17. Adv Hemodynamic Monitoring Flashcards
cardiac index normal range
2.2-2.4 L/min/m2
CVP normal range
5-12 mmHg
when is CVP most accurately measured
end of expiration
when is CVP not considered accurate
pt is “sitting”
what degree must the pt head be resting at to be considered accurate
between 0-60 degrees
coronary perfusion pressure normal
50-120mmHg
mixed venous oxygen saturation (mvO2)
60-80% in awake pt
mvO2 is approximately the same as
ScvO2
(central venous oxygen saturation)
pulmonary artery pressure (PAP)
15-30/10 mmHg
when is PAP not considered accurate
if pt is sitting
pulmonary hypertension: mild
36-49 mmHg (systolic)
pulmonary hypertension: mod
50-59 mmHg (systolic)
pulmonary hypertension: severe
> 60 mmHg (systolic)
pulmonary capillary wedge pressure (PCWP)
<12mmHg (mean pressure)
PCWP should be _______ less than pulmonary artery ______ pressure
1-4mmHg less than pulmonary artery diastolic pressure
when is PCWP not considered accurate
if pt is sitting
pulmonary vascular resistance (PVR)
100-300 dynes sec cm-5
stroke volume (adult)
60-90 mL/beat
stroke volume index
33-47 mL/m2/beat
systemic vascular resistance (SVR)
700-1200 dynes sec cm-5
ScvO2 (central venous O2 saturation)
25-30% below pt SaO2
OR
70-75% if the SaO2 is normal
what reflex control heart rate
bainbridge
baroreceptor
baroreceptor reflex
responds to changes in BP
low BP = incr HR
high BP = decr HR
bainbridge reflex
responds to change in blood volume
2 bainbridge reflexes
incr BV in RA
1. incr HR (pump extra blood out)
2. vasodilation (decr venous return)
what causes incr in HR
low CVP (baro)
high CVP (bain)
what does cardiac output vary based on
the pt weight
normal CO for 70kg pt
5L/min
200kg pt CO
higher than 5L/min
cardiac index equation
CI = CO/body SA
the cardiac index is independent of_____
weight
normal range of cardiac index is
same for all pts, regardless of size
stroke volume varies with
weight
stroke volume index equation
SVI = SV/body SA
Coronary perfusion pressure equations
CPP = DBP - LVEDP
OR
CPP = DBP - CVP
LVEDP
BP in LV at end of diastole
what is a good estimate of LVEDP
LVEDP~LAP~PCWP~PA diastolic P
CPP equations
CPP = DBP - PCWP
CPP = DBP - PA diastolic Pressure
CPP = DBP - CVP
what is required for adequate coronary perfusion pressure
adequate diastolic filling time
adequate blood pressure
thermodilution steps
- 10mL cold saline into RA (fast <4s)
- thermistor located in pulmonary artery
- thermistor monitors fluid temp
thermodilution curve: high CO
low Area Under Curve
small wave
- cold fluid passes thermistor quickly
thermodilution curve: low CO
higher Area Under Curve
large wave
- thermistor will stay colder longer
CO relationship with thermodilution curve
CO is inversely proportional to area under thermodilution curve
what has replaced thermodilution
Continuous cardiac output PACs
TEE
what can cause false readings in thermodilution
prolonged injection time
>4s
a prolonged injection time would cause
CO reading to be underestimated
R-L shunt: thermodilution curve
fluid less cold (losing 1/2 cold)
AUC smaller
overestimation of CO
L-R shunt: thermodilution
fluid less cold (diluted)
AUC smaller
overestimation of CO
triscuspid regurge: thermodilution
fluid colder longer
AUC larger
underestimation of CO
ScvO2
O2 saturation of blood taken from SVC
drawn from central line port
mvO2
drawn from PA
- mixed sample of SVC, IVC, and coronary sinus blood
which blood sample contains venous blood from the heart?
mvO2
which blood sample will be more deoxygenated?
mvO2
(coronary sinus blood is more deoxy because the heart burns more O2 than other organs)
which is lower: mvO2 or scvO2
mvO2 < scvO2
low CO: mvO2 and scvO2
low CO = lower mvO2/ScvO2
(blood is more deoxygenated)
high CO: mvO2 and scvO2
high CO = higher mvO2/ScvO2
(blood is less deoxygenated)
mvO2 and CO correlation
directly proportional
causes of Low ScvO2/mvO2
hypoxia
hypoventilation
incr metabolic rate (incr O2 demand)
low CO
causes of High ScvO2/mvO2
decr metabolic rate (decr O2 demand)
mitochondrial dysfunction
intubating the esophagus causes
decr SpO2
decr ScvO2
decr mvO2
when can mitochondrial dysfunction occur
in sepsis
how does mitochondrial dysfunction cause high ScvO2/mvO2
mitochondria unable to uptake O2 well
higher [O2] in blood
Ohm’s law
V=IR
voltage = current x resistance
resistance (R)
SVR
or PVR
current (I)
CO
voltage definition
difference in energy between two ends of a circuit
voltage (V)
MAP - CVP
difference in BP at arterial end and the venous end
OR
PAP-PCWP
difference in BP at the pulmonary arterial end and pulmonary venous end
Ohm’s law for CO
(MAP - CVP) = CO x SVR
CO equation
CO = [(MAP-CVP)/SVR]x80
OR
CO = [(PAP-PCWP)/PVR]x80
SVR equation
SVR = [(MAP-CVP)/CO]x80
SVR units
dynes/sec/cm-5
CO units
L/min
PVR equation
PVR = [(PAP-PCWP)/CO]x80
PVR units
dynes/sec/cm-5
narrow pulse pressure
<25% of systolic pressure
wide pulse pressure
> 50% of systolic pressure
does stroke volume have a great effect on systolic or diastolic?
