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Malignant Hyperthermia

Malignant Hyperthermia. Malignant Hyperthermia. Is an inherited disease Is an autosomal dominant trait-only 1 parent can carry the trait to pass on disease to child In most cases, MH is caused by defect in the ryanodine receptor. . MH Affects. Humans Certain pig breeds-autosomal recessive

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Malignant Hyperthermia

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  1. Malignant Hyperthermia

  2. Malignant Hyperthermia • Is an inherited disease • Is an autosomal dominant trait-only 1 parent can carry the trait to pass on disease to child • In most cases, MH is caused by defect in the ryanodine receptor.

  3. MH Affects • Humans • Certain pig breeds-autosomal recessive • Dogs • Horses • And other animals

  4. Support Group • WWW.MHAUS.ORG • 1-800-644-9737-Hotline for Medical Professionals • Caffeine Halothane Contracture Test- “Gold Standard” for determining if patient is at risk for MH

  5. MHAUS Recommendations • Should have 36 vials of Dantrolene available for MH crisis • Glucose, insulin, and calcium should be available to treat hypercalemia, bicarb to treat metabolic acidosis and diuretics to maintain urine output.

  6. Diagnostic Test Available • Muscle Contracture Test: Caffeine Halothane Contracture Test (CHCT) • Genetic Testing (Ryanodine Receptor [RYR1] gene sequencing

  7. Muscle Contracture Testing • Gold Standard • Cost $6-10K • 30 Approved Centers in World, 6 in US-Must be performed at an approved MH Muscle Biopsy Center • Requires 3-4 inch muscle biopsy taken from thigh, patient receives general anesthesia, but no local at biopsy site. • Abnormally high levels or contractile force indicate MH suceptibility • Close to 100% accuracy, false negatives are rare.

  8. Genetic Testing • Involves isolation of DNA from patient (blood, muscle cells, or other tissue sample) • RYRI (ryanodine receptor) found, there are currently 29 MH causative RYRI mutations. • Presence of causative mutation in RYRI gene is diagnostic for MH susceptibility. • Sensitivity based on population selected and methodology of testing utilized. • Cost: $800-4000K, some insurance companies may pay for genetic testing.

  9. Genetic TestingPros • Pros Less expensive than muscle biopsy testing Less invasive than muscle biopsy testing No need to travel to an approved center If causative mutation found in family member, other members can have predictive testing carried out with high degree of accuracy, without need for muscle biopsy.

  10. Genetic Testing Cons • Absence of causative mutation does not rule out MH susceptibility. • Muscle contracture test would be needed to confirm the individual is not susceptible to MH. • Expensive • Insurance may not cover testing expenses.

  11. Unsafe Drugs • Depolarizing muscle relaxants • Potent inhalational agents (halothane, isoflurane, • Enflurane, desflurane, sevoflurane)

  12. Safe Drugs • Antibiotics • Antihistamines • Antipyretics • Barbiturates (thiopental methoexital) • Droperidol • Ketamine (inherent circulatory effects may mimic MH) • Local anesthetics (lidocaine, bupivacaine) • Nitrous oxide • Nondepolarizing muscle relaxants(pancuronion, • Rocuronium, vecuronium) • Opioids (morphine, mepiridine) • Propofol • Propranolol • Vasoactive drugs

  13. Clinical Manifestations of MH • Hypercarbia (most sensitive indicator of MH in OR) • Tachycardia • Tachypnea • Temperature elevation (usually late sign of MH) • Hypertension • Cardiac dysrhythmias • Acidosis • Hypoxemia • Hyperkalemia (should be considered 1st in cardiac • Arrest) • Skeletal muscle rigidity (most specific sign) • Myoglobinuria

  14. Treatment for MH • 1. Call for assistance, management is involved, • Difficult for one person. • 2. Stop triggering agents! • 3. Hyperventilate patient with 100% 02. • 4. Finish or abort surgical procedure. • 5. Adminster Dantrolene (2.5 mg/kg bolus; • May repeat 2 mg/kg every 5 minutes, then 1-2 mg/kg/h) • 6. Cool patient with cold IV NS, cold body lavage, • Cold NG lavage, cooling blankets. • 7. Change to a clean circuit not exposed to volatile • Agents. • 8. Monitor/treat acidosis, monitor ABG’s and administer sodium bicarbonate. • 9. Promote urine output (lasix, mannitol) • 10. Treat hyperkalemia • 11. Treat dysrhythmias with procainamide and • Calcium chloride. • 12. Monitor creatinine kinase, urine myoglobin, and • Coags for 24-48 hours.

  15. Antidote for MH • Dantolene • FDA approved in less than 7 months • Is a proven skeletal muscle relaxant, inhibiting the release of calcium from the sarcoplasmic reticulum in skeletal muscle. • IV administration used in most major countries around the globe. • Dantrolene has dramitically reduced mortality from MH.

  16. Mortality Rates • Within 30 years, 80% mortality rate has dropped to less than 5% today!

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