Review of Hemodynamics

Review of Hemodynamics

By: Maria Lourdes B. Galima

and determine

• What is Hemodynamics?

The study of forces involved in the flow of blood through the cardiovascular and circulatory systems.

• What are the components of hemodynamics?

- Blood Pressure (BP) - Central Venous Pressure (CVP), - Right and Left Heart Pressures.

• What are the physiologic principles of Hemodynamics?

Factors that :- affect myocardial function, - regulate BP - determine cardiac performance and cardiac output (CO).

• Review of the Circulatory System

Veins and ArteriesHeart as a pumpBalance of oxygen delivery and

oxygen demandMechanisms that regulate the flow

of blood through the system

• Instant Feedback

Ms. Gallego,

“When the body’s metabolic demands increase, the blood vessels

(Dilate/Constrict?) in an attempt to force blood back to the heart.”

• “When the body’s metabolic demands increase, the blood vessels Constrict in an attempt to force blood back to the heart.”

Instant Feedback

Ms. Estrada,

“When the body’s metabolic demand decreases, the veins dilate, thus,

pooling blood in the periphery and reducing venous return to the heart.”

True or False

“When the body’s metabolic demand decreases, the veins dilate, thus,

pooling blood in the periphery and reducing venous return to the

heart.”

True

• How does the Heart work?

- cardiac cycle

- the electrical conduction system

• How does the Heart work?

a. Depolarization- electrical activation of muscle cells of the heart and stimulates cellular contraction.

b. Repolarization - return of the depolarized muscle cells to its original state of electrolyte balance.

• Instant FeedbackMs. Butawan, During systole, the __________

valves are open and the __________ are closed.

Ms. Tagalog During diastole, the __________

valves are open and the __________ are closed.

During systole, the semilunar valves are open and the AV valves are closed.

During diastole, the AV valves are open and the semilunar valves are closed.

• Cardiac Cycle

- Right atrium receives venous blood from the systemic circulation.

- Left atrium receives reoxygenated blood from the lungs.

• Cardiac Cycle

- While both atria are filling, the SA node fires and starts the process of depolarization.

- After atrial depolarization, the atria contracts forcing the remaining blood into the ventricles (Atrial Kick).

• Common terms:

1. Stroke Volume (SV)2. Left Ventricular End-Diastolic

Volume (LVEDV)3. Left Ventricular End-Systolic

Volume (LVESD)4. Ejection Fraction (EF)5. Blood Pressure (BP)6. Cardiac Output (CO)7. Systemic Vascular Resistance (SVR)

• Stroke Volume - the volume of blood that is ejected during systole.

• Left Ventricular End Systolic Volume (LVESV) or Afterload– the amount of blood that remains in the left ventricle at the end of systole.

• Left Ventricular End Diastolic Volume (LVEDV) or Preload- the amount of blood that is in the ventricle just before ejection occurs.

• Ejection Fraction- the portion of the volume the left ventricle ejects (70%).

• BP = CO x SVR• The tension exerted by blood on the

arterial walls

Cardiac output and peripheral vascular resistance directly

affects BP.

Factors affecting Arterial Blood Pressure

Mean Arterial Pressure

Peripheral Resistance Autonomic Control Cardiac Output

Blood Viscosity (influenced by

hematocrit)

Arteriolar lumen size (influenced by SNS)

Heart rate

Sympathetic & Parasympathetic

System

Stroke volume

Preload

Intraventricular pressure

Autonomic control Atrial pressure Venous pressure Venous return

Blood volume Renin –angiotensin system

• Instant FeedbackMs. Baptista,

“ If a patient’s BP decreases, then either the flow (CO) or the

resistance (SVR) will change.”

True or False

Cardiac Output and peripheral vascular resistance directly affects

BP. “ If a patient’s BP decreases, then

either the flow (CO) or the resistance (SVR) will change.”

True

• Pressure = flow x resistance

If flow or resistance is altered, then pressure is affected.

• Instant Feedback

Ms. Alcabasa,“ Narrowed vessels decrease resistance

and decrease pressure. Conversely, dilated vessels increase resistance and

increase pressure.”

True or False

False

“ Narrowed vessels increaseresistance and increase pressure. Conversely, dilated vessels decreaseresistance and decrease pressure.”

