Advanced Hemodynamic Monitoring Flashcards
normal cardiac index value (CI)
2.2-4.2 L/min/m2
normal central venous pressure value
5-12 mmHg
CVP is most accurate when measured at the end of (inspiration/expiration)
expiration
what position are CVP, PAP, and PWCP readings considered reliable?
if the backrest positions are from 0-60 degrees
-not considered as accurate if the patient is truly “sitting”
normal value of coronary perfusion pressure
auto regulated between 50-120 mmHg
normal value of mixed venous oxygen saturation (mvO2)
60-80% in an awake patient
mixed venous oxygen saturation is roughly equal to what other value?
central venous oxygen saturation (ScvO2)
normal value of pulmonary artery pressure
15-30
——— mmHg
10
pulmonary artery pressure is not considered “accurate” if the patient is in what position
sitting
-same reason as CVP
value of mild pulmonary hypertension
36-49 mmHg systolic
value of moderate pulmonary hypertension
50-59 mmHg systolic
value of severe pulmonary hypertension
> 60 mmHg
normal value of pulmonary capillary wedge pressure (PCWP)
less than 12 mmHg
1-4 mmHg less than pulmonary artery diastolic pressure
PCWP is not considered accurate if the patient is in what position?
sitting
-same reasons as CVP
normal value for pulmonary vascular resistance (PVR)
100-300 dynes:sec:cm-5
normal value for an adult stroke volume
60-90 mL/ beat
normal value for stroke volume index
20-65 mL/beat/m2
normal values of systemic vascular resistance (SVR)
700-1200 dynes:sec:cm-5
normal values of central venous O2 saturation (ScvO2)
25-30% below the patients SaO2
OR
70-75% if the SaO2 is normal
which reflex responds to a changes in blood pressure?
baroreceptor reflex
where are the baroreceptor reflexes located?
inside the carotid sinus (hypoglossal nerve)
and aortic arch (vagus nerve)
Baroreceptor reflex: when the blood pressure is low, the HR (increases/ decreases)
increases
Baroreceptor reflex: when the blood pressure is high, the HR (increases/ decreases)
decreases
which reflex responds to changes in blood volume inside the heart
bainbridge reflex
Bainbridge reflex:
when right atrial pressure increases (blood volume in the right atrium increases), the Bainbridge reflex causes
1. the HR to (increase/decrease)
2. (vasodilation/ vasoconstriction)
- HR will increase ( in an effort to get the blood out)
2. vasodilation (causes venous pooling in the legs and decreased venous return
BOTH a (high/low) CVP through the baroreceptor reflex and a (high/low) CVP through the Bainbridge reflex will cause an increase in HR
low CVP
high CVP
cardiac index allows a more accurate interpretation of cardiac output because the number is not skewed by what patient factor
weight
-cardiac index is the same for all patients, regardless of size
cardiac index equation
body surface area
stroke volume index equation
body surface area
stoke volume index allows a more accurate interpretation of stroke volume because the number is not skewed by which patient factor?
weight
-a neonate or morbidly obese patient will have a different stroke volume but the same stroke volume index if they both have normal heart function
3 equations to calculate coronary perfusion pressure
- CPP=DBP-LVEDP (need to estimate LVEDP from below)
- CPP= DBP-CVP
(diastolic blood pressure-right atrial pressure) - CPP= DBP-PCWP
- CPP=DBP-PA diastolic pressure
we can ESTIMATE LVEDP because the blood pressure in the left ventricle at the end of diastole is roughly equal to which other pressure?
Left atrial pressure (systolic pressure in the left atrium)
which pressure gives us an estimate of Left atrial pressure
PCWP
LVEDP is estimated from what pressure?
left atrial pressure
left atrial pressure is estimated from what pressure?
PCWP
-wedge pressure can estimate LVEDP and give a way to calculate coronary perfusion pressure
PCWP is estimated from what pressure?
PA diastolic pressure
-diastolic pressure in pulmonary artery will almost always equal wedge pressure
2 ways to estimate LVEDP
- PCWP or pulmonary artery occlusion pressure
2. PA diastolic pressure
in the thermodilution technique how much saline is injected and where is it injected to?
