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By Dr. Raashee Kedia
Acute vision change
A 51 year old female with a history of diabetes presented to the ED with acute onset of left eye painless blurry vision. Vitals were within normal limits. Fingerstick was 450.
On exam : Visual acuity was 20/30 in the right eye but could only count fingers in left eye at 1 foot. There were no external signs of trauma, conjunctivitis or proptosis. Pupils were equal and reactive to light. Ocular ultrasound of her right and left eyes were performed and shown below:
IN the left eye a bright echogenic linear structure can be seen floating in the posterior aspect of the globe. This was concerning for retinal detachment, which is a clear ocular emergency. Ophthalmology evaluated the patient in the emergency department and diagnosed a vitreous hemorrhage. The patient was discharged home.
How do you tell the difference between a vitreous hemorrhage and a retinal detachment?
First, a little anatomy of the eye:
The vitreous is a clear, gelatinous, and avascular substance, filling the space bound by the lens, retina, and optic disc. The retina is composed of multiple layers that form the posterior wall of the globe behind the vitreous. A retinal detachment occurs when these layers separate.
There is an internal membrane that separates the retina from the vitreous. This forms a potential space between the membrane and the vitreous called the subhyaloid space.
A vitreous hemorrhage occurs when blood extravasates into the vitreous or in the subhyaloid space. If bleeding has occurred in the subhyaloid space, it can appear boat-shaped on the surface of the retina, forming a superior straight line in an upright patient but changing with the position of the patient.
Ocular ultrasound is a quick and accessible way to assess ocular pathology. In patients with acute visual change, evaluation for retinal detachment is important to prevent complete and possibly permanent visual loss.
Ocular ultrasound is highly sensitive in the detection of retinal detachment in the ED.
With ocular ultrasound it can be difficult to distinguish between vitreous hemorrhage and retinal detachment. However, it is important to distinguish between these pathologies as they carry two different treatments and a different sense of urgency.
In an intact globe, the retina cannot be differentiated from the other choroidal layers on ultrasound.
Ultrasound of retinal detachment will show a thick hyperechoic membrane floating in the posterior globe. It never detaches from the optic nerve posteriorly.
Vitreous hemorrhage may layer and form a hyperdense linear density that can mimic a retinal detachment.
Decrease the gain to help differentiate between the two.
Vitreous hemorrhage is usually less dense and will fade as the gain is decreased. It usually layers inferiorly with gravity. Ocular movements produce a rapid, staccato motion of the hemorrhage, unlike a retinal detachment that is stiffer and slower in movements.
Schott, M, Pierog, J.,Williams, S. “Pitfalls in the use of ocular ultrasound for evaluation of acute vision loss.” Journal of Emergency Medicine, Vol 44. Nov 2012.
Yanoff M, Duker JS. Opthalmology. 3rd ed. St Louis, MO: Mosby, An Imprint of Elsevier; 2008.
DiBernardo C, Greenberg E. Opthalmic ultrasound: A diagnostic atlas. 2nd ed. New York: Thieme MEidcal Publisers; 2007.
Is ultrasound the stethoscope of the future? Is it an extension of the physical examination? Will it replace the physical exam?
Point-of-care ultrasound is a diagnostic test. It is a rapid, bedside, noninvasive, accurate, diagnostic test, but still a diagnostic test. It can certainly augment data obtained through physical examination and medical interviews, and adds to information obtained by blood assays and radiology studies.
It is performed using FDA-approved medical devices by clinicians with specialized training. Images used for medical decision-making may be archived and shared with colleagues from multiple specialties. Quality assurance programs improve clinician accuracy and accountability. These are not physical examination characteristics. These are qualities of good diagnostic tests.
There is and will continue to be debate about this issue. Whether we think about point-of-care ultrasound as a diagnostic test or part of the physical examination has ramifications for training, documentation, archiving, and billing.
We recommend checking the guidelines relevant to your specialty and making up your own mind on this issue. In either camp some things remain constant: train well and use ultrasound to enhance the care you provide your patients.
We previously reported on AIUM’s Ultrasound First initiative back in March. Since then a number of helpful articles have been published in the Journal of Ultrasound in Medicine, each highlighting the utility of ultrasound as the primary imaging modality.
