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Malignant Hyperthermia More than just… “Quick, get the ice!”. Chuck Magich, CRNA, MS University of Maryland Medical Center R Adams Cowley Shock Trauma Center Baltimore, MD October 2013. Definition of MH.

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Malignant Hyperthermia More than just… “Quick, get the ice!”


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    1. Malignant HyperthermiaMore than just…“Quick, get the ice!” Chuck Magich, CRNA, MS University of Maryland Medical Center R Adams Cowley Shock Trauma Center Baltimore, MD October 2013

    2. Definition of MH Inherited skeletal muscles disorder triggered in susceptible individuals when exposed to certain anesthetic agents resulting in: • hypermetabolism • skeletal muscle damage • hyperthermia • eventual death if untreated

    3. Background • 1962 1st MH case described (Denborough) • 1979 Dantrolene FDA approved, greatly reduces mortality • 1980’s susceptible swine prove to be most reliable animal models in study of MH • 1990’s Focus on genetics to isolate responsible gene • 2000 Properly treated, mortality still approx 10% • 2002 5 of 9 US testing centers close due to budget cuts

    4. Basic Physiology • Actin & myosin filaments • slide across each other • causes muscle shortening & contraction. • Calcium controls muscle contraction: • Contraction: Calcium released (stored in sarcoplasmic reticulum). • Relaxation: calcium’s reuptake.

    5. Pathophysiology Triggering agents (MH pt) Calcium: Massive release + Reuptake blocked Sustained muscle contraction *Ryanodine Receptor = gatekeeper Calcium release & reuptake.*

    6. Course of Events in MH Elevated Calcium Acidosis ATP depletion Hallmarks of MH: • increased CO2 production • increased O2 consumption Muscle contraction Heat Prod. (peripheral) Cellular death

    7. Causes of MH • Ryanodine receptor (RYR1) mutations responsible for majority of MH cases. • However, as many as 30 (or more 80) different mutations may be responsible for MH = (inconsistent presentation).

    8. Mode of Transmission • Autosomal dominant inheritance. • "Dominant" = only 1 mutated gene of a pair needed to posses trait. • Offspring of patient with MH have a 50% chance of inheriting the gene for MH.

    9. Incidence • Adults 1:20,000-1:50,000 • Children 1:15,000 • After puberty, males affected > females 1.5 : 1 • Geographic patterns (states with highest incidence): • West Virginia • Michigan • Wisconsin • Nebraska

    10. Mortality & Morbidity North American MH Registry • 291 MH cases (1987-2006) • 8 cardiac arrests (2.7%) • 4 died (1.4%) • Mean age = 20 y/o • Mortality higher in ambulatory setting (21%) compared to hospital cases (7%)

    11. Triggering Agents (Avoid These!!!) • All Halogenated inhalational agents: • Isoflurane • Sevoflurane • Desflurane • Halothane • Depolarizing Muscle Relaxant: • Succinlycholine (Anectine)

    12. Non-Triggers (Safe to Use) • N2O • Nondepolarizing MR • Narcotics • Benzodiazepines • Propofol • Etomidate • Barbiturates • Ketamine • Local anesthetics • ester or amide • +/- vasoconstrictors • NMB reversals • Vasoactive drugs • Catecholamines

    13. Food For Thought… • MH can occur anywhere triggers are given (ED, ICU). • MH can have delayed onset, usually presenting within 2* after triggers (PACU). • Only use triggers like succ when clearly indicated.

