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Tony Breu Profile picture
@tony_breu
Sep 20, 2020 • 7 tweets • 3 min read • Read on X
1/5
 Why is meperidine (Demerol) particularly good at treating rigors?

This is another association I learned early in training without hearing a potential mechanism.

For the second installment in my fevers, chills, and rigors tweetorial follow-up, let's have a brief look.
2/
 The ability of meperidine to treat fevers and rigors associated with amphotericin B was demonstrated in 1980 in a SMALL randomized, placebo-controlled trial.

Percent with cessation of side effects with 30 minutes:
☞ Meperidine: 100%
☞ Placebo: 30%

pubmed.ncbi.nlm.nih.gov/7362377/ Image
3/
 Meperidine is able to treat rigors (and post-anesthesia shivering) by lowering the shivering threshold.

The same temperature that would typically result in rigors isn't low enough after the use of meperidine.

pubmed.ncbi.nlm.nih.gov/9158353/ Image
4/
 The anti-shivering effect of meperidine may be related to its κ-opioid receptor activity (many opiates are pure μ-opioid receptor agonists).

This is supported by the fact that naloxone only partially blocks shivering.

pubmed.ncbi.nlm.nih.gov/8267194/ Image
5/5
 I haven't given meperidine for shaking chills, shivering, or rigors in many years.

We'll have to ask those who practice anesthesiology if it's still used post-operatively.

Is meperidine 1st line for post-op shivering, not first-line but still used, or is it avoided?
This was a second follow-up tweetorial on the topic of fevers, chills, and rigors.

Here's follow-up #1 on amphotericin B.

And here's the original tweetorial.

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More from @tony_breu

Tony Breu Profile picture
Nov 16
1/14
🤔 Why do we use iodine as an intravenous contrast agent?

The answer requires a review of the composition of the human body and a brief tour of one of my favorites, the Periodic Table of Elements. Image
2/
 To begin, it's essential to understand which elements make up the human body. Amazingly, just six compose >98% of your weight:

➤Oxygen: 61% (varies based on water composition)
➤Carbon: 23%
➤Hydrogen 10%
➤Nitrogen: 2.6%
➤Calcium: 1.0%
➤Phosphorus: 0.6%

buff.ly/3YU4dIYImage
3/
 One thing you'll notice about these six elements is that they are relatively small (i.e., they have low atomic numbers, aka are low-Z elements).

In addition to being the most prevalent elements in the universe, their low atomic number allows them to more readily form stable chemical bonds.Image
Read 14 tweets
Tony Breu Profile picture
Jun 22
1/7 - The Mystery

A patient presents with fever and confusion. After multiple weeks without a diagnosis, an astute clinician suggests a random skin biopsy.

The patient has no rash or dermatologic symptoms. And yet, the biopsy reveals the diagnosis.

🤔What is the condition?
2/7 - The Diagnosis I

💥Intravascular Lymphoma (IVL)💥

IVL can be an elusive diagnosis, given that many patients present without lymphadenopathy.

Instead, non-specific symptoms (e.g., fever, fatigue, weight loss, confusion) are more common.

ncbi.nlm.nih.gov/pmc/articles/P…Image
3/7 - The Diagnosis II

Some have resorted to random skin biopsies to make the diagnosis of IVL.

And multiple case series have demonstrated that a diagnosis of IVL can be made this way, even when the skin appears normal.

pubmed.ncbi.nlm.nih.gov/18053461/Image
Read 7 tweets
Tony Breu Profile picture
Jun 20
1/11
🤔Why does chronic hepatitis C infection "require" the intermediary of cirrhosis in order to cause hepatocellular carcinoma (HCC)?

Chronic hepatitis B can "skip" this step, going directly from chronic infection to HCC.

Why the difference?
2/
 To begin, let's look at how frequently HCC occurs in patients without cirrhosis.

A 2019 study of United States (US) medical centers included 5144 patients with HCC.

💡12% had no underlying cirrhosis

pubmed.ncbi.nlm.nih.gov/31475372/
3/
 A 2022 study found a similar rate, with 13% of patients with HCC showing no evidence of cirrhosis.

When looking more specifically at hepatitis C (HCV) versus hepatitis B (HBV), they found varying rates:

➣ HCV: 6% of patients with HCC were non-cirrhotic
➣ HBV: 19% of patients with HCC were non-cirrhotic

pubmed.ncbi.nlm.nih.gov/34027591/Image
Read 11 tweets
Tony Breu Profile picture
Apr 9
1/12 - Mystery #1

You are seeing a patient recently diagnosed with heart failure and started on GDMT. You notice that their hemoglobin (HGB) has increased (12 → 13 g/dL) in the intervening weeks.

🤔Which medication is the likely cause of this increase in HGB?
2/12 - An Answer

Empagliflozin

💡All SGLT2 inhibitors have been associated with an increase in hematocrit/hemoglobin soon after initiation.

The average increase is 2.3% in hematocrit and 0.6 g/dL in hemoglobin.

ncbi.nlm.nih.gov/pmc/articles/P…Image
3/12 - An Initial Explanation (I)

The effect of SGLT2 inhibitors on HCT/HGB has been noted since the very first randomized control trial of dapagliflozin, published in 2010.

Initially, investigators assumed this was related to the diuretic effect of these drugs (i.e., a reduction in plasma volume led to an increase in HCT/HGB).

pubmed.ncbi.nlm.nih.gov/20609968/Image
Read 12 tweets
Tony Breu Profile picture
Feb 22
1/10
🤔Why is pulmonary embolism (PE) relatively rare in those with Factor V Leiden?

This Factor V Leiden Paradox was pointed out to me by @DrSamelsonJones after I posted about a similar difference with Behçet Syndrome.

Let's have a look.
2/
 In 1993, Dahlback, Carlsson, and Svensson first described a heritable resistance to activated protein C.

A year later the same group found this to be the most common form of hereditary hypercoagulability.


ncbi.nlm.nih.gov/pmc/articles/P…
pubmed.ncbi.nlm.nih.gov/8302317/Image
Image
3/
 The mutation in the Factor V gene conferring resistance to activated protein C was detailed the following year by a group in Leiden, The Netherlands.

Thus the name for the condition: Factor V Leiden.

pubmed.ncbi.nlm.nih.gov/8164741/Image
Read 10 tweets
Tony Breu Profile picture
Feb 18
1/8
 🤔Why is pulmonary embolism (PE) so rare in Behçet Syndrome?

The condition is associated with a 14-fold increased risk of deep vein thrombosis (DVT) but almost none of these result in PE.

What is it about the thrombus in Behçet that makes it so unable to embolize?
2/
 Numerous case series have reported a markedly increased risk of deep vein thrombosis with Behçet Syndrome.

One reported the following rates of venous thrombosis:
➣ Behçet Syndrome: 18/73 (25%)
➣ Controls: 4/146 (3%)

pubmed.ncbi.nlm.nih.gov/11426022/Image
3/
 Another study of 882 patients with vascular Behçet Syndrome reported the following rates of deep vein thrombosis (DVT) and pulmonary embolism (PE):

➣ DVT: 592/882 (67%)
➣ PE: 0%!

pubmed.ncbi.nlm.nih.gov/24907156/Image
Read 9 tweets

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