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Malignant hyperthermia
From WikEM
Contents
Background
- Inherited disorder of skeletal muscles triggered most often by anesthesia inhalation agents, succinylcholine, heat or exercise[1]
- Results in hypermetabolism, skeletal muscle damage, hyperthermia, and death if not treated quickly
- GENERALIZED rigidity NOT always present; if it occurs, MH is almost certain
Likelihood of Complications
- Increased time from 1st sign to 1st dantrolene
- For every 30 minute increase in the interval, complication likelihood increases x 1.6
- Increased maximal temperature
- For every 2°C increase in max temp, complication likelihood increases x 2.9
Clinical Features
- Muscle contraction
- Fever
- First signs
- Hypercarbia
- Sinus tachycardia
- Masseter spasm
- Temperature abnormalities (may be early)
- Most common pattern
- Respiratory acidosis and muscular abnormalities
Presentations
- 99% Respiratory Acidosis
- 26% Metabolic Acidosis
- 80% Muscular Abnormalities
Watch for it with succinylcholine use.
Types
- Fulminant MH
- muscle rigidity, high fever, increased HR shortly after induction of anesthesia
- Masseter muscle rigidity
- jaw muscle rigidity after succinylchoine
- More common in children
- Presages MH in 20-30% cases
- All patients demonstrate elevated CK and often gross myoglobinuria
- CK >20,000IU = high likelihood of MH
- Late onset MH
- Uncommon, may begin shortly after anesthesia termination (usually within first hour)
Differential Diagnosis
Altered mental status and fever
- Infectious
- Sepsis
- Meningitis
- Encephalitis
- Cerebral malaria
- Other
- Neuroleptic malignant syndrome
- Serotonin syndrome
- Malignant hyperthermia
- Sympathomimetic toxicity (cocaine, amphetamine, ketamine)
- Anticholinergic toxicity
- Heat stroke
- Delirium tremens
- Hypothalamic stroke
- Pheochromocytoma
- Thyroid storm
Evaluation
- Core temperature
- CBC
- Chem 7
- Total CK
- PT/PTT
- ABG
Management
- Initial
- Declare MH Emergency: (call OR for anesthesia to bring MH cart)
- Discontinue Triggering Agents
- 100% Oxygen at High Flow
- Give Dantrolene
- Designate 2 or 3 people to mix sterile water into Dantrolene \
- 60ml sterile water into each vial of dantrolene; may need up to 36 vials
- If using Dantrium® (20mg/vial), each vial contains 3 g of mannitol (renal vasodilation); newer nanocrystalline dantrolene (250mg/vial) has 250mg mannitol per vial and requires mannitol supplementation
- 2.5mg/kg IV push
- Titrate to effect; may need more than 10mg/kg
- Designate 2 or 3 people to mix sterile water into Dantrolene \
- Bicarb for metabolic acidosis
- 1-2 mEQ/kg if blood gas values not yet available
- Cool the patient if core temperature >39 deg C (102.2 deg F)
- Stop cooling when temperature reaches 100.4
- Dysrhythmias usually respond to treatment of acidosis and hyperkalemia
- Standard therapy EXCEPT NO CA CHANNEL BLOCKERS:
- may cause hyperkalemia or cardiac arrest in presence of dantrolene
- Standard therapy EXCEPT NO CA CHANNEL BLOCKERS:
- Treat hyperkalemia: standard treatment, remember to check glucose levels q1h after treatment with insulin/glucose
- Call MHAUS Hotline if needed: 1-800-644-0737
- Continued Care
- Dantrolene 1mg/kg every 4-6 hours for 24–48 hours
- Monitor for recrudescence (rate is 25%)
- Follow electrolytes, blood gases, CK, core temperature, urine output and color, coagulation studies
Prognosis
Stable to Transfer Criteria
- ETCO2 is declining or normal
- HR is stable or decreasing
- No ominous dysrhythmias
- Temperature is declining
- Generalized muscular rigidity is resolving (if present)
- IV dantrolene administration has begun
Complications
- Consciousness Level Change/Coma
- Cardiac Dysfunction
- Pulmonary Edema
- Renal Dysfunction
- Disseminated Intravascular Coagulation
- Hepatic Dysfunction
- Relapse
- Death
References
- ↑ Denborough, M. (1998) ‘Malignant hyperthermia’, The Lancet, 352(9134), pp. 1131–1136. doi: 10.1016/s0140-6736(98)03078-5
