Mean Arterial Pressure (MAP) Calculator

Mean arterial pressure (MAP) is the average pressure throughout arterial circulation over the course of the cardiac cycle. It can be expressed as the product of cardiac output and systemic vascular resistance, or estimated clinically as the time-weighted mean of the arterial pressure waveform.

MAP is appealing because it is less susceptible to measurement artifacts than systolic or diastolic pressures and aligns with key physiologic mechanisms, including organ autoregulation and baroreceptor function. Consider how an arterial line, if over or under dampened, may provide inadequate systolic and diastolic pressures but the MAP will remain accurate (in the above diagram, systolic and diastolic pressures may vary, but the area under the curve will remain the same. 

In practice, MAP has become the "North Star" of resuscitation, with 65 mmHg often cited as the minimum target for adequate perfusion. This value, however, rests more on consensus than strong evidence.

The 65 Trial (Lamontagne et al., 2020) showed that targeting a lower range (60–65 mmHg) in older patients with vasodilatory shock reduced vasopressor exposure without increasing mortality, and may even be protective in some subgroups.

Conversely, ANDROMEDA-SHOCK-2 demonstrated that a MAP of 65 may be inadequate for perfusion if there is low stroke volume, or extremely low diastolic pressure (less than 50mmHg).

Studies looking at higher MAP targets (>80mmHg) in septic shock (SEPSISPAM, OPTPRESS) have shown mixed evidence on mortality and end organ perfusion). These mixed results highlight the variable phenotypes of broad overarching processes like septic shock, and how more personalized assessments and interventions are likely beneficial. 

Still, inadequate MAP can contribute to microcirculatory dysfunction, particularly in the presence of low flow states or venous congestion (Hemodynamic Interfaces Calculator). For this reason, MAP should be interpreted in context: as one piece of a broader hemodynamic assessment that incorporates patient comorbidities, perfusion endpoints, and individualized goals, rather than a rigid target applied universally.