7- Mean Arterial Pressure

KYJ7-MAP- Mean Arterial Pressure
Knowing your Jargon (KYJ)

In this episode of KYJ we explore the forgotten vital sign. Mean arterial pressure. Indirectly we obtain it from the patient's BP.

The MAP is what I call the Magic number. It is a determination of the net flow of blood perfusing organs.   Measured as a pressure it is calculated by adding the diastolic BP to one third of the pulse pressure. Confused???

Look its easy-  start with an example- BP is 110/70

Pulse pressure = systolic - Diastolic.

Do this bit first :  110-60 =50
Pulse pressure is 50.

Now take 1 third of this PP

50 / 3 = 16.66 (round up to 17)

Now add this 17 to the Diastolic (60)
17+60
MAP= 77.  See, so simple.

Now the mean pressure of blood going through brain , heart, lungs, kidneys and all other organs is a direct result of the MAP.

The MAP in an adult should be between 70-110.

Above 110 (hypertension), physical damage to vessels in the kidneys,eyes and brain may occur.  Stroke risk is high.

So at what point is MAP considered to be too low to offer adequate perfusion .  55-60 is our critical point where kidney perfusion suffers.  So aiming for a Magic number of 60 is desirable.

Below 55 brain and cardiac function starts to deteriorate.

Next time you use an electronic BP machine, look carefully at the display- most machines calculate that MAP for You.

It's a Magic number!!

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