Ethylene Oxide Gas Sterilization Research Articles

Comparison of ion plasma, vaporized hydrogen peroxide, and 100% ethylene oxide sterilizers to the 12/88 ethylene oxide gas sterilizer.

The performance of a standard gas sterilizer, which uses a mixture of 12% ethylene oxide (EtO) and 88% chlorofluorocarbon as the sterilizing gas (12/88), was compared to selected gas, ion plasma, and vaporized hydrogen peroxide (H2O2) sterilizers that do not use chlorofluorocarbons. The effect of serum and salt on sterilizer performance was evaluated. Test carriers (porcelain and stainless steel penicylinders, or 125-cm lengths of plastic tubing [internal diameter of 3.2 mm]) were inoculated with Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, Mycobacterium chelonei, Bacillus stearothermophilus spores, Bacillus subtilis spores, and Bacillus circulans spores and then subjected to sterilization using 12/88, 100% EtO, ion plasma, or vaporized H2O2. The bacterial inoculum was prepared with and without 10% serum and 0.65% salt, and the residual bacterial load after sterilization as determined using viable counts. All of the sterilizers tested effected a six-log10 reduction of the bacterial inoculum on penicylinders, unless 10% serum and 0.65% salt were present, in which case the 100% EtO, vaporized H2O2, and ion plasma sterilizers were not as effective as the 12/88 sterilizer. None of the sterilizers could eradicate 10(6) CFU of all of the bacteria in 10% serum and 0.65% salt when inoculated inside a narrow lumen. The margin of safety for the 100% EtO, vaporized H2O2, and ion plasma sterilizers is less than that of the 12/88 sterilizer. The inability of all sterilizers, including the 12/88, to kill organisms in narrow lumens reliably when serum and salt were present raises concern about the current practice of gas sterilization of flexible endoscopes.

Ethylene oxide gas sterilization does not reduce the osteoinductive potential of demineralized bone in rats.

It has been shown that different sterilization procedures of demineralized bone may influence its osteoinductive properties. The aim of this study was to evaluate the effect of ethylene oxide sterilization for 1, 3, and 6 hours on the osteoinductive potential of allogeneic demineralized bone implanted heterotopically in rats. Sixty male Wistar rats were randomly assigned to one of four groups, A through D, and four demineralized bone chips (2.8 mg) were implanted in a pouch created between the right oblique abdominal muscles in each animal. In Group A, the demineralized bone was implanted without prior sterilization of the material, whereas the demineralized bone implanted in Groups B, C, and D had been sterilized in ethylene oxide gas for 1, 3, or 6 hours, respectively, and aerated for 48 hours. At 4 weeks postoperatively, bone formation was evaluated quantitatively by strontium 85 uptake and qualitatively by light microscopy of histological sections. One-way analyses of variance at the 0.05 level revealed no significant difference in strontium 85 uptake of the different groups, and no qualitative differences in osteoinduction could be detected by light microscopy. Ossicles consisting of bone and bone marrow were seen in the recovered implants of all groups.

Ethylene oxide sterilization of bone grafts. Residual gas concentration and fibroblast toxicity.

We examined the concentration of ethylene oxide in bone allografts after gas sterilization. Chips of the human femoral head were investigated. Residual gas concentration was determined by gas chromatography after the bone chips had been subjected to defatting and freeze-drying, followed by ethylene oxide gas sterilization. Bones were prepared in various ways in an attempt to reduce the concentration of residual ethylene oxide. The concentration was higher when gas sterilization was performed before freeze-drying than when it was done afterwards. An experiment performed with fibroblasts showed the high toxicity of residual ethylene oxide in bone chips, even when the concentration was very low. The growth of fibroblast was reduced more in medium which had been shaken with bones sterilized with ethylene oxide before freeze-drying than in medium which had been shaken with bones sterilized after freeze-drying. The higher residual ethylene oxide concentrations resulted in a decrease in fibroblastic culture activity. Our experiment showed the importance of reducing the residual ethylene oxide gas concentration. Defatting and freeze-drying result in lower residual ethylene oxide concentrations.

