Cleaning Challenges: Can Extended Soil Dry Times Be Reversed?

Background: Cleaning is essential to ensuring the safe processing of reusable medical devices, and most manufacturers' instructions for use (IFUs) specify that clinical soil should not be allowed to dry on devices. If soil is allowed to dry, the cleaning challenge could be increased due to change in soil solubility. As a result, an additional step could be needed to reverse the chemical changes and return a device to a state where cleaning instructions are appropriate. Methods: Using a solubility test method and surrogate medical devices, the experiment described in this article challenged eight remediation conditions to which a reusable medical device might be exposed if soil is dried on a device. These conditions included soaking with water or neutral pH, enzymatic, or alkaline detergent cleaning agents, as well as conditioning with an enzymatic humectant foam spray. Results: The results demonstrated that only the alkaline cleaning agent was able to solubilize the extensively dried soil as effectively as the control, with a 15-minute soak being as effective as a 60-minute soak. Discussion: Although opinions vary, the overall data demonstrating the risk and chemical changes that occur when soil dries on medical devices are limited. Further, in cases in which soil is allowed to dry on devices for an extended time outside of the guidance from leading practices and manufacturers' IFUs, what additional steps or processes may be necessary to ensure that cleaning can be effective? Conclusion: This experiment demonstrated the effectiveness of a soaking step with an alkaline cleaning agent as an additional step if soil is dried on reusable medical devices, thus reversing the effect of an extended soil dry time.

Effects of Time, Temperature, and Humidity on Soil Drying on Medical Devices.

In the healthcare environment, delays can occur that prevent reusable devices from being processed within the specified time outlined in manufacturers' instructions for use. It has been suggested in the literature and industry standards that residual soil components, such as proteins, may undergo a chemical change when they are exposed to heat or experience prolonged drying times under ambient conditions. However, little experimental data are available in the literature to document this change or how is may be addressed for cleaning efficacy. This study presents the effects of time and environmental conditions on contaminated instrumentation from the point of use until the cleaning process begins. It demonstrates that soil drying after a period of eight hours changes the solubility of the soil complex, with a significant change occurring after 72 hours. Temperature also contributes to chemical changes in protein. Although no significant difference occurred between 4°C and 22°C, temperatures greater than 22°C demonstrated a decrease in soil solubility in water. An increase in humidity prevented the soil from completely drying and prevented the chemical changes affecting solubility from occurring.

Chemical Changes Over Time Associated with Protein Drying.

Upon drying, physical changes of the characteristics of proteins are observed by coagulation, but the nature and chronology of these changes have not been well studied. Coagulation changes the structure of protein from liquid to a solid or a thicker liquid by heat, mechanical action, or acids. Changes may have implications regarding the cleanability of reusable medical devices; therefore, an understanding of the chemical phenomena associated with drying of proteins is essential to ensuring adequate cleaning and mitigation of retained surgical soils. Using a high-performance gel permeation chromatography analysis with right-angle light-scattering detector at 90°, it was demonstrated that as soils dry, the molecular weight distribution changes. From the experimental evidence, the molecular weight distribution trends over time with drying to higher values. This is interpreted as a combination of oligomerization, degradation, and entanglement. As water is removed through evaporation, the distance between proteins decreases and their interactions increase. Albumin will polymerize into higher-molecular-weight oligomers, decreasing its solubility. Mucin, commonly found in the gastrointestinal tract to prevent infection, will degrade in the presence of enzymes releasing low-molecular-weight polysaccharides and leaving behind a peptide chain. The research described in this article investigated this chemical change.

Validation of the Device Feature Approach for Reusable Medical Device Cleaning Evaluations.

The identification of worst-case device (or device set) features has been a well-established validation approach in many areas (e.g., terminal sterilization) for determining process effectiveness and requirements, including for reusable medical devices. A device feature approach for cleaning validations has many advantages, representing a more conservative approach compared with the alternative compendial method of testing the entirety of the device. By focusing on the device feature(s), the most challenging validation variables can be isolated to and studied at the most difficult-to-clean feature(s). The device feature approach can be used to develop a design feature database that can be used to design and validate device cleanliness. It can also be used to commensurately develop a quantitative cleaning classification system that will augment and innovate the effectiveness of the Spaulding classification for microbial risk reduction. The current study investigated this validation approach to verify the efficacy of device cleaning procedures and mitigate patient risk. This feature categorization approach will help to close the existing patient safety gap at the important interface between device manufacturers and healthcare facilities for the effective and reliable processing of reusable medical devices. A total of 56,000 flushes of the device features were conducted, highlighting the rigor associated with the validation. Generating information from design features as a critical control point for cleaning and microbiological quality will inform future digital transformation of the medical device industry and healthcare delivery, including automation.

Improving Protein Assay Methods to More Accurately Assess Medical Device Cleanliness.

