Hemodynamic monitors & equipment 3 Flashcards
When does pulmonary artery occlusion pressure overestimate left ventricular end-diastolic volume? (Select 2)
a. PA catheter tip in West zone 3
b. PEEP
c. Diastolic dysfunction
d. aortic insufficiency
b. PEEP
c. diastolic dysfunction
Conditions where PAOP overestimates LVEDP include
mitral valve disease
COPD
pulmonary hypertension
PEEP
non West zone 3 placement of PAC
impaired LV compliance (ischemia)
left-to-right cardiac shut
tachycardia
PPV
_________ causes PAOP to underestimate LVEDV
Aortic insufficiency
Which situation underestimates cardiac output obtained by the thermodilution method?
a. over warmed injectate
b. right-to-left intracardiac shunt
c. high injectate volume
d. partially wedged pulmonary artery catheter
c. high injectate volume
_________ is the most common method of measuring cardiac output.
The thermodilution method
Cardiac output is underestimated when
the injectate volume is too high or the injectate solution is too cold
Cardiac output is overestimated when
the injection volume is too low, the injectate is too hot, the PAC is partially wedged, or there’s a thrombus on the tip of the PAC
Advantages of continuous cardiac output monitoring includes
providing continuous data & avoiding inaccuracies from the human element
The major drawback of continuous cardiac output monitoring includes
slower response time & the data is typically averaged over time
An injection of _______________________ is bolused through _____________- for the thermodilution method
5% dextrose or 0.9% NaCl of known quantity & temperature is bolused through the proximal port on the PAC
Each injection should occur during
the same phase of the respiratory cycle and be completed in <4 seconds
If CO is high, the injectate
rapidly travels towards the distal tip of the PAC
The area under the curve will be _______________, if CO is higher.
smaller
These conditions can make it difficult to predict the accuracy of CO:
intracardiac shunt
tricuspid regurgitation
When would it be preferential to measure CO using the standard thermodilution technique over continuous cardiac output?
in a hemodynamically unstable patient (due to a delay time between measurement and the data appearing on the monitor)
Factors that increase mixed venous oxygen saturation include: (select 2)
a. thyroid storm
b. sodium nitroprusside toxicity
c. anemia
d. sepsis
b. sodium nitroprusside toxicity
d. sepsis
SvO2 is a function of four variables:
cardiac output
arterial oxygen saturation
amount of hemoglobin
oxygen consumption
When Hgb, SaO2, and VO2 are held constant, then SvO2 becomes an indirect monitor of
cardiac output
Factors that decrease SvO2 can be split into two categories:
increased O2 consumption
decreased O2 delivery
Examples of increased O2 consumption include
stress, pain, thyroid storm, shivering, fever
Examples of decreased O2 delivery include
Decreased SaO2, Hgb, or CO
Factors that increase SvO2 can be split into two categories:
decreased O2 consumption
increased O2 delivery
Examples of decreased O2 consumption include
hypothermia
cyanide toxicity
Examples of increased O2 delivery include
O2 therapy
increased Hgb
increased CO
Normal SvO2 is
65-75%
The equation for SvO2 is
SaO2 - (VO2)/(CO x 1.34 x Hgb x 10)
Why do you need a PA catheter to measure SvO2?
a true mixed venous sample must contain blood returning from the superior vena cava, inferior vena cava, and the coronary sinus & the PA artery is the best place to get the sample
Preload responsiveness is expected to be present if a 250 mL fluid bolus increases the stroke volume in excess of:
10%
____________ analysis provides a measure of preload responsiveness
Pulse contour analysis
Methods of pulse contour analysis include
plethysmogroapthy variability index (requires pulse ox)
stroke volume variation (requires esophageal doppler)
systolic pressure variation (requires direct arterial pressure)
pulse pressure variation (requires arterial pressure)
To ensure accuracy of pulse contour analysis, the patient must be receiving
positive pressure ventilation
As a general rule, preload responsiveness can be assumed when a 200-250 mL fluid bolus improves SV more than
10%
Factors that reduce the accuracy of pulse contour analysis include
spontaneous ventilation
open chest
RV dysfunction
dysrhythmias
small tidal volume
PEEP
A _____________- patient will have a greater degree of stroke volume variation through the respiratory cycle as a function of __________________________
hypovolemic; intrathoracic pressure’s effect on RV filling & function
Which conditions limit the reliability of the esophageal Doppler monitor? Select 2
a. hypovolemia
b. aortic stenosis
c. aortic cross-clamp placement
d. esophageal disease
b. aortic stenosis
c. aortic cross-clamp placement
What can the esophageal doppler measure?
stroke volume
stroke index
stroke volume variation
stroke distance
peak velocity
flow time
The esophageal Doppler can help you determine if you should treat with
fluid
vasopressors
or inotropes
Where should the esophageal Doppler be positioned?
~35 cm from the incisors (T5-6)
The position of the probe is based on
the sound and waveform quality
The esophageal Doppler should not be used if the patient has
esophageal disease
Factors that reduce the reliability of the esophageal doppler data include
aortic valve disease
aortic cross-clamping
disease of the thoracic aorta
pregnancy
after CPB