• SVR = Mean Arterial Pressure MAP – CVP x 80

Cardiac Output (CO)

SVR is a reflection of peripheral vascular resistance and is the opposition to blood flow from the blood vessels.

It is affected by the tone of the blood vessels, blood viscosity and resistance from the inner lining of the blood vessels.

The resistance against which the left ventricle pumps (inverse relationship with CO)

The diameter of the blood vessel is one of the major factor that influence SVR.

• Vasoactive drugs are often used in the critical care setting to change the size of the arterioles to decrease or increase blood pressure.

• Instant FeedbackMr. Valles,

“SVR decreases when the blood vessels constrict and it increases

when blood vessels dilate.”

True or False

False

• “SVR decreases when the blood vessels relax and it increases when blood vessels constrict.”

• Instant Feedback

Ms. Reyes,

“If the SVR decreases, then cardiac output increases.

SVR increases to maintain BP when the cardiac output decreases.”

True or False

• “If the SVR decreases, then cardiac output increases.

• SVR increases to maintain BP when the cardiac output decreases.”

True

Elevations of Systemic Vascular Resistance

Two (2) primary reasons for elevation:

1. Vascular disturbances (vasoconstriction caused by HPN or excessive cathecholamine release)

2. Compensatory responses to maintain BP in decreased CO.

• Instant Feedback

Ms. Arciaga,

“Elevations of SVR increases the workload of the heart and myocardial

O2 consumption.”

True or False

“Elevations of SVR, increases the workload of the heart

and myocardial oxygen consumption.”

True

Decreases in Systemic Vascular Resistance

Potential causes are sepsis, neurologically mediated vasomotor tone loss.

• Instant FeedbackMs. Gallego,

“Thus, when SVR increases, CO increases in an attempt to

maintain BP.”

True or False

True

• “Thus, when SVR decreases, CO increases in an attempt to

maintain BP.”

• Common Medications and Habits that Affect SVR

Smoking and stress can cause vasoconstriction

Vasodilators enlarge (dilate) the size of the arterioles in an attempt to decrease BP.

Vasoconstrictors constrict the size of the arterioles in an attempt to increase BP

• CO = SV x HR• Normal Value: 4-8 liters /min

Cardiac output is the amount of blood ejected from the heart in one full minute.

It has two components: the SV and HR

A major goal in assessing CO is ensuring adequate oxygenation.

• Stroke Volume

The amount of blood ejected from the heart with each beat.

Three (3) factors that influence SV:1. Preload2. Afterload3. Contractility

• Preload

The filling volume of the ventricle at the end of diastole.

Reflects the amount of cardiac muscle stretch at end diastole just before contraction.

• PreloadIt is dependent on the volume of blood

returning to the heart.

Measured by Pulmonary artery wedge pressure (PAWP)

• Instant Feedback

Ms. Estrada,

“Increase fluid volume and venous constriction increases Preload.” WHILE

“Hypovolemia and vasodilation decreases Preload.”

True or False

True

“Increase fluid volume and venous constriction increases Preload.”

WHILE“Hypovolemia and vasodilation

decreases Preload.”

Preload is directly related to the force of myocardial contraction.

An enlarged heart will increase preload and is measured by an elevated PAWP.

• AfterloadThe amount of resistance against

which the left ventricle pumps.Primarily influenced by the blood

vessels, blood viscosity, flow patterns and condition of the valves.

It is determined by BP and arterial tone.

• Afterload “The greater the resistance, the more the

myocardium has to work to overcome the resistance.”

Left ventricular afterload is measured by the assessment of the systemic vascular resistance (SVR).

Pulmonary vascular resistance (PVR) measures the resistance against which the right ventricle works.

• Instant Feedback

Ms. Butawan,

“Vasoconstriction results from an increase systemic arterial tone which increases

BP and causes an increase in Afterload.”

True or False

True

“Vasoconstriction results from an increase systemic arterial tone which increases BP and causes

an increase in Afterload.”

• Contractility

The strength of myocardial fiber shortening during systole.

Allows the heart to work independently regardless of changes in preload, afterload or fiber length.

• Contractility

It is a determinant of stroke volume and affects ventricular function.

