HOW TO PALPATE FEVER

Most studies say that palpation of fever is inaccurate. I am not so sure. Many of the studies use oral temperature as a gold standard, which of course can be as low as 50% sensitive for true fever. These studies conclude that the mothers’ palpation over-called the diagnosis but I wonder whether rectal temperature assessment would not have proven many mothers to be correct.

 

I see people put their palm on the forehead to check for fever, and then pull it away 1 second later. I believe this is wrong on several levels. First, use the back of the hand, not the palm. The back of the hand is more sensitive to temperature. Second, don’t feel the forehead, try something less subject to the ambient environment. I often use the neck. Third, don’t pull it away, rather, leave it there. You are not feeling for whether it is warm. You are feeling for whether it is hot. I think we can tell the difference. Remember the sting of a hot tub? Hot tubs are never supposed to be above 104. Yet they really sting sometimes. Hold your hand there and if you feel that sting, it is probably a fever.

 

I found that once I used the above techniques I became a lot more accurate. I would ask skeptical nurses for rectal temperature assessment, and they would come back astonished at my predictive abilities. Palpate for the hot tub sting with the back of your hand in the axilla or neck and see if it works for you. My hope is that future studies would show better methodology.

 

Take home points:

Palpate for a fever using the back of the hand, not the palm

Palpate the neck or core body area, not the forehead

Palpate for at least 10-15 seconds

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HYPOTENSION: A PHYSIOLOGIC DIFFERENTIAL DIAGNOSIS

A patient presents with hypotension after a syncope event. Clearly the issue was a temporary lack of perfusion to the brain related to the low pressure. But what caused the drop? The physiologic formula for blood pressure can help.

MAP = CO x SVR

(CO = SV x HR)

The heart rate (HR) is normal. You see no evidence of sepsis and doubt the systemic vascular resistance (SVR) has dropped. Vasovagal reactions temporarily drop the heart rate or SVR, but this does not fit that, with ongoing hypotension. Something caused the stroke volume (SV) to drop. The laboratory results show anemia, and the rectal examination is heme positive. This is an occult gastrointestinal hemorrhage.

Take home points:

MAP = SV x HR x SVR

A drop in blood pressure suggests a drop in stroke volume, heart rate, or systemic vascular resistance

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

HYPOXEMIA: A PHYSIOLOGIC DIFFERENTIAL DIAGNOSIS

You are taking care of a patient with sepsis of unclear cause and find hypoxemia.  The chest x-ray is normal.  What is causing the hypoxemia?

When the history and physical examination do not reveal an explanation for hypoxemia, it helps to think physiologically. Air, chest vasculature, and blood all are essential.

Classically, hypoxemia is caused by:

Low PiO2 (example, altitude)

Lungs: Impaired diffusion (now thought to be an uncommon contribution)

Alveolar hypoventilation

V/Q mismatch (diseases of the chest)

Shunt (a type of V/Q mismatch with theoretically zero ventilation)

Dead space (a type of V/Q mismatch with theoretically zero perfusion)

At the bedside, the relevant differentiation is alveolar hypoventilation from V/Q mismatch.  Is the patient alert and breathing adequately? Order an arterial blood gas if there is doubt, and look for elevated CO2 as an indicator of underventilation.  For everything else, consider the lungs and the heart.

In this case, further questioning of the patient revealed longstanding tobacco use and subsequent chronic obstructive pulmonary disease.  The patient has chronic V/Q mismatch.

Take home points:

For unexplained hypoxemia, assess ventilation

If ventilation is normal, pursue diseases of the chest

TACHYCARDIA: A PHYSIOLOGIC DIFFERENTIAL DIAGNOSIS

A patient is found to have unexpected tachycardia.  What is the cause?  We use associated symptoms and signs to guide the diagnostic approach.  When that isn’t clear, a physiologic approach might enhance bedside diagnostic reasoning:

 

Cardiac output (CO) = stroke volume (SV) x heart rate (HR)

 

Although the simple equation in a living organism belies much deeper complexity, we can reason that an increase in heart rate means one of three things:

 

1. Stroke volume is decreased

a. Decreased preload (hypovolemia, pulmonary embolism)

b. Decreased inotropy (congestive heart failure)

c. Increased afterload (hypertensive congestive heart failure)

2. Cardiac output is increased

3. Primary disturbance in heart rate

 

Using this approach generates its own differential diagnosis, and may help in subtle presentations.

 

Take home points:

-CO = SV x HR

-An increased heart rate suggests increased cardiac output or decreased stroke volume