Advanced Hemodynamic Monitoring COPY Flashcards
Cardiac Index Normal Value
2.2-4.2 L/min/m^2
Central venous pressure CVP normal value
5-12 mmHg
when is CVP most accurately measured?
end of expiration
in what patient position is CVP considered NOT accurate?
if a patient is sitting
should be backrest from 0-60 degrees
coronary perfusion pressure normal value
50-120 mmHg
mixed venous oxygen saturation (mvO2) normal value
60-80% in awake pt
roughly equal to central venous oxygen saturation (ScvO2)
pulmonary artery pressure (PAP) normal value
15-30/10 mmHg
not as accurate when sitting
mild pulmonary Htn value of PAP systolic
36-49 mmHg systolic
moderate pulmonary Htn value of PAP systolic
50-59 mmHg systolic
severe pulmonary Htn value of PAP systolic
> 60 mmHg systolic
pulmonary capillary wedge pressure (PCWP) normal value
less than 12mmHg
not considered accurate if sitting
PCWP is _____ mmHg less than pulmonary artery diastolic pressure
1-4mmHg
pulmonary vascular resistance (PVR) normal value
100-300 dynesseccm-5
stroke volume normal value
60-90mL/beat
stroke volume index normal value
20-65mL/beat/m^2
systemic vascular resistance (SVR) normal value
700-1200 dynesseccm-5
central venous O2 saturation (ScvO2)
25-30% below patients SaO2
what do the bainbridge and baroreceptor reflex have in common?
both control the heart rate
baroreceptor reflex definition
responds to changes in blood pressure inside the carotid sinus and aortic arch
bainbridge reflex definition
responds to changes in blood volume inside the heart
what are the two things the bainbridge reflex causes if the right atrial pressure increases?
increased heart rate
vasodilation (decreasing venous return)
what happens to the heart with a low CVP baroreceptor reflex and high CVP bainbridge reflex?
increase in HR for both
What does the normal cardiac output values depend on?
the size of the patient
cardiac index definition
allows more accurate interpretation of cardiac output b/c number is not skewed by weight
cardiac index equation
cardiac output/body surface area
assuming two patients are healthy which would differ and which would be the same?
cardiac output
cardiac index
cardiac output would differ
cardiac index would be the same
Stroke volume index equation
=stroke volume/body surface area
stroke volume index definition
allows more accurate interpretation of stroke volume because the number is not skewed by weight
coronary perfusion pressure (CPP) equation 1
CPP= DBP-LVEDP
how can we estimate LVEDP?
because it is roughly equal to systolic pressure in the left atrium (left atrial pressure) which is roughly equal to PCWP
coronary perfusion pressure (CPP) equation 2
CPP= DBP - CVP
what are the 3 estimations for LVEDP
~ left atrial pressure (LAP)
~left atrial pressure (LAP) ~ PCWP
~PCWP ~ PA diastolic pressure
what are the 3 equations CPP can be estimated by?
CPP= DBP-CVP CPP= DBP- PCWP CPP= DBP- PA diastolic pressure
what are the four parts to thermodilution technique
10mL saline injected into RA (<4sec)
cold fluid travels to thermistor
cold fluid is warmed to a degree
monitor produces waveform based on coldness of fluid
high cardiac output thermistor chart
get cold fast but warm up quickly
area under curve is lower than normal
low cardiac output thermistor chart
will stay cold for longer period of time
area under curve is higher than normal
a factor that decreases the area under the thermodilution curve will over or underestimate CO?
overestimate CO
a factor that increases the area under the curve will over or underestimate CO?
underestimate CO
how is cardiac output related to the area under the thermodilution curve?
inversely
what would happen if you prolonged the injection time?
the curve would be larger than normal which means the cardiac output reading would be underestimated
what are the two things that have replaced thermodilution?
continuous cardiac output (CCO) pulmonary artery catheters
transesophageal echocardiography TEE
central venous O2 saturation where is the blood draw from and with what?
oxygen saturation of blood from superior vena cava drawn from the central venous line port
which will be lower mvO2 or ScvO2? why?
mvO2
because coronary sinus blood is more deoxygenated than other blood
what are the three things that make up mvO2?
superior vena cava
inferior vena cava
coronary sinus
how does mvO2 and ScvO2 relate to low cardiac output?
lower mvO2 and ScvO2 bc the blood has more time to become deoxygenated
how does mvO2 and ScvO2 relate to high cardiac output?
higher mvO2 and ScvO2 bc the blood has less time to become deoxygenated
what are the two reasons that ScvO2 and mvO2 are rarely used anymore?
requires drawing blood from central line or swan
CO can be estimated by other effective methods
Ohms law
V= IR
what does ohms law describe
the factors that affect flow through an electrical circuit
V=
voltage
MAP - CVP
I=
current
analogous to cardiac output
R=
resistance
systemic vascular resistance or
pulmonary vascular resistance
applying ohms law to cardiac output 2 equations
CO= (MAP-CVP/SVR) (80) CO= (PAP-PCWP/PVR) (80)
What are the three factors that affect pulse pressure?
stroke volume
systemic vascular resistance
aortic compliance
Does stroke volume primarily effect systolic or diastolic blood pressure?
systolic pressure
increased stroke volume does what to systolic pressure?
increase
does systemic vascular resistance primarily effect systolic or diastolic pressure?
diastolic pressure
increased SVR does what to diastolic pressure?
increased
out of the three factors that effect pulse pressure which one of them is inversely related to pulse pressure?
