Ch 16 Cardiac Output Measurement

Mean Arterial Pressure (MAP)

(S + 2D)/3

If the CVP is higher than normal, the problem being caused by the RV because it is not pumping out enough. Therefore what happens?

- Blood backs up to the RA - RA pressure goes up

The normal individual Cardiac Output varies with what 5 things:

- age - sex (10% higher in men) - body size - blood viscosity (hematocrit) - the tissue demand for oxygen

List negative inotropic agents:

- beta blockers - barbiturates - antidysrhythmic agents (cainamide and quinidine)

What can occur if the MAP decreases lower than 60 mm Hg

- brain perfusion decreases - kidneys shut down - coronary artery does not perfuse

List positive inotropic drugs:

- calcium - digitalis - epi - NE - dopamine - dobutamine - amrinone - isoproterenol - caffeine

PVR is increased by conditions that decrease blood flow through the pulmonary artery, such as:

- contraction - obstruction (emboli) - compression of the pulmonary vasculature

4 things that cause the pulmonary artery to constrict

- decrease in PO2 - high CO2, hypercapnia - high hydrogen levels, acidemia - allergic reaction to drugs

How does Positive Pressure Ventilation affect Cardiac Output when the chest wall compliance is decreased and lung compliance is increased?

- decreases venous return - increases pulmonary vascular resistance - decreased cardiac output

physiologic depressants of cardiac contractility include:

- hypoxia - hypercapnia - acidosis

What drugs elevate the SVR?

- norepinephrine (levophed) - methoxamine (vasoxyl) - epinephrine (adrenalin)

SV is determined by the following 3 factors:

- preload - afterload - contractility

Overtime, increased PVR results in:

- pulmonary hypertension - eventual cor pulmonale (right sided heart failure)

List the 3 factors that decrease ventricular compliance and therefore cause the pressure to increase out of proportion to the volume include the following:

- right ventricle dilation and overload (cause the septum to shift to the left and impinge on the left ventricle) - PEEP or CPAP - inotropic drugs (increase the force of contractility)

myocardial contractility is affected by the following factors:

- sympathetic nerve innervation - inotropic drugs - physiologic depressants

The presence of which conditions increases intrathoracic pressure and thereby decreases venous return:

- tension pneumothorax - valsalva maneuver - breath holding in children - prolonged bouts of coughing - PPV

What is afterload?

- the hemodynamic factor that represents all resistance to blood flow. - the work the left ventricle has to by working against the resistance in the blood vessels.

Elevated SVR is associated with clinical conditions that cause:

- vasoconstriction (such as cold) - inadequate perfusion - hypertension - administration of vasopressors

What does the presence of LOW OXYGEN concentration and increased levels of HYDROGEN IONS and CO2 at the tissue level causes?

- vasodilation - increased blood flow to the affected area

What are the two components of afterload?

- ventricular wall stress - peripheral vascular resistance

What can help decrease the SVR?

- warming a patient to normal temperatures - administering nitroprusside

5. Which of the following statements are true regarding the distribution of blood flow and venous return? 1. 60% to 70% of the total blood volume is in the venous system 2. Blood is shunted to vital organs during cardiac failure 3. Circulatory function and pressures can be maintained with a loss of 20% of the blood volume 4. 50% of the total blood volume is in the venous system a. 1, 2, and 3 b. 2 and 3 c. 1 and 2 d. 2, 3, and 4

1. 60% to 70% of the total blood volume is in the venous system 2. Blood is shunted to vital organs during cardiac failure 3. Circulatory function and pressures can be maintained with a loss of 20% of the blood volume

19. Which of the following are noninvasive techniques for determining cardiac performance? 1. Echocardiography 2. Transthoracic electrical bioimpedance 3. Partial CO2 rebreathing 4. Thermodilution a. 1, 2, and 3 b. 1, 2, and 4 c. 2, 3, and 4 d. 2 and 4

1. Echocardiography 2. Transthoracic electrical bioimpedance 3. Partial CO2 rebreathing

The pressure created by each stroke depends on 3 things:

1. Efficacy of my heart as a pump 2. vascular resistance 3. fluid volume (too much fluid means increase in pressure)

15. Which of the following abnormalities would increase PVR? 1. Hypoxemia 2. Acidosis 3. Pulmonary emboli 4. Hypervolemia a. 1, 3, and 4 b. 1, 2, and 3 c. 2 and 4 d. 1, 2, 3, and 4

1. Hypoxemia 2. Acidosis 3. Pulmonary emboli

List the 3 main factors affecting the amount of blood returned to the heart:

1. changes in the circulating blood volume 2. changes in the distribution of the blood volume 3. atrial contraction

What is the normal range of oxygen uptake (VO2) ?

