What is the management of malignant hyperthermia?

Malignant Hyperthermia: Recognition and Management

Malignant hyperthermia is a life-threatening hypermetabolic crisis triggered by volatile anesthetic agents and succinylcholine that requires immediate cessation of trigger agents and administration of dantrolene to prevent death. 1

What is Malignant Hyperthermia?

Malignant hyperthermia is a genetic disorder of skeletal muscle cells affecting calcium homeostasis that manifests as a hypermetabolic reaction during or shortly after anesthesia. 1, 2 Any patient can develop MH when exposed to trigger agents, even those with previous uneventful anesthesia. 1

Trigger Agents

The only triggers for MH are: 1

• All volatile (inhalation) anesthetic agents (sevoflurane, desflurane, isoflurane, etc.)
• Succinylcholine

Clinical Presentation

Key signs to recognize: 1

• Masseter spasm following succinylcholine administration
• Generalized muscle rigidity
• Rapid increase in end-tidal CO₂ (EtCO₂ can rise to 60+ mmHg) 3
• Tachycardia (heart rate >190 bpm possible) 3
• Hyperthermia (can reach 41°C or higher) 3
• Hypotension
• Metabolic and respiratory acidosis
• Hyperkalemia

The clinical signs are not unique to MH, requiring pattern recognition for rapid diagnosis. 1 Temperature elevation may be a late sign. 3

Immediate Crisis Management

First Actions (Do These Simultaneously)

1. Stop all trigger agents immediately 1, 4

• Discontinue volatile anesthetics
• Disconnect the vaporizer (do not waste time changing the circuit or machine) 1

2. Hyperventilate with 100% oxygen 1, 4

• Use minute volume 2-3 times normal at high flow
• This eliminates volatile agents and addresses hypercarbia

3. Declare an emergency and call for help 1, 4

4. Switch to non-trigger anesthesia (TIVA) 1, 4

5. Inform surgeon and request termination/postponement of surgery 1, 4

Dantrolene Administration (The Definitive Treatment)

Dantrolene dosing: 1, 5

• Initial dose: 2 mg/kg IV (European guidelines) or minimum 1 mg/kg IV (FDA label)
• Mix each 20 mg vial with 60 mL sterile water 1, 5
• Repeat doses continuously until symptoms resolve 1, 5
• Maximum dose: 10 mg/kg, but may need to be exceeded 1, 5
• Obtain additional dantrolene immediately - at least 36-50 ampoules may be needed for an adult 1, 4

The effective dose depends on individual susceptibility, trigger exposure duration, and time to treatment initiation. 5 Dantrolene administration is not a substitute for supportive measures but is the specific antidote. 5

Monitoring and IV Access

Establish robust monitoring: 1, 4

• Continue routine anesthetic monitoring (SpO₂, ECG, NIBP, EtCO₂)
• Measure core temperature
• Establish wide-bore IV cannulas
• Consider arterial line, central venous line, and urinary catheter

Laboratory monitoring: 1

• Potassium (K⁺)
• Creatine kinase (CK)
• Arterial blood gases
• Myoglobin
• Glucose
• Renal and hepatic function
• Coagulation studies
• Monitor for compartment syndrome

Treatment of Specific Complications

Hyperthermia Management

Active cooling measures: 1, 4

• 2000-3000 mL chilled (4°C) 0.9% saline IV
• Surface cooling: wet cold sheets, fans, ice packs in axillae and groin
• Other cooling devices if available
• Stop cooling when temperature drops below 38.5°C 1

Hyperkalemia Treatment

Immediate interventions: 1

• Dextrose 50%, 50 mL with 50 units insulin (adult dose)
• Calcium chloride 0.1 mmol/kg IV (e.g., 7 mmol = 10 mL for 70 kg adult)
• Dialysis may be required in severe cases

Acidosis Management

Correction strategy: 1

• Hyperventilate to normocapnia
• Give sodium bicarbonate IV if pH < 7.2

Arrhythmia Treatment

Antiarrhythmic approach: 1

• Amiodarone 300 mg (3 mg/kg IV) for adults
• Beta-blockers (propranolol/metoprolol/esmolol) if tachycardia persists

Renal Protection

Maintain urinary output > 2 mL/kg/h: 1

• Furosemide 0.5-1 mg/kg
• Mannitol 1 g/kg
• Crystalloid fluids (lactated Ringer's or 0.9% saline) IV

Post-Crisis Management

Mandatory monitoring: 1, 4

• Monitor patient for minimum 24 hours in ICU, HDU, or recovery unit
• Risk of recrudescence (recurrence) exists 2

Post-crisis dantrolene: 5

• Oral dantrolene 4-8 mg/kg/day in divided doses for 1-3 days following crisis
• IV dantrolene may be used postoperatively if oral administration not practical, starting with 1 mg/kg or more 5

Family counseling and testing: 1, 4

• Refer patient and family members to regional MH center for investigation
• In vitro contracture testing (IVCT) is the diagnostic gold standard 1
• Genetic testing when indicated 1

Prevention in Susceptible Patients

Preoperative prophylaxis: 5

• Dantrolene 2.5 mg/kg IV starting 1.25 hours before anesthesia, infused over 1 hour
• OR oral dantrolene 4-8 mg/kg/day in 3-4 divided doses for 1-2 days prior to surgery
• Last oral dose given 3-4 hours before surgery with minimal water

Anesthetic preparation for MH-susceptible patients: 5

• Avoid all known triggering agents (volatiles and succinylcholine)
• Use trigger-free anesthetic technique (TIVA with propofol)
• Monitor for early clinical and metabolic signs, as attenuation rather than complete prevention is possible 5
• Have dantrolene immediately available 1

Critical Pitfalls to Avoid

Common errors that increase mortality: 2

• Delayed recognition - MH signs are nonspecific; maintain high index of suspicion 1
• Delayed dantrolene administration - early treatment is essential for survival 1, 6, 7
• Inadequate dantrolene dosing - continue until symptoms resolve, may need >10 mg/kg 1
• Premature discontinuation of monitoring - observe minimum 24 hours for recrudescence 1
• Failure to refer for diagnostic testing - family members may be at risk 1
• False reassurance from previous uneventful anesthesia - MH can occur at any exposure 1

The mortality from MH has increased in recent years, emphasizing the need for vigilance and preparedness. 2