10 mL cold saline
right atrium through the CVP port
how fast must the thermodilution injection be?
<4 sec
thermodilution technique: the cold saline travels to the _____artery where it encounters the _____ on the swan
pulmonary
thermistor
-the cold fluid is warmed to a degree (from normal body heat) before it gets to the thermistor
thermodilution technique: the monitor produces a _____ based on how cold the fluid at the thermistor is
waveform
thermodilution technique: if the cardiac output is high, the temperature at the thermistor will get (warm/cold) fast but will (warm/cool) quickly
cold
warm
thermodilution technique: if the cardiac output is high, the total area under the thermodilution curve will be (higher/ lower) than normal
lower
-the curve is tall and narrow
thermodilution technique: if the cardiac output is low, the temperature at the thermistor will be (warm/cold) for a long period of time
cold
thermodilution technique: if the cardiac output is low, the total area under the thermodilution curve will be (lower/ higher) than normal
higher
-the curve is short and wide
interpretation of thermodilution waves:
a small wave indicates?
any factor that decreases the area under the curve will (overestimate/underestimate) cardiac output
high cardiac output
-any factor that decreases the area under the curve will overestimate cardiac output
interpretation of thermodilution waves:
a large wave indicates?
any factor that increases the area under the curve will (overestimate/underestimate) cardiac output
low cardiac output
underestimate
the cardiac output reading is (directly/ inversely) proportional to the area under the thermodilution curve
inversely
thermodilution technique:
if the anesthetist injected the saline to slow (>4 seconds), the thermodilution curve would be (smaller/larger) than normal
and the cardiac output reading would be (overestimated/underestimated)
larger (the blood at the thermistor would stay colder for longer)
underestimated (give a reading lower than what it really is)
thermodilution question:
a patient has a right to left intracardiac shunt. Would thermodilution in this patient lead to an overestimation or underestimation of cardiac output?
overestimation
-some cold fluid is lost to the left side so the blood in the PA will be warmer ( the curve is smaller)
thermodilution question:
A patient has a left to right intracardiac shunt. Would thermodilution in this patient lead to an overestimation or underestimation of cardiac output?
Overestimation
-Cold fluid is diluted by warm blood from the left side, so the blood in the PA will be warmer (curve will be smaller)
thermodilution question:
A patient has tricuspid regurgitation. Would thermodilution in this patient lead to an overestimation or underestimation of cardiac output?
underestimation
-The blood at the thermistor will stay colder for a longer period (curve will be bigger)
what 2 monitoring alternatives replaced thermodilution
- Continuous Cardiac Output (CCO) pulmonary artery catheters
(can estimate cardiac output without the anesthetist injecting saline) - Transesophageal echocardiography (TEE)
name of the oxygen saturation of blood taken from the superior vena cava
ScvO2
-since it is proximal to the right atrium, this will not include blood from the coronary sinus (the coronary sinus drains into the inferior part of the right atrium)
how can an ScvO2 sample be drawn?
through the central venous line port
name of the oxygen saturation from the superior vena cava, inferior vena cava, and coronary sinus
mixed venous O2 saturation
mvO2
where is the mvO2 sample taken?
at the distal tip of the pulmonary artery catheter
mvO2 will be slightly (lower/higher) percent O2 saturation than ScvO2
why?
