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Cardiac Output And Hemodynamic Measurements

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Cardiac Output And Hemodynamic Measurements Iskander Al-Githmi, MD, FRCSC, FCCP Asst. Professor of Surgery King Abdulaziz University Adolf Eugen Fick ( 1829 1901 ... – PowerPoint PPT presentation

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Title: Cardiac Output And Hemodynamic Measurements


1
Cardiac Output And Hemodynamic Measurements
  • Iskander Al-Githmi, MD, FRCSC, FCCP
  • Asst. Professor of Surgery
  • King Abdulaziz University

2
Adolf Eugen Fick ( 1829 1901)
3
Historical Perspective
  • Adolf Fick 1829- 1901
  • Born in Sep. 1829, in Kassel, Germany
  • Earned MD in 1851
  • 1855- Introduced a law of diffusion called Fick
    law of diffusion
  • 1870- Was the first one to develop a technique
    for measuring cardiac output
  • Fick was died in Aug. 1901

4
Cardiac Cycle
  • Phase 1 Atrial contraction
  • Phase 2 Isovolum contraction
  • Phase 3 Rapid ejection
  • Phase 4 Reduced ejection
  • Phase 5 Isovolum relaxation
  • Phase 6 Rapid filling
  • Phase 7 Reduced filling

5
Cardiac output
  • Volume of blood ejected from left ventricle in
    one minute
  • It is the determinant of global oxygen transport
    from the heart to the body
  • It reflects the efficiency of cardiovascular
    system
  • There no absolute value for cardiac output
    measurement

6
Cardiac output influencing factors
  • Ventricular Preload
  • - Volume of blood in the ventricle at the end of
    diastole
  • - Any changes in the ventricular preload will
    affect the ventricular stroke volume

7
Cardiac output influencing factors
  • Ventricular Preload

8
Frank- Starling Mechanism
  • The ability of the heart to change its force of
    contraction and therefore stroke volume in
    response to changes in venous return
  • I.E ( the greater the diastolic volume or fiber
    stretch at the end of diastole the stronger the
    force of contraction at systole
  • The force of contraction will decline once this
    physiological limit has reached

9
Frank-Starlings Mechanism
10
Cardiac output influencing factors
  • Preload assessment
  • It has been very difficult to measure the fiber
    length or volume at the bedside
  • It is clinically acceptable to measure preload as
    a pressure.
  • CVP is used to evaluate right ventricular preload
  • Pulmonary artery diastolic pressure or PCWP are
    used to evaluate the left ventricular preload

11
Cardiac output influencing factors
  • Contractility
  • Increased contractility, will shift Starlings
    curve to the left
  • Decreased contractility will shift Starlings
    curve to the right

12
Cardiac output influencing factors
  • Assessment of contractility
  • Stroke volume (SV)
  • SV EDV - ESV
  • Stroke volume index (SVI)
  • SVI CI / HR
  • Left ventricular stroke work index
  • LVSWI MAP PCWP x SVI x (0.0136)

13
Cardiac output influencing factors
  • Afterload
  • Related to ventricular wall stress
  • Laplace Law
  • Tension (T) Pr/t
  • Afterload per se does not
  • Alter preload

14
Clinical Measurement of Afterload
  • Right ventricular afterload
  • Pulmonary vascular resistance (PVR)
  • PVR MPAP- PAWP / CO x 80
  • Normallt 250 dynes/ sec /cm-5

15
Clinical Measurement of Afterload
  • Left ventricular afterload
  • -Systemic vascular resistance (SVR)
  • -SVR MAP- RAP / CO x 80
  • Normal 800 1200 dynes / sec / cm-5

16
  • Ventricular compliance
  • Compliance V/P
  • Given a change in the pressure cause a change in
    the volume

17
  • Ejection Fraction
  • Is a fraction of blood ejected by the ventricle
    relative to its end-diastolic volume
  • EF SV / EDV. 100
  • Ejection fraction is used as a clinical index to
    evaluate the inotropic status of the heart

18
Methods of calculating and measuring cardiac
output
  • Simple method
  • CO SV x HR
  • SV 2ml x pulse pressure
  • CO 2ml x pulse pressure x HR

19
Methods of calculating and measuring cardiac
output
  • Fick Principle gold standard
  • CO VO2 / O2 art O2 ven
  • Arterial O2 Hb x 1.34 x O2 sat.
  • Venous O2 Mixed venous blood
  • VO2 Oxygen consumption
  • Fick Principle relies on the total uptake of a
    substances by peripheral tissue is equal to the
    product of blood flow to the peripheral tissue
    and arterial venous concentration difference of
    the substances
  • Fick cardiac outputs are infrequently used
    because difficulties in collecting and analyzing
    exhaled gas conc. In critically ill patients
    because may not have normal VO2 value

20
Methods of calculating and measuring cardiac
output
  • Thermodilution Method
  • Based on how fast the flowing blood can dilute
    the substances introduced into the circulation
  • Stewart-Hamilton Equation
  • CO I x 60 / cm x t x 1/k
  • Area under the curve is inversely proportion to
    the rate of blood flow. This flow is equivalent
    to cardiac output in the absence of shunt

21
Methods of calculating and measuring cardiac
output
  • Thermodilution Curve

22
Thermal dilution method
  • Limitations
  • Affected by the phase of respiration and should
    be measured at the same point of respiratory
    cycle
  • Variations in the speed of cold water injection
    can result in altered measurement

23
Non Invasive Methods
  • Doppler Method
  • Based on measuring the length of blood
    flow-velocity in the ascending aorta in unit
    time. Multiplied by the cross- sectional area of
    the aorta to give stroke volume. Multiplied to
    heart rate to give cardiac output.

24
Methods of calculating and measuring cardiac
output
  • Impedance plethysmography
  • This technique was developed by NASA. Cardiac
    output can be measured across externally
    electrodes. It measures a changing impedance in
    the chest (blood volume). The rate of change of
    impedance is a reflection of cardiac output.
  • CO Art. BP / total peripheral vasc. resistance

25
Questions
  • Question 1
  • During a cardiac output reading the thermistor of
    the PAC measures the temperature of the
  • Blood
  • Injectate
  • Pulmonary artery blood
  • Mixing of blood and injectate

26
Questions
  • Question 2
  • Which of the following statements is correct
  • As it relates to cardiac output curve ?
  • The larger the curve, the larger the output
  • The smaller the curve, the smaller the output
  • The larger the curve, the smaller the output

27
Questions
  • Question 3
  • When patients take a spontaneous breath,
  • Venous return and cardiac output
  • Increase
  • Decrease

28
Questions
  • Question 4
  • A 50- year-old male with myocardial ischemia
    presents with the following
  • HR 128 BPM
  • CO 6.2 L/min
  • MAP 88 mmHg
  • SVO2 51
  • CVP 6 mmHg
  • PAWP 16
  • SaO2 94
  • Is the cardiac output for his tissue is adequate
    ?

29
Questions
  • Question 5
  • Same patient after treatment with NTG and
    morphine, his numbers are as follow
  • HR 115 BPM
  • CO 5.1L/min
  • MAP 84 mmHg
  • PAWP 13 mmHg
  • SVO2 61
  • CVP 5 mmHg
  • SaO2 95
  • Is he better or worse ?
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