Cardiac output is the total blood the heart pumps each minute, and cardiac index adjusts that number for body size to allow fair comparison between people.
Normal cardiac index (L/min/m²).
Below normal — reduced output.
Cardiogenic shock range.
High output — sepsis, anemia, thyrotoxicosis.
Each beat ejects a stroke volume; multiplied by heart rate, that's cardiac output.
Raw cardiac output naturally differs between a small and large adult even with identical cardiac health, so indexing to body surface area gives a more meaningful comparison to normal ranges.
Roughly 2.5–4.0 L/min/m². Values below about 2.2 suggest low output; below 1.8 is in the cardiogenic-shock range.
Heart rate multiplied by stroke volume (the blood ejected per beat). Multiplying by rate gives the per-minute total.
Exercise, fever, sepsis, anemia, and pregnancy all raise it. It falls in heart failure, hypovolemia, and severe arrhythmias.