Without evidence of benefit, an intervention should not be presumed to be beneficial or safe.

- Rogue Medic

A Radial Pulse Means a Pressure of At Least . . . .

Look at this! My picture on the cover of tomorrow’s British Medical Journal. Maybe they are naming me person of the year. Maybe I’m receiving recognition for writing the blog of the year. Does this mean that I have to start using a lot more of the letter U to make my spelling moure British? Does this mean that when I describe a scene as bloody, I’m being obscene?

While they do not come right out and state it on the cover, I’m sure that I am the focus of attention inside. As Arlo Guthrie was sure that the time missing from the Watergate tapes and the length of Alice’s Restaurant, both being 18 1/2 minutes, was not a coincidence.[1] The focus, on the outside, was a bit too extreme. Where are my eyes? Now, I completely understand Carmen Electra.[2]

I’m just going to be patient about looking inside. If they write too glowingly about me, I’d be embarrassed. I don’t want this to go to my head. Yeah! That’s the ticket.

Anyway, it is time for some more medical mythology. From the apparently endless supply of misinformation taught by those experts in misunderstanding science and medicine.

We’ve almost all been taught that the presence of a radial pulse means that the patient has an SBP (Systolic Blood Pressure) of at least 80, or 90, or something like that. It is a rule of thumb, although these same people will tell you not to take the pulse with your thumb. That would be a thumbless rule and that will be fodder for a different post. I did mention an endless supply, didn’t I?

So, where is the research to support the radial pulse equals SBP of . . . ?

In this study,[3] they refer to some correspondence from 1988 and the 1985 version of ATLS [Advanced Trauma Life Support® (ATLS®)]. With such scant evidence to support this claim, how did it become so commonly taught?

When the topic of assessing blood pressure comes up, I like to cover alternative methods of evaluating perfusion. After all, blood pressure is just a means of evaluating perfusion.

It is an unusual individual, who does not start reciting these numbers, as if they were based on something reliable. Maybe some of that science stuff. Apparently the basis for this is as sound as the basis for the Bogus Hour. So it is not a big surprise that we are dealing with trauma.

Is this a problem in trauma?

Many people use blood pressure to determine when to flush out the little bit of blood the hypotensive patient has remaining. This false assessment paradigm of radial pulse equal to whatever, may actually have worked in the favor of patients, since it leads people to overestimate the blood pressure. If they overestimate the blood pressure, maybe they will hold off on the fluid that the patient does not really need. That, alone may be several posts. So, No. This is not really a problem in trauma.

The basis of this appears to be some old discarded teaching by the ACS (American College of Surgeons). The 1985 version of ATLS, but not any of the later versions. The ACS does nothing, that I can see, to correct their promotion of this myth. Just ignore it an it will go away. Sometimes this works. Spouses, bleeding, . . . . Navigating the ACS web site is not very helpful, either. Many of those commenting were very critical of the authors for using an out of date version of ATLS.

Well, if the ACS is doing such a good job of teaching, why do people still recite this? Some of the rote reciters were not even born in 1985. A little responsibility might be in order. The ACS started a rumor, a completely unfounded rumor, and passed it off as based on medical research. The ACS has some responsibility for making it clear that this is inaccurate, once they believe that it is inaccurate. Silence is not an acceptable means of clarifying things. Silence only perpetuates the myth. This is just a bunch of doctors whining that they are being misunderstood. Let me grab a tissue.

Of course, why they started teaching this silliness, is not explained. Neither is why they stopped teaching it. This is the kind of medicine that leads people to believe that an idiot, like Jenny McCarthy, knows what she is talking about. She doesn’t, but does the ACS? We do not have sufficient information to make that determination, but they seem to have been doing their best to cast doubt on that, at the time of this study.

Other than that, the comments rapid responses[4] are very good. Reading the article, then reading the rapid responses, and the prepublication history of the manuscript, is like a nice seminar in the research process. One extra point is that they keep writing about people being under-resuscitated. I do not believe that is the case. I believe that we over-resuscitate.

What does a pulse indicate?

Perfusion. Perfusion up to, and including, the location of the pulse point.

Nothing else?

That is not unimportant, but it is only conjecture to go beyond that. Other indicators of perfusion are level of consciousness, as a way of assessing cerebral perfusion. Again it involves a lot of conjecture. Is the confused individual confused because of a lack of perfusion, because of any of the AEIOU TIPS[5] conditions, because this is normal for this patient, . . . ?

It is often a good bet that perfusion at the radial artery means good perfusion in all of the areas that matter. However, that does not mean that you should not perform a thorough exam of the patient. If you end up in court, stating that something is often a good bet is probably the legal equivalent of, I never inhaled. This is not a rule, so there are plenty of exceptions. Then there are the half a dozen patients I have had, who were awake, alert, and oriented, but did not have any palpable pulses.