lower
the heart burns more oxygen than other organs so the coronary sinus blood is more deoxygenated
low cardiac output= (low/high) mvO2/ScvO2
low
-with low cardiac output, blood is more deoxygenated by the time the blood gets back to the heart because it traveled more slowly throughout the body and had more time to unload oxygen to tissues
high cardiac output= (low/high) mvO2/ScvO2
high
-in high cardiac output states, blood is less deoxygenated by the time it returns back to the heart because it traveled faster through the body and had less time to unload oxygen to the tissues
list 2 reasons why mvO2 and ScvO2 are rarely used to estimate cardiac output
- it requires drawing blood from a central line or a swan
2. cardiac output can be measured by other effective methods (CCO swan, TEE, Flotrac sensor)
the equation for ohms law
V= IR
v= voltage I= current R= resistance
resistance is equivalent to ____ or ____in the body
SVR or PVR
current (I) is equivalent to _____ _____ in the body
cardiac output
voltage (v) is equivalent to the difference in blood pressure at the _____end of the body and the blood pressure at the ____ end of the body
arterial (MAP)
venous (CVP)
MAP-CVP
So, if we can measure CVP (with a central line) and monitor MAP (with an A-line) and cardiac output (with a Swan), we can CALCULATE _____
SVR
cardiac output equation from ohm’s law
V= IR MAP-CVP = CO X SVR
what number is used in the cardiac output equation to convert the units used for blood pressure and SVR into the units for cardiac output
80
MAP=89
CVP=9
CO=4
Calculate SVR
(89-9/4) X (80) = 1600
BP= 100/80
CVP=3
SVR=900
Calculate cardiac output
(87-3/900) X (80) = 7.5
Therefore, if we can measure PAP, PCWP, and cardiac output (with a Swan), we can CALCULATE _____
PVR
pulmonary equation from ohm’s law
V= IR (PAP-PCWP) = CO X PVR
PAP= 28/10 PCWP= 6 CO= 4
What is the PVR?
(16-6)/ 4 X (80) = 200
PAP = 24/6
PCWP= 4
PVR=150
What is the cardiac output?
(12-4)/ 150 X 80= 4.2
3 things pulse pressure is affected by
stroke volume
systemic vascular resistance
aortic compliance
stroke volume is proportional to _____ blood pressure
systolic
increased stroke volume = ( increased/decreased) systolic pressure
increased
decreased stroke volume = (increased/decreased) systolic pressure
decreased
SVR is proportional to _____ blood pressure
diastolic
increased SVR (vasoconstriction) = (increased/decreased) diastolic BP
increased
decreased SVR (vasodilation) = (increased/decreased) diastolic BP
decreased
if the aorta has good compliance, the systolic pressure will be (higher/lower)
lower
if the aorta has poor compliance (stiff), the systolic pressure will be (higher/lower)
higher
systolic pressure (pulse pressure) is (directly/ inversely) proportional to aortic compliance
inversely
A patient is hypovolemic. Should an anesthetist expect a wide or a narrow pulse pressure?
Narrow; lower stroke volume and vasoconstriction
A patient has congestive heart failure (CHF). Should an anesthetist expect a wide or a narrow pulse pressure?
Narrow; also due to low stroke volume and vasoconstriction
You just got done running 3 miles on a treadmill. Would you be expected to have a wide or a narrow pulse pressure?
Wide; increase stroke volume and vasodilation
A patient has cardiac tamponade (blood in the pericardial sac). Should an anesthetist expect a wide or a narrow pulse pressure?
Narrow; decrease stoke volume and vasoconstriction
A patient has aortic stenosis (narrowing of the aortic valve). Should an anesthetist expect a wide or a narrow pulse pressure?
Narrow; decrease stoke volume and vasoconstriction
A patient is on a Milrinone drip, which causes an increase in cardiac contractility and a decrease in SVR. Should an anesthetist expect a wide or a narrow pulse pressure?
wide
A patient has aortic regurge. Should an anesthetist expect a wide or a narrow pulse pressure?
Wide; due to lower diastolic volume
fluid overload causes high or low CVP
high
heart failure causes high or low CVP
high
pulmonary hypertension causes high or low CVP
high
trendelenburg causes high or low CVP
high
high intrathoracic pressure (tension pneumothorax) = causes high or low CVP
high
-high intrathoracic pressure decreases venous return from the head (in addition to the legs) which causes pooling of blood in the central veins = increased CVP
hypovolemia causes high or low CVP
low
sitting position causes high or low CVP
low
vasodilation causes low or high SVR
low
vasoconstriction causes low or high SVR
high
decreased cardiac contractility causes a low or high cardiac index
low
bradycardia causes a low or high cardiac index
low
hypovolemia causes a low or high cardiac index
low
hypervolemia (if patient has HF) causes a low or high cardiac index
low
increased afterload (aortic stenosis or high SVR) causes a low or high cardiac index
low
increased contractility/ stroke volume causes a low or high cardiac index
high
tachycardia causes a low or high cardiac index
high
vasodilation causes a low or high cardiac index
high
-decreased afterload leads to increased stroke volume (due to the left ventricle pumping against less resistance)
how is hypotension due to hypovolemia treated?
fluids/blood products
how is hypotension due to vasodilation treated?
vasopressors
reversing cause of vasodilation (decreasing anesthetic)
how is hypotension due to heart failure (decreased contractility) treated?
