Steam Sterilization and Internal Count Sheets: Assessing the Potential for Cytotoxicity

Steam Sterilization and Internal Count Sheets: Assessing the Potential for Cytotoxicity ANNE D. LUCAS, PHD; NANCY CHOBIN, RN, AAS, ACSP, CSPDM; RAMONA CONNER, RN, MSN, CNOR; EDWARD A. GORDON, AA; SHEILA MITCHELL, RN, BSN, MS, CNOR; BEN PERRY; MEL E. STRATMEYER, PHD

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he AORN recommended practices are systematically developed, reviewed, and updated by the AORN Recommended Practices Committee. During the review process for the AORN “Recommended practices for sponge, sharp, and instrument counts”1 in 2005, the committee identified questions regarding the uncertainty and lack of evidence-based research about the exposure of inks and papers to the steam sterilization process and implications for patient safety.2 Nancy Chobin, RN, AAS, ACSP, CSPDM, a member of the AORN Recommended Practices Committee and the principal recommended practices author, initiated collaboration with major toner and paper manufacturers to explore strategies for determining the best way to examine whether the toner ink and paper commonly used in health care facilities for count sheets creates patient care risks (personal communication, Consumer Response Center, Georgia Pacific Paper, and J. Kerns, Xerox Corp, November 17, 2005). Of the manufacturers contacted, Brother International Corporation and Xerox Corp responded to the request for collaboration. Neither company was aware of any published data in the surgical literature on this topic. After initial meetings and clarification of the project goals, Chobin contacted the US Food and Drug Administration (FDA) Center for Devices and Radiological Health for additional guidance. Neither the FDA, the manufacturers, nor a literature review identified any published or unpublished data on this specific topic. Therefore, we began an initial collaboration and exploration to © AORN, Inc, 2009

provide evidence-based guidance for a recommendation on placing count sheets in steam sterilized sets containing stainless steel instruments.

BACKGROUND The practice of using count sheets (ie, tools to expedite counting instruments and recording the number of items used)3 is common in health care settings.4-7 When a sheet of printed paper is placed in contact with an instrument and then steam sterilized, ink can transfer from the paper to the instrument. Although previous studies from the 1960s and 1970s on laboratory mice and involving graphic arts employees noted the potential toxicity of inks,8-10 most inks today are considered nontoxic if ingested.11-13 The composition and use of inks has changed significantly in the

ABSTRACT Count sheets, when placed in contact with surgical instruments during steam sterilization, can transfer ink to the instruments. To explore whether this poses a safety concern, stainless steel instruments were placed on top of completely inked paper and subjected to steam sterilization, extracted, and tested for cytotoxicity. Preprinted labels were examined in a similar fashion. Extracts from stainless steel devices exposed to ink, toner, or labels showed no significant cytotoxic response, although the ink residue on the devices after steam sterilization is difficult to remove and detrimental to the instrument. Placing a barrier between the count sheet and the devices facilitates reuse of the instruments. Key words: steam sterilization, autoclave, count sheets, ink toxicity, stainless steel instruments. AORN J 89 (March 2009) 521-531. © AORN, Inc, 2009.

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past few decades. The material safety data sheets of many inks can be found on the Internet; some list all chemicals used and others are labeled “trade secret.” To date, the evidence-based literature has not examined whether the small quantities of ink that may be transferred from count sheets to surgical instruments pose any potential toxicity.14 The use of preprinted or bar-coded labels in place of count sheets extends this question to the possible transfer of toxic material and outgassing (ie, slow release of a gas) from such labels to surgical instruments.

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selection and use of packaging systems for sterilization” advises that Count sheets should not be placed inside wrapped sets or rigid containers. Although there are no known reports of adverse events related to sterilized count sheets, there is no available research regarding the safety of toners and/or various papers subjected to any sterilization method. Chemicals used in the manufacture of paper and toner ink pose a theoretical risk of reaction in some sensitized individuals.2(p475)

SAMPLE Some commonly used inks and paper were tested under very exaggerated conditions to assess the presence, if any, of resultant cellular toxicity.

