Malignant Hyperthermia
Overview
- Definition: Malignant hyperthermia is a severe reaction to certain drugs used as anesthesia in surgeries and invasive procedures.
- Risk: Increased in individuals with malignant hyperthermia susceptibility (often indistinguishable from general population except for susceptibility).
- Incidence: Occurs in 1 in 5,000 to 50,000 cases on exposure to anesthetic gases.
- Mortality: Without treatment, fatal in 75% of cases; with treatment, risk reduces to 5%.
- Demographics: Men are more likely to have an episode than women.
Causes
- Trigger Agents: Volatile anesthetics (e.g., halothane) and depolarizing muscle relaxants (e.g., succinicoline).
- Genetic Susceptibility:
- At least six forms, often due to genetic mutations.
- RYRI Gene: Mutation responsible for MHS1.
- CACNA1S Gene: Mutation responsible for MHS5.
- CACNAD21 Gene: Linked to MHS3.
- Inheritance: Autosomal dominant manner (only one mutant gene copy needed).
- Other Factors: Biological stress from exercise or heat exposure, some inherited muscle diseases (e.g., central core disease).
- Pre-surgery Note: Inform doctor if family has history of susceptibility.
Symptoms
- High temperature.
- Muscle rigidity.
- Rhabdomyolysis (muscle fiber breakdown).
- Rapid heart rate and abnormally rapid breathing.
- Acidosis (increased acid level in blood and tissues).
- Increased carbon dioxide production.
Diagnosis
- Symptoms: Appear minutes or hours after anesthesia.
- Early symptoms: Muscle rigidity, fast heart rate, elevated blood CO2.
- Testing: Recommended for those with personal/family history.
- CHCT (Caffeine-Halothane Contracture Test): Tests muscle tissue response.
- Genetic Testing: Determines susceptibility.
Treatment
- Dantrolene: Only effective drug for treatment.
- Other Measures:
- Rapid cooling.
- Discontinuation of triggering agents.
- Supportive therapy for organ dysfunction and acidosis.
Ensure to inform healthcare providers about familial susceptibility to malignant hyperthermia before undergoing surgery.