What is the immediate treatment for refractory hyperpyrexia?

Immediate Treatment for Refractory Hyperpyrexia

For refractory hyperpyrexia due to malignant hyperthermia, immediate administration of dantrolene 2 mg/kg IV with rapid cooling measures is the essential first-line treatment to prevent mortality. 1, 2

Malignant Hyperthermia Management Algorithm

Step 1: Immediate Actions

• Stop all triggering agents (volatile anesthetics and succinylcholine) 1
• Hyperventilate with 100% oxygen at high flow (2-3 times normal minute volume) 1
• Call for help and declare an emergency 1
• Switch to non-triggering anesthesia (TIVA) if anesthesia must continue 1
• Disconnect vaporizers (do not waste time changing the circuit/machine) 1
• Insert activated charcoal filters on inspiratory and expiratory limbs if available 1

Step 2: Administer Dantrolene

• Give dantrolene 2 mg/kg IV immediately (mix 20 mg ampoules with 60 ml sterile water) 1
• Continue dantrolene infusions until cardiac and respiratory systems stabilize 1
• Be prepared to exceed the maximum dose of 10 mg/kg if necessary 1, 3
• Ensure adequate dantrolene supply (36-50 ampoules may be needed for an adult) 1

Step 3: Active Cooling Measures

• Administer 2000-3000 ml of chilled (4°C) 0.9% saline IV 1
• Apply surface cooling: wet cold sheets, fans, ice packs to axillae and groin 1
• Utilize other cooling devices if available 1
• Stop cooling once temperature drops below 38.5°C 1

Step 4: Treat Complications

• Hyperkalaemia:

  • Administer 50% dextrose 50 ml with 50 IU insulin (adult dose) 1
  • Give CaCl₂ 0.1 mmol/kg IV (approximately 7 mmol for a 70 kg adult) 1
  • Consider dialysis in severe cases 1

• Metabolic acidosis:

  • Hyperventilate to normocapnea 1
  • Administer sodium bicarbonate IV if pH < 7.2 1

• Cardiac arrhythmias:

  • Give amiodarone 300 mg for adults (3 mg/kg IV) 1
  • Consider β-blockers (propranolol/metoprolol/esmolol) for persistent tachycardia 1

• Maintain adequate urine output (>2 ml/kg/h):

  • Administer furosemide 0.5-1 mg/kg 1
  • Give mannitol 1 g/kg 1
  • Provide adequate fluid resuscitation with crystalloids 1

Monitoring Requirements

• Core temperature monitoring (esophageal, bladder, or pulmonary artery catheter) 2
• Continuous cardiac monitoring (ECG, blood pressure) 1
• End-tidal CO₂ monitoring 1
• Establish good IV access with wide-bore cannulas 1
• Consider arterial and central venous lines 1
• Insert urinary catheter to monitor output 1
• Laboratory monitoring: K⁺, CK, arterial blood gases, myoglobin, glucose 1
• Check renal/hepatic function and coagulation 1
• Monitor for compartment syndrome 1

Important Considerations

• Delay in commencing treatment is associated with increased mortality 1
• Monitor patient for at least 24 hours in ICU/HDU 1
• Consult with your local Malignant Hyperthermia Investigation Unit 1
• Consider peritoneal dialysis with cold dialysate in extreme cases 4

Post-Crisis Management

• Administer oral dantrolene 4-8 mg/kg/day in four divided doses for 1-3 days following the crisis 3
• If oral administration is not practical, continue IV dantrolene starting at 1 mg/kg 3
• Refer patient and family members for diagnostic testing at an MH center 1

Pitfalls and Caveats

• Do not waste time changing the anesthetic circuit/machine - simply disconnect the vaporizer 1
• Do not delay dantrolene administration while waiting for laboratory confirmation 1
• Remember that MH can occur even in patients who have had previous uneventful anesthesia 1
• Recognize that generalized muscle rigidity during an MH reaction may indicate irreversibility 1
• Avoid using 5% dextrose or acidic solutions for dantrolene reconstitution 3