PURPOSE The purpose of this project was to examine the potential cytotoxicity of inks and toners on count sheets and preprinted labels that is transferred to surgical instruments under worst case scenarios. We placed instruments in direct contact with fully inked sheets (ie, not a standard practice) to maximize ink and toner transfer before steam sterilization to assess whether there was an immediate concern regarding patient safety because of toxicity.

LITERATURE REVIEW An extensive review of the literature was conducted and demonstrated a paucity of research regarding the potential toxicity of inks and papers subjected to the steam sterilization process and the implications for patient safety. The lack of information on the practice of placing count sheets inside instrument sets prepared for sterilization prompted this project. AORN’s “Recommended practices for

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A small convenience sample was used. Only • black ink and toner, • stainless steel instruments, and • two types of labels were tested. There is a profuse quantity and many types of inks and papers used in health care settings. It is unreasonable to test all combinations of ink and paper. Some commonly used inks and paper were tested under extremely exaggerated conditions (ie, worst case scenarios) as a first pass assessment of the presence, if any, of resultant cellular toxicity. Large facilities, such as government agencies, presumably have similar purchasing practices as health care organizations (ie, lowest cost). With this in mind, we used the paper, ink, machines, and toner available at the FDA White Oak research facility in Silver Spring, Maryland, to test the cytotoxicity of surgical instruments after they had been placed in contact with inked paper and had undergone steam sterilization. Because preprinted labels are sometimes used in health care settings in a similar fashion as count sheets, two different types of labels were also tested to assess cytotoxicity.

MATERIALS To simulate count sheets, the copier used in this project was a Canon imageRUNNER 330S with a Canon GPR-2 black toner cartridge. The printers were a Hewlett Packard (HP) Deskjet 930c with an HP 45 black inkjet print cartridge and an HP Laserjet 9000PS with an HP 43X toner cartridge. Paper was 30% recycled copy

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paper from Staples®. Preprinted bar code labels were S1 Medical bar code labels, supplied by Community Medical Center, Toms River, New Jersey, and Brother P-Touch® TZ-251 tape. The stainless steel devices that we used were spatulas, large dissecting scissors, small dissecting scissors, microdissecting forceps, and microdissecting spring scissors. The reagents for the neutral red assay and the propidium iodide were purchased from Sigma, St Louis, Missouri. The Getinge Castle Model 533LS autoclave was operated under the following conditions: • purged one minute to 30 psi, • conditioned under prevacuum for three minutes at 30 psi and approximately 100° C (212° F), • operated for 20 minutes at 121° C (250° F), and • dried for 10 minutes at 4.75 psi. Cells were obtained from the American type culture collection (ATCC), Manassas, Virginia.

CYTOTOXIC ASSAY METHODS The neutral red cytotoxicity assay procedure is a cell survival/viability chemosensitivity assay, based on the ability of viable cells to incorporate and bind neutral red, a supravital dye.15,16 Neutral red is a weak cationic dye that readily penetrates cell membranes by nonionic diffusion, accumulating intracellularly in lysosomes, where it binds with anionic sites in the lysosomal matrix. Alterations of the cell surface or the sensitive lysosomal membrane lead to lysosomal fragility and other changes that gradually become irreversible. Such changes brought about by the action of xenobiotics result in a decreased uptake and binding of neutral red. It is therefore possible to distinguish between viable, damaged, or dead cells that are the basis of this assay. We used L929 cells (ie, mouse fibroblast cells from ATCC, No, CCL 1 NCTC clone 929) in this assay. Propidium iodide is a dye actively excluded from viable, healthy cells. Damaged and dead cells, unable to remove this dye, generate a fluorescent signal as the propidium iodide binds to the DNA.17,18 Using a flow cytometer (FACScan, BD Biosciences, San Jose, California), cell viability can be evaluated after the addition of 5 mcg/mL propidium

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Alterations of the cell surface or the lysosomal membrane brought about by the action of xenobiotics result in a decreased uptake and binding of neutral red, making it possible to distinguish between viable, damaged, or dead cells that are the basis of the neutral red cytotoxicity assay.

iodide (final concentration). Changes in cell populations were evaluated by gating on the normal cell population and comparing the percentage of dead cells to the test groups over time. We used Jurkat cells (ie, human lymphoma cells from ATCC, No, CRL 8163) in this assay. The data generated by this method use an average of the percentage of dead cells in three separate samples, each of which contained at least 10,000 cells. The variability of the assay is expressed as the standard deviation.

