MAP, Mean Arterial Pressure

Formula and why it isn't (SBP + DBP) / 2

MAP  =  (SBP + 2 × DBP)  ÷  3

The heart spends roughly twice as long in diastole as in systole during a normal-rate cycle, so a simple average overweights the systolic peak. Multiplying DBP by 2 corrects for that. At very high heart rates (≥120 bpm), the ratio shifts and arterial-line MAP becomes more accurate than the cuff estimate.

Perfusion thresholds, what to do when MAP drops

• MAP ≥ 65 mmHg, minimum target for organ perfusion in sepsis, septic shock, and most adult ICU patients (Surviving Sepsis Campaign).
• MAP ≥ 80–90 mmHg, used in TBI and post-stroke to maintain cerebral perfusion pressure (CPP = MAP − ICP).
• MAP 60–65 mmHg, concerning. Reassess fluid status, pull labs, notify provider.
• MAP < 60 mmHg, emergency. Vasopressor titration, fluid bolus per protocol, escalate.

Worked example

BP 110/70:

1. (110 + 140) / 3 = 250 / 3 = 83.3 mmHg.
2. Above the ≥65 sepsis target. Adequate for organ perfusion in most adult contexts.

Common pitfalls

• Reading the displayed MAP from the cuff and assuming it's correct. Cuff MAPs over-read at high heart rates and arrhythmias, confirm with arterial line in critically ill patients.
• Ignoring trend. A MAP of 70 that just dropped from 90 is more dangerous than a stable 65.
• Not reassessing after intervention. Recheck MAP within minutes of fluid bolus or vasopressor titration, not at the next vitals window.