Thermal Emergencies: Causes, Diagnosis, and Management

Hyperthermia: Causes, Diagnosis, and Treatment

Causes of Hyperthermia

The body's normal temperature is controlled by the Hypothalamus, which maintains thermal homeostasis. Hyperthermia occurs when the thermoregulatory mechanism is overwhelmed by:

1. Increased environmental heat or strenuous exercise.
2. Increased heat production by the body (e.g., metabolic disorders).
3. Decreased heat emission or impaired thermoregulation.

Diagnosis (Dx) of Hyperthermia

I. Clinical Features (CF)

• Sweating (may be absent in severe heatstroke)
• Central Nervous System (CNS) changes (e.g., confusion, delirium)
• Tachycardia
• Pupillary changes

II. Instrumental and Laboratory Tests

• Body Temperature Measurement (Core temperature is essential)
• ECG: May show QRS widening or Osborn waves.
• Blood Tests:
  • Complete Blood Count (CBC)
  • Creatine Kinase (CK)
  • Calcium Level
  • International Normalized Ratio (INR)
• Urine Test (Specific Gravity and Protein)
• Imaging: Chest X-ray or Head CT (if CNS changes are severe or etiology is unclear)

Treatment (Tx) of Hyperthermia

Immediate action is critical; do not wait for laboratory results. The goal is to cool the patient rapidly until the core temperature is below 38.8°C (101.8°F).

A. Stabilization and Cooling Protocol

1. Secure the airway and administer high-flow oxygen.
2. Remove all clothing immediately.
3. Initiate Cooling Techniques:
   • Evaporative Cooling (considered the best method).
   • Ice Packs (applied to neck, axillae, and groin).
   • Cold Gastric or Peritoneal Lavage (invasive, used in refractory cases).
4. Administer 1–2 liters of intravenous saline solution (crystalloids).

B. Medications

• Lorazepam: 2–5 mg IV (for agitation or muscle rigidity).
• Phenytoin: 20 mg/kg IV for seizures.
• Oral Glucose: Administer if hypoglycemia is suspected or confirmed.

Hypothermia: Clinical Presentation and Management

Diagnosis (Dx) of Hypothermia

I. Clinical Features (CF)

• Confusion and Agitation (early stages)
• Decreased Heart Rate (Bradycardia)
• Decreased Blood Pressure (Hypotension)
• Arrhythmias
• Coma (severe stages)

II. Diagnostic Tests

• Accurate Core Temperature Measurement (using a low-reading thermometer).
• Blood Tests:
  • Urea and Creatinine
  • Electrolytes
  • Glucose
  • Thyroid function tests
  • Amylase
• ECG: May show J waves (Osborn waves) and wide QRS complexes.

Treatment (Tx) of Hypothermia

1. Follow the ABCDE protocol (Airway, Breathing, Circulation, Disability, Exposure).
2. Remove wet clothing and initiate slow rewarming (approximately 0.5°C per hour) to prevent complications.
3. Provide humidified and warmed oxygen.
4. Continuous cardiac monitoring is essential due to arrhythmia risk.
5. Assess for and prevent pneumonia.
6. Insert a urinary catheter to monitor renal function.

Note on Immersion Hypothermia: If hypothermia results from immersion (e.g., cold water), rapid temperature increase may be necessary, depending on the clinical scenario and severity.

Complications of Thermal Emergency Treatment

Complications of Hypothermia Rewarming

1. Acidosis:
   • Rewarming causes peripheral vasodilation, leading to the return of cold, lactic acid-rich blood from the periphery to the core circulation.
   • This influx results in a reduction in core pH.
2. Rewarming Shock:
   • As warming and vasodilation progress, the body is unable to maintain blood pressure (BP) due to low effective blood volume (relative hypovolemia caused by widespread vasodilation).
3. Afterdrop (Deep-ended Hypothermia):
   • The core temperature drops further initially as cold peripheral blood returns to the core.
4. Dysrhythmia:
   • Rewarming places additional stress on the myocardium, increasing the risk of cardiac arrhythmias.
5. Hyperglycemia:
   • Insulin function is impaired when the core temperature is below 32°C (89.6°F).

Prevention of Rewarming Complications

• Use slow rewarming (approximately 0.5°C per hour).
• Continuously monitor BP, pulse, temperature, and respiratory rate (RR).

Complications of Hyperthermia Treatment

Complications arise primarily due to overly rapid cooling, which can induce peripheral vasoconstriction, paradoxically preventing effective heat loss from the core.

1. Frostbite: Can occur if ice packs or cold applications are used improperly or excessively, leading to localized tissue damage.