Psychic vs. RAD-57
02/23/2012 by 1 Comment
.jpg)
Also posted over at Rogue Medic (now at EMS Blogs).
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Continuing what I wrote Tuesday and Wednesday about the repeated failure of Masimo’s RAD-57 to correctly discriminate between CO (Carbon monOxide) poisoning and no exposure to CO.[1], [2]
Given the whimsical nature lack of reliability of the RAD-57, should this be an example of what ambulances will look like?
Maybe I should ask a psychic.
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There are two big advantages that the RAD-57 has over the psychic.
1. Many cases of CO poisoning are probably not diagnosed due to vague symptoms that go away when the person leaves the environment.
2. Sometimes the RAD-57 does seem to get it right, but only sometimes.
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There is one big disadvantage of the RAD-57 compared to the psychic.
Nobody is going to send a firefighter back to fight a fire based on the word of a psychic – at least I hope not.
Firefighters are probably being screened to safety with the RAD-57.
How many hospitalized firefighters, or dead firefighters, will it take to demonstrate that the RAD-57 is not accurate enough to use to screen for CO poisoning?
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MK, from Probie To Practitioner, writes –
We have the RAD-57, and I would agree that it’s a fairly unreliable device. I once put it on my finger to try it out on the way to a call, and it gave me a reading of 7%. I have never smoked a day in my life, and before getting on the ambulance, I had spent almost 4 hours doing station chores outside.[3]
This is above the 6.6% cut-off for CO poisoning recommended in the most recent study.[4]
Maybe MK did not use the RAD-57 correctly.
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Quick and easy-to-use—requires no user calibration and does not require patient cooperation or consciousness.[5]
While Masimo is not exactly stating that the RAD-57 is So easy a caveman could use it, ease of use and simplicity are emphasized in their sales pitch.
Claims of operator error demonstrate dishonesty on the part of Masimo.
Is the RAD-57 easy to use, or do we have to align it with the patient’s chi forces, when the moon is just right, after doing a voodoo dance?
The Masimo slogan appears to be –
Trust Masimo. It’s always operator error, never equipment failure.
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Too Old To Work, from Too Old To Work, Too Young To Retire, writes –
Funny you should bring this up. A few months ago we were sent to a “possible CO leak” with mulitple patients. The only problem was the the FD got readins of 0 when they tested the air for CO. Which was confusing to say the least because the first unit on scene with a RAD 57 got a reading of 18 ppm on an elderly gentleman who had some dypnea and chest pain.
The supervisor was convinced that the FD didn’t know what they were doing because of the RAD 57 readings.
Too Old To Work goes on to provide more details in the rest of his comment.[6]
The problem identified in the Touger study was that the RAD-57 was not sensitive enough. The Rad-57 missed most of the actual cases of CO poisoning.[7] The solution seems to be to increase the sensitivity to the point where saying, Carbon monoxide, will set it off.
The question still unanswered is –
How many cases of CO poisoning does the RAD-57 miss?
We will probably only learn this from the lawyers, because Masimo has not been providing useful information.
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Footnotes:
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[1] Accuracy of Noninvasive Multiwave Pulse Oximetry Compared With Carboxyhemoglobin From Blood Gas Analysis in Unselected Emergency Department Patients
Paramedicine 101
Tue, 21 Feb 2012
Article
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[2] Mass sociogenic illness initially reported as carbon monoxide poisoning.
Paramedicine 101
Wed, 22 Feb 2012
Article
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[3] Mass sociogenic illness initially reported as carbon monoxide poisoning.
Paramedicine 101
02/22/2012 at 13:44
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[4] Accuracy of noninvasive multiwave pulse oximetry compared with carboxyhemoglobin from blood gas analysis in unselected emergency department patients.
Roth D, Herkner H, Schreiber W, Hubmann N, Gamper G, Laggner AN, Havel C.
Ann Emerg Med. 2011 Jul;58(1):74-9. Epub 2011 Apr 2.
PMID: 21459480 [PubMed - indexed for MEDLINE]
Annals of Emergency Medicine podcast
Podcast Download in MP3 Format
Because a false-negative reading could have serious medical consequences, this device should be tested in a much larger number of poisoned patients to confirm the generalizability of our stated cutoff values.
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[5] RAD-57
Masimo
Product information page
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[6] Mass sociogenic illness initially reported as carbon monoxide poisoning.
Paramedicine 101
02/23/2012 at 03:00
Comment by Too Old To Work
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[7] Performance of the RAD-57 pulse CO-oximeter compared with standard laboratory carboxyhemoglobin measurement.
Touger M, Birnbaum A, Wang J, Chou K, Pearson D, Bijur P.
Ann Emerg Med. 2010 Oct;56(4):382-8. Epub 2010 Jun 3.
PMID: 20605259 [PubMed - indexed for MEDLINE]
Free Full Text Article from Ann Emerg Med with links to Free Full Text PDF Download
The RAD device correctly identified 11 of 23 patients with laboratory values greater than or equal to 15% carboxyhemoglobin (sensitivity 48%; 95% CI 27% to 69%).
Less than half?
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Mass sociogenic illness initially reported as carbon monoxide poisoning
02/22/2012 by 4 Comments
Also posted over at Rogue Medic (now at EMS Blogs).
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This is adding to what I wrote yesterday about the continuing failure of Masimo’s RAD-57.[1] The RAD-57 does not demonstrate any kind of acceptable sensitivity or specificity to be marketed as a mass screening device – and especially not to screen firefighters to go back to fighting fire. This is just more evidence that the RAD-57 does not accurately measure carboxyhemoglobin (COHb).
Here is a report of a mass delusion that seems to have been compounded by the use of the Masimo RAD-57 non-invasive CO monitor. CO (Carbon monOxide) is a significant cause of poisoning in the US, but not relevant in this case. The RAD-57 incorrectly identified CO poisoning in half a dozen people who do not appear to have had any exposure to CO.
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Sociogenic illness is a rare but well-described phenomenon. It involves a constellation of physical signs and symptoms without an organic cause in a group of individuals with a common ‘‘exposure’’ (1–8). It often occurs in the setting of large gatherings such as schools or when large numbers of people are living or working in close proximity.[2]
I wrote about a different example of mass delision a couple of weeks ago.[3] We underestimate our ability to delude ourselves, but we are great at self-delusion and we are most delusional in groups. No need for any objectivity. Just go with the feeling of a group.
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Approximately 15 min into the mass, one child fainted, followed by another child. The children did not have any seizure activity and immediately awoke with normal mental status and were removed from the church. Within minutes, several more children reported a variety of complaints, including nausea, hand paresthesia, and dyspnea.[2]
A poison strong enough to cause people to pass out, is not going to result in a return to normal mental status right away.
