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how is doppler velocity measured?
Examples of doppler and ultrasonic measurement in OR:
- Blood velocity in peripheral veins- vascular surgery
- Detection of air embolims
- return-to-flow systolic blood pressure
- Cardiac output- (transtracheal/transesophageal) pulmoary artery or aortic root
What are the two types of transtracheal and esophageal doppler? what equation is this based on?
- Continuous wave- measures velocity of blood flow (v)
- Gated- diameter of aortic root or pulmonary artery (A=pi*d)
What are the limitation of doppler measurement?
- based on blood flow in descending aorta will not be accurate bc doesn't account for blood to head
- blood flow may not be accurate if turbulent
- probe placement contraindication with esoph or coagulopathy
- not tolerated in non intubated pt's
What is transcranial doppler used for? what does it measure?
- emboli detection during carotid surgery and CPB, useful in detecting brain death
- temporal bone to basilar arteries
Contactless Heart monitoring:
doppler aimed at should and neck to calculate CO
What is the FICK EQUATION for CO determination?
- Q= (VO2)/(CaO2-CvO2)
- *VO2 O2 consumption
- *CaO2 O2 arterial content
- *CvO2 mixed venous blood
measured by dilution or direct venous vs arterial measurement of O2
What is approximate O2 consumption?
Dye-dilution method also known as _______ ____________ ___________. Bolus injection of _________ ______or _________ _________ into __ _______, followed by continuous withdrawal of arterial blood. Commonly used- T or F? what is required to use this method?
- Stewart-Hamilton Method
- Indocyanine green
- Cardio green
- Kidney function
Indicator dilution method of CO measurement is performed using ____ or ___. _____ ___ ______ of the volume is ____. requires adequate ______, no ____ __ _______, non-_______.
- D5W or NS
- rate of change
- Mixing, loss of indicator, toxic
_____ gained by _______ = Heat _____ from ______. how amny should be performed and averaged?
What equation is used to determine thermodilution?
with thermodilution a small curve means ____ ______.
In the 3rd stewart hamilton equation given, what is K2? Why is this used?
- computation constant that includes heat change in transit, dead space of catheter, and injection rate. adjusts units to liters per min.
- Considers inadvertant warming of fluid through tube.
Example question. Using thermodilution, is monitor is set to read 10ml of fluid injectate and you give 5ml, what will be the result?
CO will read erroneously high
What is the difference in the K1 factor of Normal saline and D5W?
F = ? (thermodilution equation number 398 :( )
empiric factor employed to correct for heat transfer through injection catheter
modified stewart hamilton?
CO= (Vi(Tb-Ti))/(integral change in blood temp) * k
What can influence thermodiltion accuracy?
- intracardiac shunts
- tricuspid/pulmonic valve regurg
- inadequate delivery of indicator
- clot or fibrin thermistor malfunction
- PA blood temp fluctuations (CPB or IV admin)
- resp cycle influences
What should the diff btw injectate and blood temp be to be accurate? What else should be done to ensure accuracy?
- >10 C
- don't slow IV after injection and before reading (false low)
- vent cycling can change venous return *go for repeatability
- Electrocaudery may interfere with signal
Thermodilution accuracy is operator dependent and one should aim for ___________ and ______________. 5% is good goal but most measurements range from ____ to _____.
- accuracy and repeatability
_______ IV fluid with give more accurate thermo reading.
warms blood with a filament, then temp diff measured.
Transpulmonary Thermodilution uses a ___- ______ artery but also requires a central line. Usually used in ____.
What type of CO measurement uses electrodes?
Impedence cardiography factors _____ and _____ into measurement. What are some problems with this method?
- motion artifact, procudure prevent electrode placement, pleural or cardial effusions, hematomas, pulmonary edema, metallic osteosynthesis material, pregnancy, chest tubes, obesity, myocardial valvular insufficiency
NICO uses partial rebreathing of what. What equation is used with this method? what does it stand for?
- Non-invasive Cardiac output
______ ________ is attached to a-line and measures CO. Used in ICU. What factors are used to determine this?
- Pulse Contour
- PCCO= cal * HR * )integral of : area under pressure curve * aortic compliance * shape of pressure curve) in systole
Flotrac system uses CO=
SV measured by pulse rate and compliance of vessels
Lithium dilution uses ____ ______.
Calibration of pulse countour measurment requires ______ ________.