In shock, which BP should you trust? CVP? A-line? Cuff? Why?
CVP because cuff can underestimate by an average 30mmhg
When is an arterial pressure unreliable?
when vascular impedance is abnormal
What happens to systolic pressure as it is measured further and further in the periphery?
it gradually increases
What is the most accurate measure of central aortic pressure?
What other factor significantly amplifies systolic pressure?
What is the most common cause of inaccurate MAPs?
heart rates over 60bpm
How many channels does a typical PA catheter have?
What is the placement of the tips of the two lumens?
PA and right atrium (30cm)
How does the PA catheter measure CO?
thermistor (temperature change detector) measures the flow of cold fluid injected by the proximal catheter as it passes the distal sensor
identify wave forms (pic)
right atrium, rv, wedge PA, PA
what is the normal systolic right ventricle pressure?
What is normal PA diastolic pressure?
Define the pulmonary capillary wedge pressure (aka wedge pressure)?
venous pressure in the left side of the heart representing the left atrial pressure and LV diastolic pressure
What do you have to do to the catheter on initial insertion to get an appropriate wedge pressure reading?
inflate the balloon so that the wedge pressure is obtained (asystole looking wave form) then deflate the balloon so that the wave form reappears
What should you do if a patient has a complete heart block with the catheter in place?
withdraw the catheter
What if the wedge pressure is not producing a reading?
use the pulmonary artery diastolic pressure as a substitute
When measuring CO how many measurements are necessary?
at least 3 if they differ by less than 10%
What if the CO measurement drops by 10% and the patient is asymptomatic?
That is a normal variation in the measurement process
What is the formula for calculating pulmonary vascular resistance?
PVR = PAP (mean pulmonary artery pressure) - wedge pressure
What kind of hypotension is associated with low CVP, low cardiac index and high systemic vascular resistance?
What kind of hypotension is associated with high CVP, low cardiac index and high systemic vascular resistance?
What kind of hypotension is associated with low CVP, high cardiac index and low systemic vascular resistance?
What kind of shock is associated with high CVP, low cardiac index, high systemic vascular resistance, normal venous O2?
heart failure shock (low output state)
What kind of shock is associated with high CVP, low cardiac index, high systemic vascular resistance, low venous O2?
What is the positional consideration when measuring wedge pressure?
the patient should not be in the lateral position because it will be inaccurate
When shoul dintravascular pressures be measured?
at the end of expiration
When will transmural pressures differ at end-expiration?
only if there is positive intrathoracic pressure as in mechanical ventillation which prevents complete alveolar emptying
In a ventilator dependent patient, when should intravascular pressures be measured?
at end-expiration when disconnected from a ventilator momentarily
In a spontaneously breathing patient vs ventilated patient what is the end-expiratory pressure difference?
In spontaneous it is the highest pressure and in ventilated it is the lowest pressure
What is the benchmark for a significant change in CVP or wedge pressure?
picture a normal CVP tracing, explain components
what anatomical consideration should be taken in to account when taking a wedge pressure
Wedge pressures are only accurate from lung regions below the left atrium
How do you check to ensure that the pulmonary catheter tip is in the correct position in a supine patient?
check lateral chest xray, no marked respiratory variations in wedge pressure and wedge pressure increases
Under which conditions is there a discrepancy between left-atrial pressure and left-ventricular end-diastolic pressure (3)?
aortic insufficiency, noncompliant ventricle, respiratory failure
You have a patient with low calculated VO2, what should you check next?
ensure that the patient does not have lung inflammation because that will cause the calculated value to be underestimated by as much as 20%
What is considered a significant change in calculated VO2?
greater than 18-20%
What is considered a significant change in measured VO2?
greater than 5%
How is VO2 correlated with tissue oxygenation?
Values below 100 mL/min/m2 are indicative of impaired tissue oxygenation
What are the three ways to correct VO2 deficits?
Augment cardiac output, correct anemia and correct hypoxemia
If a patient with low cardiac output (s the next step in evaluation?
measure the ventricular filling pressure (CVP or PCWP)
How do you treat low CO with low CVP?
volume resuscitation until a CVP of 10 or PCWP of 15
How do you treat low CO with normal/high CVP?
In what situation should anemia be corrected?
hgb < 7
What side effect of transfusion can decrease VO2?
increases blood viscosity and decreases cardiac output as a result
To what extent should hypoxia be corrected?
to 90% unless the patient is in septic shock in which case oxygen utilization is the issue rather than availability
What is the mechanism of increased oxygen utilization in sepsis?
increases in released neutrophils and macrophages have significantly increased oxygen consumption. Called respiratory burst.
How is decreased oxygen delivery measured?
venous O2 sat below 70%
At what critical value is venous O2 too low?
venous O2 below 50% indicates a global state of tissue dysoxia or impending dysoxia
What is considered a significant changed in measured venous O2 Sat?
greater than 5%
What is considered an abnormal lactate level?
above 2 but above 4 impacts morbidity/mortality
What are other sources of hyperlactatemia besides hypoperfusion(4)?
hepatic insufficiency (reduced clearance), thiamine deficiency (inhibits storage), severe sepsis (endotoxin accumulation), intracellular alkalosis (glycolysis stimulation increases lactate production)