Hemodynamics Flashcards
Exam 2
What is Hemodynamics?
Forces that control blood flow through the body
What is the end goal of hemodynamics?
we use hemodynamics to identify and address problem to restore adequate tissue perfusion
What are compensatory mechanisms in hemodynamics?
Mechanisms that change hemodynamic forces
Think about increased heart rate, respiratory rate, and blood pressure
When do we use hemodynamic monitoring?
When compensatory mechanisms fail due to illness
What is the pathway of blood flow through the heart?
IVC/SVC -> RA -> tricuspid valve -> RV ->Pulmonic valve -> Pulmonary artery -> Lungs -> Pulmonary veins -> LA -> Mitral valve -> LV -> Aortic valve -> Aorta
What are arteries?
Strong, elastic, three-layered vessels.
Arteries dilate or constrict to meet metabolic demand.
What are capillaries?
Microscopic vessels, one cell-layer thick walls.
What are veins?
Weak, elastic, three-layered vessels with one-way valves help return blood to heart; low pressure system
What is the average amount of blood in an adult body?
5L
What do vasopressors and vasodilators act on?
Receptors in the middle muscle layer of the arteries and veins
What is the effect of vasopressors and vasodilators?
Causing contraction or expansion of arteries and veins
What does the body produce to change the diameter of arteries and veins?
Catecholamines
What is the heart?
Mechanical pump of cardiovascular system
Muscular components and one-way valves
What can cause heart failure?
Muscle or valve failure
How is muscle contraction controlled?
Electrical stimulation (ECG)
What factors affect valve function?
Pressures on the valves
What does electrical dysrhythmia cause?
Abnormal muscle contractions
What does valve dysfunction cause?
Failure of one-way flow of blood through the heart
What is valve function dependent on?
Pressure
low pressure is where you get value/pressure problems
What happens during the diastolic phase of the cardiac cycle?
Heart is at rest
Blood flows into the right and left atrium
Why are the tricuspid and mitral valves open during the diastolic phase?
Pressures in the atria and ventricles are the same
What happens during the active diastolic phase?
Atria contract and squeeze blood into the ventricles
What causes the tricuspid and mitral valves to close?
Ventricular pressure exceeds atrial pressure this is S1 and S2
What is the approximate contribution of complete atrial emptying to cardiac output?
~30% % of total cardiac output. (this is sometimes called the “atrial kick”
What defines the diastolic phase?
Ventricles at rest
What defines the systolic phase?
Ventricles working
How do high heart rates affect chamber filling?
Reduces amount of time and less pressure
What sends a signal for the ventricles to contract?
Electrical stimulation down the bundle branches and through the Purkinje fibers
What happens during the systolic phase of the cardiac cycle?
Ventricles squeeze and push blood forward through the pulmonic and aortic valves into the lungs and the aorta.
What causes the S2 heart sound?
the pressure in the arteries exceeds the pressure in the ventricles, the pulmonic and aortic valves snap shut
What is SBP?
Highest pressure in the systolic phase.
What is DBP?
Lowest pressure in the diastolic phase.
When does the heart perfuse the coronary arteries?
During the diastolic phase when the heart is at rest.
What is the formula for cardiac output?
CO = HR x SV
What factors can affect heart rate?
ANS stimulation, temperature, electrolytes, adrenal stimulation, catecholamine release
Slow HR can decrease CO…..
Slow HR can decrease CO if the body is unable to compensate with an increase in SV
Why can a fast heart rate decrease cardiac output?
The heart does not have enough time to fill with blood
What is stroke volume?
The amount of blood pumped by the heart in one beat
What factors can affect stroke volume?
Preload, afterload, and contractility
Decreased stroke volume decrease cardiac output…
Unless the body compensates with increased heart rate
What is the normal CO in adults?
4-8L
Why does a fast heart rate not give the heart enough time to fill?
Not enough time for valves to fill
What is preload?
Stretch on the ventricular myocardium at the end of diastole.
Volume and outside pressure dependent.
What is afterload?
Resistance against which the ventricle must overcome to push blood forward.
the downstream resistance that the heart must beat against.
What is contractility?
The strength of muscle contraction in the myocardium.
What effects preload?
Increased intrathoracic pressure reduces preload; High PEEP, pneumothorax, and drugs like nitroglycerine affect it. Right heart heavily depends on preload.
What increases afterload?
Stenotic valves, pulmonary hypertension, systemic hypertension, vasopressors, hypoxia, hypothermia.
What medications increase contractility?
Digoxin, Levophed, Dobutamine, Milrinone
What conditions decrease contractility?