Preload directly influences contractility.

• Instant Feedback

Ms. Tagalog,

“As resistance to ventricular ejection (afterload) decreases, Left ventricular

work increases and stroke volume may decrease.”

True or False

False

• “As resistance to ventricular ejection (afterload) decreases, Left ventricular work increases

and stroke volume may increase.”

• Heart Rate

The number of heartbeats per minute Important in maintaining CO and

included in the CO formula.

• Instant Feedback

Ms. Baptista,

“When contractility is depressed or if Cardiac Output is decreased, HR will increase to maintain blood flow for metabolic demand.”

True or False

True

“When contractility is depressed or if Cardiac Output is

decreased, HR will increase to maintain blood flow for

metabolic demand.”

• Manipulation of Cardiac OutputSTROKE VOLUME HEART RATE

PRELOAD AFTERLOAD Contractility

Increased Decreased Increased Decreased Decreased Increased Decreased

Mgt:

Diuretics &Vasodilators

Mgt:

Fluids &Vaso –constrictors

Mgt:

Arterial Vaso -dilators

Mgt:

Vaso -constrictors

Mgt:

Positive Inotropes

Mgt:

Beta Blockers & Ca Channel Blockers

Mgt:

Sympatho-mimetics & Cardiac pacing

• Physiologic Principles that Affect Cardiac Performance

1. Frank-Starling Law of the Heart Augmenting ventricular filling during

diastole before the onset of a contraction will increase the force of contraction during systole.

“The greater the stretch, the greater the force of the next contraction.”

• Physiologic Principles that Affect Cardiac Performance

2. InotropismThe ability to influence contractility of

muscle fibers.A positive inotrope enhances contractility

and a negative inotrope depresses contractility.

Instant Feedback

Ms. Alcabasa,

“Diastolic Filling time is shortened when heat rate is <60 beats/min

(bradycardia) and diastolic filling time is lengthened when heart rate is >100

beats/min (tachycardia).”

True or False

False

• “Diastolic Filling time is lengthened when heat rate is <60 beats/min (bradycardia) and diastolic filling

time is shortened when heart rate is >100 beats/min (tachycardia).”

• Physiologic Principles that Affect Cardiac Performance

3. Force-Frequency RatioAny changes in HR or rhythm can change

diastolic filling time of the ventricles therefore altering fiber stretch and the force of the next contraction.

This ratio influences the SV and CO.

• Instant Feedback

Mr. Valles,

“When HR increases, myocardial O2 demand increases so when diastolic filling time is

shortened, coronary artery filling increases.”

True or False

False

“When HR increases, myocardial O2 demand increases so when diastolic filling time is shortened, coronary

artery filling decreases.”

• Physiologic Principles that Affect Cardiac Performance

4. Miscellaneous Influences Hyperkalemia, hyponatremia, hypoxia,

hypercarbia & myocardial scar tissue decreases myocardial contractility.

• Instant Feedback

Ms. Reyes,

“Sympathetic stimulation increases myocardial contractility and

Parasympathetic stimulation (via the vagus nerve) depresses the SA node, atrial

myocardium and AV junctional tissue.”

True or False

True

“Sympathetic stimulation increases myocardial contractility and

Parasympathetic stimulation (via the vagus nerve) depresses the SA node, atrial myocardium and AV junctional

tissue.”

Hemodynamic Monitoring

• What is Hemodynamic Monitoring?

- Hemodynamics or pressures of the cardiovascular and circulatory systems can be measured by invasive methods:

a. direct arterial BP monitoringb. CVP monitoringc. indirect measurements of left ventricular

pressures via a flow-directed balloon-tipped catheter (e.g. PA catheters, Swan-Ganz catheters)

• Goals of Hemodynamic Monitoring:

1. Ensuring adequate perfusion2. Detecting inadequate perfusion3. Titrating therapy to specific end point4. Qualifying the severity of illness5. differentiating system dysfunction like:

- differentiating between cardiogenic and noncardiogenic pulmonary edema

Direct Arterial Blood Pressure Monitoring

- allows for accurate, continuous monitoring of arterial BPs.

- it provides a system of continuous sampling of blood for arterial gases without repeated arterial punctures.

