Perfusion: Myocardial Hemodynamics, Perfusion & Cardiac Cycle Flashcards
perfusion
- the process of nutrient delivery of arterial blood to a cap bed
- supplying an organ or tissue with oxygen and nutrients
What is the purpose of invasive hemodynamic monitoring?
- The primary purpose of invasive hemodynamic monitoring is the early detection, identification, and treatment of life-threatening conditions such as heart failure and cardiac tamponade
- ii. By using invasive hemodynamic monitoring the nurse is able to evaluate the patient.
What are noninvasive assessments of perfusion?
- LOC
- Skin: Tenting of skin
- Urine output
- Low because GFR is reduced
- Color, BP, HR
a. Cyanosis
b. Hypotension
c. Volume status is low so BP goes down - Heart rate
a. Tachycardia: The heart will try to beat really fast to try to compensate - Capillary refill time
a. Longer than 3 seconds
What are 3 types of perfusion scanning methods?
- CT
- MRI
Nuclear medicine perfusion
Cardiac output is characterized by what 2 things?
HR, SV
What is stroke volume made up of?
- preload
- afterload
- contractility
What 2 things make up preload?
- Central venous pressure
2. PAWP
What 2 things make up after load?
- SVR
2. PVR
What 2 things make up contractility?
- EF %
2. SV
What is a normal CO?
4-8 liters/min.
Why is cardiac index a better indicator vs CO?
Because it corrects for body size - someone who is smaller is going to need less pump
What is a normal CI?
2.4-4.0 L/min
What is stroke volume?
volume of blood pumped with each heartbeat
What is a normal SV?
60-70 mL with each ventricular contraction
What will a change in the heart rate have an immediate change in?
Change in the CO if the SV stays constant
What does a severe increase in HR cause?
A decrease in stroke volume, due to decreased filling time. This causes the CO to decrease
Tachycardia with CO?
Reduced CO
AFIB with CO?
reduced CO
Bradycardia with CO?
Increase in CO
Why is having a slow heart rate ok with CO?
Rate is not enough but if they are athletic then their cardiovascular function is very efficient – heart rate doesn’t have to be that high to maintain good heart function.
Vtach with CO?
decrease in CO
Asystole with CO?
Reduced CO
What happens if the SV stays the same but HR goes up?
CO goes up
What is preload?
- the amount of blood in ventricle at the end of diastole
2. the amount of stretch in the myocardial fibers at the end of diastole.
What does high preload mean?
high volume; large volume of blood returns from the venous system to the ventricle, the myocardial fibers are stretched.
What does low preload mean?
low volume; small volume of blood returns from the venous system to the ventricle, the myocardial fibers aren’t stretched
What is contractility?
pump function. The force of myocardial contraction.
What is contractility an indication of?
- INDICATION OF EF
2. CI AND CO ARE INDICATIONS OF CONTRACTILITY
What is after load?
the resistance the ventricle must overcome to eject blood
What does high after load mean?
vasoconstriction; decreased SV
What does low after load mean?
vasodilation; increased SV
So if after load increases then SV does what?
decreases; because there is more resistance pushing against the pump
What does preload represent?
the end diastolic ventricular volume (EDVV)
Preload is a function of what 2 things?
- volume
2. ventricular compliance
What are 3 factors that affect preload.
- volume - venous return, total blood volume, atrial kick.
- compliance
- stiffness and thickness of ventricular wall
Decreased preload is evident with?
a. Tachycardia
b. Decreased U/O
i. Reduced perfusion to the kidneys
c. Increase in specific gravity–> Dehydration
d. Dry mucous membranes
i. Dehydration
ii. Pinch skin it will not return to its normal
e. Tented skin
f. Sunken eyes
g. Orthostatic hypotension
Increased preload is evident when?
- JVD
a. Reliable indicator of volume/pressure in the right side of the heart - Pedal edema
- S3 (increased fluid), S4
a. S4 – S - Crackles
- Fluid overload
- Dyspnea
- Pink frothy sputum
a. Patient might need Lasix or any diuretic - Ascities, hepatic engorgement
What does an increase in JVD tells us?
An increase in JVD tells us about the patient’s CVP (central venous pressure)
- -> CVP low – hypovolemic
- -> CVP high – hypervolemic
How to measure JVD:
a. HOB 45 degrees
b. Head turned to right
c. Identify sternal angle
d. Locate superior sternal notch
e. Measure distance between top pulsation and sternum in centimeters.