Dot plot showing the distribution of systolic blood pressure according to palpable pulses (group 1: radial, femoral, and carotid pulses present; group 2: femoral and carotid pulses only; group 3: carotid pulse only; group 4: radial, femoral, and carotid pulses absent); shaded areas indicate blood pressures expected according to advanced trauma life support guidelines.[6]

Read the study. It is nice and short. Then read the rapid responses and the prepublication history of the manuscript.

Most important – there needs to be a study to assess this more thoroughly. BMJ lists no other studies citing this study, so this may be the only study ever published on the topic.

In a letter, one unpublished study addressed this. This was one of the 2 citations for the study in footnote [3], the other was the 1985 ATLS text. Here is part of that letter.

Blood pressures ranged from 36 to 89 torr systolic. In only five of the 20 patients did the ATLS guidelines correctly predict the range of patient’s blood pressures. In three cases, the ATLS rules underestimated the actual blood pressure, while in ten, the blood pressure was falsely overestimated. False overestimation of blood pressure was greatest in patients whose blood pressures were the lowest. There were four patients with systolic blood pressures less than or equal to 50 torr (two less than 40 torr); in each of these, the ATLS rules predicted the blood pressure to be more than 70 (more than 80 in three). Of the ten patients whose blood pressures were falsely overestimated, the mean difference between actual and estimated blood pressures (using the midpoint of the predicted range) was 34 torr.[7]

Clearly, there should be some research on this.

Footnotes:

^ 1 “Guthrie later wrote a follow-up recounting how he learned that Richard Nixon had owned a copy of the song, and he jokingly suggested that this explained the famous 18½ minute gap in the Watergate tapes. Guthrie rerecorded his entire debut album for his 1997 CD Alice’s Restaurant also known as Alice’s Restaurant: The Massacree Revisited, on the Rising Son music label, which includes this expanded version.”
Wikipedia – links are from the Wikipedia quote
Alice’s Restaurant Massacree

If I remember correctly, Mr. Guthrie stated that others may disagree with his conclusion, but he prefers his own interpretation. So it is with the BMJ cover and my interpretation. Don’t even try to explain to me that the cover might not be about me.

^ 2 The Simpsons
The Frying Game
Carmen Electra: “Homer my eyes are up here.”
Homer, while staring at her chest: “I’ve made my decision and I’m sticking to it.”

^ 3 Accuracy of the advanced trauma life support guidelines for predicting systolic blood pressure using carotid, femoral, and radial pulses: observational study.
Deakin CD, Low JL.
BMJ. 2000 Sep 16;321(7262):673-4. No abstract available.
PMID: 10987771 [PubMed – indexed for MEDLINE]
Free Full Text . . . . Free PDF

Prepublication History of Manuscript

^ 4 Rapid Responses to:
PAPERS:
Charles D Deakin and J Lorraine Low
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
Scroll down from the list to all of the rapid responses printed in line. There are some very good points in these comments.
Apparently Free Full Text

^ 5 Here is a look at the mnemonic AEIOU TIPS (I have repeated several of the words, since there are several ways to use this mnemonic. You may eliminate the ones that are duplicates, that do not help you remember. Endocrine, Insulin, OverDose, UnderDose, and Pharmacy overlap. Infection, Sepsis, and Temperature overlap, too – but they get you to think about similar things differently. That may be helpful.)

A – Alcohol

E – Electrolytes and Encephalopathy and Endocrine

I – Infection and Insulin

O – OverDose and Oxygen

U – Uremia/UTI and Underdose (not taking medications that should be taken)

T – Temperature (Hypo/HyperThermia) and Toxidromes (OverDose) and Trauma

I – Infection and Insulin, again

P – Pharmacy and Psych and Porphyria

S – Sepsis and Space occupying lesion and Stroke and Subarachnoid Bleed and Seizure

^ 6 same source as footnote [3] – Accuracy of the advanced trauma life support guidelines for predicting systolic blood pressure using carotid, femoral, and radial pulses: observational study.
Deakin CD, Low JL.
BMJ. 2000 Sep 16;321(7262):673-4. No abstract available.
PMID: 10987771 [PubMed – indexed for MEDLINE]
Free Full Text . . . . Free PDF

^ 7 ATLS paradigm fails.
Poulton TJ.
Ann Emerg Med. 1988 Jan;17(1):107. No abstract available.
PMID: 3337405 [PubMed – indexed for MEDLINE]

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  1. […] The old rule of thumb about what pressure is indicated by what pulses, that I wrote about in A Radial Pulse Means a Pressure of At Least . . . ., where I describe the research from the BMJ from 2000[1] (not 2001 as I stated on the show). There […]

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