Top 3 Articles: FAST

The FAST exam is the prototypical application of emergency ultrasound. However, it is important to know that there are limited randomized controlled trials assessing the utility of the FAST exam. Despite this, let’s look at three good articles that  all emergency residents should know.

1. In this Cochrane review, the authors’ conclusion was that there was insufficient evidence for the use of ultrasound-based clinical pathways in the initial diagnostic workup of patients with blunt abdominal trauma. Ultrasound was not sensitive and lacked diagnostic accuracy. However, the use of ultrasound did reduce the use of CT scans. The take-home message is that ultrasound should not be used as a single rule-out test for significant intra-abdominal injury and the ED resident should be aware of ultrasound’s limitations.

Stengel D, Bauwens K, Sehouli J, Rademacher G, Mutze S, Ekkernkamp A, Porzsolt F. Emergency ultrasound-based algorithms for diagnosing blunt abdominal trauma (Review). The Cochrane Collaboration. February 18th, 2008.

2. Interestingly, this review used the same methodology as the Cochrane review and found that an adequately performed FAST exam can predict the need to send a patient to the operating room, with a high degree of sensitivity (98.9%) and specificity (98.1%).

Melniker LA. The value of focused assessment with sonography in trauma examination for the need for operative intervention in blunt torso trauma: a rebuttal to “emergency ultrasound-based algorithms for diagnosing blunt abdominal trauma (review)”, from the Cochrane Collaboration. Critical Ultrasound Journal. 2009;1:73-84.

3. Thoracic ultrasound has become part of the standard assessment of the trauma patient. Ultrasound has been shown to be much more sensitive than CXR in the detection of pneumothorax when compared to CT as the gold standard. There are many studies proving this point and this is a good example.

Blaivas M, Lyon M, Duggal S. A prospective comparison of supine chest radiography and bedside ultrasound for the diagnosis of traumatic pneumothorax. Acad Emerg Med. Sep 2005;12(9):844-849

Airway Mythology

As promised, here are selected references from today’s talk on Airway Management Mythology. Thanks to the organizers of the International Conference on Emergency Medicine (ICEM) for the invitation to speak.

Some of the topics discussed are supported by plenty of evidence (ie the use of RSI as an intubation technique), some were simply fun to discuss (holding your breath while intubating) and some remain quite reasonably controversial (the use of etomidate for RSI in sepsis).

I highly recommend visiting Dr. Reuben Strayer’s blog for a brief and enlightening discussion of the use of rocuronium for RSI. Also, Dr. Scott Weingart’s EMCrit blog and podcasts are an excellent source for ED critical care topics. Finally, The Airway Site contains links to key airway management references as well as information on the Difficult Airway Course.

Selected References:

Status Epilepticus

Here are some key references from today’s lecture on Status Epilepticus at ICEM:

FERNE’s seizure and status epilepticus management guide

Key practice guidelines related to seizures:

  • ACEP Clinical Policy: Critical Issues In The Evaluation And Management Of Adult Patients Presenting To The Emergency Department With Seizures
  • Treatment of convulsive status epilepticus. Epilepsy Foundation of America. JAMA 1993; 270:854-859.
  • The neurodiagnostic evaluation of the child with first simple febrile seizure. AAP. Pediatrics 1996; 97:769-775.
  • The role of phenytoin in the management of alcohol withdrawal syndrome. Am Soc Addiction Med 1994 / 1998
  • Evaluating the first nonfebrile seizure in chilren. AAN. Neurology 2000; 55:616-623.
  • Role of antiseizure prophylaxis following head injury. BTF / AANS. J Neurotrauma 2000; 17:549-553.
  • Treatment of the child with a first unprovoked seizure. AAN. Neurology 2003; 60:166-175
  • Antiepileptic drug prophylaxis in severe traumatic brain injury. Neurology 2003; 60:10-16

Special thanks to Professor Andy Jagoda (Department of Emergency Medicine, Mount Sinai, New York)

Tips and Tricks- The gallbladder / duodenum conundrum

One of the most common pitfalls in gallbladder sonography is confusion with the structure which abuts it in the right upper quadrant – the duodenum. This loop of bowel can easily be mistaken for the gallbladder especially if it contains a mixture of fluid and solid materials. So how can we tell them apart?

The gallbladder:

  • has a bright (echogenic) wall
  • is surrounded by liver
  • attaches to the middle hepatic ligament
  • is a contained structure
  • can be traced to the portal vein

The duodenum:

  • has a darker (hypoechoic) wall
  • is next to the liver, not in it
  • cannot be traced to the middle hepatic ligament
  • is a tubular structure
  • does not connect to the portal vein

More images and explanation after the break!

Continue reading “Tips and Tricks- The gallbladder / duodenum conundrum”

Artifacts 1 – You mean… it’s not real?

Artifacts are ultrasound images on the screen that do not correspond exactly what is in the body. Artifacts can be useful in determining true anatomy:

1. The presence of some artifacts can help us to identify anatomy:  e.g. “an aorta” is  “the aorta” because it’s resting on the spine, which is “the spine” because it casts a shadow (what if the spine does not cast a shadow….?)

2. The absence of artifacts can also reveal pathology:  e.g. in  FAST with right hemothorax, loss of the mirror image of the liver above the diaphragm not only reveals the blood and superior aspect of the diaphragm, it also allows  the vertebral column (above the diaphragm) to show up! The spine above the diaphragm is never seen because the normal aerated lung scatters all of the ultrasound energy above the diaphragm.

3. Both the real image and artifact arise because of certain assumptions that that ultrasound machine makes. When they are all met, you get a real image; when any assumption is not, well, you get an artifact. And thankfully, there are only four such assumptions. Here’s a quick review of them as we begin this series of what’s real and what’s not.

Assumption ONE:

A pulse of ultrasound beam emitted by the transducer travels in a straight line, is reflected at an interface, and travels back to the transducer (exactly along the path it was emitted, only in the reverse direction)

Assumption TWO:

All the returning echoes of the beam are presumed to have arisen only from the center (i.e. axis) of the beam and hence are displayed as such (i.e. along a vertical line on the screen that represents the axis)

Assumption THREE:

The speed of ultrasound beam (emitted and/or reflected) is always and exactly 1540m/s

Assumption FOUR:

The intensity of the displayed echo is dependent on the acoustic properties and size of the interface where it is being reflected

And with that, we’ll make good use of what’s not really there to find out what’s really going on.

Publication – Bret Nelson on Prehospital Ultrasound

Prehospital Ultrasound by Paramedics - PMID 20491683Bret Nelson and Mt. Sinai’s director of Disaster Preparedness and Prehospital Care, Kevin Chason, collaborated on this pilot study on use of Prehospital FAST and Aorta US which showed that paramedics can obtain and interpret these studies.