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Nurse exposure to waste anesthetic gases in a post anesthesia care unit

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Title:
Nurse exposure to waste anesthetic gases in a post anesthesia care unit
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Book
Language:
English
Creator:
Flack, Larry A
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University of South Florida
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Tampa, Fla
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Subjects / Keywords:
Nitrous oxide
Isoflurane
Desflurane
Sevoflurane
Occupational air sampling
Dissertations, Academic -- Public Health -- Masters -- USF
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bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )

Notes

Abstract:
ABSTRACT: It has been estimated that over 200,000 healthcare professionals may be exposed to waste anesthetic gases and are at risk of occupational injury. In 1977, the National Institute for Occupational Safety and Health (NIOSH) issued the publication: Criteria for a Recommended Standard....Occupational Exposure to Waste Anesthetic Gases and Vapors. This publication was based primarily on scientific evidence from human and animal studies suggesting that chronic exposures to anesthetic gases increases the risk of both spontaneous abortion and congenital abnormalities in offspring among female workers and wives of male workers exposed to waste anesthetic gases. In this recommended standard, NIOSH defines the recommended exposure limits (REL) for nitrous oxide and halogenated anesthetics. NIOSH recommended a time-weighted average (TWA) REL of 25 parts per million (ppm) for nitrous oxide over the period of administration. The REL for halogenated anesthetic gases is a ceiling lim it of two ppm.In this study, waste anesthetic gas exposures to seven Post Anesthesia Care Unit (PACU) nurses were quantified during one day of air sampling within their breathing zones.Nitrous Oxide was sampled using a ChemExpressTM Personal Monitor (Assay Technology, Inc. Pleasanton, CA) attached to the nurse's lapel for approximately three hours. A total of 15 samples were collected. Isoflurane, desflurane, and sevoflurane were sampled using a ChemExpressTM Personal Monitor (Assay Technology, Inc. Pleasanton, CA) attached to the nurse's lapel for approximately three hours. A total of 15 samples were collected. In addition, Isoflurane, desflurane, and sevoflurane were also sampled using Anasorb© 747 sorbent tubes (SKC, Inc. Eighty Four, PA) to compare the passive and active sampling methods. The tubes were attached to the nurses lapel for one hour. A total of 15 samples were collected.The exposures to nitrous oxide and halogenated anesthetics were below the NIOSH RELs.An Analysi s of Variance (ANOVA) showed a statistically significant difference (p < 0.05) in the active and passive sampling methodologies.
Thesis:
Thesis (M.A.)--University of South Florida, 2006.
Bibliography:
Includes bibliographical references.
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System requirements: World Wide Web browser and PDF reader.
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Mode of access: World Wide Web.
Statement of Responsibility:
by Larry A. Flack.
General Note:
Title from PDF of title page.
General Note:
Document formatted into pages; contains 52 pages.

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aleph - 001795703
oclc - 154311497
usfldc doi - E14-SFE0001579
usfldc handle - e14.1579
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ABSTRACT: It has been estimated that over 200,000 healthcare professionals may be exposed to waste anesthetic gases and are at risk of occupational injury. In 1977, the National Institute for Occupational Safety and Health (NIOSH) issued the publication: Criteria for a Recommended Standard....Occupational Exposure to Waste Anesthetic Gases and Vapors. This publication was based primarily on scientific evidence from human and animal studies suggesting that chronic exposures to anesthetic gases increases the risk of both spontaneous abortion and congenital abnormalities in offspring among female workers and wives of male workers exposed to waste anesthetic gases. In this recommended standard, NIOSH defines the recommended exposure limits (REL) for nitrous oxide and halogenated anesthetics. NIOSH recommended a time-weighted average (TWA) REL of 25 parts per million (ppm) for nitrous oxide over the period of administration. The REL for halogenated anesthetic gases is a ceiling lim it of two ppm.In this study, waste anesthetic gas exposures to seven Post Anesthesia Care Unit (PACU) nurses were quantified during one day of air sampling within their breathing zones.Nitrous Oxide was sampled using a ChemExpressTM Personal Monitor (Assay Technology, Inc. Pleasanton, CA) attached to the nurse's lapel for approximately three hours. A total of 15 samples were collected. Isoflurane, desflurane, and sevoflurane were sampled using a ChemExpressTM Personal Monitor (Assay Technology, Inc. Pleasanton, CA) attached to the nurse's lapel for approximately three hours. A total of 15 samples were collected. In addition, Isoflurane, desflurane, and sevoflurane were also sampled using Anasorb¨ 747 sorbent tubes (SKC, Inc. Eighty Four, PA) to compare the passive and active sampling methods. The tubes were attached to the nurses lapel for one hour. A total of 15 samples were collected.The exposures to nitrous oxide and halogenated anesthetics were below the NIOSH RELs.An Analysi s of Variance (ANOVA) showed a statistically significant difference (p < 0.05) in the active and passive sampling methodologies.
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Occupational air sampling.
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PAGE 1