What is normal JVD?
4 cm or less
What meds affect preload?
- fluids
- diuretics –> low CO because they are losing volume.
- Venodilators –> vessels are dilated, pressure decreases, low CVP.
a. Nitrates
b. Morphine
- -> Before giving, check vitals especially BP
- -> They may become hypotensive
- -> If their BP is too low, put them on something that doesn’t affect BP - Ace inhibitors
What is the frank starling law of heart regarding preload?
the heart pumps the amount of blood it receives w/each beat. Preload increases, SV increases. Preload decreases, SV decreases.
What is the physiological limit of the heart according to the frank starling law of heart?
300 mL of filling
What can too much preload cause?
cause excessive stretching of the myocardial fibers.
- the ventricles cannot effectively contract
- the SV goes down.
What 4 things affect preload?
- aortic impedance –> 1. Stenosis or regurgitation, there will be an interruption of forward flow
- blood viscosity –> 1. Thicker blood will be more difficult to push out
- blood volume –> 1. Hypervolemic = harder to push out
- vascular tone –> 1. Vessels are constricted which makes it harder for the left ventricle to push the blood out because the diameter is so low.
What does a high after load mean?
vessels are constricted
What are meds that can help with vasodilation?
nitroglycerin
What does a low after load mean?
vessels are dilated
What are meds that help with vasoconstriction?
norepinephrine and epinephrine
What is systemic vascular resistance with after load?
Afterload of the left side of the heart
What does a Low SVR mean?
dilation, so you need vasoconstriction
What is the formula for SVR?
MAP – CVP/CO x 80
What is a normal SVR?
800 - 1200
What is pulmonary vascular resistance with after load?
Resistance to ejection from right side of the heart.
What is a normal PVR?
50 - 250
What are s/sx of increased after load? - constriction
a. Pale, cool, clammy skin
b. HTN
c. Non-healing wounds
i. Low perfusion
d. Thick, brittle nails
e. Slow cap refill
f. Decreased urine output
What are s/sx of decreased after load? - dilation
a. Warm, flushed skin
b. Increased CO
c. Decreased BP
What is ohm’s law?
Pressure = flow x resistance Pressure = BP Flow = CO Resistance = after load
What is contractility?
the ability of a muscle to shorten when stimulated; the force of myocardial contraction.
What are 2 types of meds that are given to induce contractility?
- dopamine
2. digoxin
How is contractility measured? What is the formula?
a. EF
b. Ef = SV/EDV
What is a normal EF?
60-70%
What is the mineral used to control contractility?
calcium
- hypertensive –> calcium channel blocker
- hypotensive –> calcium
When do you see an increased contractility?
increased BP bc sympathetic nervous system stimulation
When do you see a decreased contractility?
- Hypotension
- Fatigue
- SOB
- Dizziness
- Low urine output
bc parasympathetic nervous system stimulation.
When is hemodynamic monitoring indicated?
a. Alterations in CO
b. Alterations in fluid volume
c. Alterations in tissue perfusion
What is CVP w/hemodynamic monitoring?
Volume/pressure on the right side of the heart
Where do you want to take CVP from?
distal port because that is the closest to the right atrium
What does CVP w/hemodynamic monitoring reflect? What does it guide?
Reflects filling pressures in the right ventricle. Guides overall fluid balance.
What are 2 noninvasive hemodynamic technologies?
a. Impedance Cardiography
- -> Assesses cardiac function by measuring resistance to the blow of high-frequency, low-amplitude current. Measures SV, CO, SVR, and contractility
b. Doppler Ultrasound
- -> Measures blood flow velocity in the vessel. Helps to determine CO, preload, afterload, and contractility
What are 3 minimally invasive hemodynamic technologies?
- CVP
- Arterial access line
- MAP
What is the formula for MAP?
Mean Arterial Pressure (MAP) MAP = ((SBP) + 2 (DBP))/3
When is an arterial line indicated?
a. Monitoring blood pressure
- -> Arterial line to measure because if a patient is taking a vasoactive medication you don’t want to have to take BP all the time.
b. Frequent ABG’s, labs
What is the difference between intra-arterial blood pressure monitoring and cuff monitoring?
a. A-line measures flow inside artery; cuff from outside artery
What are the number differences between intra-arterial blood pressure monitoring and cuff monitoring?
