review of hemodynamics
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Review of Hemodynamics.pptxTRANSCRIPT
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.