Mount Sinai Emergency Medicine Ultrasound

A middle-aged male presented to the ED with 2 weeks history of increasing exertional dyspnea. Air entry was reduced clinically. A focused bedside ultrasound demonstrated the above findings. What artifact is missing?

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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:

• Farmery AD, Roe PG: A model to describe the rate of oxyhemoglobin desaturation during apnoea. Br J Anaesth 1996; 76:284-91
• Naguib et al. Optimal dose of succinylcholine revisited. Anesthesiology 2003; 99:1045-1049
• Bozeman et al. A comparison of rapid sequence intubation and etomidate-only intubation in the prehospital air medical setting. Prehosp Emerg Care: 2006; 10:8-13
• Sackles et al. Airway management in the emergency department: a one-year study of 610 tracheal intubations. Ann Emerg Med 1998; 31:325-332
• Li J et al. Complications of emergency intubation with and without paralysis. AJEM 1999: 17(2); 141-143
• Mallon WK et al. Rocuronium vs. succinylcholine in the emergency department: A critical appraisal. JEM 37(2); 183-188
• Strayer RJ. Rocuronium vs. succinylcholine revisited. JEM 2010 Apr 22. [Epub ahead of print]
• Cardiopulmonary resuscitation by bystanders with chest compression only (SOS-KANTO): an observational study, Lancet 369 (2007), pp. 920–926.
• Bobrow et al. Passive oxygen insufflation is superior to bag-valve-mask ventilation for witnessed ventricular fibrillation out-of-hospital cardiac arrest. Ann Emerg Med. 2009;54:656-662.
• Brimacombe JR and Berry JM. Cricoid pressure. Can J Anaesth. 1997 Apr;44(4):414-25

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:

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

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.

Bret Nelson recently filmed a webinar on critical care ultrasound at Gulfcoast Ultrasound Institute in Florida. He discussed evaluation of the hypotensive patient, incorporating Scott Weingart’s RUSH exam as well as other literature on acute assessment of the heart, IVC, FAST exam, and pleura.
Information on the webinar is available at Gulfcoast.

References for a variety of hypotension evaluations are included below, as well as a few screenshots from the webinar!

• UHP protocol
  • Rose JS et al,  Am J Emerg Med 2001 (PMID: 11447518)
• Trinity Protocol
  • Bahner D,  JDMS 2002
• RCT of ultrasound in hypotension
  • Jones AE et al, Crit Care Med 2004 (PMID: 15286547)
• FATE: Focused Assessed Transthoracic Echocardiography
  • Jensen et al, Eur J Anaesthesiol 2004 (PMID: 15595582)
• FEER: Focused Echocardiographic Evaluation in Resuscitation
  • Breitkreutz et al, Crit Care Med 2007 (PMID: 17446774)
• CAUSE: Cardiac Arrest Ultrasound Exam
  • Hernandez et al, Resuscitation 2008 (PMID: 17822831)
• RUSH: Rapid Ultrasound in Shock and Hypotension
  • Weingart et al, emCrit.org 2008, EMedHome 2009
• ACES: Abdominal and Cardiac Evaluation with Sonography in Shock
  • Atkinson et al, Emerg Med J 2009 (PMID: 19164614)
• RUSH: Rapid Ultrasound in Shock
  • Perera P et al, Emerg Med Clin N Am 2010 (PMID: 19945597)

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