    14. Clinical Presentation • Unexplained tachycardia (earliest, most consistent sign, seen in 96% of cases) • Suddenly increased & rising ETCO2 (2-3X’s normal, despite adequate MV) • Muscle rigidity (75-80%) • Cyanosis (70%) • Hemodynamic instability (85%), BP initially then

    15. Clinical Presentation Less Common Signs: • Masseter muscle rigidity (50%) • Tachypnea • Rhabdomyolysis • PVC’s and VT • Exhausted CO2 absorber • Labs: • Ca, K, CPK, myoglobin, lactate • mixed venous O2 & pH • Marked temperature elevation

    16. More About Temperature… • Hyperthermia is a late & inconsistentsign!!! • If present, very specific sign! • Skin temp doesn’t adequately reflect core temp. • Can rise 1* Celsius Q 5 mins, may reach 43*C (110*F). • Cold environments may mask temp rise (large field, cold room, CPB).

    17. Temperature Monitoring Sites in order of preference: • Pulmonary artery • Distal esophagus • Nasopharynx • Tympanic • Bladder • Axilla • Forehead skin

    18. Differential Diagnosis • Thyroid storm • Pheochromocytoma • Sepsis • Light anesthesia • Drug reaction • OD – cocaine, amphetamines, ecstasy • Neuroleptic Malignant Syndrome (NMS) • CO2 insufflation during laparoscopy

    19. Clinical Management • Discontinuetriggers: • Get HELP –STAT! • Get MH cart. • Inform surgeon stop surgery! • Hyperventilate: • 3-4 x’s normal minute volume. • 100% O2 @ high flows. • via “clean” source – ambu bag. • Dantrolene: • 2.5 mg/kg rapid IV push. • repeat Q 5-30 minutes. • shortcut: approx 1 mg/lb.

    20. Management • Multiple large bore IV’s (central line) • Foley (3-way): monitor urine + active cooling • A-line to monitor BP and serial lab draws. • Monitor core temp continuously. • Bicarb 1-2 mEq/kg given empirically. • Active core cooling measures: • gastric lavage • foley irrigation • ice packs • iced (or room temp) IVF • hypothermia blanket • cold irrigation of surgical field

    21. Management • Treat dysrhythmias with usual ACLS drugs: • Ca Ch blockers absolutely contraindicated if Dantrolene given! • Dysrhythmias = tx acidosis + hyperkalemia. • Dysrhythmias = need more Dantrolene. • Treat hyperkalemia: • hyperventilation • bicarb • diuresis • dextrose + insulin(10 units regular insulin /50cc D50) • avoid parenteral potassium (LR) • Calcium chloride

    22. Management • D50 + insulin: • provides quick acting energy substrate. • Prevent myglobin induced renal failure: • non-K IVF: (cold NSS 15 ml/kg Q15 min X3). • Mannitol / Lasix: keep U/O >2 ml/kg/hr. • Alkalinize urine w/Bicarb. • Watch for and treat DIC • Check coags. • Replace clotting factors (FFP, plts, cryo). • Call MH hotline: 1-800-MH-HYPER (1-800-644-9737)

    23. Additional management points: • Treatment is labor intensive, need lots of help fast! • Objective of cooling: • decrease O2 consumption • CO2 production • Core cooling superior to surface cooling. • Titrate Dantrolene and Bicarb: • HR • temp • PaCO2 (ETCO2)

    24. Post MH Complications • DIC: results from cell destruction + death • Renal failure: myoglobin induced • Recrudescence: • 24-36 hour window • occurs in 25% of all MH cases

    25. Follow-up • ICU monitoring X 24-36*. • Dantrolene 1mg/kg IV Q4-6hrs x 24-36*. • Next oral Dantrolene X3 days. • Dantrolene continued 2* to recrudescence. • Register patient: • North American MH Registry: 1-800-986-4287. • Counsel patient &family: • Potential for MH in other family members. • Refer for testing.

    26. Dantrolene Sodium • Decreases muscle tone & metabolism. • Prevents Ca ion release + increases % bound Ca. • Direct–acting skeletal muscle relaxant. • Doesn’t work @ neuromuscular junction (NMB’s).

