🌡️ Chapter 98: Temperature Instabilities in PICU

Hypothermia · Hyperthermia · Fever vs. Hyperthermia · Malignant Hyperthermia · Neuroleptic Malignant Syndrome · Rewarming strategies · Heat stroke · Isolation precautions & temperature measurement

🔍 Core Concepts: Temperature Instabilities in PICU

📌 Children vs adults
Higher BSA/weight ratio, less fat, poor glycogen stores → hypothermia ominous. Fever common but hypothermia more dangerous in infants.
🌡️ Definitions
Normothermia 35.5–37.5°C. Hypothermia <35°C (mild 32-35, moderate 28-32, severe <28). Fever = hyperthermia due to set point elevation (>38.3°C). Hyperpyrexia ≥40°C, life-threatening if ≥41.5°C.
🧊 Hypothermia causes
Increased loss (trauma, burns, post-op), decreased metabolism (hypothyroidism), impaired regulation (CNS injury, sepsis, drugs). Therapeutic hypothermia for neuroprotection post-cardiac arrest.
🔥 Hyperthermia syndromes
Heat exhaustion → weakness, sweating, hypotension. Heat stroke → core >40°C, dry skin, CNS changes, DIC, MODS (mortality 70% if untreated).
⚠️ Neuroleptic malignant syndrome (NMS)
Antipsychotics (haloperidol, risperidone) → fever, lead-pipe rigidity, autonomic instability. Tx: stop drug, supportive, dantrolene? controversial.
💥 Malignant hyperthermia (MH)
Inhalational anesthetics + succinylcholine → hypermetabolism, rigidity, hypercapnia, fever. Tx: dantrolene 1-2 mg/kg, cooling, avoid triggers.
🩺 Measurement & documentation
Gold standard: pulmonary artery. PICU: esophageal (lower 1/3) or bladder (thermistor). Document site (tympanic/rectal) without adjusting numbers.
📈 Rewarming principles
Passive (mild hypo): warm environment, insulation. Active external (forced air). Active internal (warm IV, humid O2, lavage). Avoid afterdrop, rewarming acidosis.

🩺 Stepwise Approach: Temperature Instability

1
Assess & stabilize ABCs
Secure airway, breathing, circulation. Severe hypo/hyperthermia may cause arrhythmias, shock. Obtain core temperature (esophageal/bladder).
2
Identify etiology: Hypothermia vs Hyperthermia
Hypothermia: environmental exposure, sepsis, endocrine, drugs. Hyperthermia: infection (fever), heat stroke, NMS, MH, thyrotoxicosis.
3
Hypothermia management algorithm
Mild (32-35°C): passive rewarming (warm blankets, remove wet clothes). Moderate (28-32°C): active external (forced air Bair Hugger). Severe (<28°C): active internal (warm IV fluids 43°C, warm humid oxygen, peritoneal/pleural lavage, ECMO). Avoid afterdrop.
4
Hyperthermia (fever) workup
Treat underlying infection, antipyretics if febrile. For heat stroke: rapid cooling (tepid water + fan, ice packs axilla/groin, target 38.9°C). IV fluids, monitor for DIC, rhabdo, renal failure.
5
Suspected NMS or Malignant Hyperthermia
NMS: stop antipsychotics, supportive care, consider dantrolene (controversial). MH: dantrolene 1 mg/kg IV bolus repeated up to 10 mg/kg, 100% oxygen, cooling, correct acidosis, avoid trigger agents. Send CK, urine myoglobin.
6
Continuous monitoring & prevention
Temperature q15-30min during active rewarming/cooling. Monitor for dysrhythmias, coagulopathy. Prevention: maintain normothermia post-op, avoid overbundling, early recognition of drug-induced syndromes.