120 to 160 mL/min/m2

2. Calculate the arterial and mixed venous oxygen contents and C(a-v)O2. For example, given a hemoglobin of 14 g/dL, an arterial oxygen saturation (SaO2) of 90%, and a mixed venous oxygen saturation (SvO2) of 60%, the C(a-v)O2 is computed as follows:

120 to 160 ml/mon

When the PAWP is less than _____ there is an issue in the LV.

18

What is the normal Central Venous Pressure?

2-6 mmHg

What is the commonly cited RESTING Cardiac Index?

2.5 - 4.0 L/min/m2

How much can the heart pump when stimulated by the SNS?

20 - 25 mL/min

12. Which of the following are possible hemodynamic effects of using mechanical ventilation? 1. Reduced preload 2. Reduced CO 3. Increased PVR 4. Increased preload a. 1, 2, and 3 b. 2, 3, and 4 c. 1 and 2 d. 3 and 4

3. Increased PVR 4. Increased preload

What is the normal range of the C(a-v)O2?

3.0 to 5.5 mL/dL

What is the normal cardiac output range ?

4 to 8 ml//min

What is the average cardiac output for men and women of all ages ?

5 L/min

What is the normal pulmonary artery wedge pressure?

6-12 mmHg

What is the normal adult stroke volume?

60 - 130 mL/beat

What is the normal Ejection Fraction ?

65%-70%

What is the normal MAP?

70 - 105 mm Hg

How is cardiac index obtained?

CO/BSA (L/min/m2)

If the right ventricle fails the __________ will be higher.

CVP

Oxygen Transport equation (DO2)

CaO2 x CO x 10

_____________ ______________ is often used to describe flow output.

Cardiac Index

The filling of the right side of the heart is right atrial pressure, commonly measured as the ________________________________________________________________.

Central Venous Pressure (CVP)

What disease process occurs when the diseased or damaged heart can no longer pump all of the blood returned to it?

Congestive Heart Failure (CHF)

Calculation for Cardiac Output

HR X SV

_______________ (+/-) pressures around the heart pull blood toward the heart but make it more difficult for blood to leave the heart.

Negative

Patients with CHF will have higher _____________.

PCWP

________________ (+/-) pressures around the heart push on the heart, making it harder for blood to enter the heart, but easier for blood to be ejected

Positive

Pulmonary artery wedge pressure (PAWP) is also known as

Pulmonary capillary wedge pressure (PCWP)

EF calculation

SV/EDV

How does the TDCO, thermodilution cardiac output, work?

Sterile dextrose in water or normal saline solution at least 2°C colder than blood temperature is injected into the proximal port (right atrium) of the PA catheter. The resultant cooling is detected by a thermistor bead located just behind the balloon of the catheter, which is positioned in the pulmonary artery

Ficks cardiac output equation

The CO is calculated as the quotient of oxygen uptake and the difference of the arterial and mixed venous oxygen content

1. Given a stroke volume of 62 mL and an HR of 88 beats/min, what is the CO? a. 5.5 L/min b. 6.2 L/min c. 7.0 L/min d. 11.0 L/min

a. 5.5 L/min

4. What happens to CO in the presence of sympathetic nervous stimulation? a. Increases significantly b. Decreases significantly c. Remains unchanged d. Decreases by only 20%

a. Increases significantly

16. Which of the following is TRUE regarding cardiac contractility? a. It cannot be measured directly b. It is increased by β-blocking drugs c. It is increased by hypercapnia d. It is increased by parasympathetic neural stimulation

a. It cannot be measured directly

9. The amount of precontraction stretch applied to the ventricles is called: a. Preload b. Afterload c. Contractility d. EF

a. Preload

Starling's law of the heart

addresses the contractile properties of the heart: the more the muscle is stretched, the stronger it will react, until it is stretched to a point at which it will not react at all