DEVICE EVALUATION METHODS A pilot test was conducted to examine whether ink extracted from printed paper alone would cause a cytotoxic reaction when applied directly to the cells in either of the two assays: the neutral red assay15,16 and a propidium iodidebased assay.17,18 Four paper preparations were extracted: paper with • no ink (ie, the control); • Laserjet toner; • Deskjet ink; and • copier toner. Except for the blank pieces, the paper had a solid block of black ink printed on it (7.5 inches x 10 inches). One set of the four different papers was extracted in 40 mL of phosphate buffered saline (PBS) at 37° C (98° F) for 24 hours, and a second set was extracted in 25 mL of hexane at AORN JOURNAL •

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room temperature under a fume hood for 24 hours. Hexane extract was evaporated to dryness and reconstituted with a small volume of 100% ethanol, and then PBS was added to a final volume of 25 mL. All of the extracts were filtered (0.22 micron) before they were added to cells in culture. None of the paper extracts showed any significant toxicity in the neutral red assay in the pilot test. The Deskjet and the Laserjet ink PBS extracts demonstrated some cytotoxicity in the propidium iodide-based assay only with the PBS extracts. Therefore, a more thorough examination was conducted for the PBS extracts using the propidium iodide-based assay. It should be noted that the difference in cytotoxicity assays is most likely caused by the difference in sensitivity of the different cell types. Four sets of five different stainless steel instruments were used. Each set included • a spatula, • a large pair of dissecting scissors, • a small pair of dissecting scissors, • a large forceps, and • a small forceps. All instruments were cleaned in soap and water, thoroughly rinsed in deionized water, rinsed again in acetone, and dried in a fume hood. One set of instruments (ie, the control set) was extracted in 10 mL PBS for 24 hours at 37° C (98.6° F) after steam sterilization on a blank piece of paper. A second set of instru-

ments was placed on paper printed with a solid block of Deskjet ink (Figure 1a). A third set was placed on paper with a solid block of Laserjet toner. The last set was placed on paper with copier toner. To maximize any potential transfer, instruments were placed in direct contact with these fully-inked sheets before undergoing steam sterilization, although this would not be the normal practice. All instrument sets were steam sterilized for 20 minutes at 121° C (250° F) under the prevacuum setting with a 10-minute drying time. Only the Laserjet paper had a visible transfer of ink from the paper to the instruments (Figure 1b). The control set was sterilized separately to prevent any cross contamination. After sterilization, samples were extracted immediately. The instruments were all extracted in 10 mL of PBS for 24 hours at 37° C (98.6° F). The steam sterilized paper in the area where the instruments were not resting (5 inches x 3.75 inches) was extracted to determine whether steam sterilization increased the cytotoxicity of the printed paper. The same surface area of corresponding non-steam sterilized paper was extracted for use as a positive control. Following extraction, all samples were filtered (0.22 micron) and placed, in triplicate, with an equal volume of Jurkat cells. At 24 and 48 hours, an aliquot of cells was removed, and their viability was assessed. Preprinted labels were tested in a similar

Figure 1a • Placement of the stainless steel instruments on the grossly exaggerated printed count sheet before steam sterilization.

Figure 1b • Stainless steel instruments after steam sterilization on the grossly exaggerated printed count sheet demonstrate staining from the Laserjet sheets.

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fashion as the count sheets, except that normal print densities (ie, instead of exaggerated print areas) were used. Figure 2 illustrates how the preprinted labels were placed in an instrument tray before the tray was covered with a stainless steel lid and sterilized. No towel or barrier was placed between the labels and the stainless steel devices for the purpose of this project. It is important to note that sterile processing personnel usually place a barrier between the labels and instruments, so this project exaggerated ink exposure to the instruments. In addition, labels were placed outside of a sterilization pouch containing scissors and forceps and, as an absolute worst case scenario, labels were placed directly on an instrument and then steam sterilized. Control samples were identical instruments being sterilized in the autoclave in a tray with no labels. After steam sterilization, these devices were treated the same as those used in the count sheet projects. Finally, one of each label was extracted in its entirety—as it was with no adhesive exposed— in PBS to evaluate cytotoxicity from the steam sterilization process. There was no visible transfer of material from the label to the device.

