Module 9: Hemodynamics Flashcards
What is Hemodynamics?
The study if forces (pressure) that influence the circulation of blood
What are 3 routes (lines) to collect data?
Arterial lines
Central lines
Pulmonary artery lines
What do arterial lines tell us?
Collect information about the systemic system
TLDR:
Measures perfusion and how well oxygenated blood is carried from left ventricle to tissue and picks up CO2 + waste
Central lines elucidate information on…
fluid balance and function of the right heart
Pulmonary artery lines
Information on the pulmonary system fluid balance and the function of the left heart
Direct measurements
BP
MAP (mean arterial pressure)
CVP (central venous pressure)
RAP (right arterial pressure)
Mean pap (mean pulmonary wedge pressure)
PAWP (pulmonary artery wedge pressure)
CO (cardiac output)
Calculated values in hemodynamics
SV (stroke volume)
-SVI
CI (cardiac index)
SVR (system vascular resistance)
-SVRI
PVR (pulmonary vascular resistance)
-PVRI
Slide 4: how dynamic measurements and calculated values reflect blood flow path
Ohm’s Law physics is splint into two types, what are they?
Electrical
- voltage - current x resistance
Fluid
- change in pressure = Flow x Reistance
-change in pressure = driving pressure
What does Hemodynamics tells us at the tissue level?
Movement of blood at the tissue level tells us:
how much perfusion we are getting in to bring in oxygen and nutrients in addition to waste removal.
Where are the tricuspid and Mitral (bicuspid) valves located.
Tricuspid = between right atrium and right ventricle
Mitral = between left atrium and left ventricle
What is the order of valves does blood pass through?
Tricuspid -> Pulmonic -> mitral -> aortic
TPMA
Cardiac output: Define the frank-starling relationship
Show how changes in ventricular preload lead to changes in stroke volume.
where does the blood in the right atrium come from?
Superior vena cava
Inferior vena cave
Coronary sinus
What is the function of the coronary sinus?
To drain deoxygenated blood from the heart muscle into the right atrium
(the hearts supply of blood that was used)
What is arterial pressure monitoring?
A invasive blood pressure monitor done through the cannulation of a peripheral artery.
Indications for arterial pressure monitering?
Used for patients with severe hypotension/hypertension
patients who need frequent ABGs
Patients who exp’d respiratory failure
2 locations for a Arterial line
Radial artery (preferred + easy access)
Femoral artery (harder + less vasoconstriction)
Why is the radial artery preferred over the femoral artery?
Radial artery has collateral circulation while the femoral doesn’t
Arterial Pressure Wave forms:
What does the dicrotic notch represent?
Aortic valve closure
Expected vitals for hypertension
hypertension = > 160-90
Expected vitals for hypotension
Hypotension = < 90/60
What is hypotension a late sign of?
Low cardiac output
What causes hypotension?
Low blood volume
Poor cardiac function
Low vascular resistance
why is low diastolic pressure dangerous?
Compromised coronary artery perfusion
Complications of Arterial Pressure monitoring
Ischemia
Hemorrhage
Infection
what happens when arterial pressure monitoring result in Ischemia? why is it dangerous?
Occurs with embolism, thrombus, or arterial spasm
Can result in tissue necrosis
How can arterial pressure monitoring caused a hemorrhage?
occurs if line becomes disconnected
What is CVP?
Central venous pressure.
pressure in the thoracic vena cava near the right atrium
Why is CVP important?
Assess circulating blood volume and filling pressures of the heart.
and
**Gauge right ventricle function **
Normal CVP pressure?
8 - 12mmHg
Who would need a CVP catheter/monitoring ?
patients who had major surgery or trauma
+
Patients with pulmonary edema
Triple lumen (catheter) has 3 ports/functions. what are they?
- allow infusion of meds
- has a port to obtain blood samples.
- internal jugular = site for insertion
CVP waveforms reflect pressures in the right atrium.
What are the three waves?
A = occurs with atrial contraction
C = occurs with AV valves back towards atrium during
systole
V = Occurs with atrial filling during ventricular systole.
How does respiratory function affect CVP waveforms?
Spontaneous inspiration cause CVP to decrease.
Positive pressure breaths cause CVP to increase.
Factors that increase CVP
Fluid overload
Right/left heart failure
Pulmonary hypertension
Tricuspid valve stenosis
Pulmonary embolism
Increased venous return
Causes of decreased CVP
Reduced circulating blood volume
Vasodilation (reduced venous return)
Leaks in the pressure system
Spontaneous inspiration
Complications during placement of CVP monitoring process
Bleeding
Pneumothorax
Complications for CVP monitoring over time
Infection
Embolus
Air embolus
Catheter insertion: what is the path it is “floated” through?
Right atrium -> right ventricle -> pulmonary artery -> wedge position
What happens when the catheter wedges into place?
The balloon inflates
Normal pressure: Right atrium
2 - 6 mmHg
Normal pressure: right ventricle
Systolic: 20-30 mmHg
Diastolic: 0 - 5 mmHg
Normal pressure: Pulmonary artery
Mean pressure?
Systolic: 20 - 30 mmHg
Diastolic: 6 - 15 mmHg
Mean pressure: 10 - 20mmHg
Normal pressure:
Pulmonary capillary wedge pressure
4 - 12 mmHg
PA systolic pressure
20 - 30 mmHg
PA diastolic pressure
8 - 15 mmHg
what increases PA systolic pressure?
high pulmonary vascular resistance
what decreases PA systolic pressure
poor right heart function
pulmonary vasodilation
what does PA diastolic pressure reflect?
what condition does it not reflect it?
Left heart filling pressures.
it cannot be accurately interpreted when pulmonary vascular resistance is elevated.