5-10 mmHg
When is a cuff unreliable?
shock or low CO
What is the Vigileo monitoring device system?
Minimally invasive; connects to existing arterial line; requires no manual calibration; automatically calculates hemodynamic values every 20 seconds; accurate when validated against swan catheter.
What does the Vigileo monitoring device system provide?
Data on…
a. CO – Cardiac Output
b. CI – Cardiac Index
c. Central Venous Oxygen Saturation: Determine oxygen extraction vs demand. Oxygen utilization.
d. Stroke Volume: Assessment of ventricular performance
e. Stroke volume variation: Variation in stroke volume given as a percentage. >15% may indicate hypovolemia
- -> Reaches 10-12 - stop giving fluids.
f. Systemic Vascular Resistance (SVR): Indicator of afterload.
What kind of measurements does the swan PA Cath provide?
a. Pulmonary artery pressure (PAP) (systolic, diastolic, mean)
i. Pulmonary hypertension
b. Pulmonary artery wedge pressure (PAWP , PCWP, wedge, LVEDP)
c. Central venous pressure (CVP, RAP, RVEDP)
d. Cardiac output (CO), cardiac index (CI)
e. Systemic Vascular resistance (SVR)
f. Pulmonary vascular resistance (PVR)
What are the advantages of a swan Cath?
a. Real-time data
b. Simultaneously measures a variety of hemodynamic parameters
c. Able to rapidly assess pts. Response to interventions.
What are the disadvantages of a swan Cath?
a. Infection
b. Insertion complications: pneumothorax, bleeding, damage to blood vessels or heart, dysrhythmias
c. Air emboli, exsanguination (loose connections)
d. Balloon rupture (rare)
e. Pulmonary artery rupture (rare)
What is a normal PAWP? What does it reflect?
4-12 mmHg; reflects left sided preload
What is a normal CVP? What does it reflect?
2-6 mmHg; reflects right sided preload
What is a normal PAP? What does it reflect?
20-30/10’s mm; reflects blood pressure in the lungs
What is a normal CO? What does it reflect?
4-8 L/min; volume ejected/minute with each beat
What is a normal CI? What does it reflect?
2.4 - 4.0 L/min; Volume ejected/minute with each beat
What is normal PVR? What does it reflect?
50-250 dynes/sec/cm-5; Reflects right sided afterload
What is normal SVR? What does it reflect?
800-1200 dynes/sec/cm-5; Reflects left sided afterload
What are 2 causes of elevated PA pressures?
- Pulmonic valve stenosis/calcification
2. pulmonary hypertension
What does pulmonic valve stenosis/calcification cause?
increased after load on the right ventricle
What does pulmonary hypertension cause?
increased after load on the right ventricle, which impacts right vent. emptying
What are interventions for PH?
- Find the cause/root of problem.
- Reduction in Preload (circulating volume).
- Decrease venous return to the right side.
- Increase/improve contractility.
- MEDS: Vasodilators (Viagra), diuretics, Na and fluid restriction, valve replacement/repair.
a. Aortic valve disease – fluid overload
KNOW THIS
i. Perfusion – supply of oxygen & nutrients
ii. Cardiac Output – Heart Rate X Stroke Volume
iii. Cardiac Index – Best indicator of cardiac function
iv. Preload – Blood presenting to both right & left side of heart
v. Afterload – resistance to contraction both right & left side of heart
What is ANP?
a hormone released during atrial stretch
What is BNP?
a hormone released during ventricular stretch
What is heart failure?
- a condition where the heart can not pump blood at a volume required to meet the body’s needs.
Heart failure occurs due to either…
- systolic dysfunction - poor contraction
2. diastolic dysfunction - poor filling. Or increased increased afterload
What are 5 possible causes of heart failure?
- CAD
- Valvular dysfunction
- Infection
- cardiomyopathy
- uncontrolled hypertension
What are 3 ways that heart failure may be discovered?
- acute MI
- Decreased exercise tolerance
- fluid retention
What 2 things are decreased with left HF?
- contractile function of the left ventricle
2. cardiac ouput
What are 2 things that are increased with left sided HF?
- SVR
2. after load
How does Left HF affect the lungs?
pulmonary congestion and edema. Crackles, rhonci, pink tinged sputum