Guidelines for managing the patient who is susceptible to malignant hyperthermia (MH)

The information contained within is designed for use within Australia & New Zealand only.  

Who is treated as susceptible?

Patients with one of the following: 

1. Previous malignant hyperthermia reaction
2. Positive in vitro contracture test (IVCT) on muscle biopsy
3. Positive DNA test for MH
4. If an IVCT has not been done:
   1. Relative has positive IVCT
   2. Patient (with MHS relative) has negative DNA result
   3. Relative with clinical MH reaction

Preparation of a Boyles anaesthesia machine (or equivalent):

Remove vaporiser, replace sodalime with fresh sodalime  Replace hoses and rebreathing bags with new hoses and bags  Flush with 10 L/min oxygen or medical air for at least 20 minutes (at least 30 minutes if isoflurane has been used recently in the anaesthetic machine)¹ through the circuit using a new rebreathing bag as an artificial lung, including the ventilator and carbon dioxide absorber in the circuit.

Anaesthesia Workstation preparation:

Different workstations may require longer times for flushing. See the table on next page for your workstation. Manufacturers do not tend to have information on flushing of machines so if your machine is not present on this list you may have to consult the appropriate peer reviewed publication for more information.

Charcoal filters may be effective alternatives to long flush times.

Use a new mask, new LMA or new ETT.

Continue to use HIGH FLOWS throughout the anaesthetic to avoid accumulation of small quantities of volatile agent  Preferably place MHS patients first on the operating list.

Monitoring:

During surgery monitor and record temperature and respiratory rate in addition to standard ANZCA guidelines (PS18).

After surgery continue minimum mandatory monitoring as per PS4  All patients should have a temperature recorded on arrival and on leaving PACU  There is no requirement to keep patients in PACU for longer than for standard patient care².

INSERT LARGE TABLE

Drugs that MUST be avoided with MHS patients

1. Depolarising muscle relaxants (ie suxamethonium)
2. ALL potent inhalational agents – including; desflurane, sevoflurane, isoflurane, enflurane, halothane, methoxyflurane

Drugs that can be used with MHS patients   

ALL other pharmacological agents are safe including the following common drugs.

• Nitrous oxide (and xenon)
• Propofol and all intravenous induction agents including ketamine and benzodiazepines
• Nondepolarising muscle relaxants
• All local anaesthetics with or without adrenaline
• Opioids and other analgesics
• Syntocinon
• Ergometrine
• Magnesium sulphate
• Ephedrine
• Metaraminol
• Phenylephrine

Patients with a negative in vitro contracture test can receive normal anaesthesia

Followup:

Refer patient for IVCT or DNA testing, if not already carried out, to: 

• New South Wales: Department of Anaesthesia, Westmead Children’s Hospital. 61-2-9845-0000
• New Zealand: Department of Anaesthesia, Palmerston North Hospital. 64-6-356-9169
• Victoria:   Department of Anaesthesia, Royal Melbourne Hospital. 61-3-9342-7000
• Western Australia: Department of Anaesthesia, Royal Perth Hospital. 61-8-9224-1038

References:

1. Schonell LH, Sims C, Bulsara M. Preparing a new generation anaesthetic machine for        patients susceptible to malignant hyperthermia. Anaesth Intensive Care 2003;31:58-62
2. Pollock N, Langton E, Macdonell N, Tiemessen J, Stowell K Malignant Hyperthermia and day stay anaesthesia Anaesth Intensive Care 2006;34:40-45
3. Birgenheier, Nathaniel MD; Stoker, Robert BA; Westenskow, Dwayne PhD; Orr, Joseph PhD. Activated Charcoal Effectively Removes Inhaled Anesthetics from Modern Anesthesia Machines. Anesthesia & Analgesia. 112(6):1363-1370, June 2011.