IM4.1-8 | Fever Foundations — Summary & Reflection

KEY TAKEAWAYS

Fever is a controlled hypothalamic thermostat reset driven by endogenous pyrogens (IL-1β, IL-6, TNF-α) acting via COX-2-generated PGE2. Hyperthermia is an uncontrolled temperature rise without set-point elevation; antipyretics are ineffective. Key distinction: fever responds to antipyretics; hyperthermia requires physical cooling.

Common causes in India: malaria (falciparum in central/eastern belt, vivax elsewhere), dengue (urban, monsoon, WHO 2009: dengue/warning-signs/severe), enteric fever, leptospirosis (flood/water exposure), scrub typhus (eschar, Himalayas/south India), kala-azar (Bihar/Jharkhand/West Bengal), TB (NTEP). Non-infectious: autoimmune (SLE, Still's, HLH), malignant (lymphoma, RCC, HCC), drug fever.

Special populations modify the febrile response: elderly mount a blunted response; immunosuppressed patients (especially IL-6 blockers) may have NO fever in sepsis; neutropenic patients require antibiotics for a SINGLE temperature of 38.3°C; HIV patients develop opportunistic infections at CD4 <200.

Sepsis (Sepsis-3): life-threatening organ dysfunction from dysregulated host response to infection; SOFA ≥2. Septic shock: MAP <65 mmHg requiring vasopressors + lactate >2 mmol/L. Hour-1 bundle: cultures → antibiotics → lactate → fluids → vasopressors. qSOFA ≥2 = bedside screening trigger.

Heat-related illness spectrum: heat cramps (normal temperature, electrolyte loss, treat with ORS) → heat exhaustion (T <40°C, sweating intact, sensorium intact, IV fluids) → heat stroke (T >40°C + CNS dysfunction; classic = dry skin, exertional = may have sweating; IMMEDIATE physical cooling is the treatment; antipyretics are NOT effective).

REFLECT

Think about the opening clinical vignette: two patients, both at 41°C, one with hyperthermia (heat stroke) and one with fever (malaria). The entire treatment strategy differed based on the mechanism — ice packs and cooling versus antimalarials. Now consider a patient you might see in your medical ward: a 68-year-old woman admitted with 'just a mild fever of 37.9°C' who is also confused. How would you approach her differently from a 25-year-old with the same temperature reading? Which of the danger signs you have learned would change your immediate management from 'observe' to 'resuscitate now'? Connecting mechanism to management — and recognising when the number on the thermometer underestimates the clinical danger — is the core skill this module is designed to build.