Mean Arterial Pressure (MAP)

[Summit]

When someone asks what is MAP, most people respond with the approximation of DP + PP/3 (or the more common equivalent). If you want to teach it properly, we should discuss the true value of CVP+(SVR*CO) and how/why we approximate with other values. If one is to treat with data, one must understand the limitations of the data.

For further reading on approximation with heart rate, read this paper:
http://www.ncbi.nlm.nih.gov/pubmed/10727067

 

[Ecgg]

The same exact thing I would do to treat DBP & SBP. Which is usually nothing.

MAP is simply another way of looking at blood pressure. It gives you the same exact info as DBP and SBP, only presented in a simpler, more meaningful way. MAP is the mean (the "average") of the arterial pressure variations over the course of a single cardiac cycle.

The calculation commonly used to estimate MAP is simple: (2DBP+SBP)/3. A more accurate formula takes into account heart rate (since the length of the diastolic phase depends on HR), but I don't have it memorized or handy.

If you are going to look at a single number as an indicator of whether BP is adequate to supply systemic perfusion, then it makes more sense to look at MAP then SBP, which is what most people seem to focus on. So if we are really worried about keeping things as simple as possible for basics, then EMT courses should teach EMT's to look at MAP and not even worry about DBP or SBP.

What is the formula for corrected rate that you have?


One study states

MAP = DP + [0.33 + (HR x 0.0012)] x [PP] where SP and DP are systolic and diastolic pressure and HR is heart rate. The current study validates the new MAP formula in the same patient at increasing paced heart rates.

PP I think was a mistake and should read SP?

http://www.ncbi.nlm.nih.gov/pubmed/15558774

 

[JPINFV]

Most likely not. Another calculation for MAP is 1/3PP+DP=MAP. It's algebraically the same as 1/3SP+2/3DP=MAP.

 

[Ecgg]

Most likely not. Another calculation for MAP is 1/3PP+DP=MAP. It's algebraically the same as 1/3SP+2/3DP=MAP.

Yeah it's my mistake. PP= pulse pressure (SP-DP).

 

[usalsfyre]

In situations where MAP is a critical component of care (shock, pressor titration, increasing ICP) I wouldn't even trust NIBP calculated MAP. Especially not the automatically calculated MAP that does not account for heart rate. However, MAP off an Arterial line is a fantastic diagnostic tool.

According to SEVERAL reliable sources the MAP is the most accurate number on an NIBP (not sure of the science/engineering but apparently MAP is what's actually measured). An a-line is obviously ideal but not absolutely necessary by any means.

 

[Carlos Danger]

I see no need for an EMT to be worried about MAP. Many Paramedics don't even know what MAP is.

Personally, I usually only pay attention to it when orders are to maintain MAP >65 with pressors or patient is shocky and getting fluid resuscitation.

This explains it well.