What is an average cardiac output?

5 L per minute: The average cardiac output is somewhere around 5 l per minute. Cardiac output varies with the size of the patient (larger patients have larger cardiac output). Cardiac output is increased in conditions such as fever, anemia, or pregnancy.

By Size: 2.6-4.2 l/min of blood per m^2 of body surface area. Most "normal" sized people are ~2m^2 bsa, but few people in this country count as normal :) figure something over 4 l/min to be safe. Cardiac shock occurs below ~2l/min.