PA Catheters Flashcards
What are absolute contraindications for PA catheters?
Infection at insertion site + presence of an RV assist device + lack of consent
What are relative contraindications for PA catheters?
RA/RV masses + LBBB + newly inserted PPM/ICD lines + severe coaguloapthy + Eisenmenger’s syndrome + TV or PV stenosis + persistent left SVC
What is the difference between a RV and PAP waveform?
The diastolic portion is different; in the RV there is an upstroke while in the PA there is a downslope
What are complications of PA catheter placements?
Arrhythmias (most common) + complete heart block + endobronchial hemorrhage + pulmonary infarction + catheter knotting + valvular damage
What left-sided values can you get with a PA catheter?
PCWP, LA pressure, and LVEDP
What does the PCWP measure?
Indirectly measures LA pressures which estimates the LVEDP (aka the LV preload)
What does the PA diastolic pressure estimate?
The PCWP (assuming normal pulmonic valve)
What requirements are needed to use PCWP to accurately measure LA pressures?
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
How is LAP and LVEDP related?
Depending on the MV pressure gradient
What do you see with MR in terms of PCWP and LAP?
You have a large V wave on PCWP which may cause you to overestimate LAP
When is PCWP higher than actual LVEDP?
PPV + high PEEP + increased intrathoracic pressure + Non-West lunge zone III PAC placement + COPD + increased PVR + LA myxoma + MV disease (stenosis or regurgitation)
When is PCWP lower than actual LVEDP?
Noncompliant LV + aortic regurgitation
What is the formula for PVR?
PVR = (mean PA pressure - LA pressure) / CO
What is the units for PVR?
Wood unit or mmHg * min/L or PVR (Wood units) * 80 = dynes*sec/cm5
What is a normal PVR?
Less than 2 Wood Units or 30-180 dynes*sec/cm5
Normal intracardiac pressures table
See Excel
What is the formula for cardiac output and cardiac index?
CO = HR * SV; CI = CO/BSA
What is the formula for CO via the Fick Principle?
CO = VO2 / (CaO2 - CvO2); CaO2 = (SaO2 * Hbg * 1.34) + (PaO2 * 0.003); you CvO2 is from the venous side; estimated VO2 = 250 cc/min
What are the pitfalls of indirect Fick cardiac output?
Changes in O2 extraction (i.e. emergence from anesthesia, pulm HTN, heart failure, obesity, fever, shivering, and sepsis)
What is the formula for mixed venous O2 sat?
SvO2 = SaO2 - (VO2 / CO * 1.34 * Hbg)
What factors affect mixed venous O2 sats?
CHAT: Cardiac output, Hemoglobin, Arterial oxygenation, and Tissue consumption
How does the PA catheter calculate cardiac output?
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
Explain thermodilution for calculating cardiac output
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
What happens if the injectate volume is low or high when calculating CO?
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
When is CO via thermodilution inaccurate (not from a mistake in injection or structural issues)?
At the extremes of CO (<3 L/min or > 15 L/min)
How does a continuous CO PA catheter work?
It has a thermal filament that pulses heat and the temp change is measured at the thermistor, allowing for CO to be calculated
How can you calculate CO via TEE?
CO = (EDV - ESV) * HR; CO = SVlvot * HR where SVlvot = Arealvot * VTIlvot
Why does sepsis decrease SvO2?
Sepsis causes decreased O2 extraction