Nurse Exposure to Waste Anesthetic Gases in a Post Anesthesia Care Unit by Larry A. Flack II A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Public Health Department of Environmenta l and Occupational Health College of Public Health University of South Florida Major Professor: Steven Mlynarek, Ph.D. Yehia Hammad, Sc.D. Eugene Szonntagh, Ph.D. Date of Approval: March 24, 2006 Keywords: Nitrous Oxide, Isoflurane, Desflurane, Sevoflurane, Occupational Air Sampling Copyright 2006, Larry A. Flack II

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Acknowledgements A special thanks to Dr. Steven Mlynarek for his expertise, encouragement, and support for this study. I would like to thank Drs. Hammad, Szonntagh, Bernard, Rentos and Roets for their support and guidance throughout my academic career at the College of Public Health. I would also like to thank my parents for allowing me the opportunity to pursue this graduate degree. Your love and support through the years has been an insp iration. I am very fortunate and grateful to have you both as parents.

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i Table of Contents List of Tables ii List of Abbreviations and Acronyms iii Abstract iv Introduction 1 Literature Review 4 NIOSH Recommended Exposure Limits 4 Controversy Surrounding the Developm ent of NIOSH RELs 9 PACU Nurses Breathing Zone during Patient Care 11 Anesthetic Agents 12 Nitrous Oxide 12 Halogenated Anesthetic Gases 14 Studies of PACU Nurse Exposures to Waste Anesthetic Gases 16 Controlling Waste Anesthetic Gas Conc entrations in a PACU 17 Purpose and Hypotheses of this Study 19 Methods 20 Participants 20 Sampling Protocol 20 Results 23 Nitrous Oxide 23 Halogenated Anesthetics (Isoflurane, Sevoflurane, and Desflurane) 24 Nitrous Oxide in Combination with Halogenated Anesthetics 30 Comparison of Active and Passive Sampling Methods 32 Discussion 33 Nurse Exposures to Waste Anesthetic Gases 33 Comparison of Active and Passive Sampling Methods 36 PACU Ventilation 39 Conclusions 41 References 43 Appendices 46 Appendix A: Laboratory Analytical Report 47

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ii List of Tables Table 1. Chemical and Physical De scriptions of Anesthetic Agents (Merck, 2001). 15 Table 2-A. PACU Nurse Exposu re Levels to Nitrous Oxide. 23 Table 2-B. Summary of Nurse Exposures to Nitrou s Oxide. 24 Table 3-A. PACU Nurse Exposure Levels to Isoflurane (Passive Sampling). 25 Table 3-B. PACU Nurse Exposure Levels to Isoflurane (Active Sampling). 25 Table 4-A. PACU Nurse Exposure Levels to Sevoflurane (Passive Sampling). 26 Table 4-B. PACU Nurse Exposure Levels to Sevoflurane (Active Sampling). 27 Table 4-C. Summary of Nurse Exposures to Se voflurane. 27 Table 5-A. PACU Nurse Exposure Levels to Desflurane (Passive Sampling). 28 Table 5-B. PACU Nurse Exposure Levels to Desflurane (Active Sampling). 29 Table 5-C. Summary of Nurse Exposures to Desflurane. 29 Table 6. PACU Nurse Exposure Levels to Nitrous Oxide used in Combination with a Halogenated Anesthet ic. 31 Table 7. Comparison of Ac tive and Passive Sampling Methods for Halogenated Anesthetic Gases. 32 Table 8. Summary of Waste Anesthet ic Gas Exposure Data 35 Table 9. Summary of Occupation al Exposure Limits for Waste Anesthetic Gases (ACGIH, 2005 and NIOSH, 1977). 36

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iii List of Abbreviations and Acronyms ACGIH American Conference of Governmental Industrial Hygienists AIHA American In dustrial Hygiene Association ANOVA Analysis of Variance CI Confidence Interval ICU Intensive Care Unit MAC Minimum Alveolar Concentration NIOSH National Institute of Occupational Safety and Health OSHA Occupational Safety and Health Administration PACU Post Anesthesia Care Unit PPM Parts Per Million REL Recommended Exposure Limit TWA Time-Weighted Average

