Map

[daedalus]

Lately after reading about MAP- mean arterial pressure- I have been using it in my assessments to determine if a patient is truly not perfusing well. For example, today my partner seemed concerned about a pressure he got when we picked someone up out of an LAPD drunk tank, and I asked him to average the systolic and diastolic, he came out with 70 something, and I said as long ad the average is above 65, and taking into account your complete assessment, the patient is hemodynamicly. Am I correct in my thinking or am I giving out wrong information?

 

[JJR512]

I do not know much about MAP, but I didn't think it was just a simple average of SP and DP. So I looked it up on Wikipedia, which as we all know, is never, ever wrong.

MAP can be approximately calculated at "high heart rates" by simply averaging SP and DP. However, at "normal resting heart rates" a slightly more complicated (though still fairly simple) formula is needed.

This formula can be written a few different ways, but the simplest seems to be: MAP approximately equals ((2xDP)+SP)/3

http://en.wikipedia.org/wiki/Mean_arterial_pressure

 

[snaketooth10k]

Pulse pressure can give you a good idea of how hard the heart is pumping in comparison to the diastolic arterial pressure. Like most other vital sign findings, the relevance of this data is only visible in a trend. For instance: in a patient with no visible external bleeding, a dropping pulse pressure with a maintained diastolic could mean internal bleeding and compensated shock. When the diastolic starts falling you know the body has lost too much blood to compensate.

I've heard that you can provide evidence for a AAA based on pulse pressure and blood pressure, but that seems a bit unlikely to me. Anyone wanna weigh in on that?

 

[JJR512]

I think that when the topic is about MAP, to come in and start talking about PP, it might be a good idea first to establish what PP is, what it means, how it's measured or calculated, etc.

I only know about pulse pressure from my research into MAP yesterday. It wasn't part of my EMT-B training that I recall, so perhaps not everyone here might know what it is. Maybe I'm wrong.

Pulse pressure is basically the strength of the heartbeat, and is simply calculated as SP − DP.

 

[daedalus]

My bad, as MAP is calculated diastolic - 1/3 of systolic - diastolic. And I think thats a rough estimate.

 

[Ridryder911]

Here is my post from a previous discussion:

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.
.
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...

 

[mikie]

This is very interesting. Thanks Rid for that great post. So how does one go about calculating that in the back of the rig? I don't carry a calculator and I'm probably not quick enough on my feet (so to speak) to perform that kind of math! With time, paper & pen, maybe. (ya, cal me stupid)

 

[Ridryder911]

Once you start doing them routinely you begin to notice the "parameters" of what the normal would be in. Take a little time with paper & pen or a calculator (most cell phones have them).

Again, once you repeatedly do this over and over on almost all blood pressures then you will find that you will recognize abnormal. When I teach blood pressures to basics, I require the MAP before te reading. Installing the understanding of how important the permission level is over than just the numbers of the blood pressure reading. (really what does 120/80 really mean?). I have found by repetition practice, I can give you the MAP instantaneously.

As well, many of the blood pressure machines has it built in.

R/r 911

 

[JJR512]

Rid, I'd also like to hear your take on pulse pressure, what it means, what's good and what's not, and whether it's important or not.

 

[mikie]

As well, many of the blood pressure machines has it built in.

I always wondered what that third number was...thanks!

Rid, I'd also like to hear your take on pulse pressure, what it means, what's good and what's not, and whether it's important or not.

Ditto!

 

[mikie]

So if the BP is 120/80, the MAP is 93 (rounded)?

(checking my skills, used my computer's calc)

 

[Ridryder911]

I look at pulse pressure as an indicator on how compliance the arterial systemic circulation is.. (how flexible and pliable).

I could go on, but here is a nice site and some excerpt in regards to how valuable an assessment can be by looking at things such as pulse pressure. I really suggest looking at all the indicators and effects one can see how valuable understanding hemodynamics can be. Again, although it may appear complicated at first, when one uses an analogy of an car engine and hoses and pumps.. it begins to make sense. Don't let big words overwhelm you.. look them up (one tends to remember them longer) It really is not that hard.

