Related Experiment Video
Updated: Mar 13, 2026
O-Ring Aortic Banding Versus Traditional Transverse Aortic Constriction for Modeling Pressure Overload-Induced Cardiac Hypertrophy
Published on: October 6, 2022
Carotid Doppler flowmetry correlates poorly with thermodilution cardiac output following cardiac surgery
C Roehrig1, M Govier1, J Robinson2
1Intensive Care Unit, Liverpool Hospital, Sydney South West Local Health District, Liverpool, NSW, Australia.
Insights
Carotid Doppler flow monitoring is not interchangeable with cardiac output measurements in post-operative patients. While correlated, the weak link means these vascular ultrasound methods cannot replace standard cardiac output assessments.
Area of Science:
- Cardiovascular Physiology
- Critical Care Medicine
- Medical Imaging
Background:
- Monitoring cardiac output and volume responsiveness is crucial in post-operative patients.
- The utility of carotid arterial flow, measured by time velocity integral using vascular Doppler ultrasound, for this monitoring remains unclear.
Purpose of the Study:
- To evaluate if carotid Doppler flow measurements can effectively monitor cardiac output.
- To assess the correlation between carotid Doppler flow and volume responsiveness in post-operative cardiac surgery patients.
Main Methods:
- Carotid Doppler flow (time velocity integral and peak flow velocity variation) was measured in 33 post-coronary bypass surgery patients.
- Measurements were taken before and after passive leg raising to assess volume responsiveness, comparing with thermodilution cardiac output.
- Pearson's correlation and ROC analysis were used.
Main Results:
- A significant correlation was found between carotid Doppler flow and cardiac output (r=0.80) and relative changes (r=0.79).
- Peak flow variation >10% predicted responders to passive leg raising (AUC=0.81).
- However, wide limits of agreement (-19% to 16%) indicate poor interchangeability.
Conclusions:
- Common carotid Doppler flow shows weak correlations with cardiac output, limiting its use.
- These vascular ultrasound methods cannot be interchangeably used with thermodilution for cardiac output monitoring in this patient group.
Background:
It remains unclear whether measuring carotid arterial flow by the time velocity integral using vascular Doppler ultrasound can be used to monitor cardiac output and volume responsiveness.
Methods:
The carotid Doppler flow (time velocity integral and peak flow velocity variation) was assessed in triplicate by an intensivist with formal vascular ultrasound training. Thirty-three patients admitted following coronary by-pass surgery were studied before and after a passive leg-raising manoeuvre to investigate volume responsiveness (more than 10% increase in cardiac output) along with indices of arterial load measuring cardiac output by thermodilution. Pearson's correlation coefficient and area under the curve (AUC) by receiver operating characteristics were calculated.
Results:
A significant correlation between carotid Doppler flow and cardiac output was demonstrated in post-operative cardiac surgery patients (r = 0.80 [95%CI 0.61-0.89]), including relative changes following passive leg raising (r = 0.79 [95%CI 0.60-0.89]) that showed a mean difference of 2% with wide limits of agreements (-19% to 16%). Changes in carotid Doppler flow following passive leg raising correlated with the baseline arterial resistance but not with compliance or effective elastance. A peak flow variation > 10% before passive leg raising discriminated responders to the manoeuvre with an AUC of 0.81 [95% CI 0.55-0.95].
Conclusions:
Weak correlations between common carotid Doppler flow and cardiac output mean that the methods cannot be used interchangeably in post-operative cardiac surgery patients.
Related Concept Videos
01:22Cardiac Output II: Effect of Stroke Volume on Cardiac Output
Preload
Preload refers to the initial elongation of the cardiac myocytes before contraction and is related to the volume of blood filling the heart at the end of diastole, or end-diastolic volume. The...
01:19Cardiac Output I:Effect of Heart Rate on Cardiac Output
Cardiac output (CO) refers to the total amount of blood ejected by one of the ventricles in liters per minute (L/min). In a resting adult, CO ranges from 5 to 6 L/min, adjusting according to the body's metabolic requirements.
Effect of Heart Rate on Cardiac Output
Cardiac output adapts to metabolic demands during stress, physical activity, or illness. The autonomic nervous system regulates heart rate via the sinoatrial node. The parasympathetic nervous system decreases heart...
01:11Cardiac Output and Stroke Volume
In an average resting adult male, the typical cardiac...
01:26Imbalances in Cardiac Output
CHF can occur due to the failure of either side of the heart. Left-side failure leads to pulmonary congestion—the right side continues to send...