Manufacturing
standards. One of the important criteria for medical device regulation is based on whether the device is invasive or non-invasive and the length of time the device comes into contact with the patient. “Where possible, medical devices which are implanted in patients will be terminally sterilised (the process of rendering medical devices and materials free of all forms of microbial life before they are packaged for distribution and used) using an approved method regulated according to the Medical Devices Regulations 2002 (SI 2002 No 618, as amended) (UK MDR 2002),” said a spokesperson for MHRA. Its online guidance offers information about the potential risks that should be considered with regard to sterile and non-sterile best practices. “There is no single main contamination risk in sterile and non-sterile manufacturing – multiple risks exist, all of which must be managed concurrently to ensure product safety,” according to the MHRA. “The MHRA does not recommend specific sterilisation methods, it requires manufacturers to validate and control their chosen processes to ensure device sterility. The selection of an appropriate sterilisation method should consider the device’s material, design, and intended use, adhering to regulatory standards and guidelines,” said the MHRA spokesperson.
Hidden dangers of biofilm accumulation Despite a range of sterilisation technologies being available, steam sterilisation is the most widely employed method around the world, according to the UK’s professional body for decontamination science practitioners, the Institute of Decontamination Sciences (IDSc). “Steam sterilisation is relatively cost-effective, extremely effective on organic matter, easily installed and repeatable,” says Rob Warburton, the ISDc’s Trust Decontamination Lead. However, the process is not appropriate for use on all devices – some medical instruments are too heat-sensitive and delicate. “Invasive devices are generally made out of stainless steel and have to undergo steam sterilisation. But some devices – such as flexible endoscopes, for example – are heat liable so they can’t be subjected to that process,” explains Warburton. Flexible endoscopes comprise a flexible plastic tube with internal channels and a camera on the tip. These complex and expensive devices are easily damaged and, therefore, more suited to low- temperature sterilisation methods. However, these often involve chemicals. And when chemicals are involved, the cost of the process rises along with the hazards of toxic emissions. “Vapourised hydrogen peroxide is a low-temperature sterilisation method that is almost as effective as steam, but it does require a lot of venting because it’s a noxious chemical so you can’t sterilise loads to the same size you can with steam,” says Warburton.
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Then there’s ethylene oxide sterilisation, which
Warburton describes as an effective but very expensive and hazardous sterilisation agent. Despite its sweet smell, the colourless gas is extremely flammable and toxic. Its ability to kill organic matter makes it an effective sterilising agent but also accounts for its potential to cause cancer in humans who are exposed to it. Devices that are sterilised with ethylene oxide include wound dressings, lateral flow devices and specialised devices that are used inside the body. As with vapourised hydrogen peroxide, the process also requires a lot of venting and stringently controlled laboratory environments. “It’s the most dangerous option because it’s the most volatile,” says Warburton. “It’s a toxic gas and if there are any naked flames around its extraction it can cause an explosion.”
Also requiring a stringently controlled process, along with a factory-sized hangar, is the radiation method, which is used for the mass sterilisation of consumable medical instruments. Warburton believes one the biggest blind spots in healthcare in terms of sterilising and decontaminating medical instruments is biofilm accumulation. Biofilm is a sticky layer of bacteria that can accumulate on surfaces that are hard to access, such as the inner channels within the tubes of endoscopes. These bacteria can potentially contain pathogens.
“Several studies on biofilms over the past six to seven years have suggested they’re resistant to high- level disinfection. It’s highly likely the biofilm will contain pathogens,” says Warburton. Biofilms can also form on catheters, which can lead to catheter- associated urinary tract infections (CAUTIs).
Innovative solutions for biofilm control The biofilm issue has been researched by both The University of Sheffield and Sheffield Hallam University. The former has developed strategies to treat biofilm infections in medical devices, including an integrated system for detecting and treating biofilms on urinary catheters, plasma polymerisation of nitric oxide release coatings to inhibit biofilm formation and development of strategies for treating biofilm infections in indwelling
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New automated decontamination technologies promise faster, safer cleaning of surgical instruments, reducing reliance on chemicals.
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