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Malignant Hyperthermia

Malignant Hyperthermia. Malignant Hyperthermia. Definition : a metabolic disease of the muscle, a hypermetabolic state caused by exposure of susceptible individuals to known trigger agents. Malignant Hyperthermia . Sustained, significant hypermetabolism Inherited component

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Malignant Hyperthermia

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  1. Malignant Hyperthermia

  2. Malignant Hyperthermia • Definition : a metabolic disease of the muscle, a hypermetabolic state caused by exposure of susceptible individuals to known trigger agents.

  3. Malignant Hyperthermia • Sustained, significant hypermetabolism • Inherited component • Abnormal handling of intracellular calcium levels • “Triggered” by pharmacologic agents , possibly by heat/exercise

  4. MH Trigger Agents Potent Volatile Anesthetics (eg. halothane, sevoflurane, desflurane) Succinylcholine Not MH Triggers Intravenous agents Opioids Non-depolarizing agents Ketamine Propofol Anxiolytics Trigger Agents for MH

  5. Spectrum of Presentations of Malignant Hyperthermia • The classic case • Masseter muscle rigidity • Associated with muscle disorders • MH without anesthesia

  6. Specific Muscle Rigidity Increased CO2 Production Rhabdomyolysis Marked Temperature Elevation Non Specific Tachycardia Tachypnea Acidosis (Resp/Metabolic) Hyperkalemia Signs of Malignant Hyperthermia

  7. Summary of Clinical Signs

  8. Muscle Rigidity and MH • Jaw muscle rigidity may occur after succinylcholine • More common in children • Presages MH in 20-30% • Generalized rigidity not always present • When present, regularly associated with MH susceptibility • With muscle breakdown and creatine kinase above 20,00IU, the likelihood of MH is very high.

  9. Masseter Muscle Rigidity Stop Inhalation Agent No further succinylcholine Continue with nontrigger agents Awaken follow ET C02 patient Observe in ICU for 24 hours CK/electrolytes,Myoglobin Dantrolene as needed Recommend for biopsy

  10. Disorders Associated with MH Susceptibility • Central Core Disease • Evans Myopathy • Hypokalemic Periodic Paralysis • ?sodium channel myotonias

  11. Fever (without rigidity) Thyrotoxicosis Sepsis Pheochromocytoma Iatrogenic overheating Anticholinergic syndrome Faulty equipment Tourniquet (children) Fever and muscle symptoms NMS Hypoxic encephalopathy Ionic contrast agents in CSF Cocaine, amphetamine, ecstasy Mimics of Malignant Hyperthermia

  12. What Tests Are UsedTo Diagnose MH? Current Concepts: • Halothane, caffeine contracture test is the only gold standard Current Investigations: • Molecular genetics • Nuclear magnetic resonance for assessing ATP and creatine phosphate with/without exercise in vivo • Calcium flux measurement in cultured muscle cells • Local increase in pC02 following IM caffeine • EMG changes in MH patients

  13. What is the Incidence of MH? • Original Concepts: • Rare. One in 50,000 anesthetics • 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

  14. Immediate Therapyof Malignant Hyperthermia • Have a plan! • Discontinue inhalation agents, Succ • Hyperventilate with 100% 02 • Bicarbonate 1-2 mg/kg as needed • Get additional help • Dantrolene 2.5mg/kg Push. Repeat PRN • Cool patient: gastric lavage, surface, wound • Treat arrhythmias-do not use calcium channel blockers • Arterial or venous blood gases • Electrolytes, coagulation studies

  15. Treatment of Malignant Hyperthermia - Acute Dantrolene-1 • The only specific treatment for MH • Administer as soon as diagnosis made • 20mg/bottle-dissolve with 60ml sterile water • Shake vigorously or warm bottles to dissolve • Give 2.5mg/kg STAT • Repeat as needed to control signs of MH

  16. Treatment of Malignant Hyperthermia Dantrolene-2 • After crisis controlled, give dantrolene 1mg/kg every 4-6 hours for 24 hours • Continue dantrolene for 36 hours • Recrudescence rate is 25%

  17. Management of Malignant Hyperthermia Biochemical Markers • Blood gasses – esp pCO2, pH, CK • Myoglobinuria • PT, PTT, INR, fibrin split products • Liver enzymes, BUN

  18. Morbidity and Mortality RHABDOMYOLYSIS RENAL FAILURE DIC if temp >41.50 C Hyperkalemia Acidosis

  19. Prevention of Malignant Hyperthermia • Preop personal/family history of anesthetic problems, neuromuscular disorders • Temperature/endtidal CO2 monitoring during general anesthesia • Recognition of masseter rigidity • Investigation of unexplained tachycardia, hypercarbia, hyperthermia • Availability of Dantrolene • Avoiding MH triggers in MH susceptibles • Using Succinylcholine in indication

  20. Principles of Management ofMH Susceptible • Dantrolene not necessary preoperatively (dantrolene available) • Avoid succinylcholine • Avoid potent inhalation agents • Discharge after about 2 hours in the recovery room if all signs are stable

  21. Preparation for MH Susceptible • Shut/disable vaporizers • Flow 02 @ 10L/min for 20 minutes (through machine and ventilator) • Change carbon dioxide absorbent • Use non-trigger agents or local anesthesia • Monitor temperature • Have dantrolene available

  22. Suggested Regimen for MH Patient • Anxiolytic (ketamine permissible) • Propofol/opioid induction • Non-depolarizing relaxant • Nitrous/narcotic/propofol • Reversal of muscle relaxant • Observe 4 hours

  23. MH Trigger Agents Potent Volatile Anesthetics (eg. halothane, sevoflurane, desflurane) Succinylcholine Not MH Triggers Intravenous agents Opioids Non-depolarizing agents Ketamine Propofol Anxiolytics Drug Safety in MH

  24. Credits • http://www.mhaus.org/index.cfm/fuseaction/Content.Display/PagePK/ProfessionalInfoCenter.cfm, Website of MHAUS, Malignant Hyperthermia Association of the United States, Professional Information Center.

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