Reevaluation of ethylene oxide hemolysis and irritation potential.

The in vitro hemolytic and in vivo mucosal irritation potential of ethylene oxide (EO) was investigated with standard procedures used to determine the biocompatibility of medical devices. Test solutions containing EO at concentrations of 25, 50, 100, 250, 500, 1,250, 2,500, 5,000, or 10,000 microg/mL were prepared in saline to simulate a worst-case aqueous extraction of standard medical devices containing 125, 250, 500, 1,250, 2,500, 6,250, 12,500, 25,000, or 50,000 microg/g of EO, respectively. Concentrations of EO up to 500 microg/mL were not hemolytic ( < 5% hemolysis after a 4-h exposure), whereas > or =1250 microg/mL of EO resulted in significant hemolysis. Hamster cheek pouches exposed to cotton pellets saturated with EO at concentrations of up to 2500 microg/mL for 4 h with a recovery period of 14 days were without effects attributable to EO. However, at > or =5000 microg/mL of EO, significant histomorphological alterations of the buccal mucosa were observed and attributed to EO exposure. It was concluded that solutions of EO of up to 500 microg/mL representing an aqueous extract of a general medical device containing at least 2500 microg/g of EO residue do not result in significant hemolysis and irritation.

Variables affecting simulated use determination of residual ethylene oxide in medical devices.

In autumn 1993, AAMI/ST/WG 63, Sterilization Residuals Working Group undertook the task of studying factors involved in determining the amount of residual ethylene oxide in medical devices after sterilization and developing a protocol for controlling the relevant variables. The protocol was evaluated by conducting a round robin study consisting of 8 participating laboratories from around the country. Results of this round robin study demonstrated the range over which results may vary despite controls placed on the time and temperature at which determinations were conducted. The data from the study suggest that small, random variations in technique during short sample extraction times can lead to variability in the results. Variables such as initial water temperature, oven temperature, weighing of sample, and length of extraction should be carefully controlled. Inherent variations in the material composition of similar devices are possible contributing factors. The efforts of this working group and the subsequent evaluation and discussion of its findings are presented.

Ectoparasites of commensal rodents in Sulawesi Utara, Indonesia, with notes on species of medical importance.

Ectoparasite records are presented for four species of commensal murid rodents (Rattus rattus palelae Miller & Hollister, R. argentiventer (Robinson & Kloss), R. exulans (Peale) and Mus musculus castaneus Waterhouse) in Sulawesi Utara, with particular reference to the potential for these arthropods to bite and transmit pathogens to humans. The flea, Xenopsylla cheopis (Rothschild), was most common on R.r. palelae and is capable of transmitting plague and other pathogens to humans although no current foci for these diseases are known in Sulawesi. Hoplopleura pacifica Ewing and Polyplax spinulosa (Burmeister) sucking lice parasitized all three Rattus species although H. pacifica was mainly associated with R. exulans and P. spinulosa with R.r. palelae. These lice do not bite humans but may be intramurid vectors of murine typhus and other zoonoses. The mites Laelaps echidnina Berlese and L. nuttalli Hirst were both collected; the latter was recorded from all four murid species, mainly R. exulans. The mite Ornithonyssus bacoti Hirst was rare. Only one chigger mite, Walchiella oudemansi (Walch), was retrieved from murids (from R. exulans) and a single Leptotrombidium deliense (Walch) chigger was taken from a human subject. Although L. deliense is a significant vector of scrub typhus, a disease known from Sulawesi, the L. deliense-R. argentiventer relationship frequently noted in the ecology of this rickettsial disease, was not evident in this survey. Other ectoparasites collected from murids were the ticks, Ixodes granulatus Supino (first record for Sulawesi), Haemaphysalis sp. and Dermacentor sp., the mites Myocoptes musculinus (Koch) and Listrophoroides cucullatus (Trouessart), acarids and a uropodid.(ABSTRACT TRUNCATED AT 250 WORDS)

Interlaboratory comparison of analytical methods for residual ethylene oxide in medical device materials.

An interlaboratory comparison of four gas chromatographic test procedures for the quantification of ethylene oxide in an acrylic polymer was conducted by thirteen laboratories. The procedures included extractions with water, acetone, and N,N-dimethylformamide, and headspace gas analysis. The results of this study, using only the data from the labs that did not deviate from the procedure, showed that the average estimated total coefficient of variation ranged from 8 to 22% for the four different methods. Each of the methods is suitable for use as a reference test method for determining residual ethylene oxide in polymeric materials.