ARTICLE FOCUS:

• Hospital acquired infections are on the rise
• Disinfecting medical devices is critical
• Aggressive sterilization can affect polymers and devices

Health-care personnel have patient safety and comfort at the forefront of their minds. Doctors and nurses want reassurance that medical tools and devices are effective, sterile, and safe. But with increasing concerns over hospital-acquired infections (HAIs), patient safety and comfort may be more critical now than ever.

According to the Centers for Disease Control and Prevention (CDC), HAIs kill nearly 100,000 people a year, with 8% to 10% of patients becoming infected while in the hospital. The CDC estimates that costs of HAIs range from $28.4 to $33.8 billion annually. The CDC also reports that recently Medicare and Medicaid shifted the responsibility for costs associated with HAIs from their organizations to hospitals.

To help cut the number of HAIs, hospitals are using highly aggressive disinfectants and sterilization methods. Unfortunately, this approach can cause plastic medical devices to crack, lose critical properties, or change color. Thus, medical device manufacturers need to understand the effect of sterilization on polymers and the final medical devices.

A clear choice
Understanding how the medical device functions helps manufacturers make educated material choices. Manufacturers can then work closely with suppliers to select polymers that offer minimal color shift after sterilization and the best chemical resistance to disinfectants. Color stability is of critical importance because health-care personnel often rely on the color-coded attributes of devices to determine their size, type, and function. Color coding also helps surgeons distinguish among different devices and tools, helping to reduce medical errors and wasted time.

Medical grades of Eastman Tritan copolyester are polymers that maintain clarity, color, and functional integrity after exposure to gamma radiation, compared to other materials.

In addition, clear, colorless medical devices can be as valuable as color-coded devices. For instance, devices with excellent clarity provide healthcare personnel unobstructed views that let them more easily and quickly see foreign substances, bubbles, clots, and fluid levels. Such devices also ensure that the medicine is being properly delivered to the patient. Recognizing potential issues can prevent the onset of bigger, more serious health problems such as embolisms or insertion-site infections.

Additionally, doctors, nurses, and patients associate devices that have excellent clarity with cleanliness. Crystal-clear devices look new, clean, and safe. When a device has changed color as a result of chemical disinfectants or sterilization, its sterility, function, and safety become questionable.

The effects of sterilization on the color and clarity of a particular material depends on the material’s mechanical properties and inherent chemistry as well as the sterilization method used. For example, in radiation sterilization, the type and dose of radiation and the length of time polymers are left to rest after irradiation affect the final polymer color.

Chemical resistance
The wide range of chemical disinfectants that hospitals use includes alcohol, chlorine and chlorine compounds, formaldehyde, hydrogen peroxide, and orthophthalaldehyde. Chemical resistance is controlled largely by polymer type, chemical type, and application. Other factors include temperature, time, molecular weight, mechanical stress, aging, and annealing. Manufacturers should investigate these effects before selecting a polymer for a medical device. A good way to do this is through the testing of material samples in the form of tensile bars, discs, or plaques and subjugating them to the appropriate conditions. These might include applying various stresses and strains, temperatures, chemicals, and exposure times. It’s possible to measure a material’s response to chemicals by appearance, crazing or cracking, or changes in mechanical properties.