ABSTRACT
This chapter discusses the approach to fever in the CCU. Usually, there are clinical signs pointing to a particular organ/source of the infection.
Clinically, Cunha’s “102°F rule” (in general, <102°F likely indicates an infectious etiology) has great differential diagnosis (DDx) utility, providing a relatively efficient way to differentiate infectious from most non-infectious disorders.
The relationship of temperature to pulse is next in diagnostic importance in the DDx and is covered in detail. If there is a pulse temperature deficit, i.e., relative bradycardia, then the DDx is rapidly narrowed. With the exception of infectious myocarditis, relative tachycardia suggests a non-infectious etiology. Extreme temperature elevations >106°F (extreme hyperpyrexia) are nearly always non-infectious.
The clinical approach to the DDx of fever in the CCU is based on characteristics of the fever, the fever pattern, the relationship of the pulse to the fever, the acuteness and duration of the fever, and the presence or absence of (relevant aspects of the patient’s history, physical exam, routine laboratory tests, and imaging studies) characteristics of the patient’s fever in the appropriate clinical context determine DDx possibilities. These findings are the basis of formulating a clinical syndromic diagnosis (narrowed based on probability DDx, not possibility). Then, it is usually relatively straightforward to order specific tests to arrive at a diagnosis.
