Clinical Case: Pulmonary Edema

A 63-year old lady was admitted to the coronary care unit post cardiac arrest with return of spontaneous circulation. She was intubated for a decreased level of consciousness following resuscitation and was placed on a hypothermia protocol. You are called to assess her for low blood pressure and increasing oxygen requirements.

On exam, her blood pressure is 100/60 with a pulse of 90. Temperature is at target for the hypothermia protocol. Oxygen saturations are 90% with an Fi02 of 0.8 and a PEEP of 10 cm H20. Her JVP is difficult to appreciate. Heart sounds are rapid, with no additional heart sounds or murmurs appreciated on initial assessment. There are crackles on lung auscultation.

You quickly review the chart, and noticed that this patient was given a 500 mL bolus earlier this afternoon for hypotension and decreased urine output. Her urine output has been minimal (30 mL total) since the bolus 4 hours ago. Also, the PEEP has been increased from 8 to 10 cm H20, and the Fi02 was progressively increased from 0.6 to 0.8.

You've ordered an initial chest X-ray, ECG and bloodwork. While waiting for these tests to be performed, you perform a quick bedside lung ultrasound which reveals this image.

It can be difficult in critical care settings to determine the etiology of worsening respiratory status. In the right clinical context, lung ultrasound can provide useful information that can change management. The society of critical care medicine recommend in their guidelines on page 2485 that ultrasound may be used as a primary diagnostic modality for the ICU patient with respiratory failure. This was a case that I had while on call for CCU a few months ago, and the lung ultrasound images confirmed my clinical suspicion and helped me make my management decision. Although this isn't the ultrasound image from that patient, this image does provide the same ultrasound finding. 

That finding is a B-line, or "comet tail sign" which has seven distinct features on lung ultrasound:

1. Comet tail artifact
2. Arises from the pleural line
3. Moves with lung sliding
4. Hyperechoic
5. Long without fading
6. Erases A-lines
7. Well defined (laser-ray like)

These seven features help to distinguish B-lines from other comet-tail artifacts. Three or more comet tails with these features seen between two ribs in an anterior or lateral ultrasound confirms the presence of an interstitial syndrome. Given her history of recent cardiac arrest and subsequent fluid bolus, the diagnosis of pulmonary edema is likely, which would require diuretic therapy. After giving a dose of intravenous Lasix to this patient, her oxygenation, blood pressure and urine output all improved.

A quick explanation of B-lines by Dr. Daniel Lichtenstein with some notes (including the seven features above) can be seen on video DL-11 at the Hands on Echo Website.