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The fire department initially evaluated the patients with complaints, including obtaining carboxyhemoglobin (COHb) oximetry and oxygen saturation readings from a hand-held portable Masimo® device (Masimo Corporation, Irvine, CA). At the scene, 6 patients were reported to have elevated COHb levels. As such, the church was closed and paramedics, as well as the city’s hazardous materials (HAZMAT) team, were called to the scene.[2]
If only someone had told them that the RAD-57 doesn’t work, much of the chaos could have been avoided.
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Blood COHb levels, obtained in all patients soon after arrival in the ED, ranged from 0.2% to 1.2% (mean 0.65%). The hospital laboratory reference range for COHb is < 1.5% for non-smokers and as high as 5% for smokers. However, this upper value can be much higher in heavy smokers (9). None of our patients had elevated blood COHb levels.[2]
A magic diesel cure?
It’s a miracle!
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In the ED, all patients had normal physical examinations, including neurologic and respiratory examinations.[2]
Were their physical exams much different on scene?
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Subsequent evaluation of the church, classrooms, and surrounding premises by fire department and HAZMAT personnel found no evidence of carbon monoxide or any other toxicants.[2]
The interesting part that is not well described is the initial response of the fire department. Almost always, they have atmospheric CO alarms on their gear. When a firefighter walks into a room with elevated CO, the alarm goes off. When there is a report of a possible CO exposure, a couple of fully geared up firefighters will investigate everywhere they can in a building, looking for areas where CO might be leaking and for areas where CO might have accumulated.
There is no mention of any finding of CO at any time on scene.
No – the RAD-57 is not an indication of the presence of CO.
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The affected persons were sitting in various areas of the church and many of the unaffected individuals were sitting near affected persons. This variability is not consistent with a simple asphyxiant. Furthermore, several patients became symptomatic after leaving the church, which would not be seen with a simple asphyxiant.[2]
Exposures to gasses should present with a predictable pattern. The people in the most heavily concentrated area should be the most affected, with the smallest people (generally children) and the most active people (also generally children) being more affected than the larger and less active people. That was not the case. This suggests MSI (Mass Sociogenic Illness, or mass delusion).
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the escalation of symptoms and increased number of persons affected along with increasing fire and ambulance presence is a common phenomenon in MSI, referred to as ‘‘line of sight transmission.’’[2]
Even if it appears obvious that this is a mass delusion, we should provide treatment as appropriate for the symptoms presented. In this case, some oxygen is the only treatment indicated and the only treatment provided.
I wonder if this will lead to others reporting similar cases of mass delusions compounded by Magic 8 Ball RAD-57 readiongs.
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See also –
Toxic exposure or mass sociogenic illness? The diagnosis can be challenging
The Poison Review
February 18, 2012, 12:28 am
Article
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Mass psychogenic illness attributed to toxic exposure at a high school.
Jones TF, Craig AS, Hoy D, Gunter EW, Ashley DL, Barr DB, Brock JW, Schaffner W.
N Engl J Med. 2000 Jan 13;342(2):96-100.
PMID: 10631279 [PubMed - indexed for MEDLINE]
Free Full Text from N Engl J Med.
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Footnotes:
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[1] Accuracy of Noninvasive Multiwave Pulse Oximetry Compared With Carboxyhemoglobin From Blood Gas Analysis in Unselected Emergency Department Patients
Rogue Medic
Tue, 21 Feb 2012
Article
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[2] Mass sociogenic illness initially reported as carbon monoxide poisoning.
Nordt SP, Minns A, Carstairs S, Kreshak A, Campbell C, Tomaszweski C, Hayden SR, Clark RF, Joshua A, Ly BT.
J Emerg Med. 2012 Feb;42(2):159-61. Epub 2011 Jun 11.
PMID: 21658882 [PubMed - in process]
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[3] Mysterious Tics in Teen Girls – What Is Mass Psychogenic Illness – Part I
Rogue Medic
Tue, 07 Feb 2012
Article
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Accuracy of Noninvasive Multiwave Pulse Oximetry Compared With Carboxyhemoglobin From Blood Gas Analysis in Unselected Emergency Department Patients
02/21/2012 by 3 Comments
Also posted over at Rogue Medic (now at EMS Blogs).
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The Masimo RAD-57 non-invasive CO monitor is promoted as an accurate way to identify patients at risk of life-threatening complications of CO poisoning. CO (Carbon monOxide) is a significant cause of poisoning in the US, with hundreds of fatalities each year.
Masimo claims that their RAD-57 is able to accurately measure blood levels of CO without any complicated lab equipment. If it works, the RAD-57 might save some lives. Unfortunately, the research that has not been funded by Masimo does not support a decision to buy a RAD-57 until after they improve the device.
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Suspicion of CO poisoning is very important in identifying CO poisoning. One study was conducted at a burn center among patients already suspected of having CO exposure.
The RAD device correctly identified 11 of 23 patients with laboratory values greater than or equal to 15% carboxyhemoglobin (sensitivity 48%; 95% CI 27% to 69%).[1]
A coin flip is going to be just as accurate as a test that identifies only 48% of the affected patients.
The RAD-57 was shooting at fish in a barrel and still missed most of the time.
Dr. Michael O’Reilly (Executive Vice President of Masimo Corporation) has claimed that those researchers, who are not on the Masimo payroll, are biased against his device.[2]
What does he understand about science, objectivity, or controlling for biases?
Nothing comes to mind.
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Even some people who are not on the Masimo payroll have suggested that the RAD-57 might be useful and that the next study (quoted below) would confirm the usefulness of the RAD-57.
Compared with the large population used for the calculation of bias and precision, the number of patients actually found to be poisoned was small, especially in the group of poisoned smokers. Therefore, the opportunity for false-negative results was limited. Because a false-negative reading could have serious medical consequences, this device should be tested in a much larger number of poisoned patients to confirm the generalizability of our stated cutoff values.[3]
This does not contradict the first study.
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What is the problem?
Symptoms of CO poisoning are nonspecific, ranging from mild headache, nausea, confusion, and dizziness to end-organ injury such as myocardial infarction,6 stroke,7 and death. [8] and [9] Diagnosis is therefore difficult and relies on clinical suspicion and confirmation by measurement of carboxyhemoglobin (COHb), using either venous or arterial10 blood gas analysis. However, COHb analyzers are not ubiquitously available.11 As a result, many victims of CO poisoning might be overlooked and misdiagnosed. [12] and [13] [3]
Suspicion of illness/exposure is the most important part of identification.
If we examine patients without considering suspicion, does the RAD-57 improve identification?
Maybe, but this study is not capable of testing that hypothesis.
These are only patients who are going to have ABGs (Arterial Blood Gas measurements) regardless of what the RAD-57 shows. We don’t know how many of the patients who did not have ABGs, or did not have ABGs within one hour of RAD-57 measurement, actually had CO poisoning.