    27. Dantrolene • Packaged 20 mg per vial: • Reconstitute: 60 ml sterile water (injection). • Shake vigorously until clear. • Each vial contains 3 gms Mannitol: • increases solubility of drug. • Warming medication /sterile water: • Helps dissolve drug. • Dose 2.5 mg/kg rapid IV push, • Repeat Q5-30 mins (HR, ETCO2, temp). • Total dose usually <10 mg/kg (4 rounds). • One year supply costs approx $2,400

    28. Dosing: Effective does directly related to: • Individuals degree of susceptibility. • Amount & time of exposure to triggers. • Time elapsed between onset of crisis & start of Dantrolene. Example: Initial dose for 75 kg patient: 75kg x 2.5mg/kg = 188mg 188mg / 20mg per vial= 9 vials first 5 minutes of crisis!

    29. Prevention…food for thought: • 1/2 all MH episodes proceeded by 1 - 13 uneventful anesthetics! • Succinlycholine only on indication: • RSI, difficult airway, full stomach, laryngospasm. • Increased suspicion with history: • muscle cramps, heat stroke, caffeine sensitivity. • Blood relatives of MH patient should be considered MH susceptible, unless tested & negative. • MH patients should carry some form of ID • Med Alert bracelet, wallet card, etc.

    30. Screening • Best way to prevent MH: • detection prior to anesthesia. • Ask pointed questions: • Family /personal history: • MH / anesthetic problems? • Muscular / neuromuscular disorders? • Family history: • Unexpected deaths under anesthesia? • Personal history: • Dark /tea colored urine after surgery? • High fevers after anesthesia?

    31. Planning: • Training of OR + PACU personnel. • Periodic dry-runs of MH crisis. • Monitor core temp on any GA. • No reported deaths from MH in previously diagnosed MH-susceptible patients when: • Anesthesia team was aware of the problem. • Appropriate precautions taken.

    32. Planning: • Have a plan. • Portable MH cart / kit available anywhere general anesthetics administered. • Minimum: 36 vials of Dantrolene • 4 rounds average sized patient

    33. Management of the MH Susceptible Patient (MHS) • 1st case of day. • MH cart readily available & Dantrolene not expired. • Continuous monitoring: HR, ETCO2 + temp. • Prep gas machine: • Remove vaporizers & change soda lime. • Flush system with 10 lpm O2 via circuit X 20minutes (using disposable bag on end of circuit). • Replace with clean circuit & soda lime after flushing.

    34. MH Susceptible • Dantrolene pretreatment no longer routine. • +/- if documented fulminant episode. • Well planned non-trigger anesthetic more advantageous than prophylactic Dantrolene. • Nontrigger technique, 3 options: • TIVA (G/A). • Regional (spinal / epidural). • Local + sedation. • Minimum 2.5 hour PACU.

    35. Conditions Associated with MH • Central Core disease • Duchene’s muscular dystrophy • Becker’s or other forms of muscular dystrophy • Schwartz-Jampel syndrome • King-Denborough syndrome • Myotonia Congenita • Neuroleptic Malignant Syndrome *Patients with any of the above should not receive triggering agents!!!

    36. Medical-Legal Issues Common themes from MH litigation: • Failure to obtain a thorough personal history. • Failure to monitor temperature. • Failure to have adequate supplies of Dantrolene & management plan. • Failure to investigate increased temp, increased skeletal muscle tone when associated with tachycardia and dysrhythmias.

    37. 1996 Death from MH • 16 year old female • 4 hour TMJ surgery • Temperature was not monitored during the case • Precipitous rise in ETCO2 at end of case • Dysrhythmias and cardiac arrest • Temp noted to be >106*F • Dantrolene 10 mg/kg • Died 2 days later from DIC

    38. Testing • The caffeine halothane contracture test (CHCT) is the gold standard of MH diagnosis. • CHCT: • Small piece skeletal (thigh) muscle obtained (local anes). • Muscle exposed to: • caffeine & halothane separately. • Rate & force of muscle contraction recorded electronically. • MH susceptible muscle more sensitive & contracts with greater sustained force than normal muscle.