- inotropes
2. diuretics (fluid overload can cause decreased contractility)
If a patient has hypotension due to hypovolemia, would the anesthetist expect the following to be increased or decreased?
Cardiac index
CVP
SVR
Cardiac index= decreased
CVP= decreased
SVR= increased
If a patient has hypotension due to vasodilation, would the anesthetist expect the following to be increased or decreased?
Cardiac index
SVR
cardiac index= increased
SVR= decreased
If a patient has hypotension due to decreased contractility, would the anesthetist expect the following to be increased or decreased?
cardiac index
CVP
SVR
cardiac index= decreased
CVP= increased
SVR= increased to maintain normal BP
A patient is adequately anesthetized and has a pulmonary artery catheter in place. Monitors show the following values:
HR: 98 bpm BP: 88/40 mmHg CVP: 8 mmHg PAP: 25/8 mmHG SVR: 400 dynes PVR: 200 dynes cardiac index: 3 L/min
Of the following options, which treatment will best normalize the patient’s vital signs?
A. Fluid bolus B. Vasopressor C. Inotrope D. Vasodilator E. Diuretic F. Beta blocker
B. Vasopressor
A patient is adequately anesthetized and has a pulmonary artery catheter in place. Monitors show the following values:
HR: 65 bpm BP: 85/40 mmHg CVP: 7 mmHg PAP: 25/8 mmHg SVR: 1100 dynes PVR: 250 dynes cardiac index: 1.8 L/min
Of the following options, which treatment will best normalize the patient’s vital signs?
A. Fluid bolus B. Vasopressor C. Inotrope D. Vasodilator E. Diuretic F. Beta blocker
C. inotrope
A patient is adequately anesthetized and has a pulmonary artery catheter in place. Monitors show the following values
Heart Rate = 60 bpm Blood Pressure = 170/105mmHg CVP = 7mmHg PAP = 35/10mmHg SVR = 1700 dynes·sec·cm–5 PVR = 350 dynes·sec·cm–5 Cardiac Index = 2.8L/min/m2
Of the following options, which treatment will best normalize the patient’s vital signs?
A. Fluid bolus B. Vasopressor C. Inotrope D. Vasodilator E. Diuretic F. Beta blocker
D. vasodilator
A patient is adequately anesthetized and has a pulmonary artery catheter in place. Monitors show the following values:
Heart Rate = 100 Blood Pressure = 84/55mmHg CVP = 2mmHg PAP = 20/5mmHg SVR = 1500 dynes·sec·cm–5 PVR = 100 dynes·sec·cm–5 Cardiac Index = 2.0L/min/m2
Of the following options, which treatment will best normalize the patient’s vital signs?
A. Fluid bolus B. Vasopressor C. Inotrope D. Vasodilator E. Diuretic F. Beta blocker
A. fluid bolus
refers to stroke volume and systolic blood pressure fluctuating during inspiration and expiration
stroke volume variation (SVV)
- aka “pulse pressure variation”
in healthy spontaneously ventilating patients, systolic blood pressure (increases/ decreases) ______ mmHg during inspiration
decreases 5-10 mmHg
- pulmonary vessels vasodilate during inspiration
- the vasodilation causes blood to pool in the lungs
- when blood pools in the lungs, less blood is available to pump to the body
- this leads to a slight drop in blood pressure during inspiration
the term for exaggerated stroke volume variation
pulsus paradoxus
in healthy mechanically ventilated patients, systolic blood pressure (increases/ decreases) ______ % during inspiration because of lung inflation
increases 5-10%
- Displaces the left ventricular wall inward during systole, assisting ventricular contraction (increasing ejection fraction)
- Squeezes blood out of the pulmonary capillaries and into the left atrium, increasing blood volume and stroke volume during inspiration
if stroke volume/systolic blood pressure has wider than expected fluctuations during inspiration and expiration, it is referred to as ______ _______
pulsus paradoxus
a patient is considered to have pulsus paradoxus if:
- their systolic BP (increases/decreases) more than _____mmHg during spontaneous inspiration
- their systolic BP (increases/decreases) more than _____% during mechanical inspiration
- decreases, 10mmHg
2. increases, 10-15%
how can pulsus paradoxus be detected?
