# accuracy of the ALS guidelines for predicting systolic bp using pulses



## Lifeguards For Life (Sep 15, 2009)

never done a poll before, so hopefully this works. 
I'm sure many of you have heard, if not been taught that you could roughly guage a patients systolic blood pressure by assessing peripheral pulses.
If the pt. has a radial pulse sytolic bp >80
femoral pulse > 70
and if the patient has a palpable carotid pulse, the systolic blood pressure is at least 60mmhg.
In your opinion is this a valid assessment parameter or not?


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## cm4short (Sep 15, 2009)

There is no current study today to back this claim up.


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## Lifeguards For Life (Sep 15, 2009)

actually there was a study by Deakin and Low that disproves this theory. their observational study showed that those patients that retained a radial pulse averaged 72mmhg systolic. of those patients who retained a radial pulse over 80% systolic pressure under 80mmhg. 83% of patients who had a femoral pulse had systolic pressure under 70 with a mean sys pressure of 66.4mmhg.
The only part of the above mentioned theory that held up to some extent was the carotid pulse. None of the subjects who had a carotid pulse had a systolic greater than 60


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## Akulahawk (Sep 15, 2009)

Presence of a pulse in a specific area is probably more an indicator of whether or not there's good end-organ perfusion than a concrete BP number. Loss of peripheral pulses just means to me that the patient is really starting to circle the drain...

For me, it's a part of the not-sick/sick/really sick/holy-crap assessment...


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## Lifeguards For Life (Sep 15, 2009)

agreed. back to the whole "treat the patient not the sign"


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## Medic One (Sep 15, 2009)

*Never predict*

To be a good provider never predict anything...always complete a true evaluation of the patient.

Over the 20 years of working as a medic I never predict much more than what I may eat for dinner on shift.  

I have seen new medics and EMTs use this and yes it can be found in some books but it to me is poor lazy care of your patient.


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## ResTech (Sep 15, 2009)

I too have read that the numbers always taught... 80, 70, 60, are not reliable in estimating blood pressure by pulse presence. Again, if a patient has an absent radial pulse in the presence of significant trauma, that is a good indicator of hypotension...


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## Melclin (Sep 15, 2009)

Lifeguards For Life said:


> actually there was a study by Deakin and Low that disproves this theory. their observational study showed that those patients that retained a radial pulse averaged 72mmhg systolic. of those patients who retained a radial pulse over 80% systolic pressure under 80mmhg. 83% of patients who had a femoral pulse had systolic pressure under 70 with a mean sys pressure of 66.4mmhg.
> The only part of the above mentioned theory that held up to some extent was the carotid pulse. None of the subjects who had a carotid pulse had a systolic greater than 60



That study didn't really _prove_ anything per se. It was the very model of poorly designed research. Not that I disagree with its findings at all, but it's hardly gospel truth. Twenty pts over three years? Poorly defined inclusion and exclusion criteria. No mention of the patients history or a discussion of the confounding variables (of which there must have been many).

I think the important thing that Deakin and Low showed was how easy it was to get an extreme variation in results. 

Still, anybody who has successfully completed the first grade is intimate with the idea that "everybody is different". Honestly, how an idea like "If variable and subjective vital sign X is not present then BP _must not_ be lower than ridiculously specific number Y" ever found its way into a medical curriculum is beyond me. 

Interestingly,the curriculum mentioned in the article was from 1985 and it has long since gone the way of the dodo (long before the article was published too, oddly enough). How embarrassing that some ambos are still using the rule :unsure:

EDIT:  For any who are interested who happen not to have the read the article in question:	Deakin CD, Low JL. Accuracy of the advanced trauma life support guidelines for predicting systolic blood pressure using carotid, femoral, and radial pulses: observational study. BMJ. 2000;321:673-674

http://www.bmj.com.ezproxy.lib.monash.edu.au/cgi/content/full/321/7262/673


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## Lifeguards For Life (Sep 15, 2009)

cool, thanks for posting a link to the study, I have not read the study, just about the study, and yes it is emabarrasing that we learned that "rule of thumb" last week in my medic class.


