Quiz 47, October 25th 2019

Welcome to the 47h FOAMed Quiz. 

Please feel free to comment and (if you like it) share.

Enjoy!

Kirsten, Eefje, Hüsna, Nathalie and Rick

Question 1

Last week the CRASH-3 trial was published in the Lancet. It is about the effect of tranexamic acid (TXA) in patients with acute traumatic brain injury with a Glasgow Coma Scale of ≤ 12 or intracranial hemorrhage without significant extracranial bleeding.

What did the authors find?

A: Treatment with tranexamic acid is safe and reduces head injury related death in patients with an initial GCS of 9 and higher

B: Treatment with tranexamic acid reduces head injury related death in patients with an initial GCS of 3 to 8

C: Treatment with tranexamic acid does not reduce head injury related death

The correct answer is A

The CRASH-3 trial is a massive double-blind RCT involving 175 hospitals in 29 countries.

About every Emergency Medicine blog and podcast covered this paper last week and rightfully so.

The Resus Room, St Emlyn’s, EMlitofnote, JournalFeed, RebelEM and EMCrit are among those.

In short:
It is a massive and well conducted trial.
Only secondary analysis of an underpowered subgroup was found to be statistically significant (head injury related death in patients presenting with a GCS of 9 and above).
TXA seems to be safe, but Pulmonary Embolism and Deep Venous Thrombosis were only diagnosed when found positive by accident on imaging or post-mortem examination.

Question 2

Do we need to give a fluid bolus before intubation? The PrePARE Trial investigated the effect of a fluid bolus (500 cc) versus no bolus in critically ill adults undergoing tracheal intubation. The primary endpoint was a composite of post-intubation complications including new-onset hypotension (systolic Bp <65 mm), new or increased vasopressor administration, or cardiac arrest.

What is true according to the PrePARE trial?

A: A fluid bolus prevents hypotension caused by intubation

B: A fluid bolus increases the risk of a cardiac arrest

C: A fluid bolus leads to increased administration of vasopressors

D: There was no difference in primary outcome between giving a fluid bolus or not

The correct answer is D

The PrePARE trial is a multicenter RCT that investigated patients undergoing endotracheal intubation. Prior to intubation patients were randomized to receive 500 cc fluid bolus versus no bolus. The study was stopped early for futility after including 337 patients. The outcome in both groups were exactly the same.

PulmCrit Wee: Do fluid boluses before intubation help? (PREPARE trial)

Question 3

Which of the following statements is true about hydrocarbon poisoning?

A: Cardiovascular complications are the most commonly reported adverse effect

B: Hydrocarbons are believed to produce a decrease in myocardial sensitization to endogenous and exogenous catecholamines

C: Beta-blockers like esmolol may provide benefit in the treatment of hydrocarbon poisoning

D: Topical exposure to hydrocarbons does not cause harm

The correct answer is C

emDocs covered hydrocarbon poisoning this week.

Pulmonary complications are the most commonly reported adverse effect. Hydrocarbons are believed to produce an increase in myocardial sensitization to endogenous and exogenous catecholamines. Topical exposure to certain hydrocarbons can cause cell membrane injury leading to burns and skin necrosis from prolonged contact. And indeed, esmolol may provide benefit in the treatment of hydrocarbon poisoning by decreasing the myocardial sensitization to catecholamines.

http://www.emdocs.net/toxcard-hydrocarbon-toxicity/

Question 4

Source: https://litfl.com/

The management of uncomplicated atrial fibrillation in the emergency department (ED) is an ongoing topic of discussion. Recent literature suggests we shouldn’t try to achieve sinus rhythm in stable atrial fibrillation. But if you still wanted to cardiovert a patient with stable atrial fibrillation, what would be the best method?

This study compared initial electrical (and secondary chemical cardioversion in not successful) versus initial chemical cardioversion (and secondary electrical cardioversion in not successful).

What difference did the authors find?

A: The length of stay (LoS) in the emergency department was longer in the chemical cardioversion first group

B: Patients undergoing chemical cardioversion first were more likely to be discharged home

C: ED revisits were fewer in the electrical cardioversion group

The correct answer is A

This RCT compares procainamide-first versus electrical cardioversion-first approach for patients presenting in the emergency department with uncomplicated atrial fibrillation. 84 patients were included. The authors conclude that both strategies are successful and well tolerated. The length of stay in the ED was shorter in the cardioversion-first group (no surprise there). They found no difference in QOL, ED revisits and all patients were discharged home after the initial visit (no surprise there either).

Comparison of Chemical vs Electrical Cardioversion of Acute Uncomplicated Atrial Fibrillation

Question 5

Your 24 year old female patient presents with right lower quadrant abdominal pain for 3 days, you consider appendicitis. There is no fever, but blood works show mild leukocytosis. The abdominal ultrasound is inconclusive (appendix is not seen) and by hospital policy you order an MRI. Given the pretest probability of your patient having appendicitis is 20% and MRI has a 80% specificity (and close to 100% sensitivity) in diagnosis of appendicitis, what is the chance this MRI will turn out to be false positive?

A: 24,5%

B: 34,5%

C: 44,5%

D: 54,5%

Okay, your next patient is also 24 years old and presents with right lower quadrant abdominal pain since 5 days. Blood works do not show abnormalities but you still order an ultrasound, which turns out to be inconclusive. Again, by hospital policy you proceed to MRI (specificity 80%). In this case the pretest probability has fallen to 5%. What is the chance this MRI will turn out to be false positive?

A: 40%

B: 60%

C: 80%

D: 90%

The correct answer to the first part is C, 44,5%

The correct answer to the second part is C, 80%

Justin Morgenstern points out once more You can’t interpret the results of a test without knowing the pretest probability.

The first part: In every 1000 patients, 200 will have appendicitis. Given the sensitivity is 100% these 200 patients will have a positive scan. Furthermore, of the 800 patients without appendicitis, 160 patients will have a positive scan (.2 x 800). So, eventually there is a 160 / (200+160) = 44,4% chance on a false positive result (and most likely negative laparoscopy).

The second part: In 1000 patients, 50 will have appendicitis. Given the sensitivity is 100% these 50 patients will have a positive scan. Furthermore, of the 950 patients without appendicitis, 190 patients will have a positive scan (.2 x 950). So, eventually there is a 190/ (50+190) = 79,1% chance on a false positive result (and most likely negative laparoscopy).

Why pretest probability is absolutely essential

Would you like to receive an e-mail every time a quiz is published? Please leave your e-mail address here:

This quiz was written by Eefje Verschuuren, Nathalie Dollee Kirsten van der Zwet and Hüsna Sahin

Reviewed and edited by Rick Thissen

Leave a Reply

Your email address will not be published. Required fields are marked *