View source for Malignant hyperthermia

==Background==
*Inherited disorder of skeletal muscles triggered most often by anesthesia inhalation agents, succinylcholine, heat or exercise<ref>Denborough, M. (1998) ‘Malignant hyperthermia’, The Lancet, 352(9134), pp. 1131–1136. doi: 10.1016/s0140-6736(98)03078-5</ref>
*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]]
*May have dark colored urine from myoglobinuria
*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==
{{AMS and fever DDX}}

==Evaluation==
*Core temperature
*CBC
*Chem 7
*Total CK
*PT/PTT
*ABG

==Management==
*Discontinue Triggering Agents
*100% Oxygen at High Flow
*Give [[Dantrolene]]
*Provide [[bicarbonate]] for metabolic acidosis temporization
*Actively cool the patient
*Treat any [[dysrhythmia]]
===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
*Call [https://www.mhaus.org/healthcare-professionals/ MHAUS Hotline] if needed: 1-800-644-9737 
*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

===Bicarb===
*1-2 mEQ/kg if blood gas values not yet available
===Cooling Measures===
*Most patietns will have a core temperature >39 deg C (102.2 deg F)
*Stop cooling when temperature reaches 100.4
===Dysrhythmic therapy===
*Dysrhythmias usually respond to treatment of acidosis and hyperkalemia
*AVOID CA CHANNEL BLOCKERS as they may cause hyperkalemia or cardiac arrest in presence of dantrolene
===[[Hyperkalemia]]===
*Not always present but can occur
*Treat hyperkalemia with standard treatment, remember to check glucose levels q1h after treatment with insulin/glucose

*

==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==
<references/>

==See Also==
*[[Succinylcholine]]
*[[Acute Fever (DDX)]]
*[[Toxidromes]]

[[Category:Toxicology]]