I. Background
In general, medical devices sterilized with ethylene oxide should be analyzed and evaluated for post-sterilization residues, as the amount of residue is closely related to the health of those exposed to the medical device. Ethylene oxide is a central nervous system depressant. If contacted with the skin, redness and swelling occur rapidly, blistering occurs after a few hours, and repeated contact can cause sensitization. Splashing liquid into the eyes can cause corneal burns. In case of prolonged exposure to small amounts, neurasthenia syndrome and vegetative nerve disorders can be seen. It has been reported that the acute oral LD50 in rats is 330 mg/Kg, and that ethylene oxide can increase the rate of aberrations of bone marrow chromosomes in mice [1]. Higher rates of carcinogenicity and mortality have been reported in workers exposed to ethylene oxide. [2] 2-Chloroethanol can cause skin erythema if in contact with the skin; it can be absorbed percutaneously to cause poisoning. Oral ingestion can be fatal. Chronic long-term exposure can cause damage to the central nervous system, cardiovascular system and lungs. Domestic and foreign research results on ethylene glycol agree that its own toxicity is low. Its metabolism process in the body is the same as that of ethanol, through the metabolism of ethanol dehydrogenase and acetaldehyde dehydrogenase, the main products are glyoxalic acid, oxalic acid and lactic acid, which have higher toxicity. Therefore, a number of standards have specific requirements for residues after sterilization by ethylene oxide. For example, GB/T 16886.7-2015 “Biological Evaluation of Medical Devices Part 7: Ethylene Oxide Sterilization Residues”, YY0290.8-2008 “Ophthalmic Optics Artificial Lens Part 8: Basic Requirements”, and other standards have detailed requirements for the limits of residues of ethylene oxide and 2-chloroethanol.GB/T 16886.7-2015 clearly states that when using GB/T 16886.7-2015, it is clearly stated that when 2-chloroethanol exists in medical devices sterilized by ethylene oxide, its maximum allowable residue is also clearly limited. Therefore, it is necessary to comprehensively analyze the production of common residues (ethylene oxide, 2-chloroethanol, ethylene glycol) from the production, transportation and storage of ethylene oxide, the production of medical devices, and the sterilization process.
II. Analysis of sterilization residues
The production process of ethylene oxide is divided into chlorohydrin method and oxidation method. Among them, chlorohydrin method is the early ethylene oxide production method. It mainly contains two reaction processes: the first step: C2H4 + HClO – CH2Cl – CH2OH; the second step: CH2Cl – CH2OH + CaOH2 – C2H4O + CaCl2 + H2O. its reaction process The intermediate product is 2-chloroethanol (CH2Cl-CH2OH). Because of the backward technology of chlorohydrin method, serious pollution of the environment, coupled with the product of serious corrosion of equipment, most manufacturers have been eliminated [4]. The oxidation method [3] is divided into air and oxygen methods. According to the different purity of oxygen, the production of the main contains two reaction processes: the first step: 2C2H4 + O2 – 2C2H4O; the second step: C2H4 + 3O2 – 2CO2 + H2O. at present, the industrial production of ethylene oxide Currently, the industrial production of ethylene oxide mainly adopts the ethylene direct oxidation process with silver as the catalyst. Therefore, the production process of ethylene oxide is a factor that determines the evaluation of 2-chloroethanol after sterilization.
Referring to the relevant provisions in the GB/T 16886.7-2015 standard to execute the confirmation and development of the ethylene oxide sterilization process, according to the physicochemical properties of ethylene oxide, most of the residues exist in the original form after sterilization. Factors affecting the amount of residue mainly include the adsorption of ethylene oxide by medical devices, packaging materials and thickness, temperature and humidity before and after sterilization, sterilization action time and resolution time, storage conditions, etc., and the above factors determine the escape ability of ethylene oxide. It has been reported in the literature [5] that the concentration of ethylene oxide sterilization is usually selected as 300-1000mg.L-1. The loss factors of ethylene oxide during sterilization mainly include: adsorption of medical devices, hydrolysis under certain humidity conditions, and so on. The concentration of 500-600mg.L-1 is relatively economical and effective, reducing the consumption of ethylene oxide and the residue on the sterilized items, saving the sterilization cost.
