New to the Harry Daly Museum of Anaesthesia: Hyperthermia Testing Unit

Kate Pentecost - ASA Museum Curator, Archivist and Librarian

As curator of the Harry Daly Museum, one question I'm often asked is how dangerous is modern anaesthesia? For the non-medical, non-anaesthetist visitor it is a question whispered with the scared curiosity, akin to watching a horro movie through your fingers.

Thankfully, there is often visible relief in the visitor when I explain that in Australia, having an anaesthetic is extremely safe, and indeed is so safe due to our standards, intensive training and ever evolving clinical practices.

However, it remains high risk for patients with Malignant Hyperthermia Susceptibility (MHS) – a rare pharmacogenetic disorder, characterised by reactions to certain drugs used commonly in anaesthesia. It can be fatal without prompt treatment. It induces a hypercatabolic state with symptoms including dangerously high body temperature, muscle spasms, rapid heart rate and increased carbon dioxide production. The syndrome is caused by a defect in the ryanodine receptor, with the characteristic pathophysiologic changes of malignant hyperthermia occurring due to uncontrolled rise of myoplasmic calcium. Diagnostic testing relies on assessing the in vitro contracture response of biopsied muscle to halothane, caffeine, and other drugs.

The incidence of Malignant Hyperthermia (MH) reactions ranges from 1:5,000 to 1:50,000–100,000, but the prevalence of the genetic abnormalities may be as great as 1 in 3,000 individuals. Generally, patients will not be aware if they have MHS, unless they have a known family history to fatal or near fatal anaesthetic reactions.

One of our latest donations to the Museum is an original MH testing machine from The Children’s Hospital at Westmead (CHW), Sydney. This unique and custom-built unit was developed and designed by the late Dr Neil Street AM, a pioneer in MH research and testing.

The machine for in vitro contracture testing (IVCT) of muscle samples was decommissioned in 2022, as the MH Unit at CHW is being upgraded, twenty years after Drs Street, David Baines AM, Margaret Perry and Mark Lovell founded the team in 2002. The MH Unit was one of only four of its kind across Australia and New Zealand. Staff tested patients from across New South Wales, Queensland, and Canberra through genetic analysis or muscle biopsy. Dr Gail Wong noted during the donation that it is thought to be the first IVCT testing set up accredited outside of Europe by the European Malignant Hyperthermia Group, whose testing protocol remains the standard for IVCT (accredited circa May 2006).

Dr Wong further described the machine as “not having been altered from its original condition when I had taken over the IVCT testing. At a pinch, it may well still work! The main components – the tissue baths, transducer set-up and heating system – were designed and created by Neil Street with his biomedical engineering colleagues at Children’s Hospital Westmead, and are very elegant and well thought-out. He had factored in some measure of portability in its design as he had considered taking it to country NSW (Central West region) where MH susceptibility ran in a large family. He thought to take his machine to the patients rather than the other way around and to test the family members en masse whilst visiting from time to time.”

This object represents the engineering, drive and passion of a great Australian anaesthetist. It will be a key part of communicating to a general audience the risks, and risk minimisation, of contemporary anaesthetic practices – emphasising of course, how rare these genetic risk factors are. In fact, with recent research in understanding the clinical manifestation and pathophysiology of MHS, the mortality rate from MH complications has dropped from over 80% thirty years ago to less than 5% today.

Thanks to Dr Gail Wong and Dr Justin Skowno for the donation, and to Dr Michael Cooper for assisting with the acquisition process.