What is the appropriate intravenous treatment for malignant hypothermia?

Treatment of Malignant Hyperthermia

The appropriate treatment of malignant hyperthermia is intravenous dantrolene, which should be administered as soon as malignant hyperthermia is recognized at an initial dose of 2-3 mg/kg based on actual body weight. 1, 2

Initial Management Algorithm

1. Recognize MH and discontinue triggering agents

   • Stop all volatile anesthetics and succinylcholine immediately
   • Administer 100% oxygen 3

2. Administer dantrolene sodium

   • Initial dose: 2-3 mg/kg IV based on actual body weight 1, 2
   • Administer each syringe as soon as it is reconstituted, don't wait to prepare the full dose 1, 2
   • Continue giving additional doses of 1 mg/kg until treatment goals are achieved 1
   • Although the product data sheet mentions a maximum cumulative dose of 10 mg/kg, this can be exceeded if necessary for symptom control 1, 3

3. Implement supportive measures

   • Aggressive body cooling (especially in severe cases) 1, 2
   • Hyperventilation to manage respiratory acidosis 1
   • Monitor core temperature, arterial blood pressure, and obtain blood samples 1

Treatment Goals

Monitor for these specific targets to determine treatment effectiveness:

• ETCO₂ < 6 kPa with normal minute ventilation
• Core temperature < 38.5°C
• Stabilization of heart rate
• Resolution of muscle rigidity 1, 2

Management of Complications

1. Acidosis

   • Primary management through hyperventilation
   • Low threshold for sodium bicarbonate administration 1

2. Hyperkalaemia

   • Treat with sodium bicarbonate and/or glucose (50 ml 50%) with insulin (10 units)
   • Important caveat: Intravenous calcium should only be used in extremis, as it may contribute to calcium overload in the myoplasm 1

3. Myoglobinuria

   • Target urine output > 2 ml/kg/h
   • Consider sodium bicarbonate for urine alkalinization 1

4. Disseminated intravascular coagulopathy

   • Empirical treatment with platelets, fresh frozen plasma, and cryoprecipitate
   • Note: Tranexamic acid is not indicated 1

Post-Crisis Management

• Monitor for recrudescence, which occurs in 10-15% of cases 1, 2
• If recrudescence occurs within 6 hours of initial treatment, administer 1 mg/kg
• If recrudescence occurs more than 6 hours after initial treatment, administer 2-3 mg/kg 1, 2
• Continuous infusion is not recommended due to high risk of thrombophlebitis 1, 2

Availability Requirements

Dantrolene should be available wherever volatile anesthetics or succinylcholine are used, with a recommended stock of:

• 36 vials (720 mg) immediately available
• Additional 24 vials (480 mg) accessible within 1 hour 1, 2

Important Considerations

• Dantrolene dosing should be based on actual body weight, even in obese patients 1, 2
• The same weight-based dosing applies to children 1, 2
• Traditional dantrolene formulation requires 60 ml of sterile water for reconstitution 2, 3
• Side effects include muscle weakness, visual symptoms, dizziness, and fatigue, but these do not outweigh the life-saving benefits 2

The evidence clearly demonstrates that prompt administration of dantrolene has dramatically reduced mortality from malignant hyperthermia from approximately 80% to less than 10% 4. Delays in dantrolene administration are associated with increased complications, making immediate availability and rapid administration critical for patient survival.