1.2 MH Crisis Initial Management

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  1. The most senior anaesthetist present should  coordinate crisis management
  2. If an MH crisis is suspected/confirmed:
  3. Declare Emergency (complete or abandon surgery)
  4. Call for HELP
  5. Send for the MH box and refrigerated supplies
  6. Turn off volatile agent and remove vaporisers from  anaesthetic machine
  7. Hyperventilate with 100% oxygen and high fresh gas flows (>15L/min)

(Do not waste time changing machine or circuit)   

Commence intravenous anaesthesia maintenance

eg Propofol infusion (target 4mcg/ml or 30-50ml/hr)

Task Cards: The MH box contains individual task cards for MH crisis management:    Give each available staff member a card (or two) and ask them to complete the self-explanatory instructions.  Task Cards can be downloaded here

There are multiple high priority tasks, but ……

Dantrolene administration is the priority.

(Assign as many staff as possible to this task)

How can I tell if it’s really Malignant Hyperthermia?

MH can be difficult to diagnose.

Know who is susceptible: Malignant Hyperthermia may occur in any patient, including patients who have previously had uneventful general anaesthesia.

 MH is more likely with: Diagnosed malignant hyperthermia susceptibility after halothane / caffeine contracture test on biopsied muscle, Malignant Hyperthermia susceptible relatives, significantly & consistently raised resting serum CK, several very rare muscle disorders.

Know the signs & symptoms:

Not all need to be present to initiate treatment 

Early:

  • Prolonged masseter spasm after suxamethonium
  • Inappropriately raised end tidal carbon dioxide or tachypnoea during spontaneous respiration
  • Inappropriate tachycardia
  • Cardiac arrhythmias, particularly ventricular ectopic beats

Developing:

  • Rapid rise in temperature (0.5oC per 15 min)
  • Progressive respiratory and later metabolic acidosis (ABG)
  • Hyperkalaemia
  • Profuse sweating
  • Cardiovascular instability
  • Decreased SpO2 or mottling of skin
  • Generalised muscular rigidity

Late:

  • “Cola” coloured urine – due to myoglobinuria
  • Generalised muscle ache (in an awake patient)
  • Grossly raised serum CK
  • Coagulopathy
  • Cardiac arrest

Differential Diagnoses:

  • Inadequate anaesthesia / machine malfunction
  • Sepsis or infection
  • “Thyroid Storm”
  • Ecstasy or other recreational drugs
  • Phaeochromocytoma
  • Neuroleptic Malignant Syndrome
  • Intracerebral infection or haemorrhage

An arterial blood gas is the single most useful investigation to perform