Comparison of European and US biological indicators for ethylene oxide sterilization

Biological indicators (BIs) are used to monitor ethylene oxide (EO) gas sterilization processes for medical devices. Several European and United States BIs for EO sterilization were evaluated for resistance according to both United States Pharmacopeia (USP) XXI and United Kingdom's (UK) tests for D-values. US BIs areB. subtilis var. niger spores on paper strips or disc carriers while European BIs use aluminum strips, quartz sand, or cotton yarn. Numerous BIs per run and runs per lot, as well as 2–3 different lots of BIs from each manufacturer, were examined. Both British and US BIs met their respective label claims for rates of inactivation when tested against British and USP EO test parameters, respectively. However, Danish BIs, on cotton yarn or quartz sand, were not inactivated following USP specifications during the exposure dwell times tested (600 mg L−1 EO, 54°C, 60% RH, 0–110 min). The Danish BIs will require further testing in order for us to determine if theirB. subtilis spores are unusually resistant to EO or if the spore carrier substrates protect the spores from the sterilizing gas. In conclusion, the British and American BIs for EO sterilization are equivalent in resistance despite differences in carrier substrate, recovery conditions, calculation methods for D-values, and the labeled sterilization conditions for use.

Variability in reprocessing policies and procedures for flexible fiberoptic endoscopes in Massachusetts hospitals

Concern is increasing regarding the risk of transmission of blood-borne pathogens by means of improperly reprocessed medical devices. On-site surveys of policies and practices were performed in 18 reprocessing areas in eight randomly selected hospitals in Massachusetts to assess current practices for reprocessing of flexible fiberoptic endoscopes. Manufacturers' and internal written protocols, were reviewed, employees were interviewed, and procedures were observed. Reprocessing included high-level disinfection in 17 of 18 areas, with 16 areas using 2% glutaraldehyde; ethylene oxide gas sterilization was used in one area. Considerable interhospital and intrahospital variability was found in high-level disinfection procedures, including equipment, contact time (range 10 to 45 minutes), disinfectant testing, and rinsing. Disinfection of internal channels was inadequate in three areas, recommended sterilization of biopsy forceps was not performed in five, and written protocols were unavailable in three. Ad hoc deviation from established written or verbal protocols occurred in eight areas during reprocessing of flexible fiberoptic endoscopes from patients known to have AIDS; ethylene oxide sterilization was used in seven areas and a separate device was used in one. Interviews with personnel revealed that lack of knowledge of high-level disinfection contributed to the discrepancies between policy and practice. We conclude that reprocessing of flexible fiberoptic endoscopes is inconsistent and potentially ineffective. Knowledge that a flexible fiberoptic endoscope was used for a patient with AIDS influences practice.

Nature of Metallic Implant Surfaces and the Importance of their Preparation

SUMMARY In addition to implant design and fabrication, surgical techniques, case selection, periodontal considerations, prosthetic devices, and occlusal forces, the host response can be adversely affected by organic and inorganic contaminants on the implant surface at the time of implantation. These may be caused by inadequate implant preparation, handling, cleaning, or sterilization procedures. Therefore, it is necessary to investigate the effects of cleaning and sterilization methods prior to device implantation to understand the events of ion exchange, mineralization, wound healing, and bioadhesion. The most common source of inorganic and organic contaminants on implant devices is conventional sterilization procedures. It should be noted that conventional processes such as steam autoclaving, ethylene oxide gas sterilization, glass bead immersion, and glutaraldehyde and alcohol soaking all leave surface residues on the implant device. Other techniques, such as UV light treatment or radiofrequency glow discharge treatment, offer both sterilization and cleaning of surface contaminants with resultant surface activation and increased bioadhesion at implant surfaces.

1病院における酸化エチレンによるガス滅菌作業の実態調査

The health and environmental problems of ethylene oxide gas sterilization in a hospital are reported. Eight nurses who had been engaged in the gas sterilization, sometimes operated the auto-sterilizer in an inadequate manner; they exposed more than several hundred ppm of ethylene oxide once or twice a week. The main acute effects on these nurses after massive exposure were headaches, general fatigue and irritation of the eyes and throat. But no signs of polyneuropathy were seen. This survey suggests that there is a great risk of ethylene oxide poisoning while sterilizing instruments in a hospital.

The effect of ethylene oxide gas sterilization of semen straws on mouse embryo survival in vitro

The effect of ethylene oxide gas sterilization of semen straws on mouse embryo survival in vitro

Reactions during hemodialysis caused by allergy to ethylene oxide gas sterilization

In patients receiving long-term hemodialysis (HD), we have examined the presence of IgE-dependent sensitization to ethylene oxide (EO) gas, which is used for sterilization of disposable medical products including dialyzers. Serum was obtained from 25 patients who experienced acute allergic reactions during HD, five patients receiving HD with isolated eosinophilia, and 37 unselected patients receiving HD. Sera from 22 of 25 of the allergic reaction group and from five of 35 of the unselected group were demonstrated to contain IgE antibodies with specificity for EO. Corresponding IgG antibodies were also present. No such antibodies were detected in serum from normal controls or ragweed-allergic patients. The serum from one patient with isolated eosinophilia had a borderline elevated IgE antibody level. These results demonstrate a close relationship between the presence of IgE antibodies to EO and HD-related allergic reactions in this patient population.

