Ed's Cardiac Output Lecture / Final Exam Prep Flashcards
Cardiac Output
Formula ?
C.O = HR X SV ml/min = beats/min X ml/beat
Cardiac Output (resting range)
4 - 8 L/m
6 Factors affecting Cardiac Output
MOBGAP
- Metabolic rate
- Oxygen demand
- Body size / type
- Gender
- Age
- Posture
The most potent determinate of cardiac output is
metabolic oxygen demand
5 Things that increase metabolism:
- exercise
- sepsis
- strong emotion
- trauma/surgery
- temperature
C.O. of a female Vs. C.O. of a male?
female = 10% lower than a male of the same body size
In general, females have ____ skeletal muscle mass than males.
Smaller
How do we adjust for individual differences??
- Calculate cardiac index!
- Adjusts C.O. to a
defined measurement
Of body tissue
(BSA)
Cardiac Index formula ?
C.O. / BSA
Normal adult C.I. range?
2.5 - 4.2 L/min/m2
How do we calculate BSA??
(w^.425)(H^.725)(.007184)
Advantages of CI ?
Normalizes cardiac output relative to body surface area
Disadvantages of CI ?
The relationship of metabolism to surface area can be very different from patient to patient
When is CI at its highest?
Childhood
Neonates may have
X3 the CI as an adult
when a person stands up, what happen?
C.O. decreases
S.V. formula =
C.O. / HR X1000
DO2 (delivery) formula=
CaO2 X C.O. X 10
PVR formula =
80 X (MPAP-PAWP) /C.O.
SVR formula =
80 X (MAP - RAP) / C.O.
Stroke volume is a function of:
A. Preload (EDP)
B. Afterload (Pa)
C. Contractility
Normal S.V. =
60 - 100 ml/beat
E.F. Formula =
S.V. X 100 / EDV
Normal E.F. =
65%
Frank-Starling Law
describes what?
relationship between SV and cardiac performance
Preload definition = LVEDP
y = Press
X = Volume
the amount of -myocardial fiber stretch &/or - amount of volume in the ventricle at the end of diastole
Afterload definition =
resistance, impedance, pressure the ventricles must overcome
To eject its blood volume
Clinically the most sensitive measure of afterload is ?
SVR/PVR
SVR formula =
(MAP-RAP) X 80
_________________
C.O.
PVR formula =
(MPAP - PAWP) X 80
_________________
C.O.
What has an inverse relationship to afterload ?
Afterload
Inotrophism definition ?
inherent property of shortening of the myocardial
muscle fibers, apart from preload
What pathologies invalidate that the RV C.O. and LV C.O. are equal ?
- Intra-cardiac shunts
- Reguritant lesions
3 Invasive techniques to measure C.O. ?
Fick Method
Dye dilution
Thermal dilution
2 Non Invasive techniques to measure C.O. ?
Doppler
Bioimpedance
3 requirements for the Fick Principle?
- Arterial sample
- Mixed venous sample
- Spirometer
Fick Principle measures what ?
- total O2 uptake per minute 2. amount into each 100 cc blood
The Fick method for cardiac output determination equation ?
C.O. (Q) = VO2
____________
CaO2 - CvO2 X 10
“Gold standard” for measuring CO is ?
Thermodilution
What are the two methods of thermodilution that are available:
1) bolus thermodilution
2) continuous cardiac output (CCO)
Catheter in the pulmonary artery monitors change in temperature of passing blood after a bolus of room temperature saline is deposited into the right atrium.
Thermodilution Method
In thermodilution process, the injectate port should be in ?
SVC or IVC or RA
In thermodilution process, the thermistor to monitor the blood’s temperature is located near the catheter’s distal tip, which should lie in ?
PA
to calculate the area beneath the curve. This area is
inversely proportional to what ?
C.O.
Small area under the curve =
higher C.O.
Large area under the curve =
lower C.O.
In bolus thermodilution, the CO curve is
displayed on the monitor and validates
Correct Injection technique
The accuracy of the thermodilution method depends on several assumptions:
1) Blood and injectant have mixed adequately.
2) Blood flow is forward. 3) Baseline temperature in the PA is steady.
4) Appropriate technique is used.