I have installed teaching basic hemodynamics in the Basic EMT instead of the traditional method. One has a clean slate and does not question or get confused as easily from other explanations. It appears to really helped those that went forward in their education as well as understanding things such as shock, poor ventricular compliance, CHF, and many other life threatening disorders.

http://www.modern-psychiatry.com/pulse_pressure.htm


..."Peripheral pulse pressure is the difference of the systolic blood pressure minus the diastolic blood pressure. You want to keep the pulse pressure under 60. A high pulse pressure is a measure of stiffness of the arteries. A high pulse pressure is a risk factor for heart disease and premature death.

Systolic blood pressure and pulse pressure increase continuously throughout adult life and the prevalence of arterial hypertension rises accordingly, reaching 53-78% among those aged 65-74 years. Estimates of the prevalence of isolated systolic hypertension in the elderly range from 34-65%, with more women than men affected. It has been shown that within all age groups a difference in usual systolic blood pressure of 20 mm Hg or a difference in usual diastolic blood pressure of 10 mm Hg is associated with an approximately 2-fold difference in the risk of dying from stroke or ischemic heart disease"....

 

[mycrofft]

So, "pulse weak and thready" can be quantified. Good.

They tried an artificial heart or two with no pulse just constant flow. Unlike heart-lung bypass the pt was not cooled and the oxygen was room %. The test subjects (animals) died fairly quickly because apparently we are built to not only withstand those systolic waves, but to use them.
I think of it as a Venn diagram mentally; diastolic, systolic, and pulse speed as the three constant factors, and complaint, S/S, and/or situation as the variable(s). Not quantifiable, but fast and a little on the cautious side.
(EMT-B, "B" for "Boolean").

 

[VentMedic]

Interesting point mycroft

Continuous-flow LVAD proves mettle as bridge to transplantation

August 29, 2007 | Steve Stiles

http://www.theheart.org/article/807979.do

Boston, MA - With a design that can be traced back about 2200 years to Archimedes and his screw-based pump, a left-ventricular assist device (LVAD) that propels blood in a continuous stream successfully bridged patients to heart transplantation or sustained them at least six months while they were waiting for a donor heart in three out of four transplant candidates who received the devices, according to an observational study reported this week [1].

As the "pivotal US experience" for the HeartMate II (Thoratec, Pleasanton, CA), the findings represent a milestone of sorts for the device and an assortment of other continuous-flow LVADs in various stages of development, according to lead author Dr Leslie W Miller (Washington Hospital Center, Washington DC). Reported in the August 30, 2007 New England Journal of Medicine, the study establishes the viability of continuous axial-flow devices—which are smaller, quieter, and possibly longer-lasting than the currently available pulsatile LVADs, Miller said—for bridging patients to transplantation. "We think this is the pump design of the future," he told heartwire.

The current study from Miller et al, Stevenson said, represents a clear advance for the field of mechanical support. But she cautioned that pulsatile LVADs, used for both bridging and destination therapy, have a much longer track record. "Proving that [the continuous-flow devices] get people to transplant is a good first step, but it doesn't say that this is a lifetime therapy or a durable support therapy for longer than a few months."

Phasic coronary blood flow pattern during a continuous flow left ventricular assist support

http://ejcts.ctsnetjournals.org/cgi/content/full/28/5/711

Yoshio Ootaki, Keiji Kamohara, Masatoshi Akiyama, Firas Zahr, Michael W. Kopcak, Jr., Raymond Dessoffy, Kiyotaka Fukamachi *
[SIZE=-1]Eur J Cardiothorac Surg 2005;28:711-716[/SIZE]
[SIZE=-1]© 2005 Elsevier Science NL [/SIZE]

Objective: Continuous flow left ventricular assist devices (LVADs) have been introduced and tested as a bridge to heart transplantation, bridge to recovery, and destination therapy, and several studies have been conducted to assess the physiologic effects of continuous flow LVADs. However, the effect of reduced pulsatility on the phasic coronary blood flow pattern is unknown. The aim of this study was to investigate the phasic coronary blood flow patterns during continuous flow LVAD support.

Conclusion: Use of a continuous flow LVAD decreased TCBF, LAD flow, and LCX flow secondary to reduced systolic LAD flow and LCX flow, and decreased TCBF and LCX flow in the presence of LAD stenosis. These findings are potentially relevant to understanding the physiology of myocardial blood perfusion during continuous flow LVAD support especially in patients with coronary artery disease.