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## Akulahawk (Sep 15, 2009)

ResTech said:


> I too have read that the numbers always taught... 80, 70, 60, are not reliable in estimating blood pressure by pulse presence. Again, if a patient has an absent radial pulse in the presence of significant trauma, that is a good indicator of hypotension...


Finding a radial pulse shouldn't take (literally) more than a couple seconds, and can be done as part of your initial greeting of the patient. An absent radial pulse will make me check the other side, and if absent there, bumps my index of suspicion that my patient might soon be circling the drain, regardless of what the measured BP values are... ESPECIALLY IN TRAUMA. How long does this take? Literally, seconds. And I do it while checking for other things. I'm not looking for anything but presence and fast/slow.

It all goes back to treat the patient, not the equipment. 

My class was told about that rule of thumb. We also were told that patients generally lose pulses in this sequence: Radial, Brachial, Femoral, Carotid. If you're starting to see loss of peripheral pulses, your patient is already WAY behind the 8-ball and might just be headed for a long-duration dirt nap.


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## Melclin (Sep 16, 2009)

Yeah you can't deny that the progressive loss of pulses indicates and increasingly sick pt. Its just putting a number on exactly how sick, and saying that it will always be true, that I have a problem with.

Again I don't disagree with the idea..But does anyone have some research showing which pulses disappear first. It seem like one of those "obvious things" but I'd feel more comfortable espousing it as obvious if I had a big fat study behind me..Anyone? 

Oh and I just re-read my post and it seemed a little curt. Just for the sake of saying it, I wasn't having a go at you Lifeguards for Life.

I think an interesting corollary to this question is whether or not a pulse means adequate perfusion. In an article I wrote recently, I argued that there was a big difference between the "blood pressure adequate for perfussion" and the "blood pressure of a person with a pulse" but as to whether that means a person with a pulse _isn't_ perfusing properly....I'm not sure (Example: a pt can have a carotid pulse but still not have adequate cerebal perfusion). Akula, you mentioned something about it showing good end organ perfusion. Why was that?


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## Akulahawk (Sep 16, 2009)

Melclin said:


> Yeah you can't deny that the progressive loss of pulses indicates and increasingly sick pt. Its just putting a number on exactly how sick, and saying that it will always be true, that I have a problem with.
> 
> Again I don't disagree with the idea..But does anyone have some research showing which pulses disappear first. It seem like one of those "obvious things" but I'd feel more comfortable espousing it as obvious if I had a big fat study behind me..Anyone?
> 
> ...


Excellent question. While I don't have a definitive number nor do I have access to labs and other equipment, it's basically a logical thing. If the heart is moving blood out that far that you have a good radial pulse, it likely is moving blood through the tissues, specifically the end organs, at an adequate level to actually perfuse them. Actually, if I could feel a pulse in a finger artery, I'd be even more comfortable with that... It isn't always going to be the case (embolism, hemorrhage, etc), but generally speaking, I feel that if you do have a radial pulse, you'll have sufficient blood flow through the tissues. 

Now if I knew that the patient's kidneys were producing urine at an adequate rate, regardless of what the patient's BP numbers were, I'd be more confident in stating that there's likely to be good end-organ perfusion...

Patients will certainly not adhere to that...  

Good example... you take an altered patient who's BP is 120/80 and they're normally at 180/110... yes, they've got a good "textbook" BP, and a good, strong radial pulse, but if their body has acclimated itself to the higher BP... you're not going to see entirely good end-organ perfusion... Patients like that probably are not the norm... That's where doing a good assessment and having a good educational foundation comes into play... 

Most patients, however, will likely fall into the category of good radial pulse = likely good end-organ perfusion. 

