Cardiac Output and Blood Flow Flashcards
What are techniques for measuring CO and blood velocity? (7)
Fluid velocity
Flow probes– ultrasonic, electromagnetic
Balistocardiography
Fick determination (indicator dilution)
Indicator dilution
- Dye (Indocyanine green (ICG) or cardio green)
- Thermal
- Lithium
Bioimpedance
Airway gases
Rebreathing methods
How does velocity relate to frequency when using doppler or ultrasonic method?
the change in frequency is directly proportional to velocity
The frequency of the doppler/ultrasonic beam is generally in _____.
MHz
Doppler and ultrasonic velocity measurement is often used in the operating room to determine what?
venous air embolism
cardiac output
blood velocity in peripheral vessels during vasc surgery
return-to-flow systolic BP
locating arteries (ultrasound)
How does a transtracheal doppler measure cardiac output?
flow = velocity * area
Continuous wave doppler measures velocity of blood flow in the PA or aortic root
Gated doppler doppler determines the diameter of the pulmonary artery or the aortic root.
Why would espohageal doppler cardiac output be slightly off with respect to total CO?
- Estimate of CO is based only on descending thoracic aorta, which does not include the portion of CO in the ascending aorta.
- Not accurate when flow is turbulent with tachycardia and aortic stenosis
When is an esophageal Doppler contraindicated?
esophageal disease
severe coagulopathy
poorly tolerated in awake pts
Why do we use transcranial doppler?
Useful for detecting emboli during carotid surgery and CPB
Useful for detecting brain death
Where does the transcranial doppler transmit sound waves anatomically?
temporal bone
basilar arteries
What is balistocardiography?
It is quantitative seismocardiography.
Seismocardiography is non-invasive measurement of the accelerations in the chest wall produced by myocardial movement to determine CO.
Uses a marble slab and mercury.
What is the Dagmar CHM system?
What is this schematic circuit comprised of?
Contactless Heart Monitoring
Band pass active filter, amplifier, oscilloscope, display
What is the Fick determination of CO?
Flow (Q dot) = O2 consumption
(CaO2 - CvO2) /100ml blood
What does this information allow you to calculate?
Fick determination of CO
When determining CO using the Fick principle, how are the following values collected?
oxygen consumption (VO2)
CvO2
CaO2
Exhaled air is collected to measure O2 consumption per min.
Blood is withdrawn from the PA through a catheter into a cuvette oximeter
Arterial oxygen content is measure from any systemic artery.
What is the Stewart-Hamilton method? (4)
Dye dilution CO
Bolus injection in RA
Continual withdrawal of arterial blood from brachial/radial artery through a densitometer to get concentration of indicator as a function of time
Volume = mass of indicator / concentration
What indicators are used in Stewart-Hamilton method?
Indocyanine Green (ICG)
Cardio Green
What do the arrows indicate when using the Stewart-Hamilton method of determining CO?
Exponential curve– below the curve (area) is primary circulation.
Then, recirculation curve appears.
Where does the injectate disperse from the Swan-Ganz catheter?
proximal port, 30 cm from distal end
How do you expect the thermodilution curve to appear?
Exponential curve reaches a peak then exponential decay.
Peak of curve indicates max. temp change.
What does the textbook say regarding thermodilution?
Take 3 thermodilutions then take the average in succession.
What is the equation for CO?
RT injectate can be within ___% accuracy instead of icing injectate.
20
What situation can result in an erroneous CO reading?
Warm room with a cold patient
Identify the following thermodilution curves
A. Normal
D. Interrupted Injection
C. Low CO
F. Baseline temp shift following CPB
B. High CO
E. Tricuspid regurgitation – result in underestimation of CO
