What is HLD?
HLD is a term first proposed by Eugene Spaulding, the originator of the Spaulding Classification system. (See What Is The Spaulding Classification?) These general guidelines have been adapted and updated over time with more specific recommendations by regulatory agencies.
According to the Centers for Disease Control (CDC), Spaulding’s method divided medical equipment into three categories: Critical, Semi-Critical, and Non-Critical, based on the risk of spreading infection. He further divided the Semi-Critical classification into High-Level Disinfection and Intermediate Level Disinfection. He then assigned different procedures for rendering equipment at each level safe for patient use.
Spaulding said that items requiring HLD (other than dental equipment) consisted of equipment that comes in contact with mucous membranes or intact skin. Examples would include flexible gastrointestinal endoscopes and TEE probes.
Methods of HLD
After following a cleaning procedure, HLD equipment must be disinfected according to the manufacturer’s instructions. In some cases, the device may be steam disinfected or it may require chemical disinfection at room temperature. A third option is the use of ultraviolet light, which also can kill microorganisms by interrupting their DNA sequence.
Some delicate instruments, including the flexible tubes of endoscopes, cannot stand up to hot steam. For those, the protocol for HLD may require immersion in hydrogen peroxide, peracetic acid, glutaraldehyde, ortho-phthalaldehyde (OPA), or a combination of hydrogen peroxide and peracetic acid. HLD processing times for these protocols range from 5 minutes to 90 minutes.
Each of these chemicals can cause eye or lung irritation in the medical staff, and extended exposure to these chemicals also can damage endoscopes and other delicate instruments. Handling and disposal of these chemicals may also cause environmental problems.
In contrast, exposing a delicate instrument such as an endoscope to UV-C light for just 60 seconds can reliably inactivate the full spectrum of micro-organisms without damaging the device or exposing staff to harsh chemicals.
What is disinfected and what is not in HLD?
HLD should deactivate bacteria, viruses, fungi, and mycobacteria. It should also kill some bacterial spores, though not all.
When to HLD
In some cases, an endoscope may come into contact with a patient’s bloodstream, in which case it might could be considered a Critical risk of infection. However, heat-sensitive endoscopes cannot survive sterilization with steam.
The recommendation for disinfecting equipment in these Semi-Critical and sometimes Critical cases is to cover probes with a new sterile sheath for each patient, and to subject them to high-level disinfection.
What is Sterilization?
According to Spalding, sterilization requires destruction of all infectious microbes, including bacterial spores, although it may not completely destroy prions.
Methods of sterilization
Typically, medical equipment is sterilized using steam or hot water in a dishwasher. In some cases, exposure to ethylene oxide gas or hydrogen peroxide gas plasma for a specified time is recommended by the manufacturer.
What is being sterilized and when it can be avoided
Sterilization should render all bacteria, viruses, fungi, mycobacteria, and bacterial spores unable to reproduce. However, full sterilization is not necessary in some cases where a disposable sterile probe cover can be used for each patients as long as HLD is also performed.
When to sterilize
The Spalding Classification recommends sterilization of instruments that come in contact with any sterile tissue or with a patient’s bloodstream. This Critical classification would include probes used in surgery or inserted through the skin.
Differences between HLD and Sterilization
Though the Spalding Classification dictates that any medical equipment that comes into contact with sterile tissue or the bloodstream must be sterilized, this usually involves steam or harsh chemicals to completely destroy any microbes. In those cases where sterilization procedures can harm the equipment, the next best recommendation is to apply HLD and to use a sterile probe cover for each new patient.
Disinfection technology using UV-C light can provide HLD to delicate flexible medical instruments such as endoscopes. For more information on how UV-C technology can transform your medical disinfection procedures, contact UV Smart.
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