Makindo Medical Notes

📖 Introduction

The human body maintains a core temperature of around 36.5–37.5°C through hypothalamic regulation, balancing heat production and loss. Disruption of this balance leads to hyperthermia (excess heat) or hypothermia (excess heat loss). Both conditions can be life-threatening and require prompt recognition and treatment.

🧬 Pathophysiology

• Hyperthermia: Occurs when heat generation (e.g., exertion, drugs, endocrine excess) or environmental exposure exceeds the body’s capacity for heat dissipation. Unlike fever, the hypothalamic set point is not raised.
• Hyperpyrexia: An extreme fever (>41°C) due to a raised hypothalamic set point, usually from infection, CNS disease, or drug-induced syndromes (e.g., NMS, serotonin syndrome).
• Hypothermia: Results from prolonged heat loss via radiation, convection, evaporation, or conduction. Risk factors include exposure, impaired thermoregulation (age, alcohol, hypothyroidism), and metabolic derangements.

🩺 Clinical Features

• Hyperthermia: Hot, flushed skin, tachycardia, confusion, seizures in severe cases. Red flag: Heatstroke → altered mental status + core temp >40°C.
• Hyperpyrexia: Very high fever with rigors, delirium, or neurological dysfunction. May herald sepsis, intracranial bleed, or drug toxicity.
• Hypothermia: Shivering (mild), slurred speech, confusion, bradycardia, hypotension. Severe hypothermia (<30°C) → arrhythmias (J-waves on ECG), coma, cardiac arrest.

📊 Comparison Table

⚖️ Differentials to Consider

• Fever (raised hypothalamic set point, responsive to antipyretics) vs hyperthermia (unregulated overheating, not reduced by paracetamol).
• Post-ictal hyperthermia vs infective fever.
• Hypoglycaemia, intoxication, or stroke mimicking hypothermia clinically.

🎯 Exam Pearls

• Heatstroke = medical emergency: CNS dysfunction + high temp. Treat with rapid cooling, not paracetamol.
• Malignant hyperthermia (succinylcholine/volatile anaesthetic exposure) → give dantrolene.
• Neuroleptic malignant syndrome (antipsychotics) → rigidity + fever → treat with bromocriptine/dantrolene, supportive care.
• In hypothermia, don’t declare death until rewarmed to 32°C (“no one is dead until warm and dead”).
• ECG in hypothermia: look for J (Osborn) waves.