Safety of the Ethylene Oxide Gas Sterilization

Safety of the Ethylene Oxide Gas Sterilization

Ethylene oxide: evidence of human chromosomal effects.

Ethylene oxide is a known mutagen as indicated by short-term testing in vitro and in vivo. Occupational exposure can occur during ethylene oxide gas sterilization of materials for hospital and other use. To study the problem in a hospital sterilization facility where occupational exposure was suspected, epidemiologic, analytic and bioassay tools were employed. All persons whose work activities involved some aspect of the sterilization process were considered exposed to the gas. Within this group of symptomatic and asymptomatic individuals, chronic and incidental exposure was documented by clinical history. Sister chromatid exchanges were studied in lymphocytes cultured from exposed individuals as well as comparable controls. Four chronically exposed persons who reported upper respiratory and neurologic symptoms were studied in some detail. This group showed significantly increased sister chromatid exchange at three weeks and again at eight weeks after the last known exposure. Another group of eight persons with fewer complaints studied as late as the ninth week showed significantly increased exchanges. Incidental exposure may also increase sister chromatid exchange. The measured maximum concentration of ethylene oxide in the sterilizer room was 36 ppm (within standards set by the Occupational Safety and Health Administration).

Enzymatic properties and application of L‐asparaginase–collagen membrane

AbstractThe activity of the L‐asparaginase–collagen membrane was 3.4 U/mg membrane (5.8 U/cm2 membrane) and the activity yield was 29%. The apparent Michaelis constant of the asparaginase–collagen membrane was 5.9 × 10−3M. The operational half‐life of the immobilized asparaginase column was 35–40 days. The L‐asparaginase–collagen membrane retained 90% of its original activity after ethylene oxide gas sterilization. The dried membrane stored at room temperature retained its original activity for five months, and the membrane stored in 0.05M phosphate buffer (pH 8.0) retained its original activity for one week at 37°C. The L‐asparaginase–collagen membrane tanned with 1% glutaraldehyde was stable against proteolytic enzymes. Complete degradation of L‐asparagine by the L‐asparaginase–collagen membrane occurred at a low concentration. The L‐asparagine in dog blood plasma was completely degraded within 20 min by the extracorporal shunt using the L‐asparaginase–collagen membrane.

Experiences with sterilization of the operating microscope.

Experiments were conducted to assess the feasibility of both paraformaldehyde and ethylene oxide gas sterilization of the operating microscope. From these experiments and practical experience, it is concluded that ethylene oxide sterilization of the operating microscope is a feasible and desirable alternative to cumbersome draping technique.

Outbreak of Serratia Marcescens Associated with the Flexible Fiberbronchoscope

An outbreak of pulmonary infection due to Serratia marcescens was traced to the use of the flexible fiberbronchoscope. Three patients in two different intensive care units were infected after therapeutic bronchoscopies with a fiberbronchoscope which had been used on a patient identified as having a pulmonary infection from Serratia marcescens . Fluid aspirated through the biopsy channel of the fiberbronchoscope subsequently yielded a heavy growth of the same organism. Cleaning the bronchoscope with 70 percent alcohol and periodic ethylene oxide gas sterilization was found to be inadequate and a sterilization procedure utilizing povidine iodine (Betadine solution) subsequently rendered the bronchoscope aseptic.

The use of laminaria tents for cervical dilatation prior to vacuum aspiration abortion

Laminaria tents have proved to be an extremely useful adjunct to the performance of therapeutic abortion. Their use has markedly decreased the discomfort of mechanical cervical dilatation, and has facilitated the performance of first-trimester abortion without hospitalization. In 1,000 instances of laminaria use there were no uterine perforations and only four cervical lacerations. In four patients a false passage was created at the time of insertion, which was recognized at the time of curettage. Immediate and delayed postabortal complication rates compared favorably with prelaminaria data and the tents may be safely reused after ethylene oxide gas sterilization.

Bacterial pollution and disinfection of the colonofiberscope. II. Ethylene oxide gas sterilization.

Ethylene oxide gas was found consistently to sterilize colonofiberscopes adequately for clinical purposes. The method was established by overnight exposure of the fiberscope to the gas at room temperature and pressure, or by a 30-minute exposure to the gas at 60°C and normal room pressure. Ethylene oxide was found to sterilizeEscherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, andCandida albicans in a short time −30 minutes at 40°C and 15 minutes at 60°C, under microbiologic experimental conditions. Thus, ethylene oxide gas sterilization is recommended as an effective, safe, and inexpensive means of achieving adequate sterilization of the colonofiberscope as well as other endoscopes for clinical use.

