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Category: Vital Signs

HOW TO PALPATE FEVER

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…

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HYPOTENSION: A PHYSIOLOGIC DIFFERENTIAL DIAGNOSIS

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…

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FEVER: ORAL TEMPERATURE HAS LIMITED SENSITIVITY

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…

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FEVER OF UNKNOWN ORIGIN

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…

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HYPOXEMIA: A PHYSIOLOGIC DIFFERENTIAL DIAGNOSIS

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…

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TACHYCARDIA: A PHYSIOLOGIC DIFFERENTIAL DIAGNOSIS

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…

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