Removing the leaks

“The key distinction is the difference between cylinder use and clinical use. Cylinder use was much higher, only a small portion of what was being purchased was being used clinically, the rest was leaking.”

At around the same time, work in the United Kingdom was emerging that resonated with Matt. That 83-100% of nitrous oxide in the NHS’ manifold systems was leaking out to the atmosphere before reaching point of delivery.

“It was the same experience we had, and they were looking to decommission their reticulated networks. We hadn’t considered decommissioning in Dunedin but in 2022 and 2023 our G cylinder use tipped up to 83 cylinders. We could either go through the process again to try and find the leaks or go straight to decommissioning the system.”

Matt then worked with Heads of Departments still using reticulated nitrous oxide to consider moving to point-of-care cylinders. “It isn’t about removing this option for patients, but providing other, less wasteful, ways to get the nitrous oxide”, Matt explains. “That’s smaller bottles where and when you need them. Many were already doing this.”

Changing to point-of-care wasn’t an option for maternity due to their high use of nitrous oxide for labour analgesia and occupational health and safety concerns around swapping large D cylinders. “For the paediatric and ED departments, the transition was straightforward”.

“It was also a little trickier for our operating theatres because we’re across multiple levels with different types of anaesthetic machines, so I took the de-reticulation proposal to the department. They could see the benefits and supported the change.”

“We started with a three-month pilot where we disconnected the machines from the wall in the anaesthesia department and trialled a point-of-care small cylinder system. With no major issues during the pilot, we removed the pipes to the machines altogether. Then in May 2024, we turned off key points in the system, de-reticulating all areas except maternity.”

“The hardest part has been determining how to measure what’s left in the point-of-care cylinders. Because nitrous oxide is a liquid that turns into vapour you can’t watch the pressure gauge like other gases. Our current solution for our main operating anaesthetic machines that have a yoke for the smaller A cylinders is to have a backup immediately available. In our remote locations with machines that don’t have a yoke and require a bigger D cylinder, we weigh the cylinder to estimate what’s left and replace it as required. This is done by the Technicians scanning a QR code and typing in the weight after each use.”

“We’ll refine the system as we go but we just aren’t getting through them. Since we went live in May last year the day surgery unit, maternity operating theatre, and radiology haven’t had to replace a single D cylinder. The day surgery cylinder is the lowest at about 60% full.”

“We’ll know more later this year to understand how much our cylinder use has changed but we have significantly reduced the areas where the pipes can leak by decommissioning them and are hoping to see a significant drop.”

“The decommissioning of nitrous oxide at Dunedin Hospital would not have been possible without the amazing support from our anaesthetic technicians, facilities team and my colleagues”.

Both Burwood and Riverside Theatre Block in Christchurch have recently switched off their systems too.

The decision has been made not to reticulate the New Dunedin Hospital. Aside from the maternity unit. “This was a daunting decision at the time and wasn’t the norm” Matt explains, “but since then guidelines and position statements from Australia and the UK no longer mandate reticulated nitrous oxide.

The Royal College of Anaesthetists state that reticulated nitrous oxide is no longer essential”3. These movements back up our decision here for the New Dunedin Hospital.”

“It makes sense that de-reticulation is an anaesthesia-led change as historically we were the main user of nitrous oxide along with maternity services. Various other centres have asked about doing this in their hospital too, and there is a massive movement in Australian hospitals. There’s so much to be gained – we will continue to have the option to use nitrous oxide for patients but reduce the amount wasted – an environmental win and a cost-saving win with no reduction in the ability to provide care.”