Session 2: Cleaning and Testing Part 1

Sponsored by ASTM Committee F04 on Medical and Surgical Materials and Devices

Exploring Methods of Optimizing Surgical Instrument Reprocessing Operations

Jahan Azizi, Linda Lavey, CBET, University of Michigan, Dearborn, MI

The elimination of bioburden from reusable surgical instruments represents an ongoing challenge for the manufacturers of such instruments, the hospitals using them, and the patients relying on them for their health and safety. Recognizing this challenge, a team of risk management personnel and instrument room technicians at the University of Michigan Hospitals and Health Centers have undertaken a project focusing on directed testing of the manufacturer’s recommended cleaning methods for surgical instruments.

The objective of this testing is to determine the efficacy of automated instrument reprocessing methods with the goal of finding the optimum means of sterilizing valuable surgical tools. Faced with an array of instruments available for testing, investigators settled on suction tips, useful due to their application in virtually every kind of surgery, their exposure to high levels of bioburden, and their known difficulty to clean. This study focuses on a variety of suction tips used in orthopedic, neurosurgery, and otolaryngology surgical procedures.

Methods involve a dedicated workstation designed for this project and set up with a Midbrooks reprocessing machine; a digital video outfit for taking intra-lumen snapshots using flexible scope cameras ranging in size from 1.9 mm to 2.7 mm; and supplies for determining the presence of protein, ATP (adenosine triphosphate), carbohydrate, and hemoglobin as markers for bioburden still present. In addition, enzyme solution and hand tools for manual cleaning were available for continued testing as needed. Testing so far has included three phases:

Phase 1: Visual check: Suction tips are tested for protein before and after cleaning. Still photographs are taken throughout, showing bioburden present.

Phase 2: ATP Check: A sample of suction tips is tested for ATP and hemoglobin.

Phase 3: Comparison Testing Using ATP and Channel Check (testing for protein, hemoglobin, and carbohydrate): Instruments undergo cleaning using the manufacturer’s recommended processes, requiring as many as three wash cycles. All are tested using ATP and hemoglobin test kits after each cycle.

Initial testing found bioburden remaining on 100% of the instruments. Additional cleanings were required to reach a predetermined cleanliness goal. While still focusing on suction tips, investigators also tested additional instruments as available, including samples of endoscopes and robotic control devices.

Testing is ongoing, with the ultimate goal of finding a process that will reliably produce a verifiably clean instrument after a set process is performed, time and time again, to meet the needs of a busy teaching hospital while providing patients with the best possible care. Results so far have been eye-opening, both with regard to the bioburden left behind and in the obvious limitations of the manufacturer’s recommended cleaning processes. Ample photographs and numerical data rendered in charts and other graphical means offer an opportunity to share the scope of this project.

Validation Strategy for an Automated Endoscope Reprocessor

Bradley Catalone, Thomas Gilmore, David Barlow, Olympus America, Center Valley, PA

Flexible endoscopes are complex devices with design features that present a challenge to effective reprocessing: including multiple, long, thin internal lumens that may   bifurcate and/or extend the length of the endoscope; and a variety of models, each with a unique design and particular steps for reprocessing.  One mechanism by which to address the challenges presented for effective endoscope reprocessing is to automate the parts of the process that are performed manually and which account for much of the observed variability in clinical practice.  Several studies have identified manual cleaning as the most labor-intensive and variable part of endoscope reprocessing. This presentation describes a system level approach to validating an automated endoscope reprocessor that takes over many of the manual steps in the process.

There are clear benefits to automation of a variable process, including consistency and repeatability.  However, there is also a risk in which the user is no longer intimately connected to the device and is unable to detect abnormal conditions that may present a challenge to the effectiveness of the reprocessing procedure.  As a result, the validation strategy for an automated endoscope reprocessor must be both rigorous and robust to account for any potential variability in clinical practice.

