Is hyperthermia in this case considered a severe reaction?

Hyperthermia in Malignant Hyperthermia: Severity Assessment

In malignant hyperthermia (MH), a core temperature above 38.5°C is considered a severe reaction requiring immediate intervention with dantrolene and active cooling. 1

Understanding Temperature in Malignant Hyperthermia

• Hyperthermia is a cardinal sign of MH, though it typically appears after increased end-tidal CO2 (ETCO2) and tachycardia in the progression of an MH reaction 2
• Temperature increase that begins before any evidence of increased carbon dioxide production is not caused by an MH reaction, though MH can occur in patients who are already pyrexial 1
• The treatment goal for core temperature in MH is to reduce it below 38.5°C, indicating this is the threshold considered clinically significant 1

Why Hyperthermia is Considered Severe in MH

• Elevated body temperature enhances muscle cell calcium release and sensitizes myofilaments to calcium effects, causing:
  • Generalized muscle rigidity 1
  • Compromised perfusion 1
  • Impaired delivery of dantrolene to affected tissues 1
• Hyperthermia in MH is different from fever, as it represents an unregulated rise in temperature due to hypermetabolism rather than a defended thermoregulatory setpoint 3
• Hyperthermia contributes to multiple severe complications of MH:
  • Rhabdomyolysis and myoglobinuria 1
  • Disseminated intravascular coagulopathy 1
  • Compartment syndrome 1
  • Metabolic acidosis and electrolyte disturbances 4, 5

Management Implications

• When core temperature exceeds 38.5°C in suspected MH, immediate active cooling should be initiated alongside dantrolene administration 1
• Dantrolene dosing should continue until treatment goals are achieved, including core temperature below 38.5°C 1
• If dantrolene was required to reverse the MH reaction, the patient should be monitored in a high dependency unit or ICU for at least 24 hours after the event 1
• Even after initial treatment, temperature must continue to be monitored as recrudescence of MH is well-described, with likelihood and severity related to the severity of the initial episode 1

Clinical Considerations

• Hyperthermia in MH differs from therapeutic hyperthermia, which is controlled and used for specific medical treatments 6
• Unlike fever, hyperthermia in MH will not respond to antipyretics and requires specific treatment with dantrolene and active cooling 3
• Elevated temperature in critically ill patients is associated with poor outcomes in multiple conditions, making prompt recognition and treatment of MH-related hyperthermia crucial 7
• The combination of hyperthermia with other MH signs (increased ETCO2, tachycardia) should trigger immediate MH protocol implementation 2

In conclusion, hyperthermia above 38.5°C in the context of suspected malignant hyperthermia represents a severe reaction requiring immediate and aggressive treatment to prevent life-threatening complications.