Chlorine has a wide range of applications in the chemical industry, many products are closely related to us. It can be used as an intermediate, such as vinyl chloride, or as an end product, such as bleach. At the same time, chlorine also exists in the air, water and other environments, the harm to the human body is also obvious. Therefore, when the relevant medical devices are sterilized by ethylene oxide, a comprehensive analysis of the production, sterilization, storage and other aspects of the product should be considered, and targeted measures should be taken to control the residual amount of 2-chloroethanol.
It has been reported in the literature [6] that the content of 2-chloroethanol reached nearly 150 µg/piece after 72 hours of resolution of a band-aid patch sterilized by ethylene oxide, and with reference to the short-term contact devices stipulated in the standard of GB/T16886.7-2015, the average daily dose of 2-chloroethanol to the patient should not be more than 9 mg, and its residual amount is much lower than the limit value in the standard.
A study [7] measured the residues of ethylene oxide and 2-chloroethanol in three types of suture threads, and the results of ethylene oxide were non-detectable and 2-chloroethanol was 53.7 µg.g-1 for the suture thread with nylon thread. YY 0167-2005 stipulates the limit of detection for ethylene oxide for non-absorbable surgical sutures, and there is no stipulation for 2-chloroethanol. Sutures have the potential for large amounts of industrial water in the production process. The four categories of water quality of our ground water is applicable to general industrial protection area and human body non-direct contact with the water area, generally treated with bleach, can control algae and microorganisms in the water, used for sterilization and sanitary epidemic prevention. Its main active ingredient is calcium hypochlorite, which is generated by passing chlorine gas through limestone. Calcium hypochlorite is easily degraded in the air, the main reaction formula is: Ca(ClO)2+CO2+H2O–CaCO3+2HClO. hypochlorite is easily decomposed into hydrochloric acid and water under the light, the main reaction formula is: 2HClO+light—2HCl+O2. 2HCl+O2.Chlorine negative ions are easily adsorbed in sutures, and under certain weakly acidic or alkaline environments, ethylene oxide opens the ring with it to produce 2-chloroethanol.
It has been reported in the literature [8] that the residual 2-chloroethanol on IOL samples was extracted by ultrasonic extraction with acetone and determined by gas chromatography-mass spectrometry, but it was not detected.YY0290.8-2008 “Ophthalmic Optics Artificial Lens Part 8: Basic Requirements” states that the residual amount of 2-chloroethanol on the IOL should not be more than 2.0µg per day per lens, and that the total amount of each lens should not be more than 5.0 The GB/T16886.7-2015 standard mentions that the ocular toxicity caused by 2-chloroethanol residue is 4 times higher than that caused by the same level of ethylene oxide.
In summary, when evaluating the residues of medical devices after sterilization by ethylene oxide, ethylene oxide and 2-chloroethanol should be focused on, but their residues should also be analyzed comprehensively according to the actual situation.
During the sterilization of medical devices, some of the raw materials for single-use medical devices or packaging materials include polyvinyl chloride (PVC), and a very small amount of vinyl chloride monomer (VCM) will also be produced by the decomposition of PVC resin during processing.GB10010-2009 medical soft PVC pipes stipulate that the content of VCM cannot exceed 1µg.g-1. VCM is easily polymerized under the action of catalysts (peroxides, etc) or light and heat to produce polyvinyl chloride resin, collectively known as vinyl chloride resin. Vinyl chloride is easily polymerized under the action of catalyst (peroxide, etc.) or light and heat to produce polyvinyl chloride, collectively known as vinyl chloride resin. When polyvinyl chloride is heated above 100°C or exposed to ultraviolet radiation, there is a possibility that hydrogen chloride gas may escape. Then the combination of hydrogen chloride gas and ethylene oxide inside the package will generate a certain amount of 2-chloroethanol.
Ethylene glycol, stable in nature, is not volatile. The oxygen atom in ethylene oxide carries two lone pairs of electrons and has strong hydrophilicity, which makes it easier to generate ethylene glycol when coexisting with negative chloride ions. For example: C2H4O + NaCl + H2O – CH2Cl – CH2OH + NaOH. this process is weakly basic at the reactive end and strongly basic at the generative end, and the incidence of this reaction is low. A higher incidence is the formation of ethylene glycol from ethylene oxide in contact with water: C2H4O + H2O — CH2OH – CH2OH, and the hydration of ethylene oxide inhibits its binding to free chlorine negative ions.