Clinical Considerations for Direct Arterial BP Monitoring:

- Potential complications of thrombosis, embolism, blood loss and infection.

Right Atrial Pressure Monitoring

- can be referred to as RAP or CVP- this is a direct method

- Any condition that changes venous tone, blood volume, or contractility of the right ventricle can cause abnormality in RAP values.- Normal Value = 0-6mmHg

Instant Feeedback

Ms. Arciaga,

“Low RAP or CVPmeasurements can reflecthypervolemia or extremevasoconstriction. ANDHigh RAP measurementscan reflect hypovolemia orsevere vasodilation.”

True or False

True

“Low RAP or CVP measurements can reflect hypervolemia or extreme vasoconstriction. AND High RAP

measurements can reflect hypovolemia or severe vasodilation.”

Low RAP or CVP measurements can reflect hypovolemia or extreme vasodilation.

• High RAP measurements can reflect hypervolemia or severe vasoconstriction

• OR conditions that reduce the ability of the right ventricle to contract like pulmonary hypertension and right ventricular failure.

• Left trial Pressure Monitoring- A direct method used only in cardiac surgical procedures, cardiac catheterization and after open heart surgeries.

• Left trial Pressure Monitoring

-A catheter is inserted with the distal end tunneled through an incision in the chest wall.- LAP provides the ability to observe the pressures in the left atrium.- Normal Value = 6-12mmHg

Complications of LAP Monitoring - Major complications are air embolism and system debris which can obstruct a coronary or cerebral artery.

Prevention of Complications

- Connections must be tight and caps should be on stopcocks to avoid air entering or administering medications and fluids through this line.

Chest x-ray (A) and intracardiac echocardiogram (B) at the time of implantation demonstrating orthogonal fixation of the LAP monitoring device in the interatrial septum

(arrows).

• Instant Feedback

Ms. Gallego,

“Patients who have compliant left ventricles can have large volume changes without large

changes in pressure; conversely, patients with noncompliant ventricles may have extreme

volume changes without PCWP increase.

True or False

• It is important to remember that changes in PCWP are not always equal to volume changes because the PCWP is not the only parameter involved in muscle stretch.

• Therefore, Patients who have compliant left ventricles can have large volume changes without large changes in pressure; conversely, patients with noncompliant ventricles may have extreme volume changes without PCWP increase.

• Pulmonary Artery Monitoring

- The catheter is a multi-lumen, balloon tipped that is inserted through the venous system into the right side of the heart and into the pulmonary artery.

- May be inserted from an antecubital vein, external jugular vein, subclavian artery or any other peripheral vein into the PA through a percutaneous introducer.- Normal Value (PAP) = 10-15mmHg- Normal Value (PCWP) = 6-12mmHg

- The catheter is inserted with the balloon deflated.

- When the catheter enters the right atrium, the balloon is inflated allowing it to float with the flow of blood into the PA.

- When the balloon is deflated, the catheter directly measures the PA pressures.

- With balloon inflated, the catheter floats into a pulmonary arteriole and wedges itself in a smaller lumen.

- The opening of the catheter beyond the inflated balloon reflects pressures distal to the PA.

• The PA catheter is used to monitor high-risk, critically ill patients with goals that include detection of adequate perfusion and the diagnosis and evaluation of the effects of therapy.

• This high-risk patient group include:- Acute MI- Severe angina- Cardiomayopathy- Right & Left ventricular failure-Pulmonary diseases

• Pulmonary Arterial monitoring is a valuable tool for observing fluid balance in the critically ill patient at risk for other cardiopulmonary problems.

• To monitor hemodynamics, the equipment must include:- a transducer- amplifier- display monitor- catheter system- tubing filled with fluid

• The system provides the ability to monitor a pressure waveform that is displayed as a digital readout on the oscilloscope.

• Nursing Interventions for Hemodynamic Monitoring:

1. Provide patient education about the procedure.2. Ensure that the appropriate procedure consent forms are signed.3. Setting up the equipment and preparing the lines properly.

Nursing Interventions for Hemodynamic Monitoring:

4. Assisting the physician with catheter insertion.5. carefully monitoring the pressures.6. Making clinical decisions per institutional policy7. Must be alert to potential complications.