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Industrial sterilization of medical devices
G Briggs Phillips
Industrial sterilization of medical devices
How many times during the day do you use supplies t h a t have been prepackaged and sterilized by industry? Probably hundreds of times. You don’t worry about the sterility of those items. But industry does. Approximately 200 billion sterile items, solutions, and other preparations are used annually in health care. How does the health care industry ensure the constant sterility of the materials? How is this done without passing on excessive costs of process, testing, and control to the consumer? What assurance do
G Briggs Phillips G Briggs Phillips, PhD, is the Health Industry Manufacturers Association senior vicepresident for scientific affairs. He received his undergraduate degree from the University of Maryland, College Park, and earned his PhD from New York University, New York City. He is a fellow of the American Academy of Microbiology and the American Public Health Association.
the hospital, nurse, physician, and the patient have that the word “sterile” on a product represents the application of every possible and practical method by that company to ensure safety for the user? This article describes the methods employed by industry to provide safe health care products with maximum assurance of sterility when used. Sterility is the absence of viable microorganisms, and sterilization is a process by which all viable organisms are removed or destroyed, based on a probability function. Before 1950, the cleaning, preparation, and sterilization of most medical items were the responsibility of hospital personnel, nurses, physicians, and others in the health care field. They faced problems associated with material compatibility, pyrogenicity, and toxicity, as well as problems with packaging and sterilizing materials, sterility assurance, and storage. In the United States and other countries, nurses, hospital personnel and physicians still face many of these same problems, but to a much lesser extent because of the wide use of single-use, disposable items purchased sterile from the manufacturer. Although disposables have greatly reduced labor costs and cross infection between patients, health care practitioners and patients must still rely upon the manufacturer’s assurance that products advertised and sold as sterile are indeed sterile. While the US Food and Drug Administration (FDA) and some states
AORN Journal, May 1983, V a l 37, No 6
1225
S
terilization is considered in the early stages of product development.
have regulations and guidelines on sterilization, the responsibility for developing manufacturing and sterilization processes rests with industrial medical firms. Industry’s challenge has been twofold. One goal is to develop superior manufacturing methods and mass sterilization of products that will remain sterile until the moment of medical use. The second goal is to accomplish this without adding excessively to the cost of the product. Goals and approach. The goal of an industrial process and the sterility control program is to assure that no product labeled sterile is contaminated. In this context, sterility is a n absolute goal, and no reasonable control aspects can be disregarded. In most industrial companies, a microbiological quality assurance section or department administers sterilization control. This unit is the center of the company’s sterility control program and functions independently of other departments or profit centers. Usually it has authority over plant hygiene, sterilization procedures, sterility testing, and release of sterile products for distribution. The department usually operates through a microbiologist who has laboratory and personnel resources for all necessary work. A sterility control microbiologist officially releases each lot of a sterile product 1226
develops sterilization and sterility testing methods 0 conducts quality control for biological indicators (Biological indicators are microorganisms whose level of resistance to the sterilization cycle of choice is known.) 0 does environmental microbiology and product bioburden studies 0 conducts product development or packaging for new products investigates customer complaints 0 does collaborative studies with regulatory agencies, such as the FDA and the Environmental Protection Agency, or trade associations, such as the Health Industry Manufacturers Association. The microbiology laboratories investigate and develop studies to support the basic microbiological control programs for new and existing products. The application of biological control early in the development of new products and processes is the first element responsible for a reliable, systematic approach to product sterility. N e w product review. Quality control and sterilization are considered early in the development of new products. Proposed materials, product configuration, sterilization possibilities, pyrogenic potential due to microbial flora, package materials, seals and printing modes, regulatory requirements, and related product history influence how and if a device is developed. An early liaison be0
AORN Journal, May 1983, Vol37, No 6
