PA Catheters

Question 1

What are absolute contraindications for PA catheters?

Answer 1

Infection at insertion site + presence of an RV assist device + lack of consent

Question 2

What are relative contraindications for PA catheters?

Answer 2

RA/RV masses + LBBB + newly inserted PPM/ICD lines + severe coaguloapthy + Eisenmenger’s syndrome + TV or PV stenosis + persistent left SVC

Question 3

What is the difference between a RV and PAP waveform?

Answer 3

The diastolic portion is different; in the RV there is an upstroke while in the PA there is a downslope

Question 4

What are complications of PA catheter placements?

Answer 4

Arrhythmias (most common) + complete heart block + endobronchial hemorrhage + pulmonary infarction + catheter knotting + valvular damage

Question 5

What left-sided values can you get with a PA catheter?

Answer 5

PCWP, LA pressure, and LVEDP

Question 6

What does the PCWP measure?

Answer 6

Indirectly measures LA pressures which estimates the LVEDP (aka the LV preload)

Question 7

What does the PA diastolic pressure estimate?

Answer 7

The PCWP (assuming normal pulmonic valve)

Question 8

What requirements are needed to use PCWP to accurately measure LA pressures?

Answer 8

Needs to be in West Zone III of the lungs (dependent portion) where the alveolar pressure is less than the pulmonary venous pressure; otherwise you will be measuring alveolar pressure instead of LA pressures

Question 9

How is LAP and LVEDP related?

Answer 9

Depending on the MV pressure gradient

Question 10

What do you see with MR in terms of PCWP and LAP?

Answer 10

You have a large V wave on PCWP which may cause you to overestimate LAP

Question 11

When is PCWP higher than actual LVEDP?

Answer 11

PPV + high PEEP + increased intrathoracic pressure + Non-West lunge zone III PAC placement + COPD + increased PVR + LA myxoma + MV disease (stenosis or regurgitation)

Question 12

When is PCWP lower than actual LVEDP?

Answer 12

Noncompliant LV + aortic regurgitation

Question 13

What is the formula for PVR?

Answer 13

PVR = (mean PA pressure - LA pressure) / CO

Question 14

What is the units for PVR?

Answer 14

Wood unit or mmHg * min/L or PVR (Wood units) * 80 = dynes*sec/cm5

Question 15

What is a normal PVR?

Answer 15

Less than 2 Wood Units or 30-180 dynes*sec/cm5

Question 16

Normal intracardiac pressures table

Answer 16

See Excel

Question 17

What is the formula for cardiac output and cardiac index?

Answer 17

CO = HR * SV; CI = CO/BSA

Question 18

What is the formula for CO via the Fick Principle?

Answer 18

CO = VO2 / (CaO2 - CvO2); CaO2 = (SaO2 * Hbg * 1.34) + (PaO2 * 0.003); you CvO2 is from the venous side; estimated VO2 = 250 cc/min

Question 19

What are the pitfalls of indirect Fick cardiac output?

Answer 19

Changes in O2 extraction (i.e. emergence from anesthesia, pulm HTN, heart failure, obesity, fever, shivering, and sepsis)

Question 20

What is the formula for mixed venous O2 sat?

Answer 20

SvO2 = SaO2 - (VO2 / CO * 1.34 * Hbg)

Question 21

What factors affect mixed venous O2 sats?

Answer 21

CHAT: Cardiac output, Hemoglobin, Arterial oxygenation, and Tissue consumption

Question 22

How does the PA catheter calculate cardiac output?

Answer 22

Via bolus thermodilution; cold saline is injected into the RA and the temperature change is measured by a thermistor at the tip of the PA catheter in the PA

Question 23

Explain thermodilution for calculating cardiac output

Answer 23

The CO is the inverse of the area under the curve (temperature on the Y axis and time on the X axis); if CO is high, the cold saline washes out quickly and temperature returns to baseline quickly; if CO is low, the cold saline washes out slowly and temp will return to baseline slowly

Question 24

What happens if the injectate volume is low or high when calculating CO?

Answer 24

If the volume is too small, the thermistor will detect a fast (small injectate) temperature change and the CO will be falsely high; Vice versa for a higher volume of injectate

Question 25

When is CO via thermodilution inaccurate (not from a mistake in injection or structural issues)?

Answer 25

At the extremes of CO (<3 L/min or > 15 L/min)

Question 26

How does a continuous CO PA catheter work?

Answer 26

It has a thermal filament that pulses heat and the temp change is measured at the thermistor, allowing for CO to be calculated

Question 27

How can you calculate CO via TEE?

Answer 27

CO = (EDV - ESV) * HR; CO = SVlvot * HR where SVlvot = Arealvot * VTIlvot

Question 28

Why does sepsis decrease SvO2?

Answer 28

Sepsis causes decreased O2 extraction