Malignant Hyperthermia Lesson 4 PDF

- Malignant hyperthermia (MH) = genetic disorder of the ryanodine receptor type 1 (RYR1 gene) triggered by volatile anesthetics and depolarizing neuromuscular blockers resulting in uncontrolled calcium release and sustained muscle contraction - Hypermetabolic response -...

- Malignant hyperthermia (MH) = genetic disorder of the ryanodine receptor type 1 (RYR1 gene) triggered by volatile anesthetics and depolarizing neuromuscular blockers resulting in uncontrolled calcium release and sustained muscle contraction - Hypermetabolic response - Increased O2 consumption - Increased use of ATP increased heat - Increased production of CO2 and lactate - Cell breakdown and release of myoglobin - Increased sympathetic activity - Signs of MH - Early sign of MH = increased ETCO2 - Late sign = increased temperature - Tachycardia is almost always present during MH - Muscle rigidity may or may not be present during MH - Tachypnea or increased minute ventilation - Hot or exhausted CO2 absorbent - Myoglobinuria - DIC - Dysrhythmias - Onset can occur at any point during anesthesia or on emergence or even in the PACU - Fulminant = onset of full blown syndrome within minutes of induction of GA - Can be triggered by environment e.g. hyperthermia, stress, exercise-induced rhabdomyolysis - MH associated with central core disease, multi-minicore disease, King Denborough syndrome - Electrolyte abnormalities - Mixed respiratory and metabolic acidosis - Elevated creatinine kinase - Hyperkalemia - Hyperphosphatemia - Hypercalcemia - Abnormal coagulation tests - Immediate treatment of MH - Obtain red MH bag and vaper-clean filters - Discontinue volatile agents or succinylcholine - Hyperventilate with 100% FiO2 - Mix dantrolene 2.5 mg/kg with sterile water only - Reconstitute 250 mg/vial of dantrolene with 5 mL sterile water - Need large bore IV to prevent phlebitis - Cool the pt with cold NS fluids and ice and turn down room temperature - Treat acidosis - Treat hyperkalemia = bicarbonate, glucose/insulin, calcium for life-threatening hyperkalemia - Calcium channel blockers are contraindicated - Dantrolene or raynodex therapy must continue for days after the event to prevent recurrence - Dantrolene maintenance dose = 1 mg/kg q 4-6 hours for 24-48 hours - Why do MH patients die if we have dantrolene to treat it? - Acute mortality due to hyperkalemia and hyperthermia. - DIC, multiorgan system failure, renal failure, cerebral edema - MH is an autosomal dominant disorder = 50% chance of passing disorder to child if one parent has the mutated gene - Gold standard for diagnosing is the caffeine halothane contracture test using a muscle biopsy most commonly from the vastus lateralis - MH mimics = light anesthesia, inadequate ventilation, thyroid storm, infection/sepsis, pheochromocytoma, iatrogenic overheating, serotonin syndrome, "upper" drugs (e.g. cocaine, ecstasy, amphetamine), neuroleptic malignant syndrome, cerebral ischemia, myotonic syndromes, rhabdomyolysis, exertional heat illness - Prep of equipment for MH patients - Replace circuit and soda lime - Flush ventilator per manufacturer policy - Vapor clean filters can be used to remove volatiles from the circuit - Know where MH cart is and dantrolene - For the MH susceptible patient in an uneventful surgery, the minimum phase 1 PACU time is 1 hour with an additional hour in phase 2 is recommended