Sterile Topical Dosage Forms I: Laboratory Phase

A laboratory investigation was conducted to evaluate the use of conventional sterilizing techniques to manufacture sterile topical dosage forms. Four types of topical dosage forms were investigated: (a) an ophthalmic ointment, (b) a topical cream, (c) a topical ointment, and (d) a topical lotion. Dry-heat sterilization was found to be an acceptable method to sterilize the ophthalmic ointment vehicle. Moist-heat sterilization was found to be an acceptable method to sterilize the topical cream vehicle, part of the topical ointment vehicle, and also part of the topical lotion vehicle. Membrane filtration sterilization was found to be an acceptable method to sterilize the active ingredients in the topical cream, part of the topical ointment vehicle, and the active ingredients and part of the topical lotion vehicle. Ethylene oxide gas sterilization was found to be an acceptable method to sterilize an insoluble, inactive ingredient and the ointment tubes for all four types of topical dosage forms. Residual ethylene oxide determinations showed that longer “venting” times were required for phenolic and urea-formaldehyde capped tubes than polyethylene capped tubes. A microorganism suspension, consisting of Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, Aspergillus niger, and Candida albicans, was used in the contamination studies. In all cases, the sterilized contaminated samples passed the sterility test. A variety of analytical techniques was employed to verify that the sterilizing procedures did not degrade the sterilized material. Included in these techniques were GC, color, and rheology. Aseptic processing of the sterilized components, under conventional sterile room conditions and under laminar air flow, did not present any major problems. All samples passed the finished-product sterility test. All sterile products passed the nonsterile finished-product specifications and showed equivalent chemical and physical stability.

SIMPLIFIED GAS STERILIZATION

SUMMARY The efficacy of ethylene oxide gas sterilization is well documented. However, the inherent problems of time and expense, the addition of heat and/or pressure have proved to be deterrents in universal adoption of the method. A simplified procedure using 84 per cent ethylene oxide without heat or pressure is presented. Appropriate culture controls were maintained. Once the proper technique was developed, all routine weekly cultures have been negative since November 1966. Since this system requires no maintenance, power source or installation, it is adaptable to almost any environs including catastrophic conditions.

Comparative Chemical and Toxicological Evaluation of Residual Ethylene Oxide in Sterilized Plastics

The use of various gases for the sterilization of non-disposable and disposable plastic medical devices has become firmly established in the past decade and a half. However, the subject of sterilant residues remaining in plastic devices following an ethylene oxide gas sterilization has only recently been investigated. This study correlates ethylene oxide residues as determined by gas chromatography to the ability of these residues in polyolefins to elicit toxicological responses in several biological systems. A comparison of the results from a quantitative hemolysis test, rabbit intramuscular implantations with subsequent pathological investigation, cell culture responses, a series of fish tests, and intradermal irritation studies, to the ethylene oxide desorption data, revealed that within 24hr. after sterilization, no significant toxicities were produced by ethylene oxide-sterilized polyolefins. The concentrations of the gas had decreased from a high of 3.20 mg./g. of plastic to as little as 0.20 mg./g. of plastic after aeration at room temperature for 24hr.

Procedure for the evaluation of the virucidal effectiveness of an ethylene oxide gas sterilizer.

A quantitative, reproducible method was developed for the evaluation of the virucidal activity of test gases. Using this method, we determined the virucidal effectiveness of a Steri-Vac ethylene oxide gas sterilizer. Wool gabardine material was exposed to high concentrations of herpes simplex, vaccinia, parainfluenza, or polio viruses and was processed through the sterilizer. Two time-temperature cycles of the machine, 29 C for 180 min and 60 C for 48 min, were used in separate experiments. The viruses were exposed to the gas when freshly pipetted onto the fabric or when pipetted on the material and allowed to dry 16 to 24 hr. In two experiments carried out under each condition, the virus titers were reduced by the sterilization process to less than detectable limits. These titer reductions were for the herpes virus >/= 2.7 to 5.0 log, for vaccinia virus >/= 4.0 to 6.1 log, for parainfluenza virus >/= 1.8 to 4.9 log, and for poliovirus >/= 4.9 to 7.7 log. The observed reductions in virus titers were the same whether the virus-contaminated fabrics were sealed in polyethylene packages or held in open petri dishes during exposure to ethylene oxide.