tween design engineers and microbial control interests assures the design and development of manufacturing processes for a product will lend itself to sterilization. Initiation of product manufacturing. When the decision is made to manufacture a new product, the manufacturer’s control process begins. Critical areas are defined and monitored to ensure reliable sterilization. These areas include raw material specifications, machine cleaning materials and procedures, control of atmospheric contamination during manufacturing, control of contamination by personnel during manufacturing, and personnel training and practices. Careful control of these factors minimizes the microbial load on each product. Microbial load is the level of contamination or the number of microorganisms per product before initiation of the sterilization operation. Assurances of product sterility are based upon minimizing the probability of contaminating organisms surviving a sterilization cycle. To further reduce the probability of survival, the raw products and the manufacturing operation’s design minimize the microbial load of products that must be eliminated in a subsequent sterilization procedure. Sterilization methods. Four techniques are commonly used by industry to sterilize medical devices. These are moist heat, dry heat, radiation, and sterilizing gases. Sterilization by filtration of liquids and aseptic assembly of components separately sterilized by the other methods are also sometimes used. The selection of the best sterilization technique or combination of techniques for a product is based on numerous factors, but material compatibility and cycle reliability are the most important. Industrial manufacturers select sterilization techniques and cycles based on years of experience with similar materials and similar products. The man-
1228
ufacturer can thus assure sterrlity without product damage and with minimal cost. Industry has a well-defined approach to establishing sterilization cycles to achieve maximum product safety with minimal product cost. An examination of the unknowns related to the establishment of a sterilization cycle reveals that some biological factors can be determined while others can only be assumed. Those factors that can be determined by laboratory tests are estimates of presterilization contamination load estimates of maximum resistance of microorganisms on the product to the sterilization method selected 0 estimates of relationship of this maximum resistance as compared to that of the biological indicator to be used determination of the time required to kill the biological indicator at the selected treatment condition. Presterilization contamination loads are estimated by examining products manufactured in a production run. That is, products manufactured in the same facility, using the same equipment as will be used to produce the product. Laboratory analyses ofthe products and product packaging will reveal both the number and the types of organisms to be eliminated during sterilization, Each manufacturing procedure is then closely examined to reveal which production processes will eliminate or minimize product contamination during manufacture. The ideal is to have a manufacturing process that results in the production of products virtually devoid of microbial contamination before sterilization. Because raw materials usually are not sterile, large manufacturing areas do not lend themselves to being run as “germ-free” areas, and because people must be present for manufacturing and
AORN Journal, May 1983, Vol37, No 6
inimizing probability of organism survival assures sterilization.
M
inspection functions, it is impractical to devise a manufacturing scheme that results in a sterile product with any reasonable level of confidence. Close scrutiny of the implementation of good manufacturing practices, however, can and does result in the production of ultra-clean products. During the investigation of the product microbial load, specific microorganisms are usually tested to determine their resistance to sterilization cycles. These resistance characteristics are compared to that of the biological indicator of choice. To aid in assurance of sterilization, biological indicators are included in each sterilization cycle. The standardization and quality of the indicators are a key factor in the assurance of adequacy of sterilization cycles. It is well known that the level of resistance of a microorganism is a direct result of its history. That is, by changing growth medium, temperature, or growth conditions, an organism may be made highly sensitive or highly resistant to a particular sterilization mode. Producers of biological indicators conduct extensive laboratory evaluations to assure that the level of resistance is appropriate and as indicated on the label. The importance of determining the relationship of resistance of organisms on the products compared to the biological indicator of choice is quite apparent. By this means, industry is assured that when a sterilization cylce has 1230
been defined for destruction of the biological indicator, sufficient safeguards have been built in to destroy all organisms that may naturally contaminate the product. Sterilizer certification. After the selection of the sterilization technique for a product, the sterilization process undergoes a certification program to verify the adequacy of operation both physically and biologically. The certification program should be documented. Certification programs are sometimes divided into three phases. Phase one is a careful monitoring and characterization of the sterilization capabilities of a particular sterilizer for a specific product. Close examination of the physical parameters as well as extensive sterility testing provide a picture of the capacity of a unit to sterilize a product. Phase two proves that the sterilization cycle inactivates slow-growing microorganisms if present. These organisms could grow slowly by virtue of natural characteristics or as a result of sublethal injury induced by the sterilization cycle. The injury could be such that considerable time is required to repair the organism’s growth mechanisms. During this phase, products are subjected to the cycle and then to prolonged sterility tests. In the final phase, the experience and decisions from phases one and two are used to develop a final specification of
AORN Journal, May 1983, Vol37, No 6
ith precondit ioning, sterilization process begins under ideal conditions.
