Tag Archives: ultrasound

Algorithm: Ultrasound for Shock / Hypotension

Capture.JPGAlgorithm for ultrasound assessment of undifferentiated shock, modified from the RUSH protocol.

 

Reference:

Jankowich, Matthew and Eric Gartman. Ultrasound In The Intensive Care Unit. Print.

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How to: Transthoracic Echo

The ultrasound machine is now becoming an indispensable tool for the (non-radiologist) doctor, providing real-time, clinically-relevant information at the bedside.  While this machine may not replace the reliable stethoscope any time soon, the ultrasound has certainly proven its utility, adding to the armamentarium of the modern physician.

Interpretation of ultrasound, just like interpretation of any radiologic modality, involves a certain learning curve.  It takes time and practice to be able to superimpose the anatomy of body organs on the low-resolution images, and derive some clinical information on the function of the insonated organ.  

The transthoracic echo in particular may be more challenging to interpret, because different views are used to slice the chambers of the heart in different planes.  The method of transthoracic echo is hard taught with words and pictures, but rather, time should be spent by the sonologist visualizing the ultrasound probe and the waves that emanate from the probe slicing through the cardiac chambers. 

Here are five videos from youtube, each one a little over a minute, that wonderfully illustrates how a picture (or in this case, a video) is worth a thousand words.  A novice would very well consider watching the videos over and over, until the the images are  ingrained in his memory.
Parasternal short axis – https://m.youtube.com/watch?v=_6Ltla3NL1k

Subcostal view – https://m.youtube.com/watch?v=oMwgUo6sbyY

Apical 4-chamber view – https://m.youtube.com/watch?v=5czv-c1uUnw

Parasternal long axis – https://m.youtube.com/watch?v=CIJewMLUQkU

IVC view – https://m.youtube.com/watch?v=McUUFvnFuJU

References

YouTube,. “How To Obtain: Apical 4 (Four) Chamber Ultrasound View- Training And Techniques – ICU”. N.p., 2016. Web. 25 Jan. 2016.

YouTube,. “How To Obtain: Inferior Vena Cava Ultrasound View- Training And Techniques – ICU”. N.p., 2016. Web. 25 Jan. 2016.

YouTube,. “How To Obtain: Parasternal Long Axis Ultrasound View – Training And Techniques – ICU”. N.p., 2016. Web. 25 Jan. 2016.

YouTube,. “How To Obtain: Parasternal Short Axis Ultrasound View – Training And Techniques – ICU”. N.p., 2016. Web. 25 Jan. 2016.

YouTube,. “How To Obtain: Subcostal Cardiac Ultrasound View – Training And Techniques – ICU”. N.p., 2016. Web. 25 Jan. 2016.

Optic Nerve Sheath Diameter

The optic nerve sheath, contiguous with brain dura and containing CSF communicating with cerebral subarachnoid components, can be used as a means of indirectly detecting increased ICP.

Optic nerve is ontogenetically a part of the CNS.  It is surrounded by CSF and dura mater (called the optic nerve sheath or ONS).  The diameter of the optic nerve sheath (or ONSD) changes with variations in intracranial pressure.

Ultrasound measurement of the ONSD is a reliable means of detecting elevated ICP in patients with spontaneous intracerebral hemorrhage.  However, ONSD measurements are still not considered as a substitute for invasive ICP monitoring in critical care.

ONSD ONS

By measuring the anterior part of the optic nerve, specifically 3 mm behind the globe, ONSD can be measured via ultrasound with 5-mm ONSD roughly translating to an ICP of 20.

Method:

  1. use a linear ultrasound probe (7.5-MHz) over the upper closed eyelid
  2. keep HOB 30-45 degrees
  3. measure the ONSD 3mm behind the globe (take 2 measurements for each optic nerve sheath, sagittal and transverse)

ONSD cut off for elevated ICP:

  1. 5.7 mm       [Sn 93%, Sp 96%]
  2. 5-5.7 mm    [Sp 83%]

ONSD

 

 

NOTES:

  • Inter/intraobserver not a limiting factor
  • ONSD variation dependent on individual factors such as age and underlying pathology
  • difficult to create an absolute ONSD cutoff value for ICP crises

References

Girisgin, A. S. et al. ‘The Role Of Optic Nerve Ultrasonography In The Diagnosis Of Elevated Intracranial Pressure’. Emergency Medicine Journal 24.4 (2007): 251-254. Web. 23 Oct. 2015.

Moretti, Riccardo et al. ‘Reliability Of Optic Nerve Ultrasound For The Evaluation Of Patients With Spontaneous Intracranial Hemorrhage’. Neurocritical Care 11.3 (2009): 406-410. Web. 23 Oct. 2015.

Roh, David and Soojin Park. “Brain Multimodality Monitoring: Updated Perspectives”. Current Neurology and Neuroscience Reports 16.6 (2016): n. pag. Web.

Lung Point

Intensivists are required to put in multiple central lines in critically ill patients.  One of the dreaded complications of line placement is a pneumothorax.  This complication is typically ruled out with a post-procedural chest xray.  Since most central lines are now being inserted with ultrasound guidance, it is an easy adjunct to the procedure to check with the ultrasound for a “lung point” that is seen with a pneumothorax.

LUNG POINT is an ultrasound sign showing a fleeting appearance of a lung pattern (lung sliding or pathologic comet-tail artifacts) replacing a pneumothorax pattern (absent lung sliding plus exclusive horizontal lines) in a particular location of the chest wall.

Sensitivity: 66 %
Specificity:  100%.

This link to a video of a lung point seen with an ultrasound opens in a new window/tab.

Lung point must not be just found, but actively sought for.
A lung point found by chance (esp anteriorly near the sternum) has little chance to be a PTx.

Regular M-mode outlook of a lung point.

Mmode

Seashore sign seen on the left, arising from the pleural line.  Stratosphere sign (total absence of any dynamic arising from the pleural line) seen on the right.

References

Lichtenstein, Daniel et al. ‘The “Lung Point”: An Ultrasound Sign Specific To Pneumothorax’. Intensive Care Med 26.10 (2000): 1434-1440. Web.

Moreno-Aguilar, German, and Daniel Lichtenstein. ‘Lung Ultrasound In The Critically Ill (LUCI) And The Lung Point: A Sign Specific To Pneumothorax Which Cannot Be Mimicked’. Critical Care 19.1 (2015): n. pag. Web.