Hemodynamic Formulas Flashcards
Cardiac Afterload definition
“Afterload, also known as the systemic vascular resistance (SVR), is the amount of resistance the heart must overcome to open the aortic valve and push the blood volume out into the systemic circulation. If you think about the balloon analogy, afterload is represented by the knot at the end of the balloon. To get the air out, the balloon must work against that knot”
Cardiac Preload definition
“Preload, also known as the left ventricular end-diastolic pressure (LVEDP), is the amount of ventricular stretch at the end of diastole. Think of it as the heart loading up for the next big squeeze of the ventricles during systole. Some people remember this by using an analogy of a balloon – blow air into the balloon and it stretches; the more air you blow in, the greater the stretch.”
Cardiac Output & Cardiac Index definitions.
Cardiac output is the volume of blood the heart pumps per minute. Cardiac output is calculated by multiplying the stroke volume by the heart rate; normal cardiac output is about 4 to 8 L/min but varies depending on the body’s metabolic needs. Cardiac index is a calculation of the cardiac output divided by the person’s body surface area (BSA).
Cardiac Index Formula and normal range
CO/BSA = L/min/m2 2.5-4.0 l/MIN/M2
Cardiac Output Formula
SVxHR = L/min normal is 4-8 l/MIN
What is SVR (systemic vascular resistance)
Pressure of the systemic circulation against which the Left ventricle must contract against
What is PVR (pulmonary vascular resistance)?
The pressure the right ventricle must contract against to pump blood to the lungs trough the pulmonic valve
SVR formula and normal range
SVR= {MAP-CVP} / CO x80
700-1500 dynes/sec/cm-5
SVRI formula
Same as SVR but substitutes CI for CO
SVRI= [MAP-CVP] /CI x 80
1900-2400 dynes s m2/cm5
Stroke Volume normal range
50-100 ml/beat
Stroke Volume Index range and formula
25-45 ml/beat/m2 SV/bsa
Right Atrial Pressure (RAP)
2-6 mmHg
3-8 cm/H2O
Pulmonary Artery Pressure (PAP) range
20/8-30/15 mean <20 mmHg
PAOP normal range
8-12 mmHg
Pulmonary Vascular Resistance (PVR) formula and range
800-1200 dynes/s/cm-5 (mpap-paop) /CO x 80
Coronary Artery Perfusion Pressure (CAPP) formula and range
60-80mmhg dbp-paop
Svo2 definition and normal range
60-75 %
“Venous oxygen saturation (SvO2) is a measure of the oxygen content of the blood returning to the right side of the heart after perfusing the entire body”
“The venous blood in the pulmonary artery represents oxygen extraction in the whole body and is called mixed venous oxygen saturation (SmvO2)”
“A second, less invasive method of measuring SvO2 is via a central venous catheter (CVC) positioned in the superior vena cava and is called the central venous oxygen saturation (ScvO2).”
Pubmed, Venous Oxygen Saturation
Sanjana Chetana Shanmukhappa; Srivatsa Lokeshwaran.
Last Update: October 24, 2022.
SCVO2 definition and normal range
> 70%
SaO2
95-99%
Arterial o2 content formula and range
CaCO2 12-16ml/dl (hgb x 1.39 x Sao2) + (paO2 x 0.003)
DO2 formula and normal range
900-1100 ml/min CaO2 x CO x 10
VO2 formula and normal range
250-350 ml/min (Sao2 - Svo2) x Hgb X 13.9 X CO
What us a dyne?
“a unit of force that, acting on a mass of one gram, increases its velocity by one centimeter per second every second along the direction that it acts” (oxford dictionary)
Additionally,
Units for measuring vascular resistance are dyn·s·cm-5 or pascal seconds per cubic metre (Pa·s/m³). Pediatric cardiologists use hybrid reference units (HRU), also known as Wood units, as they were introduced by Dr. Paul Wood. To convert from Wood units to MPa·s/m3 you must multiply by 8, or to dyn·s·cm-5 you must multiply by 80.