Hypocalcemia, Hypoxia, Acidosis, Hypothermia
What are some examples of negative inotropic (weaken the force of the heartbeat) medications?
Amiodarone, Beta blockers, Calcium channel blockers, ACE inhibitors
What is Cardiac Output?
Volume of blood pumped by the left ventricle in 1 minute
What is Cardiac Index?
Volume of blood pumped by the left ventricle in 1 minute divided by body surface area
How can Cardiac Index be calculated?
CO/BSA=CI
What is the normal range for Cardiac Index?
2.5-4.2 L/min/m2
Why is Cardiac Index preferred over Cardiac Output?
Universal measurement regardless of body size
What are intracardiac pressures?
Pressures within the heart
CVP=RAP=RV diastolic during the passive diastolic phase of the cardiac cycle , RV systolic=PA systolic, PA diastolic=LAP=LV diastolic during the passive diastolic phase of the cardiac cycle, LV systolic = SBP in the aorta
intracardiac pressure
Normal Hemodynamic values for central venous pressure (CVP)
2-6 mm Hg
same as right atrium pressure
Pressure of blood in the right heart at the end of diastole. Preload of the right ventricle
Normal Hemodynamic values for pulmonary artery pressure (PAP)
15-25 mm Hg
PA diastolic=LAP=LV diastolic during the passive diastolic phase of the cardiac cycle
8-15 mm Hg
Blood pressure in the pulmonary artery. PA diastolic pressure is almost the same as PAOP, Safer than occluding PA cath.
Normal Hemodynamic values for pulmonary artery occlusive pressure (PAOP)
8-12 mm Hg
Pressure of blood in the left heart at the end of diastole. Preload of left ventricle.
What is the stroke volume amount?
60-130 mL/beat
Volume of blood ejected from LV with each heartbeat.
Normal Hemodynamic values for Systemic Vascular Resistance (SVR) (pressure in arteries) (left ventricle gov name)
770-1500 dynes/sec/m2
Resistance that LV must overcome to open aortic valve and push blood forward. Afterload of left ventricle.
Normal Hemodynamic values for Pulmonary Vascular Resistance (PVR) (right ventricle gov name)
< 250 dynes/sec/m2
Resistance that RV must overcome to open Pulmonic valve and push blood forward. Afterload of right ventricle.
Normal Hemodynamic values for Mean Arterial Pressure (MAP)
70-105 mm Hg
Average blood pressure over 1 cardiac cycle. Important for end organ perfusion
What increases as we move through the heart?
pressure
What is the normal range for ScvO2?
65%-85%
Can be drawn from the distal port of a central line or PICC line or CVP port of PA catheter.
What is the normal range for SvO2?
60%-75%
Can be drawn from distal port of PA catheter
What does a high ScvO2 or SvO2 value indicate?
Increased oxygen supply, decreased oxygen demand, or inability to extract oxygen from blood
What do low values of central venous oxygen saturation indicate?
Decreased oxygen supply or increased oxygen demand
Why is central venous oxygen saturation slightly higher?
Blood above the right atrium is measured
What does urine and EtCO2 give information on?
Cardia output
What is non-invasive hemodynamic monitoring?
Monitoring without invasive procedures
Why is cuff size important for NIBP?
To ensure accurate readings
What is the preferred measurement site for NIBP?
Upper arm
Can the forearm be used for NIBP?
Yes, but it’s less accurate
What is Jugular vein distention (JVD)?
Elevation of CVP
How is JVD measured?
Supine position with HOB at 30-45 degrees
What is lactic acid?
Byproduct of anaerobic metabolism
What does lactate measurement indicate?
Tissue perfusion
Anytime the tissues are without adequate oxygen lactic acid is produced
It is a measure of how poorly perfused the tissues are
What is the goal when trending lactate?
> 20% reduction every 2 hours until normal
What are the components of an invasive pressure monitoring system?
Invasive catheter, high-pressure noncompliant tubing, transducer with a stopcock, pressurized flush system, bedside monitor
What is the role of the transducer with a stopcock in the pressure monitoring system?
To convert the pressure into an electrical signal
What does the pressurized flush system do in the pressure monitoring system?
Maintains patency and clears any blood clots
What are invasive catheters?
Medical devices inserted into the body
Arterial lines
Central Venous Lines
Pulmonary Artery Catheters
What is high-pressure noncompliant tubing used for?
Hemodynamic monitoring
How many stopcocks should be used with high-pressure noncompliant tubing?