Blood gas analysis (arterial or venous) (Table 1) was performed later as a standard procedure in our ED on discretion of the treating physician for a variety of clinical reasons.[3]
If the patient had a low reading on the RAD-57 and did not have an ABG, should we conclude that the unmeasured carboxyhemoglobin level was also low?
Of course not.
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31% of patients who had ABGs were excluded because there was more than one hour between RAD-57 measurement and ABG measurement. How many of these patients were presenting as unstable and had the RAD-57 measurement omitted? How many of these patients were presenting as very stable and had the RAD-57 measurement over an hour before the ABG?
We do not know.
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How many of the 17 patients in the documented sample had life-threatening symptoms?
We do not know.
Maybe all 17.
Maybe zero.
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How many of the 17 patients in the documented sample had only minor symptoms?
We do not know.
Maybe all 17.
Maybe zero.
This kind of information is not included in the study.
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What was the basis of diagnosis of CO poisoning?
The diagnosis of CO poisoning was based on increased COHb levels and clinical symptoms consistent with poisoning, including headache, vomiting, abdominal pain, and loss of consciousness.[3]
Identifying 16 out of the 17 patients in the 1,578 patient sample is impressive, but when we limit the patients to those with symptoms suggesting CO poisoning, we lose any possible value of the non-invasive screening.
These are the patients who are going to have blood drawn to assess for CO poisoning regardless whether anyone uses a RAD-57.
There is no benefit to RAD-57 screening in this setting.
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What about using the RAD-57 in 1,017 EMS patients, regardless of the reason for the 911 call?
Of the 11 patients with a SpCO >15%, 10 were transported to a hospital for which the investigators had institutional review board (IRB) approval to review the patient’ s medical record. Of those 10, none had confirmatory venous carboxyhemoglobin levels. The two patients with an SpCO level of 21% did have a repeat SpCO documented at triage upon arrival to the emergency department. Their repeat levels were 8% and 2%. None of the 10 patients with levels >15% ultimately were diagnosed with and treated for carbon monoxide exposure or toxicity.[4]
The same idea, just not limited to patients chosen by having ABGs measured within one hour of RAD-57 measurement.
The result is very different.
None of the patients with elevated RAD-57 measurements had carboxyhemoglobin measured by drawing blood.
None of the patients with CO poisoning (according to the RAD-57) were treated for CO poisoning.
Is the RAD-57 reliable for determining if a patient should not go to the hospital?
Absolutely not.
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What is the target audience of RAD-57 marketing?
Firefighters.
What is the patient population studied?
Patients already being treated in the hospital. They may include firefighters, but there is nothing in the study to indicate if there are any firefighters in the sample.
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Quick and easy-to-use—requires no user calibration and does not require patient cooperation or consciousness.[5]
Dr. Michael O’Reilly (Executive Vice President of Masimo Corporation) had a bunch of excuses for the study that did not agree with the research paid for by Masimo. One excuse was that incorrect use of the RAD-57 interfered with results, even though Masimo trained the people using the RAD-57. Would Dr. O’Reilly have mentioned this if the study had produced the results he wanted?
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Image credit.
Trust me. I am here to serve you.
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Keep Firefighters Safe From CO Poisoning
> Have CO levels tested on the scene with the Masimo Rad-57.
• Just because firefighters don’t feel like they have CO poisoning doesn’t mean that they don’t have unsafe levels of carboxyhemoglobin (SpCO) in their bloodstream.
• That’s why rehab guidelines support the use of on-scene CO testing.6 To be safe, have SpCO levels tested with a Masimo Rad-57 before going back into the fire and during overhaul, even if firefighters think they’re okay.
> Get prompt on-scene treatment.
• Recognition is the key to immediate on-scene treatment. With early recognition, treatment for CO poisoning can begin immediately, which significantly reduces both immediate and long-term health risks.[6]
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To be safe, have SpCO levels tested with a Masimo Rad-57 before going back into the fire and during overhaul, even if firefighters think they’re okay.
Masimo is providing very bad advice. Is Masimo trying to kill firefighters?
And if the RAD-57 does not detect CO poisoning, is that any reason to allow a firefighter to go back into a fire?
Absolutely not.
The RAD-57 should NEVER be used to screen asymptomatic people for CO poisoning.
The RAD-57 should NEVER be used to rule out CO poisoning.
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Footnotes:
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[1] Performance of the RAD-57 pulse CO-oximeter compared with standard laboratory carboxyhemoglobin measurement.
Touger M, Birnbaum A, Wang J, Chou K, Pearson D, Bijur P.
Ann Emerg Med. 2010 Oct;56(4):382-8. Epub 2010 Jun 3.
PMID: 20605259 [PubMed - indexed for MEDLINE]
Free Full Text Article from Ann Emerg Med with links to Free Full Text PDF Download
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[2] Performance of the Rad-57 pulse co-oximeter compared with standard laboratory carboxyhemoglobin measurement.
O’Reilly M.
Ann Emerg Med. 2010 Oct;56(4):442-4; author reply 444-5. No abstract available.
PMID: 20868919 [PubMed - indexed for MEDLINE]
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[3] Accuracy of noninvasive multiwave pulse oximetry compared with carboxyhemoglobin from blood gas analysis in unselected emergency department patients.
Annals of Emergency Medicine podcast
Podcast Download in MP3 Format
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[4] Non-invasive carboxyhemoglobin monitoring: screening emergency medical services patients for carbon monoxide exposure.
Nilson D, Partridge R, Suner S, Jay G.
Prehosp Disaster Med. 2010 May-Jun;25(3):253-6.
PMID: 20586019 [PubMed - indexed for MEDLINE]
Free Full Text PDF Download from Prehosp Disaster Med.
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[5] RAD-57
Masimo
Product information page
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[6] RAD-57 for Fire/EMS
Masimo
Product information page
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Patient Perceptions of Computed Tomographic Imaging and Their Understanding of Radiation Risk and Exposure – Part IV
09/12/2011 by 1 Comment
Also posted over at Rogue Medic (now at EMS Blogs).
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Continuing from Part I, Part II. and Part III.
After assessing what it is that the abdominal pain patients want/expect from a visit to the ED (Emergency Department), how many X-rays it takes to deliver the same radiation as an abdominal CT (Computed Tomographic imaging), whether CTs increase the lifetime risk of cancer, and how many abdominal CTs equal some sort of measure of the radiation exposure of Hiroshima survivors, the authors conclude that people do not understand the risks of radiation.[1] This study is followed by an excellent editorial.
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The easy conclusion from these findings is, unsurprisingly, that patients are ill informed, and thus efforts to improve their education and awareness should help to mitigate the overuse of imaging and its consequent risks.[2]
Dr. Wears does not discuss the validity of assuming that there is only one right answer to the questions asked. There is also a podcast discussing this study and discussing the editorial, but the podcast is similarly missing the problem with the study taking for granted that there is a single right answer to the study’s questions.[3]
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First, the “rational person” assumption holds that, given correct information, people should arrive at consistent choices about alternatives (eg, to image or not) based on the net expectation of probabilities and outcomes.2[2]
If we make rational decisions, why do so many of us smoke?