3. A 75-year-old man is admitted to the ICU after aortic valve surgery. A pulmonary artery catheter yields the following data: central venous pressure (CVP): 5 mm Hg; cardiac output (CO): 4.0 L/min; mean arterial pressure (MAP): 80 mm Hg; mean pulmonary artery pressure (MPAP): 26 mm Hg; pulmonary artery wedge pressure (PAWP): 10 mm Hg; and heart rate (HR): 80 beats/min. Calculate the patient's pulmonary vascular resistance (PVR): a. 40 dynes-s/cm5 b. 320 dynes-s/cm5 c. 160 dynes-s/cm5 d. 220 dynes-s/cm5

b. 320 dynes-s/cm5

2. What is the normal range for CO in an adult? a. 2 to 4 L/min b. 4 to 8 L/min c. 6 to 10 L/min d. 10 to 13 L/min

b. 4 to 8 L/min

17. Which of the following invasive CO techniques requires the measurement of inhaled and exhaled gas concentrations? a. Thermodilution b. Fick c. Pulse contour d. Transtracheal Doppler

b. Fick

14. Which of the following is most closely related to systemic vascular resistance? a. Right ventricular afterload b. Left ventricular afterload c. CO d. Left ventricular preload

b. Left ventricular afterload

Why is the work performed by the left ventricle much greater than the right ventricle?

because it must eject against the mean aortic pressure (MAP), which is about 6x greater than the mean pulmonary artery pressure (MPAP)

6. What is the normal range for CI? a. 0.2 to 1.3 L/min/m2 b. 1.5 to 2.6 L/min/m2 c. 2.5 to 4.0 L/min/m2 d. 4 to 8 L/min/m2

c. 2.5 to 4.0 L/min/m2

8. What is the normal range for ejection fraction? a. 25% to 40% b. 40% to 55% c. 65% to 75% d. 75% to 85%

c. 65% to 75%

18. Which of the following techniques can provide beat-by-beat measurement of stroke volume and cardiac output? a. Thermodilution b. Fick c. Pulse contour d. NM3

c. Pulse contour

Why has the use of the PA catheter decreased?

costs and hazards

7. Which of the following correlates best with the oxygen requirements of the heart? a. SV b. EF c. EDV d. Cardiac work

d. Cardiac work

11. Which of the following conditions would cause a reduction in ventricular preload? a. Decreased ventricular compliance b. Increased venous return c. Cardiac tamponade d. Hypovolemia

d. Hypovolemia

10. Preload of the left ventricle is assessed by which of the following parameters? a. Arterial diastolic blood pressure b. MAP c. CVP d. PAWP

d. PAWP

13. Which of the following conditions would increase left ventricular afterload? a. Pulmonic valve stenosis b. Decreased blood viscosity c. Positive end-expiratory pressure d. Systemic hypertension

d. Systemic hypertension

What is Cardiac Work?

is a measure of energy the ventricles use to eject blood against the aortic or pulmonary pressures (resistance).

What is Preload ?

is the stretch on the ventricular muscle fibers before contraction

What is Stroke Volume?

is the volume of blood ejected by a single ventricular contraction

Drugs with a ______________ (+/-) inotropic effect decrease the strength of contraction but may also decrease the myocardial oxygen demand.

negative

What is persistent pulmonary artery hypotension treated with?

nitric oxide

Sympathetic nerve stimulation with release of ___________________ and other circulating ________________ increases the strength and rae of cardiac contraction.

norepinephrine, catecholamines

A drug with a ___________________ (+/-) inotropic effect increases the strength of contraction of the myocardial fibers, most often by increasing intracellular calcium levels.

positive

the filling pressure for the left side of the heart is left atrial pressure, commonly measured as _________________________________________________________________________________.

pulmonary artery wedge pressure (PAWP)

The resistance in the lungs is __________________ ____________________ ________________ and the resistance is much less.

pulmonary vascular resistance (PVR)

Bradycardia does not drop cardiac output as long as the heart can compensate with increased ___________ _______________.

stroke volume

the resistance in the left ventricle is the _______________ __________________ ____________________ and the resistance is much greater.

systemic vascular resistance (SVR)

What is ventricular compliance ?

the ability of the ventricle to expand as blood enters from the atrium

End-Diastolic Volume (EDV) is defined as

the amount of blood in the ventricle at the end of filling (diastole)

What is Cardiac Output ?

the amount of blood the heart pumps in a minute

What regulates capillary blood flow?

the concentrations of: - oxygen - carbon dioxide - hydrogen ions - electrolytes - humoral substances /l

What can help estimate the ventricular size?

the end-diastolic pressure

What does the Ejection Fraction (EF) represent?

the percentage of the EDV that is ejected with each heart beat

What is considered the most accurate and reproductive method for CO determination and the one to which all other methods are compared?

the pulmonary artery catheter thermodilution method

What is the venous return?

the volume of blood returning to the right atrium