Less than three
Why is it recommended to minimize the number of stopcocks with high-pressure noncompliant tubing?
To reduce the risk of leaks and errors
What is a transducer?
Converts intravascular pressure into waveforms and numerical data
Why does a transducer need to be calibrated to atmospheric pressure?
To ‘zero’ the system
What is the reference point used for leveling?
The 3-way stopcock or ‘air-fluid interface’
What is the purpose of a pressurized flush system?
Maintains patency of the tubing and catheter
What is the pressure at which the bag is inflated?
300 mm Hg
How much fluid continuously infuses per hour?
2-5 mL/hour
What are the usual flush solutions used?
0.9% NS or Heparinized solutions
What is a potential benefit of using heparin solutions?
Maintains catheter longer but increase risk for bleeding or Heparin‐induced thrombocytopenia (HIT)
What is the purpose of a bedside monitoring system?
Provide visual display of waveforms and numeric information from the transducer
What type of information does a bedside monitoring system provide?
Hemodynamic waveforms and numeric information
What is one function of a bedside monitoring system?
Data storage for integration into patient chart
What are the 4 major components of validating the accuracy of hemodynamic data?
- Patient positioning
- Leveling the air-fluid interface with the phlebostatic axis
- Zeroing the transducer
- Assessing the dynamic response (Square Wave Test)
What is the recommended position for a patient when using the phlebostatic axis?
Supine
Can the head of the bed be elevated and still give accurate readings?
Yes, up to 60 degrees
What point should be used if the patient is side-lying?
4th intercostal space mid-sternal point
When using the phlebostatic axis, what should you imagine about the patient’s body?
Transparent and level the air-fluid interface with the atria
How can the need for frequent re-leveling of the transducer be eliminated?
By affixing it to the chest wall
When should the transducer be leveled?
Each time the patient is repositioned
What can a low transducer cause?
Falsely high pressures
What can a high transducer cause?
Falsely low pressures
When should you zero the transducer?
When the catheter is inserted, beginning of shift, when repositioning, and with major changes in hemodynamic status
How can you validate the accuracy of the transducer’s readings?
Perform a square wave test
What is the Phlebostatic Axis?
Mid-point A-P chest wall and 4th ICS
What is an overdampened system?
[B]
No oscillations, slurred upstroke, or small undershoot
What is optimally dampened?
small undershoot below baseline followed by one or two oscillations before returning to the normal wave form. Data is accurate.
What are the consequences of an overdampened system?
[B]
Falsely low systolic and falsely high diastolic blood pressure
What are the possible causes of an overdampened system?
[b]
- Blood clots
- air bubbles
- loose connections
- kinks in tubing
- low flush solution
- underinflated pressure bag
What is an underdampened system?
[C]
Excessive oscillations after square wave
What are the consequences of an underdampened system?
[C]
Falsely high systolic and falsely low diastolic blood pressure
What are the possible causes of an underdampened system?
Excessive tubing length, too many stopcocks, unknown reasons, or patient anatomy
When should the dynamic response test be performed?
After catheter insertion, at least once per shift, after drawing blood, and anytime the system is opened.
What is the purpose of arterial lines?
To monitor arterial blood pressure directly
What is the most common site for arterial line placement?
Radial artery
Why are the femoral artery and dorsalis pedis not preferred sites for arterial line placement?
Considered ‘dirty’ sites
What test should be performed before inserting a radial arterial line?
Allen test
What are some complications of arterial lines?
Thrombosis, embolism, blood loss, infection
What is the Allen test?
Performing a test to assess the patency of the radial and ulnar arteries.
What can cause thrombosis in a continuous flush system?
Failure to maintain the continuous flush system.
What can cause an embolism in a catheter system?
Formation of small clots, shearing of the catheter, or installation of air.
When can blood loss occur in the system?
Anytime the system is disconnected the patient can bleed out significantly in a short amount of time
What is a potential risk of using dirty sites?
Increased risk of infection.
What are the assessments to routinely perform for arterial lines?
Color, temperature, pulse, sensation, and cap refill.
How should the wrist be positioned when an arterial line is in place?
In a neutral position
What should be done to ensure hemostasis when removing an arterial line?
Apply manual pressure until bleeding stops
(minimum of 5 minutes for radial artery).
Is it appropriate to administer medications via an arterial line?
NO
What is the arterial waveform?
The pulsatile representation of the pressure changes within an artery.
What does the arterial waveform represent?
Pressure changes within an artery.
What does the arterial line represent?
The left side of the heart
a camera looking back on the left side of the heart
- Top number is where systolic is measured; The highest point of the arterial waveform is the systolic blood pressure the lowest point of the arterial waveform is the diastolic pressure.
