Washer-Disinfectors: Why Temperature Matters During Prewash
When we think about cleaning, hot water often comes to mind. Heat can help break up soils, improve detergent performance, and support disinfection. However, when it comes to cleaning surgical instruments, hotter isn’t always better.
This is particularly true during the cleaning process in a washer-disinfector, where using excessively hot water during the initial prewash phase can make instruments more difficult to clean.
The Science Behind the Prewash
Surgical instruments frequently enter the cleaning process with residual blood, tissue, and other organic materials. Many of these contaminants contain proteins that are sensitive to temperature.
When proteins are exposed to elevated temperatures, they can undergo a process called denaturation, in which their molecular structure changes. Depending on the protein and conditions, this can lead to coagulation, causing protein-based soils to adhere more strongly to instrument surfaces.
Think about what happens when you cook an egg. As heat changes the structure of its proteins, the clear egg white becomes opaque and solid. A similar process can occur when blood and other protein-based soils are exposed to excessive heat, causing them to adhere more strongly to surgical instruments and making them more difficult to clean.
Why Water Temperature Matters
The prewash phase is designed to remove loose soil before the main cleaning process begins. Using appropriately cool water helps flush away blood and other organic material while reducing the risk of heat-induced protein coagulation.
ISO 15883-1, the international standard addressing washer-disinfectors, specifies that incoming prewash water must be cool enough to prevent protein coagulation. The standard notes that temperatures above 45°C (113°F) can cause coagulation and subsequent cleaning problems.
Importantly, 45°C should not be interpreted as a universal target temperature. Individual instruments and validated washer-disinfector cycles may require substantially cooler water. Generally, the cooler the water used during a prewash step the more effective it will be.
Conclusion
An effective washer-disinfector cycle relies on a carefully controlled sequence of cleaning and disinfection stages. Temperature, mechanical action, chemistry, and time all contribute to the overall process.
The prewash demonstrates why that sequence matters. Introducing excessive heat before protein-based soils have been adequately removed can make subsequent cleaning more difficult, even when later phases operate as intended.
Authored by: Jonathan Carfora, Technical Services Trainer