    39. CHCT • Top graph: positive for MH, showing muscle contraction after exposure to 3% Halothane. • Normal muscle (bottom). • MH + have exaggerated response to caffeine. • Cost approx $6,000-10,000. • CK not a reliable test.

    40. CHCT Sites USA: • USUHS-Bethesda, MD • UC-Davis, CA • University Minnesota, Minneapolis • Wake Forest-Winston-Salem, NC Canada: • Ottawa, Ontario • Toronto, Ontario

    41. Genetic testing • Blood test for genetic markers. • Less expensive $800-$4,000. • Insurance may not cover. • Less invasive. • Sensitivity 25-30% since only a few of the known mutations have been isolated. • Very specific if positive for one of the known mutations. • Only 2 centers in US: • Pittsburg, PA • Marshfield, WI

    42. Kids & MMR • Masseter muscle rigidity (MMR) / trismus: • Occurs after succinlycholine administration. • Forceful contraction of jaw musculature. • Prevents full mouth opening. • Extremities remain flaccid. • 1% of children receiving succinlycholine develop MMR • 50% of these have been shown to be MHsusceptible by muscle biopsy.

    43. Kids & MMR • Dantrolene need not be administered: • MMR resolves promptly. • No other clinical signs of MH. • Clinical signs of MH occur in about 20%. • What to do next??? • MMR with MH 3X’s more common in males. • MMR mostly in age ranges 4-12 y/o.

    44. Appendectomy in a 35kg, 10y/o – case study (Feb’92) • 10:30 atropine 0.3mg, Fentanyl 50 mcg premed • 10:40 Propofol 80 mg, Succ 40 mg – MMR, tachycardia, generalized rigidity • 10:55 Isoflurane 2%, Propofol 20, Atracurium 10mg – persistent spasm and tachycardia • 12:23 pH6.78, pCO2-158, pO2-414, BE-16, continued rigidity, HR180, Temp 38.4 • 13:05 pH6.88, pCO2-85, pO2-365, BE-20, temp 40.4, HR 220, cardiac arrest

    45. Kids & Succ • Sudden cardiac arrest after succ in kids should be attributed to hyperkalemia & treated as such • 40 cases since 1990 • Mortality 50%

    46. Sudden Cardiac Arrest in a Child – Case History • 5y/o male, apparently healthy • 8:00 mask induction with Halothane • 8:05 Succinlycholine 40mg • Intubated with 5.0 ET – leak • Reintubated with #5.5 • 8:06 HR 130, then v-fib, then asystole (CPR, atropine, epi, lidocaine, bretylium, shock) • 8:26 pH 6.81, pCO2 74, pO2 22, BE-21 • 11:15 dead despite 2+hour resuscitation • Autopsy: • Nectrotizing myopathy (gastroc) • CK >63,000 • Myoglobin in kidney

    47. Neuroleptic Malignant Syndrome • Very similar presentation as MH • Onset much slower (days to weeks) • Cause: typically antipsychotic & dopamine blockers: (Thorazine, Haldol, Inapsine, Reglan, Phenergan) • Problem is central in nature, MH is peripheral. • Management is drug withdrawal & symptomatic treatment. • Dantrolene can be considered. • NMS patients should not receive MH triggers

    48. 1997 Death from MH • 74 y/o male for AAA repair • Family hx of MH, confirmed by CHCT • Trigger agents used • MH episode at end of case • Treated with Dantrolene • Died 2 days post-op from DIC, renal failure and ischemic bowel

    49. Resources Malignant Hyperthermia Association of United States (MHAUS): PO Box 1069 39 East State Street Sherburne, NY 13460 1-800-98-MHAUS (non-emergency) 1-800-MH-HYPER (emergency #) http://www.mhaus.org

    50. Thanks for your attention!!!