Tag Archives: UltrasoundPodcast

Beating a Dead Horse: Why Ocular Ultrasound Beats Papilledema for Detecting Increased Intracranial Pressure

Our earlier article on ocular ultrasound for measuring intracranial pressure was met with a common question. Primarily, why not just use papilledema as your initial assessment for intracranial pressure? This is what we are taught in medical school. Optic nerve disc swelling equals increased intracranial pressure (ICP). End of Story. Right? Not exactly…  While optic disc swelling can indicate increased ICP, it is an inferior measure of acutely elevated ICP. And here is why…

  • It’s an indirect measure.
  • It’s a late sign of increased ICP.
  • It’s more subjective.
  • It’s not a dynamic measurement.
  • It’s not always practical.

pap vs oc us 1

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Keeping an Eye on Intracranial Pressure: Measuring ICP Using Ocular Ultrasound

Measuring Intracranial Pressure Using Ocular Ultrasound

Measuring ICP

  • There is a caliper function on ultrasound machines that gives you precise measurements of selected structures.
  • Take your optic nerve sheath diameter (ONSD) measurement 3 mm posterior to the globe.
    • This area has the greatest contrast with surrounding tissue (more contrast = more accurate measurements).
    • Use the calipers to determine 3 mm.
  • Measure across the optic nerve sheath (not just the optic nerve).
  • Measure ONSD for both eyes and average the two measurements.

Interpreting Your Results:

  • Increased ONSD correlates with increased ICP
  • Upper limit of normal ONSD vary with age…
    • Adults: < 5 mm
    • Children > 1 yo: < 4.5 mm
    • Children < 1 yo: < 4 mm
  • ONSD 5 – 5.7 mm: may indicate ICP > 20 mmHg, especially if symptomatic
    • > 5 mm is 100% sensitive for elevated ICP
    • All patients with elevated ICP have ONSD > 5mm
  • ONSD > 5.7 mm: indicates ICP > 20 mmHg
    • > 5.7 mm is 100% specific for elevated ICP
    • Only patients with elevated ICP have ONSD > 5.7 mm
  • ONSD measurements increase with increasing ICP.
  • ONSD measurements plateau around 7.5 mm even with significantly increased ICP.
  • In severe cases, an echoluscent circle called a crescent sign may be present.
    • Crescent sign is formed by the separation of the optic nerve sheath from the optic nerve by high ICP.

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Weekly Highlights

Hey everyone! With the large number of blogs (growing everyday), and the new emphasis toward #FOAMed, we decided to do a weekly post w/ highlights from around the interwebs. We tried to find a few that are still relavent at the med student level, and especially important as we slowly head toward the transition between medical student and residency.

We always have cool posts and interesting articles linked on our Twitter, so join us there too!

  • “Why are you ordering that test?” Asked by every attending when you present your plan and very important question to think about. [LINK = EM Res Podcast] 
  • Tweet pearls complied by the guys over at Academic Life in EM [LINK = AcademicLifeinEM] 
  • Study shows ED docs are as good as radiologists at gallbladder ultrasound. Learn from the pros at ultrasound podcast (and do forget to get their 1 min ultrasound app for you phone. One of the best resources for quick tips right before performing ultrasounds)
    [LINK = Ultrasoundpodcast] 
  • Speaking of ultrasound apps, check out Sonospot for a collection of websites and phone apps for bedside ultrasound [LINK = Sonospot]

  • MUST read before going into the ED (shadowing, rotation, for anything!). Initial assessment and management for trauma from Life in the Fast Lane [LINK = LITFL] 
  • Advice to new interns from Better in Emergency Medicine. Relevant for med students as well to see “The Ten Commandments of Emergency medicine” [LINK = Better in Emergency Medicine]

Check out these posts. Learn em well. Sound really smart. Come back for more post and links soon!

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Small Bowel Obstruction

Quick Hit:

  • Etiology:
    • Most common = Adhesions (post-abdominal surgery)
    • Other causes = hernia, malignancy, intraluminal stricture, intussusception, foreign body, duodenal hematoma
  • Symptoms
    • colicky/paroxysmal abd pain w/ episodic, hyperactive bowel sounds, diffuse abd tenderness, bilious vomit
    • failure to pass stool or flatus = signs of complete bowel obstruction
  • Diagnosis: dilated loops on x-ray, dilated fluid filled loops (air-fluid levels) on CT Abdomen
  • Management:
    • IV fluid resuscitation w/ electrolyte repletion
    • Complete obstruction, or signs of peritonitis = surgical emergency
    • Partial obstruction: non-operative management (NG tube decompression, close observation)
  • Complications: strangulation
    • Signs of strangulation = metabolic acidosis from lactic acidosis secondary to ischemic necrosis caused by strangulation

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