all aspects of facility operations, product loading, use of biological indicators if required, and quality assurance monitoring to be used in future routine production operations. Next, sterilization cycles using the new product, packaged and loaded in the sterilizer in the way as will be used during the production process are conducted. During certification cycles, the physical cycle parameters are closely monitored throughout the sterilizer unit. Biological indicators are placed in or on the product at concentrations including the one planned for normal operation as well as concentrations many times higher than those planned for the eventual production runs. Following each cycle, the physical parameters are studied, and tests are made on the biological indicators and on a number of the products to verify sterility on a statistical base. The objective of these tests is to certify, both physically and biologically, that the anticipated product load will consistently be inactivated in each unit volume within the sterilizer. Sterilization preconditioning. Before sterilization by ethylene oxide (EO) gas, a product may undergo a presterilization conditioning cycle. This is to assure that products entering the sterilization chamber do so with the temperature and relative humidity required for the effective inactivation of bacteria. Presterilization conditioning adds confi1232
dence to the sterility of the product because it ensures that the sterilization. process starts with ideal environmental conditions. The preconditioning process increases the reliability of the subsequent sterilization procedure. Preconditioning requirements a r e developed for each product during the certification program. Production operations. Following certification of the sterilization process, production begins. The product is manufactured, packaged, and loaded onto sterilization pallets, biological indicators (if used) are added, and preconditioning and other sterilization operations are implemented according to the specifications developed during the certification program. Immediately after sterilization of each product lot, the biological indicators are removed, and the product is taken immediately to a locked quarantine area until the results of sterility assurance determinations are known. Access to the quarantine area and control of the product in quarantine are the responsibility of the sterility control microbiologist. The biological indicators from each lot are taken to the laboratory for testing. All decisions of sterility or nonsterility are made by the microbiologist. If all recorded procedures and cycles are not within specification, or if product sterility is uncertain, the microbiologist rejects the lot. Only the microbiologist’s certification
AORN Journal, May 1983, Vol37, No 6
of sterility constitutes the official release of a product for sale in the company’s name. Signing the certification signifies that all biological safety procedures required have been carried out satisfactorily, and t h a t the product meets all of the company’s requirements for sterility. A carefully planned and executed industrial control program provides the
user with confidence that a product released from quarantine and shipped with a sterile label is sterile. The control program starts with the initial design of a product and ends with the certification of sterility by a competent microbiologist. The many steps between design and certification are constantly controlled and monitored. 0
Sclerotherapy may offer lower costs, risks Injection-compressionsclerotherapy is gaining popularity as a varicose vein management technique. An update on varicose veins treatment by Stephen H Tolins, MD, FACS, in the American Journal of Surgery reports that studies comparing the success rates of surgery and injection-compressionsclerotherapy continue to show little difference. However, overall costs, including hospitalization, work days lost, and complications are higher with surgery. Surgical treatment for varicose veins involves stripping of lengths of saphenous veins. To avoid recurrences, varicose vein surgery must be thorough and remove all varicosities. Dr Tolins cited studies claiming good to excellent results in 85% of varicose vein surgeries. But he also quoted Schwartz who has written that in “over half of the patients in whom there were significant varicosities, the entire greater saphenous system was normal, suggesting that the most popularly utilized operation (that of stripping) is inappropriate. . . . ” Dr Tolins conducted his own study of 66 patients with varicose veins. Fifty-eight patients were offered compression sclerotherapy treatment, and 24 received that treatment. During sclerotherapy, the empty vein near the incompetent perforator vein (which must be carefully located with the leg elevated) is injected with 0.5 ml of sclerosant, perferably 3% Sotredecol. Finger pressure 5 cm distance above and below the needle is maintainedfor 30
1234
seconds after the injection. Veins are injected in ascending order. Then a compression bandage (worn for three weeks), a foam rubber pad covered by an elastic bandage, and a stockinette are applied. After the injections, the patient should walk for one hour each day throughout treatment. Ten to 20 sites may be injected at one time. After treatment, the patient returns for checkups and more injections, if needed. Dr Tolins’s results were excellent for the majority of his patients, meaning veins disappeared and symptoms were relieved. Only two patients judged their results good, because their relief was considerable but not complete. Tolins cited a number of studies that supported his findings: Dobbs, in a follow-up article on injection-compressionvs surgery wrote that “dilated superficial veins and incompetent lower leg perforator veins are best treated by injectionlcompression.” Thomson, in 1979, said, “The stripping operation advocated in the treatment of varicose veins is questioned by the findings.” Complications are rare with injection/compressionsurgery, according to Tolins. That benefit and the lower costs of injection compression, are making it more popular than ever in varicose vein treatment.