Your patient is altered and has a good strong pulse... start looking around... something else is probably wrong.


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## Melclin (Sep 16, 2009)

Akulahawk said:


> Excellent question. While I don't have a definitive number nor do I have access to labs and other equipment, it's basically a logical thing. If the heart is moving blood out that far that you have a good radial pulse, it likely is moving blood through the tissues, specifically the end organs, at an adequate level to actually perfuse them. Actually, if I could feel a pulse in a finger artery, I'd be even more comfortable with that... It isn't always going to be the case (embolism, hemorrhage, etc), but generally speaking, I feel that if you do have a radial pulse, you'll have sufficient blood flow through the tissues.
> 
> Now if I knew that the patient's kidneys were producing urine at an adequate rate, regardless of what the patient's BP numbers were, I'd be more confident in stating that there's likely to be good end-organ perfusion...
> 
> ...



Yeah I understand the idea with a radial pulse. Even then though there are no gurantees as you say. I'd like to see some more research into the pressures required for different pulses and their relationship to perfusion. These two articles (1) (2) argued that there is a very poor correlation between BP and perfusion. I'd like to know more about the relationship between pulse, BP and perfussion during different disease processes. Flight-LP gave me an article a while back (3) that was very helpful for cerebral perfusion; under the heading of "Cerebral blood perfusion in constitutional hypotension". 

What I was getting at was more the central pulses. Specifically the carotid pulse. In my essay I criticized my service's (or my future service given that I'm a student) suggestion that fluid resuscitation in penetrating truncal trauma should only start once the carotid pulse is lost, the assumption presumably being that if you have a carotid pulse, then you have adequate perfusion. I compared the pressures required for a carotid pulse and the pressures required for perfusion in different places and found some significant differences, though looking back on it now, my arguments had some holes in them evidence wise. 

1.	Dutton RP, Mackenzie CF, Scalea TM. Hypotensive resuscitation during active haemorrhage: Impact on in hospital mortality. J Trauma 2002;52:1141-6

2.	Drummond JC. The lower limit of autoregulation: time to revise our thinking? Anesthesiology. 1997;86:1431–143

3.      Duschek S, Schandry R. Reduced brain perfusion and cognitive performance due to constitutional hypotension. Clin Auton Res. 2007 April;17(2):69-76. [http://www.pubmedcentral.nih.gov/art...medid=17106628]


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## Akulahawk (Sep 16, 2009)

The concept you're moving towards is "permissive hypotension". Basically, the idea is that you allow the patient to remain hypotensive to allow time for clots to form and once that has occurred, you don't increase volume and raise the BP, you maintain the BP at a low-ish level so that you don't pop the clot. My understanding of this is all you're looking for is (literally) just enough pressure to keep the kidneys functioning. Peripherally, you might see some blood flow via doppler, but that's about it. 

Trauma patients and medical patients have a bit different of a disease process going on. In the case of penetrating truncal trauma, early on in the case (transport to the hospital phase) you're going to need to be more concerned with simply maintaining central pulses, and not much more. You don't need to be popping the clot or diluting the blood (and all the stuff that it transports and uses for clotting) unnecessarily. 

I think you'll find that once the damage control surgery has been done, the Trauma Surgeon will begin raising BP to preclude damage to organs that, while they can tolerate periods of lowered perfusion, they still need to be adequately perfused. 

IMHO, medical patients that are experiencing loss of peripheral and starting to lose central pulses are experiencing more widespread problems than simple loss of blood, and it's those systemic/multi-systemic problems that lead to poor end-organ perfusion if the BP drops precipitously.


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## Lifeguards For Life (Sep 16, 2009)

Melclin said:


> Oh and I just re-read my post and it seemed a little curt. Just for the sake of saying it, I wasn't having a go at you Lifeguards for Life.



not at all. I was not very familiar with the study and your post caused me to take deeper look, and was surprised what i found.


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