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how is doppler velocity measured?
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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
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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)
- flow=v*A
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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
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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
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Contactless Heart monitoring:
doppler aimed at should and neck to calculate CO
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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
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What is approximate O2 consumption?
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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
- F
- Kidney function
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Indicator dilution method of CO measurement is performed using ____ or ___. _____ ___ ______ of the volume is ____. requires adequate ______, no ____ __ _______, non-_______.
- D5W or NS
- rate of change
- CO
- Mixing, loss of indicator, toxic
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Thermodilution:
_____ gained by _______ = Heat _____ from ______. how amny should be performed and averaged?
- Heat
- injectate
- lost
- blood
- 3
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What equation is used to determine thermodilution?
stewart-hamilton
CO=(Vi(Tr-Ti)Si*Ci)/(Sb*Cb*integralΔT)
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with thermodilution a small curve means ____ ______.
high output
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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.
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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
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What is the difference in the K1 factor of Normal saline and D5W?
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F = ? (thermodilution equation number 398 :( )
empiric factor employed to correct for heat transfer through injection catheter
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modified stewart hamilton?
CO= (Vi(Tb-Ti))/(integral change in blood temp) * k
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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
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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
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Thermodilution accuracy is operator dependent and one should aim for ___________ and ______________. 5% is good goal but most measurements range from ____ to _____.
- accuracy and repeatability
- 15%
- 25%
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_______ IV fluid with give more accurate thermo reading.
warmed
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pseudo-continuous thermodilution:
warms blood with a filament, then temp diff measured.
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Transpulmonary Thermodilution uses a ___- ______ artery but also requires a central line. Usually used in ____.
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What type of CO measurement uses electrodes?
impedence cardiography
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Impedence cardiography factors _____ and _____ into measurement. What are some problems with this method?
- height
- weight
- motion artifact, procudure prevent electrode placement, pleural or cardial effusions, hematomas, pulmonary edema, metallic osteosynthesis material, pregnancy, chest tubes, obesity, myocardial valvular insufficiency
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NICO uses partial rebreathing of what. What equation is used with this method? what does it stand for?
- CO2
- FICK
- Non-invasive Cardiac output
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______ ________ 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
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Flotrac system uses CO=
SV measured by pulse rate and compliance of vessels
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Lithium dilution uses ____ ______.
radial artery
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Calibration of pulse countour measurment requires ______ ________.
another method
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