SpO2 and arterial line waveforms
what is the most common cause of pulsus paradoxus?
hypovolemia
2 other circumstances that pulsus paradoxus can be seen
- cardiac tamponade
- tension pneumothorax
- Less commonly, pulsus paradoxus can be caused by vasodilation, CHF, hypervolemia, and PEEP
what is the cardiac tamponade mechanism for pulsus paradoxus
- during inspiration blood volume in the right ventricle increases
- normally right ventricle will expand and absorb this pressure - the right ventricular wall cannot expand
- because of fluid in the pericardial sac - the increase in right ventricular volume/ pressure during inspiration will force the interventricular septum to bulge over to the left
- this causes a decrease in the volume of the left ventricle, a decrease in stroke volume, and a greater decrease in blood pressure during inspiration
what is the tension pneumothorax mechanism for pulsus paradoxus
- blood volume in right ventricle increases with inspiration
- the right ventricular wall cannot expand
- because of external compression on the heart from the increased thoracic pressure - increase in right ventricular volume/pressure will force the interventricular septum to bulge over to the left
- causes a decrease in volume of the left ventricle, a decrease in stroke volume, and a greater decrease in blood pressure during inspiration
stroke volume variation on inspiration of healthy patients during spontaneous ventilation
Systolic blood pressure and pulse pressure decrease 5-10mmHg during inspiration
stroke volume variation on inspiration of hypovolemic, cardiac tamponade, or pneumothorax patients during spontaneous ventilation
Systolic blood pressure and pulse pressure decrease >10mmHg during inspiration
stroke volume variation on inspiration of healthy patients during mechanical ventilation
Systolic blood pressure and pulse pressure increase 5-10% during inspiration
stroke volume variation on inspiration of hypovolemic patients during mechanical ventilation
Systolic blood pressure and pulse pressure increase >10-15% during inspiration
the monitor used to tell us the stroke volume variation and whether or not stroke volume variation is normal or exaggerated
Flo Trac sensor
2 advantages of the Flo Trac sensor
- noninvasive monitor
2. gives a real time blood pressure without having to cannulate the artery
2 disadvantages of the Flo Trac sensor compared to arterial lines
- arterial lines give access to drawing blood from labs
2. the blood pressure readings aren’t as accurate as A-lines
4 things the Flo Trac sensor can tell us noninvasively
- stroke volume variation
- stroke volume and stroke volume index (calculated cardiac output)
- SVR (from waveform downstroke)
- cardiac output/index (by using SVR equation)
how does the Flo Trac sensor measure cardiac index
Uses the cardiac output equation
- knows the MAP from the blood pressure waveform
- knows the SVR from the waveform downstroke
- does not know CVP, so inserts a normal value of 7 mmHg
- —CVP has minimal effect on cardiac output equation
the 3 most common methods to assess volume status
- monitoring urine output
- look for hypotension and tachycardia
- monitor CVP (requires a central line)
2 ways anesthetists decide how much fluid to give
- calculating “guessing” fluid replacement
2. monitoring BP, HR, urine output, CVP
monitoring stoke volume variation on the Flo Trac sensor helps the anesthetist with _____ _____
fluid management
what is suspected If the stroke volume increases more than expected (>10-15%) during mechanical inspiration
hypovolemia
-the anesthetist should give fluids until the stroke volume variation gets down toward 10%
5 limitations of monitoring stroke volume variation using Flo Trac sensor
- the patient must be 100% mechanically ventilated
- stroke volume variation monitoring is not as accurate on spontaneous ventilating patients - RR needs to be fixed
- tidal volume needs to be greater than 8 mL/ kg
- the patients HR must be regular
- PEEP and vasodilators may alter SVV
