In podcast 78 on the management of elevated ICP, I discussed ocular nerve sheath ultrasound. Here are some additional resources.
Key Aspects of the Technique
- Must see lens or iris in the scan or you are scanning nerve off-axis. If off-axis, may underestimate OSND diameter.
- Measure Outside Diameter (OD)
- A good view of the nerve often necessitates moving the probe slightly to the temporal side and angulating the beam a little nasally.
Literature
- Crit Care 2008;12:150
- Acad Emeg Med 2003, Vol. 10, No. 4
- Tayal VS Ann Emerg Med 2006
- Emerg Med J 2007;24:251
- Annals of Emergency Medicine 2007;49(4):508-514
- Inten Care Med 2007;33:1704
- Academic Emergency Medicine 2008;15 (2) , 201-204
- Inten Care Med 2008;34:2062
- Neurocritical Care Dec 2009
- Emerg med j 2011;28:679
- J Trauma 2011;71:779)
- Neurocrit Care 2011;15:506
- Review Article (Acta Anaesthesiol Scand 2011;55:644)
Blogposts
Update 5/31/14: This Blog and Podcast is the one you must immediately check out on optic nerve sheath for ICP, from the Broomedocs podcast.
There you will find this table from Dr. Leanne Hartnett:
Media
From Ultrasound Podcast guys, a 1-minute tutorial
Link to Full Ultrasound Podcast on Ocular Nerve Sheath Exam
http://www.criticalcarehorizons.com/optic-nerve-sheath-diameter-icp/
Scott Weingart
An ED Intensivist from NY. No conflicts of interest (coi).
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Hi, I’m wondering why the ETCO2 may not match the PaCO2 in a head injury patient (who is not in shock or has any underlying cardiovascular disease). Thanks!
If they had none of those things, and no atelectasis, and no other trauma it would probably correlate fairly well–at first. Most TBI patients are not that isolated. One correlated set- of-samples doesn’t tell you that their lungs have not started to get bad later on. The TBI state leads to ALI and ARDS on its own without any coexisting external lung injury.
Got it, thanks!
This just wants me to have a Pocket ultrasound machine when I’m on calls. Besides that this is excellent stuff thanks Ultrasound guys!
[…] geschrieben habe, sehe ich, dass Scott W. auch über dieses Thema einen Blog zusammengestellt hat. Schauen Sie doch hier noch rein. Eingestellt von Prof. Dr. Michael Christ um 08:00 Diesen Post per […]
I used this technique just last week to confirm an elevated ICP reading by a Codman. I didn’t have a Tegaderm handy, so I just cut a latex glove into sort of a square sheet which I draped over the patient’s closed eye, and then applied ultrasound gel over the latex, leaving the eye completely residue free. Perfect images. Great podcast!
nice tip, my friend
[…] his eye. First he probed…is that the word…no, imaged for his optic nerves (which can be used to diagnose increased intracranial pressure) which was fairly easy to find in a controlled setting and measure. We also experimented with […]
[…] Optic Nerve Sheath Ultrasound, Emcrit-Scott Weingart […]
not sure if this is still active, but im looking for definitive measurement techniques as have had numerous discussions about measuring inside or outside diameter. When there appears to be a double lumen (not sure how else to explain) some research states measure inside and the outer lumen may only be “feedback” or “shine-through” and some say to use outer lumen as it represents the actual sheath and the inner darker lines are from the nerve. Can you help settle? Thx
it depends on the resolution of the probe. for our crappy ED/ICU ones, outside diameter is the way to go. Optho level ultrasound machines they measure differently.
[…] – orbital US useful for injury including foreign bodies and optic nerve sheath diameter for the diagnosis of raised ICP, which is better done as serial […]
thanks scott