Methods of Sterilization II: Chemical Methods

Ethylene oxide, or ETO, is a colorless gas that kills spores and microorganisms by interfering with their metabolic processes. ETO sterilizers decontaminate heat and moisture-sensitive devices like resuscitation bags. After cleaning and rinsing items with demineralized water, they are placed in the sterilizer chamber for a specified time. Items absorbing ETO must then be aerated to allow evaporation and removal of residual gas.

Chemical sterilization is recommended for heat-sensitive medical supplies and equipment containing rubber, plastic, glass, and similar materials that cannot withstand high temperatures. It eradicates bacteria, viruses, and other pathogens using low-temperature chemicals, either gases or liquids. This method prevents damage to sensitive components while effectively removing all microorganisms and their spores from medical devices.

The basic ETO sterilization cycle has five stages: preconditioning and humidification, gas introduction, exposure, evacuation, and air washes, excluding aeration time. Each stage is critical to ensuring complete sterilization of medical devices. The cycle is designed to penetrate packaging layers and reach difficult-to-access areas, such as catheters, making ETO effective for complex device geometries.

Liquid chemical sterilization submerges heat-sensitive, immersible medical devices in an active sterilant solution for a prescribed time at controlled temperature and concentration to kill all microorganisms and spores. Common sterilant solutions include formaldehyde, glutaraldehyde, and hydrogen peroxide. After sterilization, devices are rinsed with water to clear chemical remains, making them safe for clinical use.

Before ETO sterilization, items must be thoroughly cleaned and rinsed with demineralized water to remove contaminants, detergents, or tap-water residues. Items are then placed in packs and filled into baskets or carts before being loaded into the sterilizer chamber. Proper preparation ensures that ETO can effectively penetrate and sterilize all surfaces of the medical devices.

Chemical sterilization treats surgical instruments and medical supplies to help prevent transmission of infectious pathogens to patients. By eradicating all bacteria, viruses, and other pathogens using low-temperature chemicals, it ensures that medical devices are free from microorganisms before clinical use. This is essential for maintaining aseptic conditions and reducing healthcare-associated infections.

ETO sterilization is ideal for medical devices made of particular polymers such as plastic or resin, metals, or glass that cannot tolerate high temperatures. It effectively sterilizes devices with multiple layers of packaging and those located in difficult-to-reach areas, such as catheters. Hospitals widely prefer ETO sterilization because it is the only technique that effectively sterilizes sensitive medical devices without causing damage.