assay. In this particular case, it was the Deskjet ink, most likely because we used a fresh cartridge (Figure 3). Previous extracts of paper printed for the pilot test with Deskjet ink showed about half the percentage of dead cells. The Laserjet toner had approximately a 10% increase in dead cells over the control in the pilot test, but no real increase in the second test. This could have resulted because the Laserjet toner cartridge had not been changed between the pilot test and the second test. No cytotoxicity was seen in the copier printed extracts. In evaluating any toxicity of ink or toner extracted from paper or transferred to a device,

STATISTICAL ANALYSIS Figure 2 • Placement of stainless steel instruments on medical device labels without a towel or other barrier before steam sterilization.

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RESULTS Some paper with ink by itself had a cytotoxic effect in the propidium iodide-based

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Tests of significant difference are difficult to perform on these samples because no sample reached the system’s limit of detection. The limit of detection is the lowest response—in this case, percentage of dead cells— 80 that can be distinguished from the background with 60 confidence. Although there are different ways to establish 40 the limit of detection, generally it is 3.3 times the stan20 dard deviation above the average background signal.18 0 For this project, the average limit of detection would be 12.3% dead cells.

Autoclaved

Figure 3 • The percent of dead cells 24 and 48 hours after exposure to a phosphate buffered saline extract of paper printed with different inks and toners. Note: Error bars represent one standard deviation.

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subjected to steam sterilization while in contact with printed paper, no significant toxicity above that of the control devices was seen in any case. Figure 4 illustrates the lack of difference in cytotoxicity for the microdissection spring scissors extracted after being placed directly on fully inked paper. Almost identical results were 20 seen for all instruments. 24 hours 48 hours Similar results were ob15 served with the device extracts after they were steam 10 sterilized with different preprinted labels. Figure 5 illus5 trates that extracts of devices placed in a tray in direct con0 tact with the preprinted Laserjet Deskjet Copier Control labels showed no cytotoxicity over the control. Placing a Microdissecting spring scissors label on a sterilization pouch or even directly on a device Figure 4 • Percentage of dead cells observed for extracts of a microdissecting spring generated no appreciable scissors that was steam sterilized on fully inked paper. The results do not illustrate cytotoxicity in this project a statistically significant difference in toxicity. Note: Error bars represent one stan(Figure 6a and 6b). dard deviation. % Dead Cells

the age and use of the cartridge apparently plays a significant role. The chemical composition of the many types of ink or toner would probably have significant differences in any cytotoxicity based on the composition of the ink. When the devices were extracted and

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Figure 5 • Percentage of dead cells observed for extracts of each stainless steel device after steam sterilization in contact with different labels. The results do not illustrate a statistically significant difference in toxicity. Note: Error bars represent one standard deviation.

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LIMITATIONS Other sterilization modalities (eg, ethylene oxide, ozone, plasma) were not tested. Although no cytotoxicity was seen in this simulated scenario, only two commonly used labels and three black inks and toners were compared. The project findings cannot be generalized because of the sample size and type, the inability to control for extraneous variables, and testing under con-

% Dead cells

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ditions that were not similar to clinical settings. It is possible that some inks or toners may be toxic when transferred to a device or that devices made of other materials may demonstrate cytotoxicity under these conditions. This initial exploration did not address concerns regarding linting or pilling of the fibrous paper material into the set that may result in inadvertent transfer of microamounts of such foreign material into the surgical incision, in excess of the background macroamounts that 24 hours may be deposited by the tray packing materials.

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DISCUSSION AND RECOMMENDATIONS

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Figure 6a • Percentage of dead cells observed for extracts of stainless steel devices after steam sterilization in a sterilization pouch with a label or with the label placed directly on the device. The labels themselves also were extracted. Note: Error bars represent one standard deviation.

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Figure 6b • Percentage of dead cells observed for extracts of stainless steel devices after steam sterilization in a sterilization pouch with a label or with the label placed directly on the device. The labels themselves were also extracted. Note: Error bars represent one standard deviation.

