Download PA catheter- equations describing the derived parameters

This document was created by Alex Yartsev ([email protected]); if I have used your data or images and forgot to reference you, please email me.
PA catheter- equations describing the derived parameters
…Anything that called an INDEX is a variable which is corrected for body surface area
Cardiac index (CI)
This is the thermodilution cardiac output corrected for body size. Normal is 2.8 to 4.2 L/min per m2
CI =
Cardiac Output
Body Surface Area
Stroke Volume (SV)
This is the volume of blood ejected by the ventricles during systole.
SV =
Cardiac Output
Heart Rate
Stroke Volume Index (SVI)
This is the Stroke Volume, corrected for body size
SVI =
Cardiac Index
Heart Rate
Right Ventricular Ejection Fraction (RVEF)
This is the fraction of right ventricular volume ejected during systole.
It indicates the strength of ventricular contraction during systole.
It can be measured directly by using a specialized rapid-response thermistor.
RVEF =
Stroke Volume
Right Ventricular End-Diastolic Volume
Right Ventricular End-Diastolic Volume (RVEDV)
This is volume of blood left behind after systole in the right ventricle.
This is a true measure of right ventricular preload. It is calculated by rearranging the above equation.
Right Ventricular End-Diastolic Volume =
Stroke Volume
Right Ventricular Ejection Fraction
Left Ventricular Stroke Work Index (LVSWI)
This is the work performed by the ventricle to eject the ejection fraction.
LVSWI = (MAP – PAWP) x (SVI x 0.0136)
Stroke work is a function of the systolic pressure load, which is afterload minus preload.
Afterload is the mean arterial pressure (MAP), and preload is essentially the PAWP (pulmonary
artery wedge pressure). The factor of 0.0136 converts pressure and volume to units of work.
From Bersten and Soni’s” Oh's Intensive Care Manual”, 6th Edition, as well as the PA catheter section from The ICU Book by Paul L Marino (3rd edition, 2007)
This document was created by Alex Yartsev ([email protected]); if I have used your data or images and forgot to reference you, please email me.
Right Ventricular Stroke Work Index (RVSWI)
This is the work required to move the preload though the pulmonary circulation.
It is also a function of the systolic pressure load, which is right ventricular afterload (the MPAP,
mean pulmonary arterial pressure) minus the preload (which is the CVP).
RVSWI = (MPAP – CVP) x (SVI x 0.0136)
Systemic vascular resistance index (SVRI)
This is directly proportional to the pressure gradient from the aorta to the right atrium (MAP – CVP)
This is inversely proportional to blood flow, or cardiac index (CI)
SVRI = (MAP – CVP) x
80
Cardiac Index
The 80 here is again a factor necessary to convert units.
Pulmonary vascular resistance index (PVRI)
This works under exactly the same principles as the above equation.
The PVRI is directly proportional to the pressure gradient from the pulmonary artery to the left
atrium (MPAP – PAWP). Again, its inversely proportional to blood flow, or cardiac index (CI)
PVRI = (MPAP –PAWP) x
80
Cardiac Index
Oxygen delivery (DO2 )
This is the rate of oxygen delivery in arterial blood.
DO2 = CI x 13.4 x Hb x SaO2
Mixed venous oxygen saturation (SvO 2 )
This is an indirect marker of systemic blood flow.
Because your tissues extract a known proportion of oxygen from the arterial blood, one can infer that if
there is very little oxygen left over, the tissues are extracting more of it, and the reason is that the blood flow
to the tissues is decreased. Decreased blood flow means the tissues have more time to extract capillary
oxygen. All of this flies out the window in sepsis or cyanide poisoning, where tissue oxygen consumption is
unrelated to blood flow.
Oxygen Uptake or Oxygen Consumption (VO2)
This is the rate at which oxygen is sucked out of the capillaries by the tissues
.
VO2 = CI x 13.4 x Hb x (SaO2 - SvO2)
Oxygen Extraction ratio (O 2 ER)
This is the ratio of O2 uptake to O2 delivery; i.e. what fraction of the delivered oxygen is being
consumed in the tissues.
.
O2 ER = 100 x
VO2
DO2
From Bersten and Soni’s” Oh's Intensive Care Manual”, 6th Edition, as well as the PA catheter section from The ICU Book by Paul L Marino (3rd edition, 2007)