Cardiac Output is a measurement from thermodilution CO assessments with a pulmonary artery or lithium sensors on an arterial line. But CO does not accurately represent the clinical profile because patients of different sizes need different cardiac outputs. Therefore, to set a context of size and weight for cardiac assessments, the Cardiac Index is computed from the cardiac output data.
Cardiac Index (CI) = Cardiac Output/Body Surface Area
Body Surface Area is determined by a nomogram of three vertical lines: Height (centimeters) BSA (square meters) Weight (kilograms)
An example of a BSA nomogram can be found at http://www.smm.org/heart/lessons/nomogram_adult.htm
| Parameter | Calculation | Normal Range | Clinical Relevance |
| Cardiac Index (CI) |
CO BSA |
2.5 – 4 L/min/m2 | Best parameter for contractility in context of size and weight of patient |
| Mean Arterial Pressure (MAP) |
Systolic BP + (Diastolic BP X 2) 3 |
70 – 100 mm Hg | Average perfusion pressure for tissues during cardiac cycle |
| Systemic Vascular Resistance (SVR) |
(MAP – CVP) X 80 CO |
800 – 1400 dyne/sec/cm-5 | Afterload assessment for the left ventricle |
| Pulmonary Vascular Resistance (PVR) |
(Mean PAP – PAOP) Ï 80 CO |
100 – 250 dyne/sec/cm-5 | Afterload assessment for the right ventricle |
| Systemic Vascular Resistance Index (SVRI) |
(MAP – CVP) Ï 80 CI |
1,360 – 2,200 dyne/sec/cm-5 | Left Ventricular Afterload in context of size and weight of patient |
| Pulmonary Vascular Resistance Index (PVRI) |
(Mean PAP – PAOP) Ï 80 CI |
225 – 315 dyne/sec/cm-5 | Right Ventricular Afterload in context of size and weight of patient |
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