This initial exploration was designed to address whether there is any immediate or significant concern when count sheets or preprinted labels are placed in contact with stainless steel surgical instruments and subjected to steam sterilization. The practice of using count sheets and preprinted labels with stainless steel instruments during steam sterilization for the specific materials tested does not appear to generate any significant cytotoxicity, at least not in this limited project; however, this does not guarantee that this is a safe practice. This limited project indicates that the practice of using count sheets does not appear to pose an immediate health concern. However, it can be very difficult to clean some devices after they are steam sterilized in direct contact with printed inks and paper. Some of the devices used in this project were discarded because cleaning proved too arduous. AORN AORN JOURNAL •

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guidelines recommend placing a count sheet in a medical-grade, all-paper peel pouch inside the instrument set to prevent transfer of ink to the devices, thus facilitating the reuse and prolonged life of the devices.14,19 The project did not evaluate whether paper debris remains on instruments or whether linting leads to a buildup of debris in the inner sterilizer chamber. The cumulative linting effects to the inner sterilizer chamber, filters, and drains over time are not known. This project provides preliminary information to suggest that label and toner ink transferred during sterilization is not cytotoxic. Further research is needed that will incorporate a larger sample, various sterilization methods, and instruments of different composition and address additional concerns regarding the use of count sheets inside instrument sets and packaging. Note from the AORN Center for Nursing Practice: AORN recommends to central service managers that only medical products for which steam sterilization has been validated to be safe and efficacious be placed in the steam sterilizer. Evaluation processes should be implemented to weigh the risks and benefits of placing a nonvalidated product in the instrument trays against the concerns for inventory control and instrument count procedures. At this time, placing preprinted count sheets into steam sterilized instrument sets needs to be an individual decision for each health care organization. Acknowledgements: The authors thank Gail Matson, program assistant at the US Food and Drug Administration (FDA), White Oak, MD, for her editorial expertise; Terri Matthews, sterile processing manager, Community Medical Center, Toms River, NJ, and Brother International Corporation, Bridgewater, NJ, for the bar-code labels; and Elizabeth Riegel, consumer safety officer at the FDA, White Oak, MD, and James A. Tacci, MD, JD, MPH, manager of Medical, Health and Wellness Services, Xerox Corporation, Webster, NY, and assistant professor of Community and Preventive Medicine at the University of Rochester Medical Center, Rochester, NY, for technical review.

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Disclaimer: The opinions or assertions identified by brand name or otherwise are the private views of the authors and are not to be construed as conveying either an official endorsement or criticism by the US Department of Health and Human Services, the US Food and Drug Administration, Brother International Corporation, or Xerox Corporation. Editor’s notes: Staples is a registered trademark of Staples, Inc; Brother P-Touch Label Systems is a registered trademark of Brother International Corporation, Bridgewater, NJ. The other proprietary products mentioned in this article included products from Canon USA, Inc, Lake Success, NY; Hewlett-Packard Development Company, LP, Palo Alto, CA; and Getinge USA, Inc, Rochester, NY.

REFERENCES 1. Recommended practices for sponge, sharp, and instrument counts. In: Perioperative Standards and Recommended Practices. Denver, CO: AORN, Inc; 2008:293-302. 2. Recommended practices for selection and use of packaging systems for sterilization. In: Perioperative Standards and Recommended Practices. Denver, CO: AORN, Inc; 2008:473-482. 3. Burlingame BL. Count sheets in charts [Clinical Issues]. AORN J. 2007;85(1):189-192. 4. Riley R, Manias E, Polglase A. Governing the surgical count through communication interactions: implications for patient safety. Qual Saf Health Care. 2006;15(5):369-374. 5. Petersen C. Maintaining instrument count sheets [Clinical Issues]. AORN J. 2004;80(2):321-324. 6. Murphy EK. Counts, documentation revisited [OR Nursing Law]. AORN J. 1991;54(4):875-878. 7. Murphy EK. Operating room records, counts cause concern [OR Nursing Law]. AORN J. 1990; 51(6):1606-1612. 8. Carter RL, Mitchley BC, Roe FJ. Preliminary survey of 22 printing inks for carcinogenic activity by the subcutaneous route in mice. Food Cosmet Toxicol. 1969;7(1):53-58. 9. Kay K. Toxicologic and cancerogenic evaluation of chemicals used in the graphic arts industries. Clin Toxicol. 1976;9(3):359-390. 10. Heffron CL, Reid JT, Haschek WM, et al. Toxicologic studies with sheep fed colored magazines and newsprint. Cornell Vet. 1979;69(4):356-363. 11. Mofenson HC, Greensher J. The nontoxic ingestion. Pediatr Clin North Am. 1970;17(3):583-590. 12. Mofenson HC, Greensher J, Caraccio TR. Ingestions considered nontoxic. Clin Lab Med. 1984;4(3):587-602. 13. McGuigan MA; Guideline Consensus Panel. Guideline for the out-of-hospital management of human exposures to minimally toxic substances. J Toxicol Clin Toxicol. 2003;41(7):907-917.

