Treatment of Malignant Hyperthermia
The immediate treatment for malignant hyperthermia requires administration of dantrolene 2-3 mg/kg IV as the cornerstone of therapy, along with discontinuation of triggering agents and active cooling measures. 1
Immediate Management Algorithm
Step 1: Recognize and Stop Triggers
- Immediately discontinue all triggering agents:
- All volatile (inhalation) anesthetics
- Succinylcholine
- Hyperventilate with 100% oxygen at high flow (2-3 times normal minute ventilation)
- Declare emergency and call for help
- Switch to non-triggering anesthesia (TIVA - Total Intravenous Anesthesia)
- Inform surgeon and request termination/postponement of surgery
- Disconnect vaporizer without wasting time changing the circuit/machine 1
Step 2: Administer Dantrolene
- Give dantrolene 2-3 mg/kg IV initially (20 mg ampoules mixed with 60 ml sterile water)
- Continue with 1 mg/kg every 5 minutes until treatment goals are reached
- Treatment goals:
- ETCO₂ < 6 kPa with normal minute ventilation
- Core temperature < 38.5°C
- Obtain additional dantrolene from pharmacy/nearby hospitals (36-50 ampoules may be needed for an adult)
- Maximum dose of 10 mg/kg may need to be exceeded in severe cases 1
Step 3: Active Cooling
- Administer 2000-3000 ml of chilled (4°C) 0.9% saline IV
- Apply surface cooling:
- Wet, cold sheets
- Fans
- Ice packs placed in axillae and groin
- Use other cooling devices if available
- Stop cooling once temperature < 38.5°C 1
Supportive Measures
Monitoring
- Continue routine anesthetic monitoring (SaO₂, ECG, NIAP, ETCO₂)
- Measure core temperature continuously
- Establish good IV access with wide-bore cannulas
- Consider arterial and central venous lines, and urinary catheter
- Obtain samples for:
- Potassium
- Creatine kinase (CK)
- Arterial blood gases
- Myoglobin
- Glucose
- Check renal and hepatic function and coagulation
- Monitor for signs of compartment syndrome
- Continue monitoring for minimum 24 hours (ICU, HDU, or recovery unit) 1
Treat Specific Complications
Hyperkalemia
- Administer 50% dextrose, 50 ml with 50 IU insulin (adult dose)
- Give CaCl₂: 0.1 mmol/kg IV (e.g., 7 mmol = 10 ml for 70 kg adult)
- Consider dialysis in severe cases 1
Acidosis
- Hyperventilate to normocapnia
- Administer sodium bicarbonate IV if pH < 7.2 1
Cardiac Arrhythmias
- Amiodarone: 300 mg for adults (3 mg/kg IV)
- β-blockers (propranolol/metoprolol/esmolol) if tachycardia persists 1
Maintain Urinary Output > 2 ml/kg/h
- Furosemide 0.5-1 mg/kg
- Mannitol 1 g/kg
- IV fluids: crystalloids 1
Alternative Cooling Methods in Special Circumstances
In rare situations where dantrolene is unavailable or the response is inadequate, cardiopulmonary bypass for deep hypothermia has been successfully used to treat malignant hyperthermia 2. Intravascular cooling devices may also be effective for temperature management 3.
Post-Crisis Management
- Refer the patient to a tertiary assessment unit for malignant hyperthermia
- Before discharge, inform the patient and their GP about the suspected diagnosis and its implications for them and their family
- Patients should undergo diagnostic testing using in vitro contracture testing (IVCT) at a designated MH laboratory 1
Important Caveats
- Early recognition is critical - an unexplained progressive increase in ETCO₂ should raise suspicion for MH
- Dantrolene works by reestablishing normal myoplasmic calcium levels by inhibiting calcium release from the sarcoplasmic reticulum 4
- Dantrolene administration is not a substitute for other supportive measures
- Monitor for dantrolene-related skeletal muscle weakness, including possible respiratory depression 4
- MH can occur in patients who have previously had uneventful general anesthesia 1
By following this algorithm promptly and thoroughly, the mortality from malignant hyperthermia has decreased from 80% thirty years ago to less than 5% in recent years 5.