If chlorine negative ions are introduced in the production, sterilization, storage, transportation and use of medical devices, there is a possibility that ethylene oxide will react with them to form 2-chloroethanol. Since the chlorohydrin method has been eliminated from the production process, its intermediate product, 2-chloroethanol, will not occur in the direct oxidation method. In the production of medical devices, certain raw materials have strong adsorption properties for ethylene oxide and 2-chloroethanol, so the control of their residual amounts must be considered when analyzing them after sterilization. In addition, during the production of medical devices, raw materials, additives, reaction inhibitors, etc. contain inorganic salts in the form of chlorides, and when sterilized, the possibility that ethylene oxide opens the ring under acidic or alkaline conditions, undergoes the SN2 reaction, and combines with free chlorine negative ions to generate 2-chloroethanol must be considered.
Currently, the commonly used method for detecting ethylene oxide, 2-chloroethanol and ethylene glycol is the gas phase method. Ethylene oxide can also be detected by the colorimetric method using pinched red sulfite test solution, but its disadvantage is that the authenticity of the test results is affected by more factors in the experimental conditions, such as ensuring a constant temperature of 37°C in the experimental environment so as to control the reaction of ethylene glycol, and the time of placing the solution to be tested after the color development process. Therefore, confirmed methodological validation (including accuracy, precision, linearity, sensitivity, etc.) in a qualified laboratory is of reference significance for the quantitative detection of residues.
III. Reflections on the review process
Ethylene oxide, 2-chloroethanol and ethylene glycol are common residues after ethylene oxide sterilization of medical devices. To carry out residue evaluation, the introduction of relevant substances in the production and storage of ethylene oxide, production and sterilization of medical devices should be considered.
There are two other issues that should be focused on in the actual medical device review work: 1. Whether it is necessary to carry out the testing of residues of 2-chloroethanol. In the production of ethylene oxide, if the traditional chlorohydrin method is used, although purification, filtration and other methods will be adopted in the production process, ethylene oxide gas will still contain intermediate product 2-chloroethanol to a certain extent, and its residual amount should be evaluated. If the oxidation method is used, there is no introduction of 2-chloroethanol, but the residual amount of relevant inhibitors, catalysts, etc. in the ethylene oxide reaction process should be considered. Medical devices use a large amount of industrial water in the production process, and a certain amount of hypochlorite and chlorine negative ions are also adsorbed in the finished product, which are the reasons for the possible presence of 2-chloroethanol in the residue. There are also cases that the raw materials and packaging of medical devices are inorganic salts containing elemental chlorine or polymer materials with stable structure and not easy to break the bond, etc. Therefore, it is necessary to comprehensively analyze whether the risk of 2-chloroethanol residue must be tested for evaluation, and if there is sufficient evidence to show that it will not be introduced into the 2-chloroethanol or is lower than the detection limit of the detection method, the test can be disregarded to control the risk of it. 2. For the ethylene glycol Analytical evaluation of residues. Compared with ethylene oxide and 2-chloroethanol, the contact toxicity of ethylene glycol residues is lower, but because ethylene oxide production and use will also be exposed to carbon dioxide and water, and ethylene oxide and water are prone to produce ethylene glycol, and the content of ethylene glycol after sterilization is related to the purity of ethylene oxide, and also related to the packaging, the moisture in microorganisms, and the temperature and humidity environment of the sterilization, therefore, ethylene glycol should be considered in accordance with the actual circumstances. Evaluation.
Standards are one of the tools for technical review of medical devices, the technical review of medical devices should focus on the basic requirements of safety and effectiveness of product design and development, production, storage, use and other aspects of the comprehensive analysis of factors affecting the safety and effectiveness of the theory and practice, based on science, based on facts, rather than direct reference to the standard, detached from the actual situation of product design, research and development, production and use. The review work should pay more attention to the medical device production quality system for the control of the relevant links, at the same time on-site review should also be “problem” oriented, give full play to the role of the “eyes” to improve the quality of the review, the purpose of scientific review.
Source: Center for Technical Review of Medical Devices, State Drug Administration (SDA)
Hongguan care about your health.
See more Hongguan Product→https://www.hgcmedical.com/products/
If there are any needs of medical comsumables, please feel free to contact us.
hongguanmedical@outlook.com
Post time: Sep-21-2023