What is the first action for intraoperative malignant hyperthermia?

First Action for Intraoperative Malignant Hyperthermia

The first action for intraoperative malignant hyperthermia is to immediately stop all trigger agents, including volatile anesthetic agents and succinylcholine. 1

Immediate Management Algorithm

When malignant hyperthermia (MH) is suspected during anesthesia, the following actions should be taken in sequence:

1. Stop all trigger agents immediately

   • Discontinue all volatile inhalation anesthetic agents 1
   • Disconnect the vaporizer - do not waste time changing the entire circuit/anesthetic machine 1

2. Hyperventilate with 100% oxygen

   • Use a minute volume 2-3 times normal with high flow 1
   • This helps eliminate volatile anesthetics and address hypercarbia 1

3. Declare an emergency and call for help 1

4. Change to non-trigger anesthesia (TIVA - Total Intravenous Anesthesia) 1

5. Inform the surgeon and request termination/postponement of surgery 1

Dantrolene Administration

After the initial steps above, dantrolene should be administered promptly:

• Give dantrolene 2 mg/kg IV (20 mg ampoules mixed with 60 ml sterile water) 1, 2
• Obtain additional dantrolene from pharmacy/nearby hospitals - at least 36-50 ampoules may be needed for an adult patient 1
• Repeat dantrolene infusions until cardiac and respiratory systems stabilize 1
• Maximum dose may exceed 10 mg/kg if necessary 1, 2

Additional Critical Interventions

• Monitoring: Continue routine anesthetic monitoring (SaO₂, ECG, NIAP, ETCO₂) and measure core temperature 1
• Establish IV access: Place good IV lines with wide-bore cannulas 1
• Treat hyperthermia: Administer 2000-3000 ml of chilled (4°C) 0.9% saline IV and apply surface cooling 1
• Treat hyperkalemia: Administer dextrose 50%, 50 ml with 50 IU insulin (adult dose) and CaCl₂ if needed 1
• Treat acidosis: Hyperventilate to normocapnia and give sodium bicarbonate IV if pH < 7.2 1

Early Recognition Signs

Early recognition is crucial for survival. Key signs to watch for include:

• Unexplained increase in end-tidal CO₂ despite increased minute ventilation 3
• Tachycardia and tachypnea 4
• Masseter spasm if succinylcholine has been used 1
• Generalized muscle rigidity 1
• Hyperthermia (may be a late sign) 4

Common Pitfalls and Caveats

• Do not waste time changing the entire anesthetic circuit - simply disconnect the vaporizer 1
• Do not delay dantrolene administration while waiting for laboratory confirmation 2, 5
• Recurrence is possible - monitor the patient for a minimum of 24 hours in ICU/HDU 1
• Dantrolene preparation takes time - each 20 mg vial must be reconstituted with 60 ml of sterile water 2, 5
• Avoid 5% Dextrose Injection or other acidic solutions for dantrolene reconstitution as they are incompatible 2

Post-Crisis Management

• Monitor the patient for a minimum of 24 hours in ICU/HDU 1
• Continue dantrolene 4-8 mg/kg/day in four divided doses for 1-3 days to prevent recurrence 2
• Refer the patient and family to a regional MH center for investigation 1
• Arrange for diagnostic testing using in vitro contracture testing (IVCT) 1

The European Malignant Hyperthermia Group (EMHG) guidelines emphasize that early recognition and immediate treatment are essential for patient survival, with stopping trigger agents being the critical first step in management 1.