Expansion
Mean arterial pressure equals cardiac output multiplied by systemic vascular resistance
Expansion
Pressure = flow x resistance, so:
MAP - right atrial pressure = cardiac output x systemic vascular resistance
Since right atrial pressure is small, this is usually simplified to MAP = CO x SVR.
The equation is the backbone of shock classification:
| Shock type | Cardiac output | Resistance |
|---|---|---|
| Hypovolaemic | Low | High (compensatory) |
| Cardiogenic | Low | High (compensatory) |
| Obstructive | Low | High |
| Septic / distributive | High or normal | Low |
| Anaphylactic | High or normal | Low |
That single distinction, warm and vasodilated versus cold and vasoconstricted, drives treatment: fluids and inotropes for a low-output state, vasopressors for a low-resistance state.