Our validation strategy was developed at the system level to account for variables in AER performance, degradation and organic loading of the chemistry, selection of the most challenging device(s) to reprocess, and failure to follow manufacturer’s instructions prior to automated reprocessing.  The AER was modified to simulate conditions just prior to preventative maintenance and the high-level disinfectant was stressed with an organic load, diluted to its minimum recommended concentrations and used at or beyond its specified use life.  In addition, a comprehensive evaluation of all devices specified for reprocessing in the AER was performed to identify those devices that either individually or in combination with another device represented the worst-case challenge to the reprocessing procedure.  To complete the strategy, the validation accounted for user failure to perform the indicated manual process prior to automated reprocessing, thereby building into the process an inherent safety margin for effective reprocessing.

An appropriate validation must include a relevant and validated test soil.  The previously validated soil used in this study contained organic components at levels similar to worst-case patient soil levels for GI and pulmonary endoscopic procedures and two primary indicators (protein and hemoglobin) of cleaning efficacy were selected.  We targeted previously published endpoints for both residual protein (< 6.4 µg/cm2) and hemoglobin (1.8 µg/cm2 ).  These endpoints were based upon residual levels consistently achieved through optimal manual cleaning, which is the currently accepted standard for endoscope cleaning.

A total of thirty-six samples from nine endoscopes tested following AER reprocessing under worst-case simulated use conditions met the pre-established acceptance criteria for protein (<6.4 mg/cm2) and hemoglobin (<1.8 mg/cm2) residuals. Although the validation testing indicated that AER reprocessing alone provides effective cleaning of flexible endoscopes such that the manual cleaning process can be eliminated, users were instructed to perform external surface cleaning and channel brushing prior to AER reprocessing.  The additional requirement for the manual cleaning steps provides enhanced cleaning, verifying that the instrument/suction channel of the endoscope is not obstructed, and maintains the connection between the reprocessing technician and the device.

Effects of Non-Aqueous Vapor Degreasing Solvent Cleaning on Ultra-High Molecular Weight Polyethylene (UHMWPE)

Ray Gsell, M. Guo, H. Brinkerhuff Zimmer, Warsaw, IN

Introduction: Non-aqueous vapor degreaser cleaning (NAVDC) methods have been used for many years.  Their main applications have been for cleaning metal products.  These processes had become less popular because of environmental concerns and regulations on ozone depleting materials; a classification which included many of the solvents commonly used.  With recent advances in equipment technology that essentially eliminated solvent loss to the environment and the development of suitable non-ozone depleting solvents, there has been a renewed interest in this technology.  The use of NAVDC for cleaning metallic devices is relatively straight forward and well understood.  Although its application to polymeric devices requires greater knowledge and control of the solvent-polymer interactions, many polymeric systems (e.g. circuit boards) are successfully cleaned with this technology.  UHMWPE is the major polymeric material used by the orthopaedic industry in manufacturing artificial joints.  If NAVDC processes are to be used on these materials it is important to understand the effects residual solvent has on the mechanical properties (short and long term) of the UHMWPE and product packages and the biocompatibility of NAVDC materials.  The subject of this paper is to discuss some of the effects of NAVDC on UHMWPE.

Materials and Methods: Two commercially available hydrofluorocarbon solvents were evaluated: HFE-72DA (3M Company) and Heavy Duty Degreasing Solvent (Micro Care Corp.).  Both are mixtures containing trans-dichloroethene and fluorinated hydrocarbons.  The UHMWPE used was non-irradiated compression molded GUR-1050 slab (Ticona) machined into test bars approximately 6 x 12 x 40 mm.

The UHMWPE test bars were processed in the boiling solvents and their vapors with and without sonication for 2 – 5 minutes (see Table 1).  The absorption/desorption depths and rates of a solvent on a processed bar was monitored using FTIR line scan mapping techniques (Nicolet Magna 500 FTIR coupled to a NicPlan FTIR Microscope).  Desorption of absorbed solvent was evaluated at ambient conditions, elevated temperature and ambient pressure (oven) and elevated temperature and sub-ambient pressure (vacuum oven).  The presence or absence of absorbed solvent in the UHMWPE was easily detected by FTIR because each solvent has several unique absorption bands that are non-interfering with the UHMWPE absorption bands (e.g. Figure 1).