If we make rational decisions, why do so many of us eat to the point of obesity?
If we make rational decisions, why do so many of us spend so much time watching reality TV?
Dr. Wears cites some of the studies that show that we do not make rational decisions. To insist that we make rational decisions is also irrational. Isolated examples of decisions that appear rational do not mean that a person makes rational decisions any more than a stopped clock being right twice a day means that the stopped clock keeps accurate time.
The authors provide excellent examples of irrationality in one question they present.
Click on images to make them larger.
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How a multiple choice question is presented will affect way the answers are chosen.
Why is there no choice for I don’t know?
For most people not familiar with X-rays and CTs, the only honest and rational answer is I don’t know.
When graphing the results, we can further distort the results by making the distances between numbers completely arbitrary. Why present the choices as the Same radiation (the same, or zero difference is 50 x 0), 50 times more (greater by a factor of 50 x 1), 100 times more (greater by a factor of 50 x 2), 250 times more (greater by a factor of 50 x 5), 300 times more (greater by a factor of 50 x 6), and Over 350 times more (greater by a factor of 50 x at least 7).
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Why blur the distinction between 100 times and 250 times? When the numbers become blurred, the numbers lose their meaning. When there is no difference in meaning between one number and a number 2 1/2 times as large, are we providing information or are we providing confusion?
We seem to most insist on stripping information of its meaning when we create multiple choice tests. Correct answers become a simple matter of memorization separated from understanding. This is one way to create the protocol monkey – the automaton, whom we claim is rendered harmless by being prevented from thinking. This desire to prevent the use of judgment may be the ultimate irrational decision.
If the difference between 100 and 250 is the same as the difference between 250 and 300, how do we expect anyone to notice differences in dosages? 100 mg – 200 mg – 300 mg – what’s the difference? With memorized answers, the only difference is whether it is graded as correct. With real patients, the differences can be fatal.
We memorize our way to recklessness.
We do not memorize our way to safety.
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Previous literature estimates the radiation dose for an abdomen-pelvis CT to be equivalent to 100 to 250 2-view chest series.2,10-12 For the purpose of this investigation, we used the conservative estimate of 1 abdomen-pelvis CT = 100 2-view chest radiographs.[1]
I agree with their choice to use the more conservative number, but what this still does not do is put this in a context that helps people to understand. Without understanding something about the radiation exposure of an X-ray, this is an unknown. 10 times an unknown – 100 times an unknown – 1,000 times an unknown – what’s the difference?
Presenting misleading information to medically naive people and proclaiming Eureka! is misleading. We are not finding anything. We are presenting a spectacle, although not as much of one as Archimedes did running naked through the streets (assuming the legend to be true).
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The second assumption is that the problem is “out there” in patients, not “in here” in physicians. This might be viewed as a form of the psychologist’s fallacy,3 the idea that although patients’ preferences might suffer from irrationality, ignorance, or irrelevant considerations, ours (physicians’) do not.[2]
An excellent point that should be extended to researchers.
How much of the problem is in the study design?
What are we measuring?
If the purpose of controlled trials is to examine things objectively, why use a study that seems to depend insist on subjectivity?
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I will write more about Dr. Wears editorial later, because it covers a lot of important material on making decisions.
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Footnotes:
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[1] Patient perceptions of computed tomographic imaging and their understanding of radiation risk and exposure.
Baumann BM, Chen EH, Mills AM, Glaspey L, Thompson NM, Jones MK, Farner MC.
Ann Emerg Med. 2011 Jul;58(1):1-7.e2. Epub 2010 Dec 13.
PMID: 21146900 [PubMed - indexed for MEDLINE]
Free Full Text from Annals of Emergency Medicine with links to Free Full Text PDF Download
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[2] Risk, radiation, and rationality.
Wears RL.
Ann Emerg Med. 2011 Jul;58(1):9-11. Epub 2011 Apr 2. No abstract available.
PMID: 21459481 [PubMed - indexed for MEDLINE]
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[3] What patients understand about radiation exposure from CTs
David H. Newman, MD, and Ashley Shreve (spelling?)
Annals of Emergency Medicine podcast page
2011 July
Free Podcast in MP3 format
Annals of Emergency Medicine provides a podcast that summarizes the articles published that month. This is an excellent resource. The full July 2011 podcast is – Free Full Podcast in MP3 format. The full archives of Annals of Emergency Medicine podcasts is – Page with links to podcast segments and full month podcasts.
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Prehospital rapid sequence intubation improves functional outcome for patients with severe traumatic brain injury – Summary
09/01/2011 by 1 Comment
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Also posted at Rogue Medic, which is now at EMS Blogs.
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In response to my post If We Were Really Serious About Intubation Quality was a comment from drastic suggesting that I take a look at a couple of studies that demonstrate that Australian paramedics do not need to improve their intubation skills and that intubation improves outcomes.
One of the studies does show a lot of positives for intubation. The big problem is the lack of statistical significance. A larger study needs to be done to confirm the results, an LMA (Laryngeal Mask Airway) or other group should be added. Otherwise, this appears to be a great study.
Does EMS RSI (Rapid Sequence Induction/Intubation) lead to better outcomes than delaying intubation until arrival at the trauma center for patients with TBI (Traumatic Brain Injury)?
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The difference in outcomes would no longer be statistically significant whether one more patient had a positive outcome in the treatment group (P = 0.059) or one less in the control group (P = 0.061).[1]
That limitation is very important, since 13 patients were lost to follow-up (10 in the hospital intubation group and 3 in the EMS RSI group), because their families lost contact with them. This apparent independence suggests, but certainly does not prove, that these patients would not have fallen into the more severely impaired categories. Even if all of the EMS RSI patients did have severe disabilities, while all of the hospital intubation patients had good neurological outcomes, the hospital intubation group would only come up to 43% (66/152) with a good neurological outcome, which is still less than the possible 50% (80/160) for the EMS RSI group. Therefore, the results would not change to the point of demonstrating worse outcomes with EMS RSI, but the results would no longer be statistically significant.
More likely is that they all have good neurological outcomes and the results would change to 52% (83/163) vs. 43% (66/152). Both outcomes improve, but the results are still not statistically significant.
All EMS RSI patients had waveform capnography, which may explain why the results are so different from the results of the study by Davis on EMS RSI for TBI. This study raised a bunch of questions about those results, which showed worse outcomes for EMS RSI. One hypothesis was that the much higher incidence of hypocapnea contributed to the bad outcomes even though the EMS intubation success rates more than doubled for TBI patients.
