## Indexed Values

In order to take into account the size of the subject it is better to use indexed values for cardiac output (CO) and systemic vascular resistance (SVR), since a large subject will have a higher CO but lower SVR than a small subject (a small subject has small arteries which offer a greater resistance). Body surface area (BSA) is used as a measure of subject size and can be calculated using the Du Bois formula:

Example

#### if in patient 1.:

BSA = 1.7 square metres

MAP = 95 mm Hg

RAP = 5 mm Hg

then at a normal resting cardiac output (for an average adult) of 5 l/min

substituting the numbers above this gives an SVR of 1440.

So, in summary

CO = 5

SVR = 1440

CI = 2.9

SVRI =2448

#### if in patient 2.:

the pressures are the same as above but the patient is smaller with a
BSA of 0.85 and a cardiac output of 2.5, then

CO = 2.5

SVR = 2880

CI = 2.9

SVRI =2448