Figure 1

FTIR Spectra of HDS vs UHMWPE

Results: Table 1 describes some of the solvent processing conditions tested, the observed depths of solvent penetration into the UHMWPE, the desorption conditions used and the desorption test results.

Table 1

Samples of Tests and Results Using GUR 1050

Liquid

Contact Time

(Min.)

Vapor

Contact

Time (Min.)

Drying Time

(Min.)

Drying Temperature

(oC)

Drying Pressure

(Atm.)

Solvent

Absorbed (Y/N)

Maximum

Depth (µm)

2

0

0

ambient

ambient

Y

200

2

0

40

ambient

ambient

Y

500

2

0

68

ambient

ambient

Y

600

2

0

0

ambient

ambient

Y

300

2

0

30

80/oven

ambient

Y

1000

2

0

60

80/oven

ambient

Y

1100

2

0

90

80/oven

ambient

N

N/A

2

0

120

80/oven

ambient

N

N/A

Conclusions: The results of this study indicated both solvents were quickly (within 2-5 minutes) absorbed into the UHMWPE to depths of about 1 mm, but desorbed from it much more slowly.  Desorption may take several hours even at elevated temperatures and reduced pressures.  The use of elevated drying temperatures caused the absorbed solvents to penetrate deeper into the UHMWPE before being desorbed.

Breaking the Myth that Caustic Surgical Instrument Cleaners are Necessary for Safe and Effective Decontamination of Medical Devices

Marcia Frieze, Case Medical, South Hackensack, NJ

Green Chemistry is the design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances. This approach to pollution prevention is the focus of the US Environmental Protection Agency’s Green Chemistry Program. 

It is our position that caustic detergents such as alkaline cleaners followed by acid neutralizers are unnecessary for instrument processing and present significant hazard to the waste water stream, to the devices to be cleaned, and result in safety issues for staff and patients.  There are validated processes and products available that are pH neutral, environmentally friendly, and safer for human health and the environment with proven log reduction.  We propose to present a study utilizing a three step process including enzymatic cleaners that demonstrates 6Log reduction under abbreviated cleaning conditions.

Cleaning is the critical first step performed in the sterile processing process of reusable medical and surgical devices. Ineffective cleaning of these devices can interfere with the effectiveness of subsequent sterilization or disinfection and increase the risk of nosocomial infection in patients and healthcare staff.  Additionally, ineffective cleaning can affect the ability of medical devices to function properly and decrease the useful life of the devices, resulting in increased repair and replacement costs to the healthcare facility. Cleaning is defined as the removal, usually with detergent and water, of adherent visible soil such as blood, protein substances and other debris, from the surfaces, crevices, serrations, joints, and lumens of instruments, devices, and equipment by a manual or mechanical process that prepares the items for safe handling and/or further decontamination.

Worldwide industry is faced with the challenge to provide effective devices and products for surgical instrument cleaning and decontamination while recognizing the importance of sustainability and ecological compatibility. Sustainability has been defined as meeting the needs of the current generation without impacting the needs of future generations to meet their own needs. There is a social responsibility to protect the public from exposure to harm.  As a result, all manufacturers need to anticipate and are obligated to design instrument chemistries to control measures which might lead to possible harm or uncertainty.  The burden of proof that the suspected risk is not harmful falls on those taking action.

The concept of the precautionary principle includes an ethical responsibility toward maintaining the integrity of natural systems, a willingness to take action in advance of definitive scientific proof when a delay will prove ultimately most costly to society and nature as well as unfair and ultimately selfish to future generations.

Cleaning, decontamination and subsequent sterilization are essential steps in breaking the chain of infection.  Cleaning is the most critical step in the decontamination process and requires the commitment from the manufacturer to design and produce instrument chemistries with demonstrated efficacy and sustainability.

to top