🔥 Malignant Hyperthermia (MH) FULL RAPID REVIEW
⚡ Core Concept
• Genetic disorder of RYR1 receptor
• ↑ Calcium release → hypermetabolic state
• Triggered by: Succinylcholine + volatile anesthetics
🚨 EARLY vs LATE SIGNS (MOST TESTED)
| EARLY SIGNS (TEST FAVORITE) | LATE SIGNS |
|---|
↑ ETCO₂ (MOST IMPORTANT)
Tachycardia
Muscle rigidity (masseter spasm)
Respiratory acidosis
|
Hyperthermia (LATE!)
Metabolic acidosis
Hyperkalemia
Myoglobinuria
Arrhythmias
Cardiac arrest
|
❗ BIG TRAP: Fever is NOT early — ETCO₂ rise is the earliest clue
💊 DANTROLENE (HIGH-YIELD)
• MOA: ↓ calcium release from SR
• Dose: 2.5 mg/kg IV (repeat until controlled)
• Max cumulative ~10 mg/kg (or more if needed)
| Formulation | Details |
|---|
| Traditional (Dantrium/Revonto) | 20 mg/vial, requires large volume reconstitution (slow) |
| Ryanodex | 250 mg/vial, rapid reconstitution (VERY TESTABLE) |
❗ Ryanodex = FAST, LESS volume → preferred in emergency
❗ DO NOT mix with calcium channel blockers → hyperkalemia/collapse risk
⚡ TREATMENT ALGORITHM
1. STOP triggers immediately
2. 100% O₂ (high flow)
3. Dantrolene 2.5 mg/kg
4. Hyperventilate
5. Active cooling
6. Treat acidosis (bicarb)
7. Treat hyperkalemia
8. ICU monitoring
• Change circuit / remove vaporizers if possible
• Use charcoal filters if available
💀 ANESTHESIA TEST PEARLS
• Rising ETCO₂ despite ventilation = MH until proven otherwise
• Masseter spasm after succ = RED FLAG
• Hyperkalemia = lethal complication
• Myoglobinuria → kidney failure risk
🧠 QUICK TEST QUESTIONS
Earliest MH sign? → ↑ ETCO₂
Triggering agents? → succ + volatiles
Drug treatment? → dantrolene
Fastest dantrolene? → Ryanodex