TROUBLESHOOTING VISUAL ACUITY

Do your nurses have trouble getting visual acuity in triage? It is a common problem in emergency medicine practice, but fortunately there are solutions.

 

1. Patient can not open eye

Many patients say they can’t open the eye. By holding the lid open, usually the patient is able to demonstrate normal acuity. Topical anesthesia can improve compliance by alleviating pain. Clean around the eye if the finger slips because the skin is too greasy.

 

2. Patient forgot to bring glasses

There are two solutions:

 

a. Pinhole correction

Pinhole correction allows only parallel light to pass, giving a more accurate estimate of visual acuity in such patients. However, I find that this technique does not always get us back to normal vision.

 

b. Near-Snellen card

Technically this is called a Rosenbaum card but most non-ophthalmologists do not use the eponym.  This is widely available in pocket resources, on the internet, and with smartphone applications. It bypasses the need for corrective lenses in myopic patients.

 

Take Home Points

-If the patient won’t open the eye, assist him or her

-Pinhole correction can partially correct for refractive error

-Near Snellen testing can be an acceptable alternative for those who forget their glasses

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HUMAN DIVE REFLEX FOR SVT

A patient presents with racing palpitations with a heart rate of 160. Is this supraventricular tachycardia? You are waiting for the EKG. In the meantime you wonder about all those vagal maneuvers. You tried them early in your career and they didn’t work. Is it worth a second look?

 

The human dive reflex was reviewed this month in the Emergency Medicine Journal.(Smith EMJ 2012) In pediatric populations it was 90-100% effective but in adult populations for paroxysmal supraventricular tachycardia it was 5-20%. The authors note that heterogeneous studies with a low sample size limit conclusions. Until better evidence is found they recommend:

 

-Immerse the entire face, not just part of it (with cold packs)

-Employ augmentation techniques of a deep breath followed by breath holding, as well as calming measures)

-Duration of the treatment should be 30-40 seconds before abandoning it

 

Think back to your previous attempts. Did you use optimal methods? If not, maybe give it a try using the above techniques, and let me know how it goes.

 

Take Home Points

-Full face coverage

-Augmentation with deep breath, breath hold, calming techniques

-Wait 30-40 seconds before abandoning the effort

LOCALIZE VERTIGO: LIKE IN A HEAD TURN, THE VOR PULLS THE EYE TO THE UNDERACTIVE SIDE

You are seeing a patient with suspected vestibular neuritis. The resident is having trouble with the physical examination. Will localization help her comprehend the bedside findings?

 

We understand neurolgical disease by localizing it. We can often localize vertigo, though it is more difficult for 3 reasons:

– the signal is tonic (there is always a basal tone which can then go up or down)

– it is bilateral

– Its sensory representation is space, which is not just within the body but includes the external world.

 

To localize vertigo, one only needs to know 2 physiological principles:

1) A head turn activates the ipsilateral labyrinth and suppresses the contralateral labyrinth.

2) The vestibulo-ocular reflex (VOR) makes the eyes move opposite the head turn.

 

Now let’s localize this patient’s vertigo.

 

Attending: “What direction is the spinning?”

Patient: “It is spinning to the left”

 

Attending (to the resident): “Now turn your head to figure out what induces a perception of ‘spinning to the left.’ (resident turns head to the right). Correct. A right head turn does this. So the patient has a more active right ear than left ear. Thus, the left ear is the suppressed ear. Let’s confirm that at the bedside with physical findings.”

 

Attending: “If the left ear is pathological, where will we see nystagmus, on right or left gaze?”

Resident: “Well the mnemonic of eyes to the ice would say left? Wait, no, to the right?”

Attending: “Forget about the mnemonic right now and use the head turn again. The VOR makes the eyes move opposite the head turn. So the eyes want to go to the pathologic side. When they look away from that you get nystagmus as the eyes try to overcome the pull, and then fatigue. So where do you see nystagmus?”