Conclusion: Paramedic RSI protocols to facilitate intubation of head-injured patients were associated with an increase in mortality and decrease in good outcomes versus matched historical controls.[2]
airway management success rates for severely head-injured patients in our prehospital system increased from 39% in the pre-trial period to 86% during the trial.20,21[2]
In this study, the intubation success rate for TBI patients was 97%, which is dramatically higher than 86%. 1/7 lack of success vs. 1/33.
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Does this study demonstrate good outcomes with paramedic intubation for TBI?
Yes.
Does this study demonstrate excellent intubation success with RSI for TBI?
Yes.
There is a lot more to discuss about this study, but I will go into more depth later.
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Footnotes:
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[1] Prehospital rapid sequence intubation improves functional outcome for patients with severe traumatic brain injury: a randomized controlled trial.
Bernard SA, Nguyen V, Cameron P, Masci K, Fitzgerald M, Cooper DJ, Walker T, Std BP, Myles P, Murray L, David, Taylor, Smith K, Patrick I, Edington J, Bacon A, Rosenfeld JV, Judson R.
Ann Surg. 2010 Dec;252(6):959-65.
PMID: 21107105 [PubMed - indexed for MEDLINE]
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[2] The effect of paramedic rapid sequence intubation on outcome in patients with severe traumatic brain injury.
Davis DP, Hoyt DB, Ochs M, Fortlage D, Holbrook T, Marshall LK, Rosen P.
J Trauma. 2003 Mar;54(3):444-53.
PMID: 12634522 [PubMed - indexed for MEDLINE]
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Management of prehospital seizure patients by paramedics
08/01/2011 by 1 Comment
-.jpg)
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Also posted over at Rogue Medic (now at EMS Blogs).
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Why look at seizures?
In a 2001 multicenter study, patients presenting with seizures or complaints related to seizures represented 1.2% of all ED visits.1 The majority of these patients (71%) utilized emergency medical services (EMS) for transport and care. An even greater number (84%) had interventions during EMS transport or in the ED that included airway attention, establishing intravenous (IV) access, and medication administration, and 55% received antiepileptic medications.[1]
It does seem as if seizures are over-represented in EMS and it seems that seizures require some very aggressive care.
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The secondary objective was to identify other characteristics related to these cases that would help to ascertain the utility of specific ALS procedures.[1]
Of all of those interventions, such as 55% received antiepileptic medications, which ones are most important and why?
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500 consecutive adult seizure patients over a period of 9 months produced only 97 patients for analysis. Seizures are frequent. One of the advantages of research is that it allows us to acquire some of the experience of much more frequent patient contact than we would in a busy career. 97 seizure patients is not a lot. If I only see one seizure patient a month, this is 8 years of experience, but does one seizure patient a month reflect your system? Would one a week be more like it? At one a week, this is only 2 years experience.
Why do I spend time explaining this?
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These patients represent a heterogeneous group of patients including those with generalized seizures, focal seizures, and pseudo-seizures.[1]
With a very varied group, small numbers can be expected to produce results that are not representative of a much larger population. The idea is right, but the numbers are not. 500, or a thousand, would be much better for averaging the many variables. If your experience does not match what is described, here, don’t get upset. This does not match my experience, either.
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You can click on the tables for larger versions.
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That seems normal. I do not recall a lot of patients who are confused or who remain confused for more than a few minutes after arrival on scene.
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Six patients had glucose levels (BGLs) less than 80 mg/dL (range 68–79 mg/dL), which was the protocol cutoff for treatment with dextrose or glucagon; blood glucose values at this level are herein referred to as hypoglycemia. All of these patients had an IV line attempted, though only one (BGL = 69 mg/dL) received dextrose and none received glucagon. However, only one of the untreated patients had a BGL less than 70 mg/dL (BGL = 68 mg/dL) and was in an alert, conscious state. The patient who did receive dextrose and one of two hypoglycemic patients with an unsuccessful IV attempt (BGL = 76 mg/dL) had recurrence of seizure activity in the prehospital setting.[1]
There is so much about this that raises questions, rather than answering questions. Were the seizures of any of these patients attributed to the hypoglycemia? Did any of these patients have a history of seizures due to hypoglycemia? What was learned about them in the hospital?
2/6 hypoglycemic patients (33.3%) had repeat seizures, but overall 28/97 patients (28.9%) had repeat seizures, only 17 of them (17.5%) out of the hospital.
Should we compare the hypoglycemic patients with the overall seizure patients? With only 6 hypoglycemic patients, and only 56 had BGL measured (64.4%), changes of just a single patient will completely change the apparent significance. What if, instead of 2 hypoglycemic patients having seizures, only 1 did (16.7%)? Or what if 3 did (50%)? Or what if 4 did (66.7%)? Or what if none of them did (0.0%)? And how many of the patients, who did not have BGL measured, had repeat seizures and hypoglycemia?
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The hospital data are not helpful for learning more about the hypoglycemic patients. Did the hospital check BGL on every patient? Probably. Go to an ED (Emergency Department) for anything non-traumatic and expect to have a blood sugar checked.
Does that mean that we should make every medical EMS call ALS, just to check BGL?
This could be the Mechanism Of Idiocy Injury that could help minor medical calls leapfrog past trauma in ALS over-triage.
Just stop thinking and start making everything ALS, because what if we miss one?
If it saves just one life (even though maybe a dozen who would otherwise have lived will now die), it’s worth it! Go ALS!
Or we could fly all of these patients, just in case, because What if . . . ?
Anyway, back in the real world, we just don’t know what to do with the data on hypoglycemia. What about the data on repeat seizures? Some seize. Based on this study, are we able to predict which patients will have repeat seizures? No. Are we able to tell which patients have pseudo-seizures? No. Are we able to tell which patients need ALS, based on this study? No.
All but one of the 10 patients who were treated with diazepam had a less-than-alert level of consciousness (n = 7), additional prehospital seizure activity (n = 7), or both (n = 5).[1]
Maybe, we do have a good hypothesis for another study. Does the alert patient benefit from ALS?
Even if the repeat seizure patient has the full ALS workup of IV, ECG, and BGL before the repeat seizure, does it make any difference in outcome? Would any of this really prevent a seizure?
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Overall, instead of revealing inappropriate care, this review emphasized the difficulty with creating a homogeneous protocol for such a diverse group of patients.[1]
That does appear to be the case.
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We recommend further study with emphasis on concrete outcome measures to determine the impact that specific ALS interventions have on this group of patients.[1]
That is a good idea.
What is the right treatment for a seizure? This may be the wrong question. Maybe we should ask what the right treatment should be for a patient with no history of seizures and a decreased level of consciousness? Or what is the right treatment for a patient with a focal seizure that has been evaluated in the ED several times before? Et cetera.
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Footnotes:
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[1] Management of prehospital seizure patients by paramedics.
Martin-Gill C, Hostler D, Callaway CW, Prunty H, Roth RN.