An Artificial Heart That Doesn't Beat

A new concept for an artificial heart could solve some problems with older models--and test the idea that we don't need a pulse.

Thursday, September 21, 2006

http://www.technologyreview.com/read_article.aspx?id=17523&ch=biotech&a=f

Earlier this month, the first fully implantable artificial heart was approved by the Food and Drug Administration. It brings hope to patients who are near death from heart failure; yet some major problems remain with it--namely, its large size and relatively short lifespan.


A new concept for an artificial heart could solve some of those issues. But its innovative pulse-free architecture might also raise problems of its own.

Artificial hearts work by pumping deoxygenated blood from the body to the lungs. The device then pumps oxygenated blood through the body. The newly approved device, called AbioCor, made by Massachusetts-based Abiomed, uses an implanted hydraulic pumping system to simulate a natural heart beat. But an alternative design, conceived by O.H. "Bud" Frazier, a prominent heart surgeon and pioneer in the development of cardiac devices at the Texas Heart Institute in Houston, pumps blood through the body continuously, rather than with the periodic beat of the normal heart.


Pumps that work on this principle, known as continuous flow pumps, are already in clinical use as part of "ventricular assist devices," which are implanted into patients with some remaining heart function to help circulate blood through the body. (Artificial hearts replace the heart entirely.)

Thoratec HeartMate II LVAS
http://texasheart.org/Research/Devices/thoratec_heartmateii.cfm

April 24, 2008 News Release
HeartMate II Approved as Advanced-Stage Heart Failure Treatment Option
THI plays a significant role in clinical studies leading to FDA approval of left-ventricular assist device as a bridge-to-transplantation therapy.

The Pump
The HeartMate II is a high-speed, axial flow, rotary blood pump. As an axial flow device, the HeartMate II produces no pulsatile action. Weighing 12 ounces (about 375 grams) and measuring about 1.5 inches (4 cm) in diameter and 2.5 inches (6 cm) long, it is significantly smaller than other currently approved devices. As such, it may be suitable for a wider range of patients, including small adults and children.

$2.8 Million Grant to Develop Unique Total Artificial Heart

http://www.texasheartinstitute.org/AboutUs/News/artificialheart_6-08.cfm

HOUSTON (June 12, 2008) — A $2.8 million National Institutes of Health grant to the Texas Heart Institute at St. Luke’s Episcopal Hospital will fund development of a novel “pulse-less” total artificial heart.
Unlike previous heart-assist pumps that duplicated the pulse of the natural heart, this experimental device uses two small MicroMed® DeBakey VADs (ventricular-assist devices) that pump blood continuously.

One of the two VADs will be dedicated to circulation of blood throughout the body and the other to blood flow to and from the lungs. Developing a way to design the pumps to automatically respond to the body’s changing needs for blood—such as during exercise—will be a key aim of the program. Continuous flow pumps are smaller, simpler and more robust than their large, complicated pulsatile predecessors.

Abiomed's Abiocor TAH

Updated July 18, 2006

http://www.chfpatients.com/implants/artificial_hearts.htm

Artificial hearts are often called TAH these days - for Total Artificial Hearts. This separates them from LVADs, which are in heavier and heavier use for heart failure patients. I'll be focusing on Abiomed's Abiocor TAH for now, because it is in phase one safety trials in end-stage heart failure patients in the USA.This puts it ahead of all other TAH devices in the United States for now. Other artificial hearts have been in development for many years, but have not yet reached human trials.Abiomed has a lot of experience in heart assist devices but this is their first - and very well planned - attempt at a replacement heart. The Abiocor TAH is designed to fit completely inside the body, with no wires or tubes poking through your skin. The AbioCor is a quiet pulsatile device. That means it moves your blood in a contract/relax rhythm just like your natural heart does, creating a pulse.

 

[mycrofft]

Thanks! The original work was done about fifty years ago.

One of the earliest pulsatile devices was patented by the genius inventor/ventriloquist/entertainer Paul Winchell.

http://www.paulwinchell.com/artificialheart.htm

Maybe newer materials and meds can prevent other problems like mechanical haemolysis? Maybe the theory that the body NEEDS pulses is outmoded?
Imagine going to take a BP, or an apical pulse, on a pulseless pt like that!!! (Like doing a pupillary response on a good fake eye).