A 74-year-old woman arrives shivering beneath two hospital blankets, her forehead cool to the touch despite a flushed face. Her daughter says she was “burning up” at home, but the triage temporal scanner reads 37.4°C. She is tachycardic, mildly confused, and breathing faster than usual; the team is debating whether the number is reassuring. The next temperature has not yet been obtained.

— What’s your move? Read on.

Before you read
  • When does a “normal” reading fail to exclude dangerous illness?
  • How do fever, hypothermia, and hyperthermia change immediate management?

When to Think of It

Use temperature measurement to detect fever, hypothermia, occult sepsis, environmental exposure, endocrine crisis, medication toxicity, and heat illness. Fever is generally ≥38.0°C (100.4°F) rectally or orally, but dangerous infection may occur without fever, especially in older adults, neonates, immunocompromised patients, and those taking antipyretics. Core temperature is particularly important when heat stroke or severe hypothermia is possible.

Sick or Not Sick

The key call is whether the patient is physiologically unstable or has a temperature-measurement problem that could conceal an emergency. Altered mental status, shock, respiratory distress, seizure, severe rigidity, or suspected heat illness/hypothermia overrides a reassuring peripheral reading.

The First Fifteen Minutes

  • Confirm the reading with a reliable method; in an unstable patient, obtain a rectal temperature or esophageal/bladder temperature if already instrumented, because peripheral sites can substantially underestimate core temperature.
  • If suspected heat stroke—core temperature usually ≥40°C plus CNS dysfunction—move immediately to active cooling: remove clothing, mist with water and use fans, and apply ice packs to neck, axillae, and groin, because evaporative and conductive heat loss rapidly reduce core temperature.
  • If shivering hypothermia with core temperature <32°C, begin active external rewarming; use warmed IV crystalloid 1–2 L IV, typically warmed to 40–42°C, because it limits ongoing heat loss.
  • Do not give acetaminophen or ibuprofen simply to normalize a number; antipyresis does not treat the cause and is not effective for environmental hyperthermia.

Definitive Care & Disposition

Treat the underlying syndrome: sepsis evaluation and antibiotics when indicated, toxicologic consultation for sympathomimetic or anticholinergic hyperthermia, endocrine evaluation for thyroid storm, and rewarming escalation for severe hypothermia. Avoid relying on oral, axillary, forehead, or tympanic readings when perfusion is poor, the patient is intubated, or temperature extremes are suspected. Heat stroke, severe hypothermia, persistent altered mental status, or measurement discordance in a critically ill patient warrants ICU-level care.

How This One Kills

The lethal error is accepting a falsely normal temporal or axillary temperature in a patient with shock or heat illness, delaying core measurement and active treatment while cellular injury continues.
The Differential — What Else Looks Like This
  • Fever — regulated hypothalamic set-point elevation with preserved thermoregulatory responses; confusing it with hyperthermia delays cooling.
  • Heat stroke — uncontrolled temperature elevation with CNS dysfunction; confusing it with infection alone delays immediate cooling.
  • Measurement artifact — peripheral reading discordant with the patient’s appearance and physiology; confusing it with true normothermia creates false reassurance.
  • Hypothermia — core temperature <35°C; confusing cold skin with adequate core temperature can miss severe systemic illness.

The Second-Day Story

Older or immunocompromised patients may have sepsis with a normal or low temperature, while antipyretics, steroids, environmental exposure, and poor peripheral perfusion degrade the signal further. A cool forehead does not establish normothermia, and a warm skin surface does not prove fever. In a sick patient, repeat with a core-proximal method and let perfusion, mental status, respiratory effort, and lactate—not the isolated number—drive urgency.
Back to Our Patient
Back to the 74-year-old woman: her tachycardia, tachypnea, and confusion make the temporal reading unreliable and trigger immediate reassessment. A rectal temperature is 39.2°C, confirming fever; she undergoes sepsis evaluation, cultures, lactate testing, and empiric treatment based on the suspected source. The Recognize step is identifying a potentially septic older adult despite a reassuring peripheral number; the Risk Stratify step is recognizing altered mentation and abnormal vital signs as high risk; the First Fifteen step is obtaining a core-proximal temperature while stabilizing and investigating her. She is admitted for monitored treatment of suspected sepsis.
Patient Presentation to Attending
How you’d present this patient on the floor — tight, pertinent positives and negatives, no rambling
“This is a 74-year-old woman with acute confusion, chills, tachycardia, and tachypnea after reported fever at home. Her temporal temperature is 37.4°C, but that conflicts with her appearance and physiology; she has no obvious external heat exposure, and the initial exam shows altered mentation without focal neurologic deficit. I’m concerned that the peripheral reading is falsely reassuring and that she may have occult sepsis. I’ll repeat a rectal temperature, obtain IV access, glucose, CBC, CMP, lactate, blood cultures, urinalysis and imaging guided by symptoms, and start empiric antibiotics if a bacterial source remains likely. Given her abnormal mental status and vital signs, she needs monitored admission.”

Study Directive

  • Demonstrate rectal, oral, tympanic, temporal, and axillary technique and list the major sources of error for each.
  • Memorize fever ≥38.0°C, hypothermia <35°C, and the heat-stroke pattern of extreme temperature plus CNS dysfunction.
  • Practice three scenarios in which the measured temperature should be distrusted: shock, neonate, and suspected heat illness.
  • Review your institutional device instructions and compare them with an emergency medicine reference on temperature measurement.