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14. ANSI/AAMI ST79:2006—Comprehensive Guide to Steam Sterilization and Sterility Assurance in Health Care Facilities. Arlington, VA: Association for the Advancement of Medical Instrumentation; 2006: 54, 57-59. http://marketplace.aami.org/eseries /scriptcontent/docs/Preview%20Files%5CST790607 -preview.pdf. Accessed December 4, 2008. 15. Valdivieso-Garcia A, Clarke RC, Rahn K, Durette A, Macleod DL, Gyles CL. Neutral red assay for measurement of quantitative vero cell cytotoxicity. App Environ Mircobiol. 1993;59(6):1981-1983. 16. Carter NP. Measurement of cellular subsets using antibodies. In: Rickwood D, Hames BD, eds.

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Flow Cytometry: A Practical Approach. New York, NY: IRL Press, Oxford; 1990:45-67. 17. Godar DE, Lucas AD. Spectral dependence of UV-induced immediate and delayed apoptosis: the role of membrane and DNA damage. Photochem Photobiol. 1995;62(1):108-113. 18. Currie LA. Detection and quantification limits: origins and historical overview. Analytica Chimica Acta. 1999;391:127-134. 19. Babich H, Borenfreund E. Cytotoxic effects of food additives and pharmaceuticals on cells in culture as determined with the neutral red assay. J Pharm Sci. 1990;79(7):592-594.

Anne D. Lucas, PhD, is a chemist at the US Food and Drug Administration Center for Device and Radiological Health OSEL/DB, Silver Spring, MD. Nancy Chobin, RN, AAS, ACSP, CSPDM, is the corporate central service/SPD educator for the Saint Barnabas Health Care Systems, West Orange, NJ. Ramona Conner, RN, MSN, CNOR, is the manager, Standards and Recommended Practices, AORN Center for Nursing Practice, Denver, CO. Edward A. Gordon, AA, is an engineer technician at the US Food and Drug Administration Center for Device and Radiological Health OSEL/DB, Silver Spring, MD. Sheila Mitchell, RN, BSN, MS, CNOR, is a perioperative nursing specialist, AORN Center for Nursing Practice, Denver, CO. Ben Perry, certified HIPAA professional CHP, is the national sales manager—healthcare at Brother International Corporation, Bridgewater, NJ. Melvin E. Stratmeyer, PhD, is a deputy division director at the US Food and Drug Administration Center for Device and Radiological Health OSEL/DB, Silver Spring, MD.

Cochlear Implantation Surgery Has Low Complication Risk

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ochlear implantation is a safe procedure and has a low complication rate, according to a retrospective study of 500 consecutive cochlear implantations described in the December 2008 issue of Archives of Otolaryngology—Head & Neck Surgery. Data were collected from patients who had procedures at a tertiary referral center in France between 1989 and 2006. Minor complications occurred in 5.6% of procedures and major complications occurred in 3.2%. Reimplantation was required in 7.2% of patients because of device failure; “soft device failure” (ie,

failure despite normal results from integrity testing); infection; or trauma. Nearly three-quarters of the reimplantation surgeries were performed within five years. The researchers found that the risk of severe infection was 1.4%, and they recorded one case of transient facial palsy after surgery. There were no cases of postsurgical meningitis. Venail F, Sicard M, Piron JP, et al. Reliability and complications of 500 consecutive cochlear implantations. Arch Otolaryngol Head Neck Surg. 2008;134(12):1276-1281.

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