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  1. 1. MALIGNANT HYPERTHERMIA Greg Gordon MD February 2005
  2. 2. MH MH Malignant Hyperthermia Objectives Things to know and do: Participants will: 1. be able to explain the: pathophysiology, clinical presentations, testing for and management of malignant hyperthermia and the MHS patient 2. be able to explain the significance of MMR and its management. 3. keep MH somewhere in mind as they monitor patients, and not hesitate to give dantrolene. 4. easily correctly answer the questions in the MH Quiz .
  3. 3. MH MH “ If any institution does not feel it can manage the MHS child then they should not be anaesthetising any children at all, since it is not the identified child with a nontriggering technique who will cause grief, but the undiagnosed child given a trigger.” Helen Holtby M.B.,B.S. Director of Cardiovascular Anaesthesia Hospital for Sick Children Toronto, Canada PAC List, 10 Dec 04 Malignant Hyperthermia
  4. 4. MH MH pharmacogenetic hypermetabolic state of skeletal muscle induced by inhalational anesthetics or succinylcholine (and maybe stress/exercise)
  5. 5. MH MH Drugs + Genes = Pharmacogenetic
  6. 6. MH MH Historical MH 1960 Denborough and Lovell 1960’s families and pigs Gordon (?) calls it Malignant Hyperthermia 1975 dantrolene saves pigs 1979 FDA approves dantrolene 1980’s muscle biopsy for HCCT 1990’s genetic markers/RYR1
  7. 7. MH MH halothane enflurane isoflurane desflurane sevoflurane
  8. 8. MH MH 200,000 1 (without sux)
  9. 9. MH MH SUX
  10. 10. MH MH 60,000 1 (with sux)
  11. 11. Incidence - Current Concepts Clinically based information: One in 20,000 to 50,000 anesthetics depending on drugs, population Molecular Genetics based information: MH trait in 1 in 2,000-3,000 patients. Low penetrance
  12. 12. MH MH
  13. 13. MH MH Normal excitation-contraction coupling ACh at NMJ depolarizes sarcolemma SR (RYR) releases Ca Ca + troponin actin-myosin slide ATP hydrolyzed SR (RYR?) re-uptake of Ca
  14. 14. MH MH
  15. 15. MH MH RYR1 ryanodine receptor Ca release channel protein (5,032 amino acids) connects SR to T-tubules Ca gate from SR chromosome 19, region 13.1
  16. 16. MH MH Excitation-contraction coupling in MH Defective RYR Ca release channel Too much free intracellular calcium
  17. 17. MH MH Too much free Ca ATP depletion lactic acidosis VO 2 way up Too much CO 2 myonecrosis/rhabdomyolysis/ ↑↑ K myoglobinemia/uria/renal failure
  18. 18. MH MH Diagnosis of MH tachycardia + tachypnea + ETCO 2 increasing + metabolic acidosis = MH = dantrolene IV
  19. 19. MH MH HCCT for MH vastus muscle 2-3 months after MH episode nontriggers no dantrolene gentle handling of muscle test within 5 hours About $6,000
  20. 20. Guidelines for Molecular Genetic Testing <ul><li>Determine MHS by HCCT </li></ul><ul><li>If MH positive , screen for known mutation </li></ul><ul><li>If mutation positive, </li></ul><ul><ul><li>test other family members for the mutation </li></ul></ul><ul><li>If mutation negative, </li></ul><ul><ul><li>cannot screen family for mutations or determine MH status </li></ul></ul>
  21. 21. MH MH Treatment of an acute episode of MH Stop triggers 100% oxygen 10L/min Dantrolene 3 mg/kg To 10 mg/kg Rx metabolic acidosis, HCO 3 Cool, iced NS IV Rx dysrhythmias, hyperkalemia Monitor ETCO 2 , ABGs, K, UOP, clotting tests
  22. 22. MH MH verapamil + dantrolene = severe hyperkalemia + myocardial depression
  23. 23. MH MH dantrolene
  24. 24. MH MH 5 year-old boy for T&A halothane induction succinylcholine jaw “stiff” for 3 minutes then relaxed
  25. 25. MH MH
  26. 26. MH MH Masseter muscle rigidity (MMR) amyotonic mytonia temporomandibular joint (TMJ) dysfunction not enough succinylcholine not enough time
  27. 27. MH MH The stiff jaw subclinical: normal interferes with intubation: 1-3% of children “ jaws of steel”: true MMR 50% MHS Kaplan
  28. 28. MH MH MMR Rosenberg cancel elective dantrolene 1-2 mg/kg observe overnight (myoglobinuria, fever, hyperkalemia, CPK) muscle biopsy strongly considered
  29. 29. MH MH MMR Gordon AVOID SUX
  30. 30. MH MH Malignant hyperthermia susceptible (MHS) patient A safe plan prepare to treat MH use safe drugs be happy
  31. 31. MH MH preop for T&A needles terrify her history of hernia repair: fever and stiff jaw went for muscle biopsy: normal 7 year-old girl
  32. 32. MH MH Malignant hyperthermia susceptible (MHS) patient A safe plan prepare to treat MH use safe drugs be happy
  33. 33. MH MH MHAUS Malignant Hyperthermia For more information Lesson Quiz
  34. 34. MH MH