Prehosp Emerg Care. 2009 Apr-Jun;13(2):179-84.
PMID: 19291554 [PubMed - indexed for MEDLINE]
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Fentanyl in the out-of-hospital setting: variables associated with hypotension and hypoxemia
05/27/2011 by 1 Comment
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Also posted over at Rogue Medic (now at EMS Blogs).
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On the most recent episode of the EMS Research Podcast,[1] Harry Mueller, Bill Toon, and I discuss a recently published paper examining what effect prehospital fentanyl has on hypoxemia or on hypotension.
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This study’s objectives were to assess for association between prehospital fentanyl administration and the occurrence of either of the following: hypotension, defined as a drop in systolic blood pressure (SBP) to below 90 mm Hg in a patient at least 5 years of age, or hypoxemia, defined as a drop in peripheral oxygen saturation (SpO2) to below 90%.[2]
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There were 500 patients and many of them received more than one dose of fentanyl. Several received 6 separate doses of fentanyl.
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Even with so many doses given, the mean dose and maximum dose were not that high.[3]
The median dose of fentanyl per administration was 1.1 µg/kg (IQR 0.8–1.4; range 0.25–3.5 µg); the mean dose was 1.1 µg/kg (SD 0.46). Expressed as a total dose per patient (i.e., summing all doses in a given patient), the median dose was 2.5 µg/kg (IQR 1.7–3.9) with a mean of 3.0 µg/kg (SD 1.8).[2]
1.1 µg/kg per dose.
The maximum single dose is unusual and is not explained. range 0.25–3.5 µg which should be /kg.
How did one patient receive such a large single dose – 3.5 µg/kg? The thing that makes the most sense (if this was a dosing error) is that this was a small pediatric patient. I carry fentanyl in syringes that contain 100 µg in 2 ml (50 µg/ml), but they might carry vials that have a larger volume. for example, below is packaging for 250 µg in 5 ml (also 50 µg/ml). If an entire vial were given to a 140 kg patient, that would be a dose of 3.5 µg/kg.
Is that what happened?
I don’t know – and that is presuming that this is a dosing error, which may not be valid to presume.
Image credit.[4]
I like the idea of carrying 10 mg morphine syringes and 100 µg fentanyl syringes. The total dose of each syringe is roughly equivalent in its effect on a patient. Except in very unusual circumstances, even a full 10 mg morphine, or 100 µg fentanyl, is not going to produce significant problems – and that is assuming that there is no judgment going into the dosing of patients.
Should we assume that there is no judgment going into the dosing of patients?
No, but I will get back to this in a little bit.
If this was not a dosing error, it is extremely aggressive dosing. I am comfortable giving a bit more than 1 µg to otherwise healthy trauma patients or burn patients, but I will at least give this a couple of minutes to have some kind of effect and reassess the patient before giving more. Similarly, with morphine, I might give up to 0.15 mg/kg to these same patients. 3.5 µg/kg is about three times higher than I am comfortable with.
Does that make the dose inappropriate?
Without knowing the specifics, we really cannot tell.
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Should we assume that there is no judgment going into the dosing of patients?
There are prior data to support the safety of appropriately administered opioids, including fentanyl. The study of Kanowitz et al., although more methodologically rigorous than most reports, is typical in its demonstration of safety: of 2129 patients receiving an opioid (fentanyl), only 12 (0.6%) had a medication-related vital sign abnormality and an intervention was required only once (in a patient who had no sequelae)(8)[2]
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What about in this study?
It is noteworthy that, although the study HEMS program’s fentanyl protocol does not proscribe use of the drug in hypotensive patients, the crew are required to use the agent judiciously (in other words, at the lower end of the recommended dosage range). This means that the safety of fentanyl as demonstrated in the current study may be related to more conservative dosing in unstable patients, but the parallel message is that experienced EMS crews are able to exercise judgment in determining which patients should receive cautious drug dosing.[2]
Should we assume that there is no judgment going into the dosing of patients?
experienced EMS crews are able to exercise judgment in determining which patients should receive cautious drug dosing.
The authors of this study do not come to the conclusion that EMS crews cannot make dosing decisions independently. The authors come to exactly the opposite conclusion.
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What about the hypotension and hypoxemia?
New hypotension (i.e., post-fentanyl SBP < 90 in a patient at least 5 years of age, with pre-fentanyl SBP at least 90) was seen in 28 administrations (2.7% of 1055 administrations, 95% CI 1.8–3.8%).[2]
Vital signs were measured within ten minutes of each dose of fentanyl (usually within 5 minutes).
Does hypotension developing so soon after fentanyl mean that the fentanyl caused the hypotension?
No.
It is possible that fentanyl did cause the hypotension.
It is possible that fentanyl did contribute to a drop in the blood pressure.
It is possible that fentanyl did not affect the blood pressure at all.
It is possible that fentanyl had the effect of increasing the blood pressure, but that increase was outweighed by something else causing a greater drop in blood pressure.
We do not have enough information to determine what effect fentanyl has on blood pressure in these patients, but we no longer have a good reason for expecting that fentanyl will produce hypotension.
There are many possible side effects of fentanyl, but even in hypotensive patients we should not expect any sudden deterioration in blood pressure with judicious administration of fentanyl by competent EMS personnel.
The authors do make one error here. They use the total number of administrations of fentanyl in their calculation of the rate of new hypotension to come up with 2.7%.
Overall, in 45 cases (4.3% of 1055), fentanyl was administered to patients who were hypotensive.[2]
Those 45 patients should be excluded from the calculation of new hypotension. Therefore the rate should be 2.8%, rather than 2.7%. This does not change the conclusions in any way. This is just a technicality.
What about those 45 patients who were hypotensive before receiving fentanyl?
In 53% of these cases, hypotension (predictably) remained after the opioid was given—but in 47% of cases in which fentanyl was administered to hypotensive patients, the next SBP exceeded 90.[2]
About half of the patients who were hypotensive before fentanyl were not hypotensive after fentanyl.
While 45 is a small number of hypotensive patients, how many of us would like to have a treatment for hypotension that is effective on half of our patients?
I am only partly kidding.
We do not know what other treatments were being provided, but how many of these patients may have had changes to their vital signs due to severe pain?
We presume that fentanyl will make vital signs worse, but that is a mistake. We may make less of a mistake with worrying that morphine will cause hypotension, based its potential for histamine release.
What was the effect of fentanyl on vital sign abnormalities in the Kanowitz study of fentanyl?
Of the 2,315 patients who received fentanyl in the field, 66 patients had a vital sign abnormality. Of those 66 patients, three were excluded because they received a sedative in addition to the fentanyl. There were 46 patients who were excluded because their vital sign abnormalities occurred before the administration of fentanyl. Of the 46 patients who had a vital sign abnormality before the administration of fentanyl, 38 patients’ vital signs improved after the administration of fentanyl, eight patients’ vital signs remained the same, and none worsened.[5]
Of the 46 patients who had a vital sign abnormality before the administration of fentanyl, 38 patients’ vital signs improved after the administration of fentanyl, eight patients’ vital signs remained the same, and none worsened.
