Malignant Hyperthermia DR. VERED DVIR

Intro 1: Pediatric Patients 1:40000 – Adult Patients Most of the cases have been reported in young males Genetic hypermetabolic muscle disease Signs and symptoms appear with exposure to inhaled general anesthetics or succinylcholine The upper Midwest appears to have the greatest incidence of MH in the USA. Mortality rate for MH is 5-30%

Drugs know to trigger MH Inhaled general anesthetics Ether Halothane Methoxyflurane Enflurane Isoflurane Desflurane Sevoflurane Depolarizing muscle relaxants succinylcholine

Biochemical Causes Sudden release of CA + from sarcoplasmic reticulum The release of CA + removes the inhibition of troponin Sustained muscle contraction Uncontrolled increase in aerobic and anaerobic metabolism Increase in O 2 consumption Increase in CO 2 production Lactic acidosis and hyperthermia

Genetics Cases Most patients with episode of MH have history of relatives with similar episode Gene for ryanodine receptor on chromosome 19, ( Ion channel responsible for calcium release from SR) Today generic testing screens for less than 20% of recognized mutations)

Clinical Manifestations Masseter muscle rigidity (MMR) Hypercarbia Tachycardia Arrhythmias Hypertension Hyperthermia Dark colored urine reflects myoglobinemia and myoglobinuria

Signs of malignant Hyperthermia Markedly increased metabolism CO 2 production Oxygen consumption Venous oxygen saturation Metabolic acidosis Cyanosis Increased Sympathetic activity Tachycardia Hypertension Arrhythmias Muscle Damage Masseter spasm Generalized rigidity Serum creatine kinase Hyperkalemia Hypernatremia Hyperphosphatemia Myoglobinemia Myoglobinuria Hyperthermia Fever Sweating

Complications ARF DIC Cerebral edema with seizures Hepatic failure

Treatment Discontinue the triggering agent Call for help, notify the surgeon Hyperventilation with 100% oxygen Administer 2.5mg\kg dantrolene I.V. Administer bicarbonate Cooling Measures Treat severe hyperkalemia Administer antiarrhythmic agents, vasopressors and inotropes Administer Furosemide

Isolated MMR Occurs in only 15-30% of true MH episodes Less then 50% of patients in whom MMR develops prove to be susceptible to MH by muscle testing At the past elective surgery was postponed Today elective surgery is allowed using safe anesthetic agents and serum CK should be followed for 24h after an episode of MMR