mean arterial pressure

Mean arterial pressure (MAP) is the single ‘average’ pressure that best represents the steady push driving blood into your organs across a whole heartbeat. Rather than the peaks and troughs of systolic and diastolic, it is the effective pressure your tissues actually feel for perfusion.

Because the heart spends more time relaxing (diastole) than contracting (systole) at normal rates, MAP is not the simple average of the two numbers. A common bedside estimate is diastolic pressure plus one-third of the pulse pressure—roughly MAP ≈ diastolic + (systolic − diastolic) ÷ 3. Conceptually, MAP equals cardiac output multiplied by systemic vascular resistance (plus central venous pressure, usually small), tying it directly to how the body regulates flow.

MAP matters most when perfusion is at stake: in critically ill patients, clinicians often target a minimum MAP (commonly around 65 mmHg) to keep vital organs supplied, since pressure below the autoregulatory range starves the brain and kidneys. The one-third estimate is least accurate at fast heart rates, where systole takes up a larger share of the cycle.