Radiation sterilization of surgical instruments with a consideration of metal shielding on sterilization efficiency.

The feasibility of the use of radiation for sterilization of surgical instruments was evaluated. Two aspects were considered: radiation biology of relevant microorganisms, that is, bacterial spores and viruses, and shielding and radiation protection by the metal of the instruments. After proper cleaning and hot water machine washing, surgical instruments carry few, if any contaminants; however, subsequent handling increases the contamination load. Although large instruments may attenuate as much as 30% of the incident radiation, spores dried on the metal are sensitized to irradiation by some 40%. A dose of 25 kGy (2.5 Mrad) is adequate to inactivate a potential contamination load of approximately 10(7) bacterial spores or approximately 10(4) viruses. Therefore, 25 kGy will provide a high sterility assurance level, and can be recommended with a considerable degree of confidence for hospital-based sterilization of surgical instruments.