systolic
increase SV = ______ pulse pressure
incr SV = incr PP
does SVR have a greater effect on systolic or diastolic?
diastolic
increase SVR = _______ pulse pressure
incr SVR = decr PP
pulse pressure is ________ proportional to aortic compliance
inversely proportional
aorta w/good compliance (young healthy pt)
systolic pressure is lower in systole
PP is lower
aorta less compliant (older pt)
systolic pressure is higher in systole
PP is higher
pulse pressure: hypovolemic pt
Narrow PP
decr SV = decr systolic
vasoconstriction = incr diastolic
pulse pressure: congestive heart failure
Narrow PP
decr SV = decr systolic
vasoconstric = incr diastolic
pulse pressure: post-workout
Wide PP
incr SV = incr systolic
vasodilate = decr systolic
pulse pressure: cardiac tamponade
Narrow PP
decr SV = decr systolic
vasoconstrict = incr diastolic
pulse pressure: aortic stenosis
Narrow PP
decr SV = decr systolic
vasoconstrict = incr diastolic
pulse pressure: milrinone
Wide PP
incr contractility = incr SV = incr systolic
decr SVR = decr diastolic
pulse pressure: aortic regurge
Wide PP
incr SV
vasodilation
intraoperative causes of high CVP
fluid overload
HF
pulm HTN
Tburg
high intrathoracic pressure
treatment: high CVP - fluid overload
diuretics
fluid restriction
treatment: high CVP - HF
inotropes
treatment: high CVP - pulm HTN
hyperventilation
higher FiO2
pulm vasodilators
treatment: high CVP - high intrathoracic P
needle decompression
chest tube
intraoperative causes of low CVP
hypovolemia
reverse Tburg
sitting
treatment: low CVP - hypovolemia
fluid resuscitation
causes of low SVR
vasodilation
treatment: low SVR - vasodilation
lighten anesthetic
give vasopressors
causes of high SVR
vasoconstriction
treatment: high SVR - vasoconstriction
vasodilator
causes of low cardiac index
decr contractility
bradycardia
hypovolemia
hypervolemia (CHF)
incr afterload
- aortic stenosis
- high SVR
causes of high cardiac index
incr contractility
incr SV
tachycardia
vasodilation
(decr afterload = incr SV)
symptoms of HF
low cardiac index
hypotension
incr SVR
pulm HTN (pulm edema)
high CVP
what does the body do when CO is low
vasoconstricts to prevent BP from getting too low
treatments for HF
inotropes
diuretics
hypotension due to hypovolemia
CI: low
CVP: low
SVR: high
hypotension due to vasodilation
CI: high
SVR: low
hypotension due to decreased contractility
CI: low
CVP: high
SVR: high
PAP: high
stroke volume variation
SV fluctuation between inspiration and expiration
(AKA PPV)
in spontaneously ventilating pts, SBP __________ during inspiration
in spontaneously ventilating pts, SBP decreases 5-10mmHg during inspiration
why does SBP decrease during inspiration for SV?
Pulm vessels vasodilate
blood pools in legs
decr preload
decr BP
in mechanically ventilated pts, SBP _________ during inspiration
in mechanically ventilated pts, SBP increases 5-10% during inspiration
why does SBP increase during inspiration for mechanical ventilation?
lungs inflate
pushes LV wall inward during systole
incr EF
incr blood volume/SV
SV/SBP has wider fluctuations during insp/expir
pulsus paradoxus
pulsus paradoxus SBP
SBP decr >10mmHg for spontaneous inspiration
SBP incr >10-15% for mechanical inspiration
causes of pulsus paradoxus
hypovolemia
cardiac tamponade
pneumothorax
how does cardiac tamponade/tension pneumo cause pulsus paradoxus?
inspiration
incr BV in RV
RV cannot expand
interventricular septum pushes into LV
decr volume of LV
decr SV
decr BP
EV1000/Flo Trac monitors
beat to beat BP
SVR
CO
SV/SVI
SVV
EV1000/Flo Trac uses ______ for CVP
7mmHg
monitor volume status
urine output
hypotension/tachycardia
CVP
what is the FloTrac good for
fluid management
High SVV ~ hypovolemia
Flo Trac limitaitons
requires mech venitloation
fixed RR
TV > 8ml/kg
regular heart rhythm
SVV altered by PEEP/vasodilators
pulsus alternans
variation in BP every other beat
causes of pulsus alternans
severe ventricular dysfunction
electrical alternans
alternation of QRS between beats
causes of electrical alternans
cardiac tamponade
myocardial infarction
