Malignant Hyperthermia

Last updated 20.09.12

 

Index

 

Definition

-  Hyperthermia triggered by general anaesthetic agent

-  Halothane

-  Suxamethonium

 

Features

-  Anaesthetic Emergency

-  Inherited myopathy: Family Hx

-  1:50-100,000

-  Males > Females

-  Rare but life threatening: mortality 10%

-  Prompt Mx --> 0% mortality

-  Clinially similar but pharmacologically distinct from Neuroleptic Malignant Syndrome

 

Risk Factors

-  Familial muscular disorders (AD)

-  Ass w strabismus, myalgia on exercise

-  Prev GA wo adverse effects does not exclude possibility

-  Neuroleptic drugs

-  EtOH

 

Associated S/S

-  Onset during or within hours of anaesthesia

-  Masseter spasm: often first indication

-  Hypermetabolism: tachycardia

-  Hypoxia, hypercapnia, metabolic acidosis

-  Fever: late feature

-  Muscle rigidity

-  Rhabdomyolysis: myoglobinuria

-  Arythmia, cyanosis, hypotension

 

Ix

-  Muscle biopsy w contracture test: 85% spec, 100% sens: Dx

-  CK: elevated: rhabdomyolysis, 70% pts at risk

-  ABG

 

Mx

-  Switch to alternate anaesthetic agent

-  Deepen anaesthesia w opiods (Fentanyl, Morphine), BZDs or Propofol

-  Hyperventilate w 15L 100% O2

-  Dantrolene 2.5mg/kg IV bolus

-  Cease Sx if elective & signs of master spasm

-  Fulminant Hyperthermia

-  Dantrolene 2.5mg/kg IV

-  Repeat 2mg/kg every 5min until stable + normal pCO2

-  10mg/kg over next 24hrs

-  Mx of aryhtmia

-  Cool pt: NGT ice water

-  Diuretics: prevent ARF