Metabolic, toxicology and environment
Malignant Hyperthermia Algorithm
Stop the trigger, dantrolene, cool
1 Recognize the crisis
- After a volatile anesthetic or succinylcholine
- Earliest sign: unexplained rise in end-tidal CO₂ despite more ventilation
- Then tachycardia, masseter or generalized rigidity, rising temperature (often late), acidosis, high potassium
2 Stop triggers and call for help
- Stop volatile agents and succinylcholine; switch to IV anesthesia
- Hyperventilate with 100% O₂ at high fresh gas flow (10 L/min); activated charcoal filters if available
- Call the MH hotline (US: 1-800-644-9737) and get the MH cart
3 Dantrolene
- 2.5 mg/kg IV rapidly; repeat until signs resolve (more than 10 mg/kg is rarely needed)
- Ryanodex: 250 mg vial in 5 mL; Dantrium/Revonto: 20 mg vial in 60 mL sterile water (many people needed to mix)
- Then 1 mg/kg every 4–6 hours for at least 24 hours
4 Treat the effects
Drugs in this algorithm
Related one-pagers
- CapnographyPatterns and causes: Gradual rise: Hypoventilation, fever; malignant hyperthermia if it climbs despite more ventilation
- Airway and RSIRSI drugs: Avoid succinylcholine with hyperkalemia, malignant hyperthermia risk, myopathy, or burns, crush, stroke or cord injury past the acute phase (risk peaks 7–10 days).
- Toxidromes and AntidotesSerotonin toxicity, NMS and malignant hyperthermia: Malignant hyperthermia is a pharmacogenetic crisis: an RYR1 variant floods muscle with calcium on exposure to a trigger. MHAUS: stop triggers, hyperventilate with 100% oxygen at 10 L/min, give dantrolene 2.5 mg/kg IV and repeat until signs resolve (more than 10 mg/kg is occasionally needed), cool above 39 °C and stop below 38 °C, treat hyperkalem
- Hypothermia, Heat Stroke and DrowningHeat illness: types, risks and look-alikes: Also consider sepsis or meningitis, thyroid storm, sympathomimetic or anticholinergic toxicity, serotonin toxicity, NMS and malignant hyperthermia (Toxidromes and Antidotes sheet).
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