It is possible that fentanyl is improving vital signs by decreasing pain.
The problem is that so many of us do not take the pain of others seriously, so we do not expect pain to lead to problems with vital signs.
Does the improvement in vital signs so soon after fentanyl mean that the fentanyl caused the improvement in vital signs?
No.
It is possible that fentanyl did cause the improvement in vital signs.
It is possible that fentanyl did contribute to an improvement in vital signs.
It is possible that fentanyl did not affect the vital signs at all.
It is possible that fentanyl had the effect of worsening the vital signs, but that worsening was outweighed by something else causing a greater improvement in vital signs.
We do not have enough information to determine what effect fentanyl has on vital signs in these patients, but we no longer have a good reason for expecting that fentanyl will frequently produce bad vital signs. Fentanyl was much more likely to be followed by an improvement in vital signs.
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We almost forgot about hypoxemia. Hypoxemia is an even bigger concern than hypotension.
What effect did fentanyl have on hypoxemia?
Assessment of the 522 administrations in 279 non-intubated patients revealed no difference in the mean SpO 2 readings before (98.8%, 95% CI 98.5–98.9) and after (98.6%, 95% CI 98.3–99.0) fentanyl administration. There were no instances of hypoxemia in these non-intubated patients receiving fentanyl (one-sided 97.5% CI for 0/279: 0–1.3%).[2]
Not even a single instance of hypoxemia.
None.
This was such a big concern that one of the helicopter services near me (based in a university hospital) only permitted flight crews to give fentanyl after a patient was intubated.
No tube – no fentanyl.
Myth busted.
We do need to be cautious about the administration of fentanyl to any patient. We should continually monitor ECG, SpO2, blood pressure, respiratory drive, and level of consciousness. With higher doses we should also continuously monitor waveform capnography.
Fentanyl is safe in the hands of competent EMS providers.
Fentanyl should not require medical command contact for any dose.
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Contact EMS Research at:
603-397-0367
emsresearchcast at gmail dot com
EMSResearchCast on Twitter
EMS Research at FaceBook
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Footnotes:
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[1] Fentanyl Study: EMS Research Episode 9
EMS Research Podcast
Podcast
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[2] Fentanyl in the out-of-hospital setting: variables associated with hypotension and hypoxemia.
Krauss WC, Shah S, Shah S, Thomas SH.
J Emerg Med. 2011 Feb;40(2):182-7. Epub 2009 Mar 27.
PMID: 19327928 [PubMed - in process]
Full Text PDF Download at medicalscg.
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[3] Mean, Median, Mode, and Range
Purplemath
Article
It is good to be clear on what the meaning of the terminology. This has the simplest explanation I found in a very brief search.
The “mean” is the “average” you’re used to, where you add up all the numbers and then divide by the number of numbers. The “median” is the “middle” value in the list of numbers. To find the median, your numbers have to be listed in numerical order, so you may have to rewrite your list first.
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[4] FENTANYL CITRATE injection, solution
[Baxter Healthcare Corporation]
FDA Label
DailyMed
How Supplied
Free Full Text FDA Label from DailyMed with links to Free Full Text PDF Download.
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[5] Safety and effectiveness of fentanyl administration for prehospital pain management.
Kanowitz A, Dunn TM, Kanowitz EM, Dunn WW, Vanbuskirk K.
Prehosp Emerg Care. 2006 Jan-Mar;10(1):1-7.
PMID: 16418084 [PubMed - indexed for MEDLINE]
Free Full Text PDF Download from MSTC.
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Utilization of warning lights and siren based on hospital time-critical interventions
05/23/2011 by 1 Comment
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Also posted over at Rogue Medic (now at EMS Blogs).
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This study was the topic for discussion on the EMS Research Podcast.[1]
To simplify the title –
Does the use of lights and sirens get the patient to the hospital in time for life-saving treatment?
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The routine use of lights and siren (L&S) by emergency medical services (EMS) personnel has been a longstanding tradition, but with evidence mounting concerning its risks, many are now questioning their utility.1–4 [2]
This is not just appropriate, but essential.
We have too many treatments/procedures that are based on nothing more than superstition, tradition, and/or wishful thinking. We need to evaluate what we do in as unbiased a way as possible to find out if there is any benefit to any patient, rather than just blindly continue with each standard of care myth-based intervention.
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Morbidity and mortality from collisions involving emergency vehicles is a major public health hazard.[2]
Traffic fatality is always one of the top causes of line of duty death in EMS. If a patient is unstable, crashing on the way to the hospital is definitely not a good idea. Is there any benefit from the risk of L&S driving?
Roughly 70% of fatal ambulance crashes occur during utilization of warning L&S.14[2]
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As the EMS providers wrote the chart, there was a questionnaire to confirm if the times documented were accurate. If EMS personnel subjectively felt documented times were not accurate, the chart was excluded from the study.[2]
The time of travel in the control group was recorded by two medical students and one EMS fellow traveling in their personal vehicles from the location of the 9-1-1 response to the hospital. They drove during the same day of week and time of day as did the original call. They were instructed to obey all traffic laws and speed limits. All time was recorded in minutes. Any significant time delay due to weather patterns was noted and excluded from analysis.[2]
From the paper, it is not clear where they did this study. I have worked for all of the hospitals, except one. That is the University of Medicine and Dentistry of New Jersey – Robert Wood Johnson Medical School in New Brunswick, NJ. The demographics listed are not consistent with any of the other hospitals listed. RWJ is the most suburban of the hospitals and that is something that should have a bearing on the way we assess the applicability of this study to individual systems. This is a variable to consider in the way traffic affects transport times.
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A total of 112 charts were used in this analysis. The average difference in time with versus without L&S was -2.62 minutes (95% CI = -2.60– -2.63 minutes (min), paired t-test p-value <0.0001; signed rank p-value <0.0001) such that patient transport with no L&S took on average of 2.62 minutes longer than when using L&S.[2]
95% CI = -2.60– -2.63 minutes?
That is a surprisingly narrow confidence interval.
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The average transport time in minutes with L&S is 14.5 ±7.9 min (1SD) (range = 1–36 min). The average transport time without L&S is 17.1± 8.3 min (range = 1–40 min). The time difference ranged from 24 min faster with L&S to 16 min slower with L&S.[2]
Here is another point that raises questions that are not answered in the paper.
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Did one of the ambulances crash?
Did one of the ambulances get lost?
Or, should I ask, Did two of the ambulances crash/get lost/whatever?
