Just an FYI:
Yes, we all are taught to watch our patients blood pressure, and then to take it at least every 5-10 minutes on critical patients. But very few if any pay enough attention to the mean arterial pressure (MAP)? Many see it as that tiny innocent little number that is usually placed in brackets or hiding off to one side of the monitor screen of electronic blood pressure cuffs or on the cardiac monitors.
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So what the heck is that number? Is it important? Should I record it?
YES !
MAP is defined as the average arterial blood pressure during a single cardiac cycle. The amount of stroke volume (blood ejected from the ventricle) cardiac output (blood perfusion).
The reason that it is so important is that it reflects the hemodynamic perfusion pressure of the vital organs. In other words how much blood supply is reaching or going through your patient.
So what if we do not have a electronic B/P cuff, can we still obtain a MAP reading ? YES !
If so, how can we calculate it?
The simple way to calculate the patients MAP is to use the following formula:
MAP = [ (2 x diastolic) + systolic ] divided by 3. (i.e. 155/85 the MAP would be 108)
The reason that the diastolic value is multiplied by 2, is that the diastolic portion of the cardiac cycle is twice as long as the systolic. Or in other words, it takes twice as long for the ventricles to fill with blood as it takes for them to pump it out….. that is at a normal resting heart-rate.
In bradycardia or tachycardia conditions; in a patient this relationship between systolic and diastolic values may have some changes, and the formula may not be as always accurate, but still is an important.
One may see the use of invasive monitoring of BP (using an arterial line) in the ER and especially in ICU/CCU settings. This gives a true and only real accurate blood pressure reading (single digit). This uses a complex formula and real time value, very few understand the formula for this method.
Okay, if you want to know ...it is obtained via Fourier analysis of the arterial waveform, or as the time-weighted integral of the instantaneous pressures derived from the area under the curve of the pressure-time.
Understand it ?.. me neither....LOL okay a little bit...
Does EMT's need to watch it MAP?
Definitely. I would describe MAP as that as the RPM or oil pressure in an automobile.
A MAP of at least 40-60 is necessary to perfuse the coronary arteries, brain, and kidneys. The normal range is around 70 - 110 mmHg.
This should be taught as another vital sign for
all EMT'sto monitor. It should be monitored anytime the patient has a potential problem with perfusion of their organs. For example (and there are many more):
Shock : especially pt.'s with septic shock and are on vasopressors (Levophed, Dopamine, etc).
CHI :head injured patients, and those with suspected ICP.
Cardiac patients on vasodilator med.s such as NTG, Nipride drips
Patient with a suspected dissecting abdominal aneurysm (AAA)> They need to have their BP controlled within a narrow range so as not to cause increased bleeding or tear.
In the head injured patient, the brain is at risk of ischemia injury if there is insufficient blood flow if the MAP falls below 50. On the other hand, a MAP above 160 reflects excess cerebral blood flow and may result in raised intracranial pressures (ICP).
So, one can see obtaining a blood pressure is important but just getting the numbers is not the real purpose. What those numbers reflect is the
main importance. This is why, I am so picky of my blood pressure readings.
It is much more than just pumping up a sphygmometer up and listening to some lubb.. dubbs... Any idiot can do that!... Being able to distinguish the true sounds, having the knowledge of what is going on inside your patient is the whole point.
How will this affect my call.. this can lead to a more accurate diagnosis as well as knowing how well my patient is being perfused .... What kills most patients is multiple end organ perfusion.. being secondary to shock, sepsis, post arrest.. what ever. Having a knowledge of thorough assessment, just by understanding the basics of numbers ... can make one understand the "big picture".
Hopefully this answered your question + some...