Protein assays commonly used to evaluate reusable device cleanliness do not always accurately measure the low concentrations of protein that are expected on reusable medical devices after processing. Methods often are adapted to provide an estimation of protein concentration; however, sensitivity issues in the portion of standard curves at the acceptance criteria of 6.4 µg/cm2 protein have been reported. Using analytical validation criteria, method improvements for the micro-bicinchoninic acid assay for protein residuals are demonstrated by incorporating a standard addition method, increasing the well volume, and changing the working reagent ratio. These improvements increased method sensitivity and accuracy in the reliable detection of protein levels for device cleaning validations.

Test Soil and Material Affinity for Reusable Device Cleaning Validations.

While selecting the test variables for a cleaning validation for reusable medical devices, the manufacturer must provide a simulative and clinically representative challenge for the device. An appropriate challenge must be identified with care so as not to overchallenge the cleaning process by selecting the worst case for every variable, thus leading to an impossible validation or unrealistic processing requirements. To appropriately select the testing variables, an understanding of the challenge to the cleaning process is important. The relationship among device material, test soil, and application method was investigated by testing 140 variable combinations, including seven materials (stainless steel, polyoxymethylene, polyether ether ketone, nitinol, aluminum, titanium, and silicone), four test soils (defibrinated blood soil, coagulated blood, modified coagulated blood, and Miles soil), and five soil application methods (pipetting neat, pipetting spreader, painting, handling with soiled gloves, and immersion). Stainless steel was the only material that showed consistent soil application in a thickness (at ~6 µL/cm2) that fully covered the test surface without some element of pooling, cracking, flaking, or soil migration with all test soils and application methods. The data collected using solubility testing indicated that a complex relationship for material adherence may exist between device materials and test soil. Stainless steel was the most challenging material tested.

Assessing Detergent Residuals for Reusable Device Cleaning Validations.

Cleaning chemistries are detergent-based formulations that are used during the processing of reusable medical devices. Manufacturers are responsible for demonstrating the safety of cleaning formulations when they are used during a device processing cycle, including the risk of device-associated cytotoxicity over the concentration ranges for recommended use and rinsing during cleaning. However, no regulation currently exists requiring manufacturers to demonstrate such safety. Although manufacturers' safety data sheets (SDSs) provide information on the safe use of chemicals for users, this information may not provide sufficient detail to determine the risks of residual chemicals on device surfaces. SDSs are not required to contain a comprehensive list of chemicals used, only those of risk to the user. They should be supplemented with information on the correct concentrations that should be used for cleaning, as well as instructions on the rinsing required to reduce the levels of chemicals to safe (nontoxic) levels prior to further processing. Supporting data, such as toxicity profiles or cytotoxicity data that support the instructions for use, would provide medical device manufacturers and healthcare personnel with the necessary information to make informed decisions about selection and correct use of detergents. In the current work, cytotoxicity profiles for eight commonly used cleaning formulations available internationally were studied. Although all of these products are indicated for use in the cleaning of reusable medical devices, results vary across the serial dilution curves and are not consistent among detergent types. The information presented here can be leveraged by both medical device manufacturers and processing department personnel to properly assess residual detergent risks during processing. This work also serves as a call to cleaning formulation manufacturers to provide this information for all chemistries.

Thermal Disinfection Validation: The Relationship Between A0 and Microbial Reduction.

Validating a thermal disinfection process for the processing of medical devices using moist heat via direct temperature monitoring is a conservative approach and has been established as the A0 method. Traditional use of disinfection challenge microorganisms and testing techniques, although widely used and applicable for chemical disinfection studies, do not provide as robust a challenge for testing the efficacy of a thermal disinfection process. Considerable research has been established in the literature to demonstrate the relationship between the thermal resistance of microorganisms to inactivation and the A0 method formula. The A0 method, therefore, should be used as the preferred method for validating a thermal disinfection process using moist heat.

Connecting Across Competencies: Leveraging Best Practices for Processing.

The AAMI working group ST/WG 93 is finalizing a standard (AAMI ST98) for the cleaning validation of reusable medical devices based on guidance from the technical information report AAMI TIR30:2011/(R)2016. A number of analytical best practices are being considered for this new standard. Test method suitability for processing cleaning validations historically has been established using one positive control and performing an extraction efficiency. The new cleaning validation standard is proposed to require a change from only one replicate test sample to three when performing method suitability. This change will affect manufacturers; therefore, the value of and consideration for performing these additional replicates requires explanation. This article discusses how variation of validation parameters can affect the accuracy and precision during method suitability testing. Multiple replicates are needed to understand the variability of method extraction and impact on cleaning validations of reusable medical devices.

Research: Dry Heat Processing of Single-Use Respirators and Surgical Masks.

The COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2, has challenged healthcare providers in maintaining the supply of critical personal protective equipment, including single-use respirators and surgical masks. Single-use respirators and surgical masks can reduce risks from the inhalation of airborne particles and microbial contamination. The recent high-volume demand for single-use respirators and surgical masks has resulted in many healthcare facilities considering processing to address critical shortages. The dry heat process of 80°C (176°F) for two hours (120 min) has been confirmed to be an appropriate method for single-use respirator and surgical mask processing.