AORN Journal, May 1983, Vol37, No 6
Industrial sterilization of medical devices
How many times during the day do you use supplies t h a t have been prepackaged and sterilized by industry? Probably hundreds of times. You don’t worry about the sterility of those items. But industry does. Approximately 200 billion sterile items, solutions, and other preparations are used annually in health care. How does the health care industry ensure the constant sterility of the materials? How is this done without passing on excessive costs of process, testing, and control to the consumer? What assurance do
G Briggs Phillips G Briggs Phillips, PhD, is the Health Industry Manufacturers Association senior vicepresident for scientific affairs. He received his undergraduate degree from the University of Maryland, College Park, and earned his PhD from New York University, New York City. He is a fellow of the American Academy of Microbiology and the American Public Health Association.
the hospital, nurse, physician, and the patient have that the word “sterile” on a product represents the application of every possible and practical method by that company to ensure safety for the user? This article describes the methods employed by industry to provide safe health care products with maximum assurance of sterility when used. Sterility is the absence of viable microorganisms, and sterilization is a process by which all viable organisms are removed or destroyed, based on a probability function. Before 1950, the cleaning, preparation, and sterilization of most medical items were the responsibility of hospital personnel, nurses, physicians, and others in the health care field. They faced problems associated with material compatibility, pyrogenicity, and toxicity, as well as problems with packaging and sterilizing materials, sterility assurance, and storage. In the United States and other countries, nurses, hospital personnel and physicians still face many of these same problems, but to a much lesser extent because of the wide use of single-use, disposable items purchased sterile from the manufacturer. Although disposables have greatly reduced labor costs and cross infection between patients, health care practitioners and patients must still rely upon the manufacturer’s assurance that products advertised and sold as sterile are indeed sterile. While the US Food and Drug Administration (FDA) and some states
AORN Journal, May 1983, V a l 37, No 6
1225
S
terilization is considered in the early stages of product development.
have regulations and guidelines on sterilization, the responsibility for developing manufacturing and sterilization processes rests with industrial medical firms. Industry’s challenge has been twofold. One goal is to develop superior manufacturing methods and mass sterilization of products that will remain sterile until the moment of medical use. The second goal is to accomplish this without adding excessively to the cost of the product. Goals and approach. The goal of an industrial process and the sterility control program is to assure that no product labeled sterile is contaminated. In this context, sterility is a n absolute goal, and no reasonable control aspects can be disregarded. In most industrial companies, a microbiological quality assurance section or department administers sterilization control. This unit is the center of the company’s sterility control program and functions independently of other departments or profit centers. Usually it has authority over plant hygiene, sterilization procedures, sterility testing, and release of sterile products for distribution. The department usually operates through a microbiologist who has laboratory and personnel resources for all necessary work. A sterility control microbiologist officially releases each lot of a sterile product 1226
develops sterilization and sterility testing methods 0 conducts quality control for biological indicators (Biological indicators are microorganisms whose level of resistance to the sterilization cycle of choice is known.) 0 does environmental microbiology and product bioburden studies 0 conducts product development or packaging for new products investigates customer complaints 0 does collaborative studies with regulatory agencies, such as the FDA and the Environmental Protection Agency, or trade associations, such as the Health Industry Manufacturers Association. The microbiology laboratories investigate and develop studies to support the basic microbiological control programs for new and existing products. The application of biological control early in the development of new products and processes is the first element responsible for a reliable, systematic approach to product sterility. N e w product review. Quality control and sterilization are considered early in the development of new products. Proposed materials, product configuration, sterilization possibilities, pyrogenic potential due to microbial flora, package materials, seals and printing modes, regulatory requirements, and related product history influence how and if a device is developed. An early liaison be0
AORN Journal, May 1983, Vol37, No 6
