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

- Rogue Medic

Chart Version – Fentanyl in the out-of-hospital setting: variables associated with hypotension and hypoxemia

Some charts for a more visual assessment of what I wrote in – Fentanyl in the out-of-hospital setting: variables associated with hypotension and hypoxemia.[1]

In this study, hypotension was defined as a systolic blood pressure less than 90 mm/Hg. The numbers in these charts are doses and not patients. A total of 1,055 doses were given to 500 patients.

If the patient was already hypotensive there was a 53% chance that the patient would still be hypotensive after a dose of fentanyl.

That means a 47% chance that the hypotensive patient would no longer be hypotensive after a dose of fentanyl.

There were only 45 doses given to hypotensive patients, so we do not have a lot of data. We also do not know what the specific blood pressures were for each dose (before and after). A patient with a blood pressure of 72/50 before a dose of fentanyl, and a blood pressure of 88/56 after fentanyl is still hypotensive. A patient with a blood pressure of 88/56 before a dose of fentanyl, and a blood pressure of 90/56 after fentanyl is no longer hypotensive. I could go on for a while with the possibilities, but we do not have the raw data, so it is all just speculation. Similarly, a patient could be given fluids or pressors, but that does not appear to be the case in this study.

If this were a treatment for hypotension and with a much larger number of patients and about half had their hypotension resolve after fentanyl, then this might be an impressive treatment for hypotension. A lot of ifs. A lot of correlation.

What about the possibility of new hypotension after a dose of fentanyl?

Out of 1010 doses, there were only 28 cases of new hypotension. We do not know if some of these were patients who were hypotensive before a dose of fentanyl, but had their blood pressure rise after receiving that earlier dose of fentanyl. Would these be considered new hypotension? Were there any cases of this? We don’t know.

We do know that they were giving fentanyl to patients with lower pressures than 90 systolic.

What is the risk of new hypotension in a patient with a blood pressure of at least 90, who is given a dose of fentanyl?

Very low. Less than 3%.

If only all of our treatments were this safe.

When should we expect hypotension after giving a dose of fentanyl?

When the patient is already hypotensive.

A different way of looking at this chart –

Likelihood of no hypotension after a dose of fentanyl:

97+% if no hypotension at the time of the dose.

47% if there is already hypotension at the time of the dose.

What about a chart of hypoxemia after fentanyl?

No hypoxemia after fentanyl.

Zero cases.

Should we ignore the possibility of hypoxemia or hypotension after fentanyl?

No, but we should not avoid using fentanyl due to exaggerated possibilities from people who are not familiar with fentanyl.

Footnotes:

[1] Fentanyl in the out-of-hospital setting: variables associated with hypotension and hypoxemia
Rogue Medic
Article

This refers to the paper below and the podcast below that –

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.

Fentanyl Study: EMS Research Episode 9
EMS Research Podcast
Podcast

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Corrections of Misleading Charts


Also posted over at Paramedicine 101, which is now at EMS Blogs. Go check out the excellent material there.

Back in September, I wrote Furosemide and Drug Shortages 2. I was just looking at the charts I made and realized that they were not at all helpful at explaining the information.

When I look at my own charts and have trouble figuring out what I was trying to explain, then I have completely failed.

I have edited the charts to do a better job of presenting the information I was trying to make clear.


Click on charts to make them larger.

When looking at the problems with the use of furosemide (Lasix), one import point to remember is that the authors only looked at the primary diagnosis. This is an important shortcoming of the study.

How many of the patients had a secondary diagnosis of CHF?

We don’t know.

It should be noted that seven patients without an ED diagnosis of CHF received ED furosemide and 43 patients received ED nitro with only eight of those having a primary diagnosis of ACS. This data put the accuracy of the primary ED final diagnosis as a reference standard into question,[1]

Another problem is that the authors seem to think that nitro is only for ACS (Acute Coronary Syndromes – essentially heart attacks). NTG (NiTroGlycerin) is the most effective medication for hypertensive CHF.

Only 43 out of 60 patients with a primary diagnosis of CHF received NTG – this needs to be studied.

Were these 17 patients not treated with NTG because they were hypotensive?

In the ED, it is much safer to give normotensive CHF patients NTG, because of IV (IntraVenous) NTG. EMS is usually limited to SL (SubLingual) NTG.

SL NTG is not what is best for patients, unless we feel that it is important to treat patients with NTG before starting an IV.

If we have IV access, we should be giving NTG the safer and more titratable way – IV NTG. (This sentence added 11:50 02/07/11)

This chart was just to show how little difference it would make to add in the patients who did not have a diagnosis.

This chart compares the deaths between the patients treated with furosemide by EMS and receiving a primary diagnosis of CHF and those not receiving a primary diagnosis of CHF.

Due to the shortcomings of this study, it should be replicated with the secondary diagnoses included. This is essential.

Footnotes:

[1] Correlation of paramedic administration of furosemide with emergency physician diagnosis of congestive heart failure
Thomas Dobson, Jan Jensen, Saleema Karim, and Andrew Travers.
Journal of Emergency Primary Health Care
Vol.7, Issue 3, 2009
Free Full Text . . . . . . . Free Full Text PDF

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