Resident: “When the eyes look away from the pull. So you get right beating nystagmus on right gaze.”

Attending: “Exactly. Nystagmus is the conscious mind overcoming the pull. We use nystagmus in cold calorics to confirm consciousness.”

Resident: (after testing the patient) “But there is no nystagmus either side.”

Attending: Ah, but you just got another localizing finding.

Resident: The hard blinking?

Attending: Yes, that is gaze aversion. It tells you the same thing nystagmus tells you. The eye doesn’t want to look that way. You can even ask the patient which side is harder to look at. That picks up subtler deficits.

Resident: So the lesson here is that the VOR makes the ear want to go to the pathologic side.

Attending: Exactly. The fast phase of nystagmus and gaze aversion on the right mean that the eye wanted to go to the left. Now we can confirm left pathology through one more test.

Resident: Head impulse test?

Attending: Exactly (this is performed and is equivocal to the left, normal to the right)

Resident: So do we need to get an MRI?

Attending: No. The studies you are thinking of were done on a select population with severe deficits. The patients were so sick they needed to consult neuro. This patient has a very mild presentation and we would not expect a definitive catch-up saccade. Future studies will catch up with this concept.

 

Take home points:

-You will forget these rules, but do not forget that turning your head to one side activates that ear and inactivates the opposite ear

-The VOR pulls the ear to the less active (pathologic) side, so the eye has trouble looking opposite that (fast phase nystagmus, gaze aversion on looking away from pathologic side)

The world spins toward the pathologic side

Head impulse test is positive to the pathologic side

FEVER: ORAL TEMPERATURE HAS LIMITED SENSITIVITY

A patient presents with headache. The history and physical examination do not reveal the cause. You take a second look at the vital signs.  Oral temperature is 99.3.  You have the nurse check the rectal temperature. It is 101.9. What is the sensitivity and specificity of oral temperature for fever?

 

There are numerous studies on this topic, and unfortunately, the populations studied are far too heterogenous to truly give a range for sensitive and specificity. In some studies the sensitivity is as low as 47%.(Jensen J Adv Nurs 1994)

 

Correctly identifying a fever can change the workup in certain presentations. During residency I saw a patient with a 99 degree temperature elevation and back pain. The attending physician was sharp to perceive this and rectal temperature turned out to be 101.5.  We eventually diagnosed epidural abscess.

 

Another example might be delirium in the elderly. I recall a nursing home patient who presented in shock with an oral temperature of 98.1.  I asked the nurse to check rectal temperature. She was a bit skeptical. The reading was 102.1 and she was surprised and a little disappointed at how unreliable the oral temperature can be.

 

The lesson is this: oral temperature is not sufficiently sensitive.  It might work for screening, but slight abnormalities in high risk presentations may call for the gold standard: rectal temperature.

 

Take home points:

-Oral and even temporal temperature assessment can have low sensitivity

-Minor oral temperature elevation may call for rectal temperature assessment

 

FEVER OF UNKNOWN ORIGIN

In emergency medicine we occasionally encounter fever that won’t yield to a specific diagnosis. We speculate a viral cause and a self-limited course, but it is worth thinking through the next step. The term “fever of unknown origin” originates in internal medicine and refers to specific criteria that are appropriate for that setting. If the fever lasts three weeks, it is not necessarily consistent with a self-limited viral cause and this thought process is triggered.

Classic causes of fever of unknown origin are:

1. Infection

2. Connective Tissue Disease

3. Malignancy (often hematologic)

Additional noninfectious causes of elevated temperature in emergency medicine include environmental, toxicologic, and endocrine (hyperthyroidism).

Thinking about these possibilities may prompt the diagnostic process and establish the correct diagnosis early. Of course, even in the modern era, half of all cases of fever of unknown origin never have their cause discovered.(Bleeker-Rovers Medicine 2007)

Take Home Points:

-Fever of unknown origin classically is due to infection, connective tissue disease, or malignancy