Pharm 21- Malignant Hyperthermia Flashcards
What is malignant hyperthermia?
Autosomally dominant disorder of skeletal muscles
Calcium that is stored in skeletal muscle is released inappropriately causing muscles to contract and stiffen simultaneously
Rhabdomyolysis
Skeletal muscle breakdown
Faulty metabolism causes what?
Hyperthermia Rhabdomyolysis Run-away hypermetabolism Acidosis Flushed skin Myoglobinuria Hypotension Death
Hematuria
Cloudy whole blood
Hemoglobinura
Only the hemoglobin gets filtered out through kidneys; urine bright red but no cells there
How soon do symptoms appear?
Within 1 hour (but can be delayed up to 12 hours)
What patient population has the most cases?
Children and young adults < 30 years old
What are some known chemical MH triggers?
Volatile Gas and Sux
What are not MH triggers?
Intravenous anesthetics (including propofol) Opiates Non-depolarizating muscle relaxants Ketamine Sedatives and tranquilizers
How many anesthetic procedures have MH?
1:5000 - 1:100,000 cases
What races does it occur?
All races and ethnicities
International Mortality data on MH ranges from what? What is this based on?
1.4% - 20.0% which appears to be based entirely on the speed of MH diagnosis and therapy initiation
Mean age of cases in US deaths
20
What has a high predictive value for increased morbidity and mortality?
“Muscular Build”
What is a major positive prognositic indicator?
Preparedness by the medical team
Specific Clinical Signs of MH
Muscle Rigidity
Dramatically increase co2 production
Rhabdomyolysis
Profound hyperthermia
Non-specific Clinical Signs of MH
Tachycardia
Tachypnea
Acidosis (respiratory and metabolic)
Hyperkalemia
MH Clinical Presentations
Fulminant MH
Masseter Muscle Rigidity (MMR)
Late onset MH
Fulminant MH
Most common; muscular rigidity extreme hyperthermia, tachycardia. Typically occurs shortly after anesthetic induction
Masseter Muscle Rigidity (MMR)
profound jaw muscle rigidity after succinylcholine administration; may be an early sign of MH
Late Onset MH
Uncommon; occurs within the first hour of anesthetic terminiaton
Patients with a history of MMR post-anesthetic induction have what percent change of having Fulminant MH during their next anesthetic?
25-30 %
What are other prognositc indicators?
Patients with muscular disorders: muscular dystrophy, myotonias, Duchennes Disease, becker’s disease, are at much greater risk of FUlminant MH and shouldn’t receive SUX
Why does MH occur?
A mutation in the ryanodine receptor gene (RYR1) in skeletal muscles affects the muscles ability to properly utilize calcium
Treatment of Acute MH ***
Immediately discontinue volatile gas anesthetics and succinylcholine administraiotn
Hyperventilate with 100% oxygen (+/- change out gas tubing)
Give 1-2 mg/kg Bicarb
Dantrolene: 2.5 mg/kg IV push PRN
Cool patient
Tx arrhythmias but don’t give Na channel blockers
Monitor coag and electrolytes
Dantrolene (Dantrium)
Blocks release of calcium from skeletal muscle’s sarcoplasmic reticulum which prevents the pathologically massive, prolonged release of calcium through the RYR1 channels which is the etiology of Fulminant MH