What is normal wedge pressure?
4 - 12mmHg
What does wedge pressure increase/decrease?
Increase: with left heart failure or mitral stenosis
Decrease: hypovolemia
What does elevated CVP, PAP, and increased wedge indicate?
What does elevated CVP, PAP, and normal wedge indicate?
Best procedure for accurate wedge pressure?
measure at end exhalation
catheter tip must be in west zone III where blood flow is continuous.
What can cause an inaccurate wedge pressure reading?
low blood volume
high alveolar pressure
PCWP?
Pulmonary capillary wedge pressure
What does this image tell you about West zone III ?
Both the arterial and the venous pressures are higher than the alveolar.
meaning there is an uninterrupted column of blood in the vessels between the right ventricle and left atrium
PA monitoring issues
During cannulation blood vessels damage is possible along with hemothorax and pneumothorax.
Dysarthria’s (when catheter passes in heart)
Pulmonary infarction (basically any embolism type)
an catheter could be an infection source
Normal MAP
Mean atrial pressure:
80 - 100 mmHg
Insert slide 33 for normal ranges for pulmonary artery catheters
What is cardiac output (CO)
Amount of blood pumped out the left ventricle in 1 minute
CO = stroke volume x Heart Rate
What is stroke volume
amount of blood ejected from the left ventricle with each contraction
Normal stroke volume range
60 - 130 mLs
Normal CO at rest
4 - 8 L/min
What is venous return?
amount of blood returning to the right atria each minute.
Similarities between Venous return and Cardiac Output?
Same range.
In healthy hearts: venous return increases and CO does too.
What causes venous return to increase?
peripheral vasodilation
what does vasoconstriction do to venous return?
decrease venous return.
What is Cardiac Index (CI)
A measurement standard to determine the cardiac function despite different body sizes.
It is determined by dividing the CO by body surface area.
TLDR: measure of cardiac output and pump function.
Normal Cardiac Index (CI)
4.0 L/min/m^2
What is ventricular stroke work a measure of?
A measure of myocardial work per contraction.
What is ventricular stroke work
The product of:
stroke volume x the pressure across the vascular bed
Ventricular volume
estimated by measuring end diastolic pressure
Ejection fraction
Fraction of end-diastolic volume with each systole.
What is ejection fractions normal range?
60-70% but drops with cardiac failure.
Determinants of pump function
Specifically:
-Heart rate
-Preload
-Afterload
-contractility
General:
HR and SV
What is Tamponade?
Compression of heart by an accumulation of fluid in the pericardial sac
Heart rate effects on CO
Low HR is normally compensated by an increase in stroke volume (SV)
elevated HR causes SV to drop in ppl with heart diseases -> it reduces fill time.
Preload effects on pump function
The greater the stretch on myocardium before contraction = greater the following contraction.
Too much = reduce SV
Too slow = SV and CO drop
When does a drop in SV and CO typically occur?
Hypovolemia or whenever cardiac functions are slow.
What is created by end-diastolic volume
Preload
What is end-diastolic volume?
Amount of blood that is in the ventricles before the heart contracts.
Factors that affect venous return, preload, and CO
Circulating blood volume
Distribution of blood volume
Atrial contraction (adds 30% to following ventricular SV)
Effect of mechanical ventilation (3)
Spontaneous inspiration lowers intrapleural pressure:
-Improves venous return and CO:
Positive pressure breaths
-Increase intrapleural pressures and reduces venous return and CO
Can adjust to ppls level of lung/chest compliance.
2 components of Afterload
Peripheral Vascular Resistance and Tension in the ventricular wall
As afterload increases, what demand is needed in the heart?
Oxygen
what is SVR?
Systemic vascular resistance = amount of force exerted (resistance) on systemic circulation.
What happens in the heart when there is peripheral vasoconstriction?
systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR) increase
What is PVR?
measure of pulmonary vascular resistance
What is an example of pulmonary vasoconstriction that increases PVR?
Hypoxemia and acidosis
what factors reduce contractility?
hypoxia, acidosis, electrolyte abnormalities, and myocardial ischemia
Contractility is determined by
stretch before contraction
inotropic state of the heart
Inotrope class drugs can improve contraction, but what does it require as a result?
increase in myocardial oxygen demand.
Thermodilution
A method to measure CO (old) with a pulmonary artery catheter + computer
Specfically:
A coldish bolus of saline is injected into a proximal port; temperature change over time measured by a thermometer at the distal tip of the PAC.
Ficks method: what assumptions need to be met to measure CO?
Based on the idea that blood flow to an organ can be calculated using:
O2 consumption, arterial oxygen content and mixed venous oxygen content are simultaneously measured.
Not popular
Premise of Ficks method
The total uptake of oxygen is equal to the product of the cardiac output and the arterial-venous oxygen content difference.
Difference between systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR)
SVR describes resistance from peripheral circulation (transport/distribution, exchange, and storage of blood between tissue in the venous system)
PVR describes resistance offered by vasculature of the lungs.
West zones: Perfusion (Q) is highest in zone 3 and lowest in zone 1. If V/Q is highest in zone 1 and lowest in 3, where is ventilation the highest?
Ventilation and perfusion are highest Zone 3.
the ratio is highest in zone 1.
V/Q mismatch?
When the lungs receive oxygen without blood flow or blood flow without oxygen
What is V/Q ratio?
The amount of air that reaches your lungs divided by the amount of blood flow in the capillaries in your lungs.
What does an increase in v/q ratio mean?
decreased perfusion in the lungs.
Decrease in v/q ratio mean?
impaired airflow = low ventilation w/normal perfusion.
Examples: COPD or asthma
