decre ase with diminishing CI. Our findings suggest that CI may be potential ly estimated in selected patients by noninvasive assessment of OBF usi ng ocular pneumoplethysmography.