All we know is that there were 2 transports that took dramatically longer with L&S than without L&S.The major roadway connecting the university hospital with neighboring towns was frequently under construction. Although this factor could account for prolonged times in the lights and sirens group, it also could have equally affected the control group.[2]
And it could explain the two extra-long L&S transports.
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Huber regression estimates no significant effect of time with L&S on the difference between the two mean transport times, with an increase of 0.02 minutes (95% CI = -0.06–0.10) in the difference due to a 10-minute addition in transport time with L&S. This finding is contrary to the expectation of L&S being even more useful for longer distances.[2]
In other words, the longer trips did not result in significantly more time saved using L&S.
3 1/2 seconds to 6 seconds (0.06 to 0.10 minutes) for every additional ten minutes of transport time. Travelling at 60 MPH (Miles Per Hour) for 10 minutes, this would save less time, than increasing the speed to 61 MPH. Travelling at 30 MPH (Miles Per Hour) for 10 minutes, this would save less time, than increasing the speed to 31 MPH.
If the ambulance increases speed from 60 to 61 MPH, it is going to be barely noticeable in the back.
If the ambulance increases speed from 60 to 61 MPH, it is going to be barely noticeable in the back.
If the ambulance turns on the Lights & Sirens, it is going to be very noticeable in the back.
Where is the benefit that justifies the increased risk?
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The complete logs of interventions provided to the study patients were evaluated. Of the 112 patients transported with L&S, 108 (96.4%) were treated with PIs only. Five (4.5%) patients transported with L&S also received time-critical HI.[2]
PIs are Prehospital Interventions – treatments that can be provided by the paramedics (ALS or Advanced Life Support personnel).
HIs are Hospital Interventions – treatments that cannot be provided by paramedics. Fibrinolytics, neurosurgical evacuation, cardiac catheteriztion, and transvenous pacing in this study.
In other words, they were racing to the hospital, to have treatments that could have been provided by the paramedics.
However, there are times when it may be more appropriate to have something done in the more controlled setting of the hospital, rather than on scene or in the ambulance.
It is also possible that the medical command physician ordered that the paramedic not provide a treatment that is within the paramedic’s scope of practice. This can be for a treatment that is only permitted with medical command contact or a treatment that is permitted on standing orders, but that the medical command physician specifically ordered be withheld until the patient is at the hospital.
What about certain procedures that are often unsuccessful due to operator error, such as transcutaneous pacing or cardioversion. Even in the hospital, it is not unusual for some operator error to be involved when using these procedures to treat unstable patients.
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The last patient was diagnosed with an unstable, third-degree heart block and required immediate transvenous pacemaker placement secondary to ineffective capture with a transcutaneous pacemaker.[2]
Immediate? This was not done within the time saved by L&S transport, so hardly immediate.
Ineffective capture?
Is that the same as complete lack of capture?
As in pronouncing a patient dead because of ineffective cardiac output as demonstrated by being pulseless, apneic, and asystlic?
As I frequently like to point out –
Failure to capture with a transcutaneous pacemaker is frequently operator error.
Tom Bouthillet of EMS 12 Lead was not on the podcast, but he has made similar statements about transcutaneous pacing.[3]
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No HI was administered within the first 2.62 minutes of arrival. All five patients were admitted to a critical care unit and the average length of stay in the hospital was 10 days. No deaths occurred in the group who received HI.[2]
Was any time saved that made any difference in outcome?
We do not know, but this study did not provide evidence to support L&S transport.
Were any treatments provided any sooner?
We do not know, but this study did not provide evidence to support L&S transport.
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it is possible that patients with more serious illnesses had lights and siren compared with those who were less critical. Since only 7% of patients during this time interval did not have L&S, it is unlikely that this influenced the results.[2]
93% of these ALS patients require treatment EMS cannot provide?
No.
Only 5 patients did and none of them needed these treatments in the amount of time saved by L&S.
93% of these ALS patients are unstable?
That has not been my experience in any of the systems where I have worked. If anything, even the reverse is too high.
7% of ALS patients being unstable is too high.
So why all the commotion?
Because a mentality exists in the system that L&S result in improved patient care,[2]
We need to expose these myths for what they are – superstitions.
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Footnotes:
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[1] Driving with Lights and Sirens: EMS Research Episode 8
EMS Research Podcast
Podcast
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[2] Utilization of warning lights and siren based on hospital time-critical interventions.
Marques-Baptista A, Ohman-Strickland P, Baldino KT, Prasto M, Merlin MA.
Prehosp Disaster Med. 2010 Jul-Aug;25(4):335-9.
PMID: 20845321 [PubMed - indexed for MEDLINE]
The download link is in the page number – page 335.
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[3] Transcutaneous Pacing (TCP) – The Problem Of False Capture
EMS 12 Lead
Article
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Performance of the RAD-57 With a Lower Limit – Better?
05/18/2011 by 1 Comment
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Also posted over at Rogue Medic (now at EMS Blogs) and Discussed on the EMS Research Podcast – RAD-57 v. Lab: EMS Research Episode 2.
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CO (Carbon monOxide) is a significant cause of poisoning in the US, with hundreds of fatalities each year. The RAD-57 non-invasive CO monitor is a device that is supposed to make identification of these patients quick and accurate in the out of hospital setting.
There has been one study of the RAD-57 on actual patients being evaluated for CO toxicity. In that study, the sensitivity was horrible. Only 48%.[1] I could do as well flipping a coin. So could you.
The low sensitivity has been the focus of the criticism. On the other hand, the 99% specificity has been seen as a confirmation of what was already known.
Is the high specificity real?
There is a study coming out that suggests that rather than 15%, we should use 6.6% as the cutoff to provide good sensitivity. What happens to this study’s calculation of 99% specificity (only one false positive for every 100 patients screened), when the cutoff is dropped to 7% (the RAD-57 does not provide a display in fractions).
Using the 15% cutoff, 99% of the time, when the RAD-57 indicates that the carboxyhemoglobin is over 15%, the carboxyhemoglobin is over 15%.
Only one false positive out of 120 patients.
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What happens when we change the cutoff to 7%?
Not so good on the specificity. There appear to be 14 false positives out of 120 screened patients.
What will happen in the real world with these results?
With time, we will probably start to ignore the results that do not tell us what we want to see.
We will have spent $4,000 per machine to have a piece of equipment that we ignore when we do not like the results.
How does that provide any benefit for anyone with CO toxicity?
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Footnotes:
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[1] Performance of the RAD-57 pulse CO-oximeter compared with standard laboratory carboxyhemoglobin measurement.
Touger M, Birnbaum A, Wang J, Chou K, Pearson D, Bijur P.
Ann Emerg Med. 2010 Oct;56(4):382-8. Epub 2010 Jun 3.
PMID: 20605259 [PubMed - indexed for MEDLINE]
Free Full Text Article from Ann Emerg Med with links to Free Full Text PDF download
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