Episode 28: Hyperthermia and Fever
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In this episode, Dr. Lance Wheeler, DVM, DACVECC tackles the number we take on every single patient and misread more often than any other - body temperature, and the fork in the road between true fever and nonfebrile hyperthermia. Drawing from Chapter 10 of Small Animal Critical Care Medicine (3rd edition) by James Miller, Lance separates a regulated, cytokine- and prostaglandin-mediated change in the hypothalamic set point from a straightforward failure of heat balance, and walks through a practical, structured framework for reading temperature in real time: thermoregulation in the preoptic anterior hypothalamus and the heat gain, conservation, and loss mechanisms behind it, exogenous versus endogenous pyrogens and the interleukin-1, interleukin-6, and tumor necrosis factor alpha pathway to prostaglandin E2, why fever can be protective in infection and harmful in brain injury, the roughly 7 percent rise in water and caloric requirement for every 1°F above normal, and the thresholds worth memorizing - above 102.5°F is elevated, above 106°F demands immediate total body cooling, and 107°F is the organ injury danger zone. He then moves into the causes and the bedside management, including heat stroke and the closed car that exceeds 120°F in under 20 minutes on a 75°F day, nucleated red blood cells as a prognostic marker, exertional hyperthermia and hyperpyrexic syndrome, eclampsia and seizures as heat sources you have to switch off rather than cool around, malignant hyperthermia and dantrolene, opioid-associated hyperthermia in cats, why lukewarm beats ice water and why you stop active cooling at 103°F, and why antibiotics are not antipyretics. Along the way, he integrates the latest veterinary evidence, including 2020-2026 studies on juvenile canine pyrexia, triage temperature as a predictor of outcome in cats, buprenorphine and postoperative hyperthermia, cooling strategies in working dogs, nose and axillary temperature accuracy, feline vector-borne disease, and heat-related mortality, and closes with a high-yield rapid-fire board review covering every key number worth memorizing.
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