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The impact of cardiac index on cerebral hemodynamics
M Saha1, M R Muppala, J E Castaldo
1Department of Medicine, Lehigh Valley Hospital, Allentown, Pa.
Insights
Cardiac index (CI) influences noninvasive cerebrovascular measurements. Ocular blood flow (OBF) and middle cerebral artery velocities decrease with CI, suggesting CI estimation from OBF is possible.
Area of Science:
- Cardiovascular physiology
- Cerebrovascular hemodynamics
- Ocular hemodynamics
Background:
- Noninvasive testing accurately assesses cerebrovascular hemodynamics.
- The impact of cardiovascular function on these noninvasive assessments remains unclear.
- This study investigates the influence of cardiac index (CI) on key cerebrovascular and ocular hemodynamic parameters.
Purpose of the Study:
- To determine the effect of cardiac index (CI) on cerebral blood flow velocities.
- To assess the influence of CI on ocular pulse amplitude and ophthalmic systolic pressure.
- To evaluate the relationship between CI and ocular blood flow (OBF) as measured noninvasively.
Main Methods:
- Retrospective analysis of 181 patients followed by prospective evaluation of 45 patients undergoing right heart catheterization.
- Correlation of CI with transcranial Doppler sonography and ocular pneumoplethysmography.
- Exclusion of patients with hemodynamic instability, severe carotid stenosis, massive cerebral infarct, or sepsis; simultaneous recording of systemic blood pressure, heart rate, and cardiac output.
Main Results:
- A significant linear relationship was found between ocular blood flow (OBF) and cardiac index (CI): CI = 2.36 + 0.61 x OBF (r = .47, P = .0010).
- Middle cerebral artery peak systolic velocities showed a correlation with CI (r = .36, P = .0181).
- The derived equation predicted CI from OBF within 30% in all patients and within 20% in 53.3% of patients.
Conclusions:
- Ocular blood flow (OBF) and middle cerebral artery systolic velocity decrease as cardiac index (CI) diminishes.
- Noninvasive assessment of OBF using ocular pneumoplethysmography may allow for potential estimation of CI in select patients.
Background And Purpose:
Current noninvasive testing allows accurate assessment 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 index (CI) on cerebral blood flow velocities, ocular pulse amplitude, ophthalmic systolic pressure, and ocular blood flow (OBF) as currently estimated by noninvasive laboratories.
Methods:
Based on a retrospective study of 181 patients, we prospectively evaluated 45 patients undergoing right heart catheterization for hemodynamic monitoring to correlate the relation between CI, transcranial Doppler sonography, and ocular pneumoplethysmography. Patients with hemodynamic instability, severe carotid stenoses, massive cerebral infarct, or sepsis were ineligible for the study. Simultaneous recordings of systemic blood pressure, ophthalmic systolic pressure, heart rate, ocular pulse amplitude, middle cerebral artery blood flow velocities, and cardiac output were obtained on all patients. OBF was calculated from the heart rate and ocular pulse amplitude.
Results:
The relation between OBF and CI is expressed by the equation CI = 2.36 + 0.61 x OBF (r = .47, P = .0010). The middle cerebral 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 predict CI from OBF. The OBF determination predicted CI within 30% in all patients and within 20% in 53.3% of the patients.
Conclusions:
We demonstrated that OBF and middle cerebral artery systolic velocity decrease with diminishing CI. Our findings suggest that CI may be potentially estimated in selected patients by noninvasive assessment of OBF using ocular pneumoplethysmography.
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