2Malignant Hyperthermia HistoryPathophysiologyDiagnosisSigns and SymptomsTreatment
3Malignant Hyperthermia HistoryInitially identified in Australia 1961Initially very high mortalityDiagnostic testing 1971Association with Masseter muscle rigidity 1970Dantrolene 1975Genetic component identified 1990”sDNA testing ?
4Malignant Hyperthermia Caused by mutation of the sarcolamma ryanodine receptor RyR1 which is coded on chromosome 19Responsible for intracellular calcium metabolismRyR1 receptor
5Malignant Hyperthermia Incidence1/ with Succinylcholine 1/65000Mortality with treatment 10 %Poor outcome related to delay in administering Dantrolene and peak temperature
6Malignant Hyperthermia TriggersSuccinylcholineVolatile “….ane” anaestheticsNot N2OAll other anaesthetic drugs safe
7Malignant Hyperthermia MH occurs because of an increase in metabolism due to rapid and uncontrolled increase in calcium within the sarcolema (muscle cells).
8Malignant Hyperthermia 2. The increase in calcium level overwhelms the capacity of the muscle cell for active calcium reuptake.3. This results in muscle contraction and increased breakdown of ATP, enhanced glycolysis, uncoupling of oxidative phosphorylation, & activation of actin-myosin filaments yielding significant heat production causing cell damage, and membrane leak.
9Malignant Hyperthermia Familial Dominant trait but with incomplete penetranceMales more common than femalesMay not trigger with first exposure to volatilesSuccinylcholine greatly increases risk
10Diseases Associated with MH King Denborough syndromeCaution in children with delayed motor functionIon channel mutationsMyopathic syndromesDuchenne muscular dystrophyBrody’s Disease -deficient calcium, ATP (rhabdomyolysis, not MH)McArdles Diseas -glycogen storage (rhabdomyolysis, not MH)Myotonia congenitaCentral Core disease
11Malignant Hyperthermia Early SignsHypercarbia 40% - respiratory acidosisInnappropriate for case setting after considering opioids, ventilator settings, laparoscopic surgery etcIf in doubt obtain blood gasTachycardia 30%Masseter Spasm 20%Hypertension ?
13Malignant Hyperthermia Differential Diagnosis Neuroleptic Malignant Syndrome•Severe muscle rigidity and elevated temperature associated with the use of antipsychotic medication•Thyrotoxic crisis –Thyroid Storm•Cocaine toxicity•Heat stroke•Serotonin syndrome -excessive serotonin usually r/t combining meds•Status Epilepticus•Pheochromocytoma•Lymphoma
15Malignant Hyperthermia Treatment Call for assistanceImmediately terminate trigger drugs & conclude surgery as soon as possible•Hyperventilate with 100% oxygen•Initiate active cooling•Iced saline•Gastric lavage with iced salineSurface cooling
16Malignant Hyperthermia Treatment Dantrium®IV-2 mg/kg IV q4-8hrs repeated 24-48hrs or until symptoms resolve ( max 10 mg/Kg )Dantrium®IV each vial contains1. 20 mg dantrolene sodiummg mannitol3. Sodium Hydroxide to yield a pHof approximately 9.5 whenreconstituted with 60 mL sterile water
17Malignant Hyperthermia Treatment Correct metabolic acidosis(NaHCO3 1-2mEq/kg IV based on arterial ph)Maintain urine outputHydrationFurosemide ( 1mg/ kg )Treat hyperkalemia – glucose + insulinTreatment of arrythmiasAvoid Ca channel blockers – myocardial depression
18Malignant Hyperthermia Key Patient Stability Indicators ETCO2 is declining or normalHR is stable or decreasingNo ominous dysrhythmiasTemperature is decliningGeneralized muscular rigidity is resolving (if present)IV dantrolene administration has begun
19Malignant Hyperthermia What is Dantrolene ? Dantium ( Dantrolene )Skeletal muscle relaxant by inhibiting sarcoplasmic release of calciumHalf life 4-8 hrs metabolized by liverCauses generalized muscle weaknesNo cardiac effectsNo effect on train of four
20Management of MH Susceptible Patients Preparation of anaesthesia machineFresh circuit, absorber flushed at 10 lpm x 10 minTriggers disconnected from circuit and out of roomNon triggering anaestheticPropofol, ketamine, N2O,narcoticsRegional techniquesPACUExtended stayObserve 2-4 hours prior to discharge