Tiny Tips: Non-Cardiogenic Pulmonary Edema / ARDS

When you see a pulmonary edema on chest x-ray (CXR), the knee jerk reaction is to attribute it to heart failure. But what might you be missing?

Not all the glitters is gold. And not all that is wet on CXR is just plain ol’ CHF.

Non-Cardiogenic Pulmonary Edema (NCPE) is better known to the world when it it is at its most severe form – i.e. ARDS (Acute Respiratory Distress Syndrome) or ALI (Acute Lung Injury).[1] However, for the purposes of linking the concept to the mnemonic (and the CXR findings), I have chosen to file it as a Tiny Tip under NCPE.

First recognized in military casualties in the first and second World Wars, NCPE is a commonly discussed entity in critical care. In fact, an international group of experts has met in Berlin recently to redefine the definition of ARDS/ALI (see the post by the LIFTL guys on this topic for a great primer). [2,3] NCPE can be caused by direct insults to the lung tissue or indirect mechanisms such as systemic inflammation.

Mnemonic for Causes for Non-Cardiogenic Pulmonary Edema

IS NOT THE HEART

I nhaled Toxins (Ammonia, Chlorine, Phosgene, Nitrous oxide)
S IRS / Sepsis / Septic Shock

N eurogenic (seizure, strangulation, trauma)
O verdose (Heroin, methadone, cocaine)
T hyrotoxicosis

T rauma
H eat (Smoke! Remember to also consider carbon monoxide!)
E lectrocution

H igh altitude pulmonary edema
E mbolism (Pulmonary Embolism, Acute Gas Embolism, Amniotic Fluid Embolism)
A SA toxicity
R eperfusion or Re-expansion pulmonary edema (or Rocky Mountain Spotted Fever – This one is in here for the PGY5s: May the Force be with you until your quiz next year)
T ransfusion

Remember, this is NOT a comprehensive list, but it is a list that can help you think through alternative causes of a “wet” CXR. Causes that it does not contain include Uremia, Cardiopulmonary bypass, DIC (RMSF is in the above list mostly due to this), other coagulopathies, pancreatitis… and more.

The mnemonic for this Tiny Tip, as well as a bunch of others, can be accessed and memorized using spaced repetition through Boring Cards as outlined here.

References

1. Perina DG. Noncardiogenic pulmonary edema. Emerg Med Clin N Am ;21 (2003) 385–393. PMID: 12793620.

2. Nickson C. Acute Respiratory Distress Syndrome (ARDS) Definitions. Life in the Fast Lane. Revised April 16, 2014. Accessed July 13, 2014. Available at: http://lifeinthefastlane.com/education/ccc/acute-respiratory-distress-syndrome-ards-definitions/.

3. ARDS Definition Task Force, Ranieri VM, Rubenfeld GD, Thompson BT, Ferguson ND, Caldwell E, Fan E, Camporota L, Slutsky AS. Acute respiratory distress syndrome: the Berlin Definition. JAMA. 2012 Jun 20;307(23):2526-33. doi: 10.1001/jama.2012.5669. PubMed PMID: 22797452.