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INTRODUCTION

Fever, defined as a temperature greater than 38oC (100.4oF), is common after surgical and nonsurgical procedures, with reported incidence in the literature ranging from 15% to 47%. A structured approach is necessary to separate physiological from pathological causes and to identify the need and urgency of further evaluation or intervention.

This section reviews causes of fever after surgery and summarizes the approach to diagnosis and management.

THE SURGICAL INFLAMMATORY RESPONSE

Tissue damage triggers an inflammatory response that is primarily designed to promote healing, restore homeostasis, and eradicate microorganisms. This response is similar whether caused by hypoxia, ischemia, accidental trauma, or surgery and usually occurs early in the postoperative course.1 The “danger theory” posits that injury to cells and tissues leads to release of structurally diverse endogenous proteins, referred to collectively as alarmins, that activate effector cells such as macrophages, lymphocytes, endothelial cells, and stromal cells.2 Activated cells expand the inflammatory process through systemic release of pyrogenic cytokines of which TNF-α, IL-1β, IL-6, IL-8, IL-12, and IFN-γ are the most well characterized.3 TNFa, IL-1, and IL-6 trigger increased production of prostaglandin E2 by the hypothalamus leading to elevation of the thermostatic set point. Systemic levels of IL-6 have been shown to correlate with temperature elevation in the postoperative period.4 The duration and invasiveness of surgery thus is directly associated with the likelihood, magnitude, and duration of postoperative fever. This febrile response is benign and self-limiting.

CAUSES OF POSTOPERATIVE FEVER

The timing of fever after surgery is the most important predictive variable of the cause and is typically divided into immediate, early, late, or delayed. Consider a broad differential and do not assume all fever is due to infection. Table 34-1 lists common etiologies classified according to timeline of usual manifestation. The rule of W’s, an anecdotal mnemonic – Wind (pneumonia), Water (urinary tract infection), Wound (surgical site infection), Walking (venous thromboembolism), and several others – has been validated and serves as a starting point to investigating postoperative fever.5 Table 34-2 lists common etiologies associated with specific types of surgery.

TABLE 34-1Causes of Postoperative Fever
TABLE 34-2Common non-SSI Etiologies of Postoperative ...

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