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Malignant hyperthermia

Malignant hyperthermia. - A rare complication of anaesthesia. What is it?. “It is a biochemical chain reaction response triggered by commonly used general anesthetics and the paralyzing agent succinylcholine, within the skeletal muscles of susceptible individuals” –MHAUS.org

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Malignant hyperthermia

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  1. Malignant hyperthermia • - A rare complication of anaesthesia

  2. What is it? • “It is a biochemical chain reaction response triggered by commonly used general anesthetics and the paralyzing agent succinylcholine, within the skeletal muscles of susceptible individuals” –MHAUS.org • Has autosomal dominant inheritance • Incidence of 1-5 : 100,000, < 5% mortality rate • Triggered by anesthetic drugs such as all inhalation agents (except NO) and succinylcholine (depolarising muscle relaxant) • Uncontrolled increase in intracellular Ca2 because of anomaly of ryanodine receptor which regulates Ca channels in sarcoplasmic reticulum of skeletal muscle

  3. Clinical picture • It's onset can be immediate or hours after agent is administered • There will be increase in: • Oxygen consumption • ETco2 on capnograph • Tachycardia/dysrythmia • Tachypnia/cyanosis • Diaphoresis • Hypertension • Temperature

  4. Muscular symptoms • Trismus (occurs in 1% of children given SCh together with halothane) • Tender and swollen muscles due to rhabdomyolysis • Trunk or total body rigidity

  5. Pathophysiology • Alteration in the Ca induced ca release via the ryanodine receptor channel (RYR1) or! impairment in the ability of the sarcoplasmic reticulum to sequester calcium via the ca transporter • After trigger agent is administered, there is a sudden and prolonged release of ca which causes • Massive muscle contraction • Lactic acid production • Increased body temperature • Dantrolene stops the calcium released by binding to the ryanodine receptor and blocking the opening of the channel therefore stopping the release of calcium. It has little effect on heart and smooth muscles as the ryanodine receptors differ in these tissues (RYR2).

  6. Triggering vs safe anaesthetics Triggering agents Non-triggering agents PropofolKetamineNitrous oxideAll local anestheticsAll narcoticsNon depolarizing muscle relaxants: Vecuronium Rocuronium pancuronium • Volatile gaseous inhalation anesthetics: • IsofluraneSevofluraneDesofluraneHalofluraneEnfluraneMethoxyflurane • Succinylcholine • Suxamethoniumdecamethonium

  7. Complications • Coma • DIC • Rhabdomyolysis • Myoglobinuric renal failure/hepatic dysfunction • Electrolyte abnormalities (hyperkalemia) and secondary arrhythmias • ARDS • Pulmonary edema • Can be fatal if untreated

  8. Prevention • Check family history • Avoid trigger medication, use regional anaesthesia if possible and use clean equipment • Central body temperature and ETco2 monitoring • Used to use dantrolene as prophylaxis but not commonly used anymore

  9. ManagementBased on MHAUS guidelines from 2008 • Notify surgeon, discontinue agents, hyperventilate with 100% Oxygen at >10l/min, halt procedure if possible • Dantrolene 2.5mg/kg IV every 5 min (1mg/kg/dose, max dose = 10 mg/kg) • Repeat until control is obtained • Bicarbonate 1-2 mEq/kg if blood gas values are not available for metabolic acidosis • Cool patient with core temp >39C • Lavage open body cavities, stomach, bladder, rectum, apply ice to surface, imfuse cold saline IV • Stop cooling if temp reaches 38C

  10. Treat acidosis and hyperkalemia • Don't use Ca2 channel blockers as they may cause hyperkalemia and cardiac arrest with dantrolene • Hyperkalemia • Hyperventilation, bicarbonate, glucose/insulin, calcium • Bicarbonate 1-2 mEq/kg IV, Calcium chloride 10 mg/kg or calcium gluconate 10-50 mg/kg for life threatening hyperkalemia and check glucose levels hourly • Observe ETco2, electrolytes, blood gases, creatine kinase, core temp, urine output/color, coagulation studies • If CK and/or K rises more than transiently or urine output falls to less than 0.5 ml/kg/h induce diuresis to >1 ml/kg/h urine to avoid myoglobinuric renal failure • Maintain anaesthesia with benzodiazepines, opioids and propofol • Transfer to ICU

  11. Quick recap of management • Call for help (let surgeon know) • Turn off potential triggering agents • Administer dantrolene 2.5 mg/kg every five minutes • Cool patient to 38C • Monitor and correct blood gases, electrolytes and glucose

  12. Sources: • Wikipedia.com • Toronto notes 2012 • Uni-ulm.de (Malignant hyperthermia, Muscle & Nerve, January 2000)

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