- dicrotic notch vale closes and you get change in pressure; The dicrotic notch is indicative of aortic valve closure.
- is diastolic
- Up strokes indicate that pressure is increasing towards the camera down strokes indicate that pressure is decreasing.
What do the up strokes on an arterial line indicate?
Increasing pressure
What do the down strokes on an arterial line indicate?
Decreasing pressure
What does the dicrotic notch indicate?
Aortic valve closure
What is the highest point on an arterial waveform?
Systolic blood pressure
What is the lowest point on an arterial waveform?
Diastolic pressure
What is CVP?
An estimate of the preload of the right ventricle
Central Venous Pressure
How do you measure CVP?
Hook the distal port of a CVC to the invasive pressure monitoring system
When should CVP be measured?
At the end of expiration
What are the normal CVP values?
2-6 mm Hg
What is the relationship between CVP and RAP?
They are equal and can be used interchangeably
What are the causes of high CVP/RAP?
Central venous pressure or right atrium pressure
- Volume overload
- Right Ventricular failure
- Tricuspid or pulmonic valve failure
- Pulmonary hypertension
- Pulmonary embolism
- Mechanical ventilation
What are the causes of low CVP/RAP?
Venodilation, Hypovolemia
What is the significance of a pulse pressure of 9%?
Indicative of ‘fluid responsiveness’
What is the purpose of pulmonary artery catheters?
Measuring pressures in the pulmonary artery and left atrium.
What can pulmonary artery catheters measure?
Cardiac output, pulmonary artery pressure, and central venous pressure.
What is a PA catheter?
A pulmonary artery catheter used to monitor heart and lung function
How is a PA catheter placed?
Inserted into a large vein, such as the jugular or femoral vein
What can happen if the PA is occluded for too long?
Death
What dysrhythmia can occur when the PA catheter is passed through the right ventricle?
V-tach
- Notice how the PAO waveform looks kinda like v-fib?
- Ventricular dysrhythmias (V-tach) can occur when the provider passes the PA catheter through the right ventricle. This should be resolved once in the PA.
- The PA waveform has a dicrotic notch… it is indicative of pulmonic valve closure.
How is PA catheter placement verified?
Monitoring waveforms and CXR
What does the dicrotic notch on the PA waveform indicate?
Pulmonic valve closure
What is the usefulness of PA Hemodynamic Monitoring?
To assess left sided heart involvement or lung dysfunction
How does Thermodillution or continuous CO catheters help in PA Hemodynamic Monitoring?
They allow direct measurement of cardiac output
Where does the proximal port of the PA catheter lie and what is measured?
In the right atrium, measures RAP and can be used for medication administration
Where does the distal port of the PA catheter lie and what is measured?
In the pulmonary artery, measures PA pressures
Where is blood drawn for mixed venous oxygen samples?
Distal port
What is PAOP measurement?
PA occlusive pressure
when balloon is briefly inflated
Is PAOP measurement risky for patients?
Yes
What can be used as a substitute for PAOP measurement?
PA diastolic
When should pressures be measured?
At the end of exhalation
What are some risks associated with the PA catheter?
Arrhythmia, RBBB, PA injury/rupture
What should you do if a patient experiences arrhythmia during PA catheter insertion?
Support the patient and remove the catheter if the arrhythmia does not resolve
What can happen if a patient already has LBBB and develops RBBB during PA catheter insertion?
- Complete heart block can occur
- Be prepared to pace the patient
What is the most significant risk associated with the PA catheter?
Pulmonary artery injury/rupture
How does pulmonary artery injury/rupture present?
Episode of hemoptysis (when you cough up blood from your lungs) after catheter insertion or balloon inflation
What are three conditions in which the risk is highest when inserting a PA catheter?
Pulmonary hypertension, hypothermia, and anticoagulation.
What are two causes of PA rupture?
Overinflation of the balloon or migration of the catheter.
What precautions should be taken when using a PA catheter?
- Assess insertion depth frequently
- only inflate balloon when ordered and necessary
- lock balloon inflation port when not in use
- use only the syringe that comes with the PA catheter.
What is the maximum amount of air that should be used to inflate the balloon?
1.5ml
What are the complications of central venous lines?
- Pneumothorax/Hemothorax
- Air Embolism
- Laceration/Perforation of major vessels
- Accidental placement in the carotid artery
- Infection
What should you do if pneumothorax/hemothorax occurs?
Prepare to insert a chest tube if present
When can air embolism occur?