aortic compliance
if aortic compliance is high then what does that do to systolic pressure?
decrease systolic pressure
a pt is hypovolemic.
wide or narrow PP?
narrow
low SV and vasoconstriction
a pt has CHF.
wide or narrow PP?
narrow
low SV and vasoconstriction
pt ran 3 miles
wide or narrow PP?
wide
high SV and vasodilation
pt has cardiac tamponade.
wide or narrow PP?
narrow
low SV and vasoconstriction
pt has aortic stenosis
wide or narrow PP?
narrow
low SV and vasoconstriction
pt is on milrinone drip (causes increase contractility and decrease SVR)
wide or narrow PP?
wide
high SV and vasodilation
pt has aortic regurg.
wide or narrow PP?
wide
diastolic BP will be lower
What are the 5 causes of high CVP?
fluid overload HF Pulm HTN trendelenburg high intrathoracic pressure (tension pneumo)
what are the 2 causes of low CVP?
hypovolemia
sitting position
what is the cause of low SVR?
vasodilation
what are the 5 potential causes of low cardiac index?
decreased contractility bradycardia hypovolemia hypervolemia (CHF) increased afterload (aortic stenosis/high SVR)
cause of high SVR?
vasoconstriction
3 causes of high cardiac index
increased contractility/SV
tachycardia
vasodilation (decreased afterload)
hypovolemia treatment
treat with fluids and/or blood products
vasodilation treatments 2
vasopressors
reversing the cause of the vasodilation (turn does anesthetic)
HF (decreased contractility) treatment
inotropes
diuretics (due to fluid overload)
If a patient has hypotension due to hypovolemia, would the anesthetist expect the following to be increased or decreased?
CI?
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?
CI?
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?
CI?
CVP?
SVR?
Cardiac index? Decreased CVP? Increased SVR? Increased
SEE PRACTICE QUESTIONS ON SLIDES 73-76
ANSWER ON SLIDES
Stroke volume variation (SVV) definition
stroke volume and systolic blood pressure fluctuating during inspiration and expiration
another name for stroke volume variation
pulse pressure variation
in a healthy spontaneously ventilation pt does the systolic BP normally increase or decrease and by how many mmHg?
decrease
5-10 mmHg
what causes spon vent pts systolic BP to decrease during inspiration? (4 things)
pulmonary vessels vasodilate during inspiration
vasodilation causes blood to pool in lung
less blood then available to pump
leads to slight drop in BP
in healthy mechanically ventilating pt does the systolic BP normally increase or decrease and by how many mmHg?
increase 5-10%
what causes mech vent pts systolic BP to increase during inspiration? (2)
lung inflation displaces LV wall during systole assisting in contraction
squeezes blood out of pulm capillaries and into LA increasing volume and SV
pulsus paradoxus definition
SV/systolic BP has wider than expected fluctuations during inspiration and expiration
if the systolic BP decreases more than 10mmHg during spon breathing then the patient has what?
pulsus paradoxus
if the systolic BP increases more than 10-15% during mechanical breathing the patient has what?
pulsus paradoxus
where can pulsus paradoxus be detected on our monitors? 2
SpO2 waveform
arterial line waveform
what is the most common cause of pulsus paradoxus?
hypovolemia
what are the two causes of pulsus paradoxus (other than hypovolemia)?
cardiac tamponade
tension pneumothorax
what are the 4 LEAST common causes of pulsus paradoxus
vasodilation
CHF
hypervolemia
PEEP
cardiac tamponade mechanism for pulsus paradoxus
1 during inspiration blood in RV increases
2 right ventricular wall cannot expand
3 force the interventricular septum to bulge over to left
4 decrease SV and greater decrease in BP during inspiration
what does the heart normally do to compensate for the increased blood in the RV during inspiration?
the RV wall would expand and absorb the increased pressure
tension pneumothorax mechanism for pulsus paradoxus
same mechanism as cardiac tamponade
but the RV cant expand due to external compression on the heart from the increased intrathoracic pressure
what is a FloTrac Sensor (EV1000)
like an arterial line in the sense that it produces a blood pressure waveform
what are the 4 things that a EV1000 can tell us?
stroke volume and stroke volume index (from waveform upstroke)
SVR (waveform downstroke)
stroke volume variation
MAP (area under wave)
what is the noninvasive A-line?
flotrac sensor EV1000
Can the EV1000 calculate CO and CI?
yes because it just plugs in 7mmHg for CVP and calculates that way
will be fairly accurate bc CVP has minimal effect on CO
most common methods to assess volume status 3
monitor urine
look for hypotension/tachycardia
monitor CVP
anesthetists usually decide how much fluid to give by
calculating fluid replacement
monitoring BP, HR, urine, CVP
With the Flotrac sensor how would we monitor fluids?
titrate fluids until the SVV gets into a normal range
what is the implication of the EV1000?
invasive central line and swans are no longer needed to assess volume or CO
3 limitations of the EV1000?
patient must be 100% mechanically ventilation
heart rhythm must be regular (not accurate in afib)
PEEP and vasodilator may alter the SVV
what must the tidal volume be for patients on the EV1000?
> 8mL/kg
SVV> 13%, SVI is 40-50 and is not responsive to fluid bolus, next step?
suggests contractility is normal so probably dilated
pressor
SVV> 13%, SVI is <20 and is not responsive to fluid bolus, next step?
suggests low cardiac contractility
inotrope
SVV>13%, SVI is >50 and is not responsive to fluid bolus, next step?
suggests that the pt is in fluid overload
diuretic
