Mean arterial pressure

At high heart rates ${\displaystyle MAP}$ is more closely approximated by the arithmetic mean of systolic and diastolic pressures because of the change in shape of the arterial pressure pulse.

For a more accurate formula of ${\displaystyle MAP}$ for elevated heart rates use:

${\displaystyle MAP\simeq DP+0.01\times \exp(4.14-40.74/HR)\times PP}$

Where

• HR = heart rate.
• DP = diastolic pressure
• MAP = mean arterial pressure
• PP = pulse pressure which is systolic minus diastolic pressure[11]

The version of the MAP equation multiplying 0.412 by pulse pressure and adding diastolic blood is indicated to correlate better than other versions of the equation with left ventricular hypertrophy, carotid wall thickness and aortic stiffness.[12] It is expressed:

${\displaystyle MAP=DBP+(0.412\times PP)}$

where:

• DBP = diastolic pressure
• MAP = mean arterial pressure
• PP = pulse pressure

For young patients with congenital heart disease a slight alteration to the factor used found to be more precise. This was written as:

${\displaystyle MAP=DBP+(0.475\times PP)}$

where:

• DBP = diastolic pressure
• MAP = mean arterial pressure
• PP = pulse pressure

This added precision means cerebral blood flow can be more accurately maintained in uncontrolled hypertension.[13]

For neonates, because of their altered physiology, a different formula has been proposed for a more precise reading:

${\displaystyle MAP=DBP+(0.466\times PP)}$

where:

• DBP = diastolic pressure
• MAP = mean arterial pressure
• PP = pulse pressure

It has also been suggested that when getting readings from a neonates radial arterial line, mean arterial pressure can be approximated by averaging the systolic and diastolic pressure.[14]

Other formulas used to estimate mean arterial pressure are:

${\displaystyle MAP=DBP+(0.33PP)+5}$[15]

or

${\displaystyle MAP=DBP+[0.33+(0.0012\times HR)]\times PP}$[16]

or

${\displaystyle MAP=DAP+PP/3}$[17]

or

${\displaystyle MAP=DAP+(PP/3)+5mmHg}$[18]

• MAP = mean arterial pressure
• PP = pulse pressure
• DAP = diastolic aortic pressure
• DPB = diastolic blood pressure

When assessing hypotension, the context of the baseline blood pressure needs to be considered. Acute decreases in mean arterial pressure of around 25% put people at increased risk for organ damage and potential mortality.[19] Even one minute at a MAP of 50 mmHg, or accumulative effects over short periods, increases the risk of mortality by 5%, and can result in organ failure or complications.[20][21]

In people hospitalized with shock, a MAP of 65 mmHg lasting for more than two hours was associated with higher mortality.[22] In people with sepsis, the vasopressor dosage may be titrated on the basis of estimated MAP.[2]

MAP may be used like systolic blood pressure in monitoring and treating target blood pressure. Both are used as targets for assessing sepsis, major trauma, stroke, and intracranial bleeding.[23]

In younger people, elevated MAP is used more commonly than pulse pressure in the prediction of stroke. However in older people, MAP is less predictive of stroke and a better predictor of cardiovascular disease.[24][25]