Thus far, topics include:
Sonography in Postmenopausal Bleeding – Steven R. Goldstein, MD
Think Ultrasound When Evaluating for Pneumothorax – Vicki E. Noble, MD
Sonography Should Be the First Imaging Examination Done to Evaluate Patients With Suspected Endometriosis – Beryl R. Benacerraf, MD, and Yvette Groszmann, MD
Sonography of Adenomyosis – Khaled Sakhel, MD, and Alfred Abuhamad, MD
Lung Ultrasound in Evaluation of Pneumonia – Michael Blaivas, MD
Ultrasound-Guided Interscalene Blocks – Andrew Gorlin, MD, and Lisa Warren, MD
Sonography for Surveillance of Patients With Crohn Disease – Kerri L. Novak, MSc, MD, FRCPC, and Stephanie R. Wilson, MD, FRCPC
Sonography as the First Line of Evaluation in Children With Suspected Acute Appendicitis – Leann E. Linam, MD, and Martha Munden, MD
Shoulder Sonography: Why We Do It – Sharlene A. Teefey, MD
Sonographically Guided Enema for Intussusception Reduction: A Safer Alternative to Fluoroscopy – Thomas Ray S. Sanchez, MD, Aaron Potnick, MD, Joy L. Graf, MD, Lisa P. Abramson, MD and Chirag V. Patel, MD
Sonography First for Subcutaneous Abscess and Cellulitis Evaluation – Srikar Adhikari, MD, RDMS, and Michael Blaivas, MD
Sonography in the Treatment of Calcific Tendinitis of the Rotator Cuff – Gregory R. Saboeiro
More articles on best evidence are forthcoming- please check out Ultrasoundfirst.org for more information!
On November 11-12, AIUM will host its first Ultrasound First Forum in New York City.
Many new developments in ultrasound were demonstrated at the ACEP conference in Denver this week. Since airway management rivals ultrasound as my academic interest, I’d like to focus for a moment on an intubating device I saw demonstrated at an ultrasound vendor booth. I’ve seen lots of organs on my ultrasound screen- hearts, gallbladders, eyeballs, prostates. I’ve even seen airway structures, but not like this:
The VividTrac is a single use, USB video intubation device. It is a channeled blade video laryngoscope similar in concept to the King Vision or the AirTraq Optical Laryngoscope. The channel is designed to pass the endotrachel tube through. This is in contrast to non-channeled video laryngoscopes like the Storz C-MAC or the Verathon Glidescope, where the endotracheal tube is guided with a stylet and not directed through the video device itself.
What is interesting about the Vivid device is it hooks up to a monitor using a standard USB cable. Thus, it can be connected to different types of monitors, PDAs or tablets which accept USB input, or… an ultrasound machine monitor! Theoretically one could use an existing ultrasound machine with a variety of probe types as well as a device like this.
There are many device manufacturers involved in R&D of devices which might lead to a technology convergence. Ultrasound probes, video intubation devices, cardiac monitoring equipment, etc. could all transmit images to a monitor, via wires or wirelessly. Thus, pluripotent monitors could be used with a variety of devices depending on the needs of any given patient. This could increase the amount of information relayed via the monitors, and even what is transmitted to the electronic medical record. Importing vital signs, ultrasound images, EKGs, or other clinical images could all be captured in this way. It will be interesting to see how many other devices can learn to communicate with each other as the technology develops.
In critically ill septic shock patients, assessments of hemodynamic function, fluid status and improvement of clinical status are challenging. As a consequence of critical illness and large volume administration of crystalloids as recommended by Early Goal-Directed Therapy, comes the potential of acute (respiratory distress/failure) and long-term sequelae (ARDS, prolonged endotracheal intubation, anasarca, bedsores, poor IV access, increased resource utilization).
The FALLS-protocol, developed by Daniel Lichtenstein introduces novel clinical parameters useful in the assessment of fluid status dynamically. It aims to define the critical point when fluid administration is becoming deleterious to the patient (lung saturation), and we must start considering the use of vasopressors as well as the potential for respiratory failure.
Review: Lung Ultrasound basics
- Anterior Chest (Blue points)
- A-profile : normal lung parenchyma
- B-profile : interstitial edema (aka lung rockets)
Utilizing a decision tree that obligates several simple cognitive and sonographic steps in the evaluation of shock, the true protocol begins when septic shock remains the most likely etiology and resuscitation has already been initiated. By evaluating the lung parenchyma at the Blue Points, we begin with the A-profile in healthy patients. Patients with fluid overload however demonstrate a B-profile (lung rockets emanating from the pleural line) indicative of interstitial edema. In combination with vital signs, as we are administering fluids, we can evaluate the profile in either intervals of time or fluid aliquots. At any of these intervals, if the patient remains hypotensive but has an A profile, we can feel confident that we can continue to administer fluids with little risk for respiratory compromise. However, if the profile transitions to B-profile, we must consider vasopressors and advanced airway management.
Fluid administration is often guided by clinical judgment, with no clearly defined end point other than a normalized blood pressure. However, blood pressures can be corrected by vasopressors and are often given as a last ditch effort. With the current emphasis on sepsis management in the US, EDs are coming under scrutiny for our role. Although the FALLS-protocol still requires exhaustive study, it has the potential to allow a more finessed management of acute circulatory failure.
Lichtenstein, D. (2010) Wholebody Ultrasonography in the Critically Ill. London: Springer-Verlag Berlin Heidelberg
Fluid Administration limited by lung sonography: the place of lung ultrasound in assessment of acute circulatory failure (The FALLS-protocol). Expert Rev Respir Med. 2012 Apr;6(2):155-62.