If connections are not tight, especially during insertion and removal of the line
How should a patient be positioned if air embolism occurs? [Occurs most during line removal]
Trendelenberg on left side, give 100% O2
What should you do if laceration/perforation of major vessels occurs and a hematoma forms?
Hold direct pressure and notify physician
What should you do if central venous line is accidentally placed in the carotid artery?
Never remove the line, must be removed by vascular surgeon
What is the most common and deadly complication of central venous lines?
Infection
What is one way to reduce central line-associated infection?
Hand hygiene
What should be used when inserting lines to reduce central line-associated infection?
Maximum sterile barriers
What should be done to the skin prior to inserting the line to reduce central line-associated infection?
Prep with CHG scrub
What are the preferred sites for line insertion to reduce central line-associated infection?
Subclavian, IJ, femoral
What should be done to minimize the duration of line use to reduce central line-associated infection?
Remove lines as soon as possible
What should be maintained on the site to reduce central line-associated infection?
Intact dressing
What type of dressings can be used at the insertion site to reduce central line-associated infection?
CHG-impregnated dressings
What should be done prior to all access of CVC ports to reduce central line-associated infection?
Scrub the hub
What is one method of bathing that can help reduce central line-associated infection?
Daily CHG bathing
What are some causes of increased CO/CI (cardia output and index)?
- Elevated HR
- increased preload
- decreased afterload
- increased contractility
What are some causes of decreased CO/CI?
- Inadequate ventricular filling
- decreased preload
- increased afterload
- decreased contractility
What can cause an elevated heart rate and increased CO/CI?
- Activity
- anemia
- metabolic demand (e.g. seizures or shivering)
- adrenal disorders
- fever
- anxiety
How can preload be increased to increase CO/CI?
Stroke volume increase as a result of:
Fluid resuscitation or changes in ventricular compliance
How can afterload be decreased to increase CO/CI?
Stroke volume increase as a result of:
Vasodilation from medications or sepsis, decreased blood viscosity (anemia), hypermetabolic states
What can cause inadequate ventricular filling and decreased CO/CI?
HR that is too fast or too slow
What can decrease preload and lead to decreased CO/CI?
Stroke volume reduction as a result of:
Hemorrhage, hypovolemia, vasodilation, fluid shifts
How can afterload be increased to decrease CO/CI?
Stroke volume reduction as a result of:
Vasoconstriction or increased blood viscosity
What can decrease contractility and result in decreased CO/CI?
Stroke volume reduction as a result of:
Myocardial infarction/ischemia, heart failure, cardiomyopathy, cardiogenic shock, cardiac tamponade
What is thermodilution cardiac output?
Measurement of CO using a thermistor and injection of room temperature 0.9% NS
How is thermodilution cardiac output measured?
Injection of a set volume of room-temperature NS into the proximal port of the PA catheter
What does the thermistor measure?
Temperature of the blood
How is the cardiac output calculated?
By calculating the area under the curve created by the temperature measurements
Why is an average of several injections taken?
To obtain a more accurate measurement of cardiac output
What should not be infused into the proximal port if thermodilution CO is being used?
Meds
When should the solution be injected?
At the end of expiration
What does thermodilution cardiac output measure?
Temp in body and averages the results
What is Thermodilution Cardiac Output?
Measurement of cardiac output using a temperature-based method
What is Continuous Cardiac Output?
Measurement of CO through thermal filament and thermistor
How is CO measured using the thermal filament and thermistor?
By creating a washout curve based on temperature changes
How long is the average taken for CO measurement?
Over 60 seconds
Why is it not useful in hyperthermic patients?
Thermal filament only heats blood up to 44 degrees C maximum
Are PA catheters worth it?
Use of PA catheters has decreased since evidence suggested that their use increased mortality
What do PA catheter pressures estimate?
PA catheter pressures estimate preload
What can affect PA catheter pressures?
Outside forces such as stiff ventricles or increased PEEP
Should CVP be used as a sole decision-making point regarding fluid management?
No
What has research shown regarding mortality in patients managed with a PAC vs. those managed without a PAC?
No difference in mortality
Where is hemodynamic monitoring shifting?
Towards non-invasive monitoring and new devices that measure SV and changes in SV
What are pulse contour methods of hemodynamic assessment?
Monitor attaches to an arterial line and measures variation in stroke volume
What is the advantage of pulse contour methods over a PA catheter?
Less risk
What is pulse contour method’s predictability for fluid responsiveness?
Better predictor
What is the requirement for using pulse contour methods?
Full mechanical ventilation
