Hemodynamics Flashcards
what is hemodynamics?
force by which blood circulates through the body.
What does the term Hemodynamics describe?
the intravascular pressure and flow that occurs when heart muscle contracts and pumps blood through the body.
What are the two techniques of hemodynamics?
invasive
noninvasive
what is hemodynamics a combination of?
Cardiac output and blood pressure for effective tissue perfusion
What are the two types of arterial pressures?
Systemic and Pulmonary
what is preload?
Volume of blood within ventricle at end of diastole
Degree of muscle fiber stretching in the ventricles right before systole
What is left ventricular preload reflected by?
PCWP
What is right ventricular preload reflected by?
CVP
What are factors that increase preload?
- exercise
- Hypervolemia
- Neuroendocrine excitement (sympathetic tone)
- AV fistula
Why can an AV fistula cause an increase in preload?
An arteriovenous fistula can increase preload: AV shunts, and fistulas decrease the afterload of the heart. This is because the blood bypasses the arterioles which results in a decrease in the total peripheral resistance (TPR). AV shunts/fisulas increase both the rate and volume of blood returning to the heart.
Factors that decrease. preload?
- Hypovolemia
- Narrowing or stenosis of valves
- Afib
Factors that increase afterload?
- systemic resistance
- Aortic stenosis
- myocardial infarction
- Cardiomyopathy
- Polycythemia (increased blood viscosity)
Factors that decrease afterload?
- decreased volume
- septic shock
- end stage cirrhosis
- vasodilators
Why can septic shock decrease afterload?
Increased CO, decreased peripheral vascular resistance, third spacing due to vasodilation from histamine release, making capillaries more permeable.
What is afterload?
the resistance the left ventricle must overcome to circulate blood
what is contractility?
Strength of ventricular contraction
what is inotropic?
force or energy of contraction, inotropic agent increases force of contraction
What is chronotropic?
related to time, chronotropic agent changes rate of contraction
what is stroke volume?
amount of blood ejected by the ventricles with contraction
what is cardiac output?
HR x SV, determined by HR & rhythm, preload, afterload, contractility
what is cardiac index?
Cardiac Index (CI): CO adjusted for BSA (CO/BSA)- more specific to each patient
what do vasopressors do?
stimulates smooth muscle contraction of the capillaries and arteries
what do ionotropes do?
increase the force of contraction of myocardial muscle
what are some types of invasive monitoring?
- CVP
- ART
- Pulmonary Artery monitoring
How do you ensure accuracy with invasive monitoring?
- Equipment must be referenced and zero balanced to environment and dynamic response characteristics optimized
- Referencing: Positioning transducer so zero reference point is at level of atria of heart or Phlebostatic axis for cardiac pressure/systemic arterial readings
where is the Phlebostatic axis?
- 4th intercostal space
- midchest
- this is equivalent to the level of the right atrium
how do you zero a line?
-Open the stopcock to air, hit zero function on the monitor and digital returns to zero. Confirms that when pressure within system is zero, monitor reads zero
when do you zero a line?
- During initial setup of arterial line
- Immediately after insertion of arterial line
- When transducer has been disconnected from pressure cable or pressure cable has been disconnected from monitor
- When accuracy of values is questioned
what type of monitoring can use a central line?
-central venous pressure
What type of monitoring can use the PA?
- CVP
- PAP
- PAWP/PCWP
- PVR/PVRI
- SVR/SVRI
what type of monitoring can use the swan Ganz?
- CVP
- PAP
- PAWP/PCWP
- PVR/PVRI
- SVR/SVRI
- CO/CI
what does CVP measure?
Right atrial filling (preload)
what does pulmonary artery pressure measure?
Left atrial preload
what does pulmonary artery wedge pressure measure?
Left atrial pressure
What does pulmonary vascular resistance measure?
resistance of pulmonary bed
what does Systemic vascular resistance measure?
resistance of vascular bed (afterload)
Normal range of CVP
0-8mmHg
Normal range of Pulmonary artery pressure?
15-25/8-15
Normal range of pulmonary artery wedge pressure?
6-12mmHg
Normal range of pulmonary vascular resistance?
100-250dynes/sec/cm
Normal range of systemic vascular resistance?
800-1200dynes/sec/cm
Normal range of cardiac output?
4-8L/min
Normal range of cardiac index?
2.2-4L/min/M
what does central venous pressure reflect?
Reflects amount of fluid returning to the right side of the heart – preload
Fill in the blank:
Right atrial and right ventricular are _______ at end diastole.
the same
How to get a CVP (3)
- transducing a central line
- attachment of a water filled column to the line
- Proximal lumen of Swan/PA line
how does spontaneous breathing ventilation affect CVP?
inspirations decrease CVP
How does Positive pressure ventilation affect CVP?
inspirations increase CVP
Risks Associated With CVP monitoring
- Superior Vena Cava perforation
- Guidewire induced arrhythmias
- Venous thrombosis
- Infection
What might a sudden decrease in CVP indicate?
- fluid deficit
- hemorrhage
What might a sudden increase in CVP indicate?
- hypervolemia
- HF
reasons for ART line?
- Severe Hypertension
- Severe Hypotension
- Respiratory Failure/shock
- Use of pressors
- Frequent ABG’s
what is the Allens test?
- Hold the hand up and clench and unclench the hand.
- Compress the radial & ulnar arteries.
- Lower the hand and relax.
- Quickly release the ulnar artery – color should return quickly (5-7 sec)