tween design engineers and microbial control interests assures the design and development of manufacturing processes for a product will lend itself to sterilization. Initiation of product manufacturing. When the decision is made to manufacture a new product, the manufacturer’s control process begins. Critical areas are defined and monitored to ensure reliable sterilization. These areas include raw material specifications, machine cleaning materials and procedures, control of atmospheric contamination during manufacturing, control of contamination by personnel during manufacturing, and personnel training and practices. Careful control of these factors minimizes the microbial load on each product. Microbial load is the level of contamination or the number of microorganisms per product before initiation of the sterilization operation. Assurances of product sterility are based upon minimizing the probability of contaminating organisms surviving a sterilization cycle. To further reduce the probability of survival, the raw products and the manufacturing operation’s design minimize the microbial load of products that must be eliminated in a subsequent sterilization procedure. Sterilization methods. Four techniques are commonly used by industry to sterilize medical devices. These are moist heat, dry heat, radiation, and sterilizing gases. Sterilization by filtration of liquids and aseptic assembly of components separately sterilized by the other methods are also sometimes used. The selection of the best sterilization technique or combination of techniques for a product is based on numerous factors, but material compatibility and cycle reliability are the most important. Industrial manufacturers select sterilization techniques and cycles based on years of experience with similar materials and similar products. The man-
1228
ufacturer can thus assure sterrlity without product damage and with minimal cost. Industry has a well-defined approach to establishing sterilization cycles to achieve maximum product safety with minimal product cost. An examination of the unknowns related to the establishment of a sterilization cycle reveals that some biological factors can be determined while others can only be assumed. Those factors that can be determined by laboratory tests are estimates of presterilization contamination load estimates of maximum resistance of microorganisms on the product to the sterilization method selected 0 estimates of relationship of this maximum resistance as compared to that of the biological indicator to be used determination of the time required to kill the biological indicator at the selected treatment condition. Presterilization contamination loads are estimated by examining products manufactured in a production run. That is, products manufactured in the same facility, using the same equipment as will be used to produce the product. Laboratory analyses ofthe products and product packaging will reveal both the number and the types of organisms to be eliminated during sterilization, Each manufacturing procedure is then closely examined to reveal which production processes will eliminate or minimize product contamination during manufacture. The ideal is to have a manufacturing process that results in the production of products virtually devoid of microbial contamination before sterilization. Because raw materials usually are not sterile, large manufacturing areas do not lend themselves to being run as “germ-free” areas, and because people must be present for manufacturing and
AORN Journal, May 1983, Vol37, No 6
inimizing probability of organism survival assures sterilization.
M
inspection functions, it is impractical to devise a manufacturing scheme that results in a sterile product with any reasonable level of confidence. Close scrutiny of the implementation of good manufacturing practices, however, can and does result in the production of ultra-clean products. During the investigation of the product microbial load, specific microorganisms are usually tested to determine their resistance to sterilization cycles. These resistance characteristics are compared to that of the biological indicator of choice. To aid in assurance of sterilization, biological indicators are included in each sterilization cycle. The standardization and quality of the indicators are a key factor in the assurance of adequacy of sterilization cycles. It is well known that the level of resistance of a microorganism is a direct result of its history. That is, by changing growth medium, temperature, or growth conditions, an organism may be made highly sensitive or highly resistant to a particular sterilization mode. Producers of biological indicators conduct extensive laboratory evaluations to assure that the level of resistance is appropriate and as indicated on the label. The importance of determining the relationship of resistance of organisms on the products compared to the biological indicator of choice is quite apparent. By this means, industry is assured that when a sterilization cylce has 1230
been defined for destruction of the biological indicator, sufficient safeguards have been built in to destroy all organisms that may naturally contaminate the product. Sterilizer certification. After the selection of the sterilization technique for a product, the sterilization process undergoes a certification program to verify the adequacy of operation both physically and biologically. The certification program should be documented. Certification programs are sometimes divided into three phases. Phase one is a careful monitoring and characterization of the sterilization capabilities of a particular sterilizer for a specific product. Close examination of the physical parameters as well as extensive sterility testing provide a picture of the capacity of a unit to sterilize a product. Phase two proves that the sterilization cycle inactivates slow-growing microorganisms if present. These organisms could grow slowly by virtue of natural characteristics or as a result of sublethal injury induced by the sterilization cycle. The injury could be such that considerable time is required to repair the organism’s growth mechanisms. During this phase, products are subjected to the cycle and then to prolonged sterility tests. In the final phase, the experience and decisions from phases one and two are used to develop a final specification of
AORN Journal, May 1983, Vol37, No 6
ith precondit ioning, sterilization process begins under ideal conditions.
