Mean arterial pressure (MAP)
Mean arterial pressure from systolic and diastolic blood pressure
- Surviving Sepsis Campaign 2021 (ESICM/SCCM)
Sources last checked: 2026-10-13
Mean arterial pressure (MAP)
Mean arterial pressure from systolic and diastolic blood pressure
The ⅓ factor assumes a normal heart rate; at high heart rates diastole shortens and the formula underestimates true MAP. An arterial line reports measured MAP directly.
Interpretation
| < 65 mmHg | Below the initial MAP target of 65 mmHg recommended for adults with septic shock on vasopressors (Surviving Sepsis Campaign 2021). Interpret in clinical context. |
|---|---|
| ≥ 65 mmHg | At or above the 65 mmHg target used in septic shock. Says nothing on its own about hypertension, which guidelines classify by systolic and diastolic values. |
What is the Mean arterial pressure (MAP)?
Mean arterial pressure is the time-averaged pressure in the large arteries over one cardiac cycle and the main driving pressure for organ perfusion. Because diastole lasts roughly two thirds of the cycle at resting heart rates, MAP is approximated at the bedside as diastolic pressure plus one third of the pulse pressure. It is the haemodynamic target most used in intensive care and anaesthesia.
When to use it
- Comparing an estimated MAP with the vasopressor targets used in septic or other forms of shock.
- Estimating perfusion pressure from a cuff reading when no arterial line is in place.
- Calculating derived values such as cerebral perfusion pressure (MAP − ICP) or renal perfusion pressure.
When not to use it
- Diagnosing or grading hypertension — guidelines classify by systolic and diastolic values, not MAP.
- When an invasive arterial line is available — use the measured MAP instead of the estimate.
How it is calculated
MAP = DBP + (SBP − DBP) / 3
Clinical pearls and limitations
- The ⅓ factor assumes a normal heart rate; at high heart rates diastole shortens and the formula underestimates true MAP. An arterial line reports measured MAP directly.
- The 65 mmHg target is an initial target; chronically hypertensive patients may need individualised targets.
- Oscillometric cuffs actually measure MAP and derive systolic/diastolic from it, so the cuff's displayed MAP may differ slightly from this formula.
- At heart rates well above 100/min, a weighting closer to 0.4 × pulse pressure is sometimes used; the classic ⅓ rule is shown here.
Frequently asked questions
What is a normal mean arterial pressure?
In healthy adults MAP typically lies around 70–100 mmHg. Values persistently below about 65 mmHg risk inadequate organ perfusion.
Why is MAP not simply the average of systolic and diastolic?
Because the heart spends longer in diastole than in systole at normal heart rates, so the diastolic value is weighted more heavily.
What MAP target is used in septic shock?
The Surviving Sepsis Campaign 2021 recommends an initial target of 65 mmHg in adults with septic shock on vasopressors.
Evidence and guidelines
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