Q-286. Determination of Biological Parameters for Critical Devices Exposed to Ethylene Oxide Sterilization Processes
Ethylene oxide (ETO), which is compatible with a variety of materials, has been used to sterilize medical devices sensitive to the heat steam or radiation sterilization. This study aims at qualifying physically, chemically and biologically the sterilizing process by ETO of critical devices; and to set the aeration time for the devices to attain the maximum limits for a safe use of ETO and its derivatives (ethylene chlorohydrin (ECH) and ethylene glycol (EG)). The heart surgery articles were subjected to a mixture of 10% ETO (470 ± 30 mg/L) plus 90% CO2 for 2 hours (membrane oxygenator) and 8 hours (sets of PVC tubing). The synthetic absorbable surgical sutures, arterial-venous fistulae (AVF), hypodermic needles and catheters were subjected from 120 min (half cycle) to 480 min (total cycle) to ETO (650 ± 50 mg/L) mixed to inert gases (CO2 or N2), at 60±10% relative humidity and 55± 5ºC temperature. Following each cycle, the devices were held for 8±2 days in forced aeration (40 ± 5oC, 30% RH, with 26 air changes/h) climate room, for the dissipation of EO residuals, which was followed by gas chromatography determinations. The sterilization processes were monitored by Bacillus atrophaeus ATCC 9372 spores (biological indicator, BI) and by the Green Fluorescent Protein (GFP), as a gas diffusion biosensor. The mean D-value of BI for the sutures, needles, fistulas and catheters was between 10 min and 15 min for ETO (650±50mg/L at 50-60oC and 40-50%UR). The residual concentrations met lower levels than 25 ppm of ETO and ECH and lower than 250 ppm of EG as soon as after sterilization cycle for the oxygenators and 221 hours for the sets of PVC tubing. Therefore, the BI assured a SAL≤10-6 between 120-180 min exposures for the sterilization processes. Decays of the GFP intensity fluorescence were observed to be dependent on the concentration of ETO and exposure to the mixture. The ETO residual concentrations met allowed levels after prolonged aeration time exposures for PVC tubing sets.