all aspects of facility operations, product loading, use of biological indicators if required, and quality assurance monitoring to be used in future routine production operations. Next, sterilization cycles using the new product, packaged and loaded in the sterilizer in the way as will be used during the production process are conducted. During certification cycles, the physical cycle parameters are closely monitored throughout the sterilizer unit. Biological indicators are placed in or on the product at concentrations including the one planned for normal operation as well as concentrations many times higher than those planned for the eventual production runs. Following each cycle, the physical parameters are studied, and tests are made on the biological indicators and on a number of the products to verify sterility on a statistical base. The objective of these tests is to certify, both physically and biologically, that the anticipated product load will consistently be inactivated in each unit volume within the sterilizer. Sterilization preconditioning. Before sterilization by ethylene oxide (EO) gas, a product may undergo a presterilization conditioning cycle. This is to assure that products entering the sterilization chamber do so with the temperature and relative humidity required for the effective inactivation of bacteria. Presterilization conditioning adds confi1232
dence to the sterility of the product because it ensures that the sterilization. process starts with ideal environmental conditions. The preconditioning process increases the reliability of the subsequent sterilization procedure. Preconditioning requirements a r e developed for each product during the certification program. Production operations. Following certification of the sterilization process, production begins. The product is manufactured, packaged, and loaded onto sterilization pallets, biological indicators (if used) are added, and preconditioning and other sterilization operations are implemented according to the specifications developed during the certification program. Immediately after sterilization of each product lot, the biological indicators are removed, and the product is taken immediately to a locked quarantine area until the results of sterility assurance determinations are known. Access to the quarantine area and control of the product in quarantine are the responsibility of the sterility control microbiologist. The biological indicators from each lot are taken to the laboratory for testing. All decisions of sterility or nonsterility are made by the microbiologist. If all recorded procedures and cycles are not within specification, or if product sterility is uncertain, the microbiologist rejects the lot. Only the microbiologist’s certification
AORN Journal, May 1983, Vol37, No 6
of sterility constitutes the official release of a product for sale in the company’s name. Signing the certification signifies that all biological safety procedures required have been carried out satisfactorily, and t h a t the product meets all of the company’s requirements for sterility. A carefully planned and executed industrial control program provides the
user with confidence that a product released from quarantine and shipped with a sterile label is sterile. The control program starts with the initial design of a product and ends with the certification of sterility by a competent microbiologist. The many steps between design and certification are constantly controlled and monitored. 0
Sclerotherapy may offer lower costs, risks Injection-compressionsclerotherapy is gaining popularity as a varicose vein management technique. An update on varicose veins treatment by Stephen H Tolins, MD, FACS, in the American Journal of Surgery reports that studies comparing the success rates of surgery and injection-compressionsclerotherapy continue to show little difference. However, overall costs, including hospitalization, work days lost, and complications are higher with surgery. Surgical treatment for varicose veins involves stripping of lengths of saphenous veins. To avoid recurrences, varicose vein surgery must be thorough and remove all varicosities. Dr Tolins cited studies claiming good to excellent results in 85% of varicose vein surgeries. But he also quoted Schwartz who has written that in “over half of the patients in whom there were significant varicosities, the entire greater saphenous system was normal, suggesting that the most popularly utilized operation (that of stripping) is inappropriate. . . . ” Dr Tolins conducted his own study of 66 patients with varicose veins. Fifty-eight patients were offered compression sclerotherapy treatment, and 24 received that treatment. During sclerotherapy, the empty vein near the incompetent perforator vein (which must be carefully located with the leg elevated) is injected with 0.5 ml of sclerosant, perferably 3% Sotredecol. Finger pressure 5 cm distance above and below the needle is maintainedfor 30
1234
seconds after the injection. Veins are injected in ascending order. Then a compression bandage (worn for three weeks), a foam rubber pad covered by an elastic bandage, and a stockinette are applied. After the injections, the patient should walk for one hour each day throughout treatment. Ten to 20 sites may be injected at one time. After treatment, the patient returns for checkups and more injections, if needed. Dr Tolins’s results were excellent for the majority of his patients, meaning veins disappeared and symptoms were relieved. Only two patients judged their results good, because their relief was considerable but not complete. Tolins cited a number of studies that supported his findings: Dobbs, in a follow-up article on injection-compressionvs surgery wrote that “dilated superficial veins and incompetent lower leg perforator veins are best treated by injectionlcompression.” Thomson, in 1979, said, “The stripping operation advocated in the treatment of varicose veins is questioned by the findings.” Complications are rare with injection/compressionsurgery, according to Tolins. That benefit and the lower costs of injection compression, are making it more popular than ever in varicose vein treatment.
AORN Journal, May 1983, Vol37, No 6