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iv Nurse Exposure to Waste Anesthetic Gases in a Post Anesthesia Care Unit Larry A. Flack II ABSTRACT It has been estimated that over 200,000 healthcare professionals may be exposed to waste anesthetic gases and are at risk of occupational injury. In 1977, the National Institute for Occupational Safety and Health (N IOSH) issued the publication: Criteria for a Recommended Standa rd….Occupational Exposure to Waste Anesthetic Gases and Vapors. This publication was based primarily on scientific evidence from human and animal studies suggesting that chronic exposures to anesthetic gases increases the risk of both spontaneous abortion and congenital abnormalities in offspring among female workers and wives of male workers exposed to waste anesthetic gases. In th is recommended standard, NIOSH defines the recommended exposure limits (REL) for nitrous oxide and halogenated anesthetics. NIOSH recommended a time-weighted average (TWA) REL of 25 parts per million (ppm) for nitrous oxide over the period of administration. Th e REL for halogenated anesthetic gases is a ceiling limit of two ppm. In this study, waste anesthetic gas exposures to seven Post Anesthesia Care Unit (PACU) nurses were quantified during one day of air sampling within their breathing zones. Nitrous Oxide was sample d using a ChemExpressTM Personal Monitor (Assay Technology Inc. Pleasanton, CA) attached to the nurse’s lapel for approximately three hours. A total of 15 samples were collected. Isoflurane, desflurane, and sevofluran e were sampled using a ChemExpressTM Personal Monitor (Assay Te chnology, Inc. Pleasanton, CA) attached to the nurse ’s lapel for approximatel y three hours. A total of 15 samples were collec ted. In addition, Isof lurane, desflurane, and sevoflurane were also sampled using Anasorb 747 sorbent tubes (SKC, Inc. Eighty Four, PA) to compare the passive and active sampling methods. The tubes were attached to the nurses lapel for one hour. A total of 15 sample s were collected.

PAGE 7

v The exposures to nitrous oxide an d halogenated an esthetics were below the NIOS H RELs. An Analysis of Varian ce (ANOVA) showed a statistically significant difference (p < 0.05) in the active and passive sampling methodologies.

PAGE 8

1 Introduction In 1977, the National Institute for Occupational Safety and Health (NIOSH) issued the publication: Criteria for a Recommended Standard….Occupational Exposure to Waste Anesthetic Gases and Vapors. This publication was based pr imarily on scientific evidence from human and animal studies sugge sting that chronic exposures to anesthetic gases increases the risk of both spontaneous abortion and congenital abnormalities in offspr ing among female workers and wives of male workers (NIOSH, 1977). In addition, acute exposures to waste anesthetic gases have been a ssociated with headaches, nausea, fatigue, and irritability (NIOSH, 1977). The scientific evidence used to develop the recommended standard has been questioned, particularly regarding the validity and reproducibil ity of the studies. Nonetheless, NIOSH issued recommended exposure limits (REL) for nitrous oxide and halogenated anesthetic gases (e.g. sevoflurane, desflurane, isoflurane, halothane). The REL for nitrous oxide is a time weighted average (TWA) concentration of 25 parts per million (ppm) over the period of administration (NIOSH, 1977). The REL for halogenated anesthetic gases is a ceiling limit of two ppm (NIOSH, 1977).

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2 The majority of human eviden ce used to develop the NIOSH publication involved mainly hospit al operating room personnel. However, NIOSH believes that othe r anesthetizing areas have the potential for exposure to waste an esthetic gases that could produce adverse health effects in workers. As of 2006, the Occupational Safety and Health Administration (OSHA) does not have occupational exposure limits for specific waste anesthetic gases. However in 1999, they issued a Waste Anesthetic Gas Guidance Document (OSHA Fact Sheet No. 91-38) that recommends exposure limits identical to the NIOSH REL’s. OSHA does regulate exposures to waste anesthet ic gases under Section 5(a)(1) of the Occupational Safety and Health Act, referred to as the General Duty Clause. An area of particular concern ov er the past several years is the Post Anesthesia Care Unit (PACU). Nurses working in a PACU have the potential to be exposed to waste anes thetic gases at levels that exceed the RELs. The potential for nurse exposure to these gases occurs when patients are disconnected from scavenged anesthesia machines in the operating rooms and transpor ted to the PACU. While in the PACU, the patient exhales waste anesth etic gases into the ambient air. Nurses caring for these patients ofte n work within two to three feet of the patient’s breathing zone where waste anesthetic gas

PAGE 10

3 concentrations could be excessive. Nurses caring for patients throughout the day have the potential to be exposed to these gases at concentrations that exceed those recommended by NIOSH.

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4 Literature Review NIOSH Recommended Exposure Limits In 1977, NIOSH developed recommended exposure limits by investigating and compiling human and animal studies concerning exposures to nitrous oxide and vari ous volatile anesthetics. The scientific evidence derived from thes e studies showed that exposure to anesthetic gases may cause: increa sed risk of spontaneous abortions and congenital abnormalities in o ffspring among female workers and wives of male workers chronically exposed to anesthetic gases; increased risk of liver and kidn ey diseases; increased number of resorptions in pregnant animals; and decrements in performance, cognition, audiovisual ability, and dexterity (NIOSH, 1977). In one particular epidemiologic st udy, the results indicated that female anesthesiologists, nurse-anesthetists, operating room nurses, and technicians in the exposed gr oup (exposure during the first trimester of pregnancy and the preceding year) had a 1.3-2 times increased risk of spontaneous abor tion than that of the unexposed group (NIOSH, 1977). An analysis of the exposed and non-exposed

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5 female anesthesiologist groups sh owed a 60% (p<0.01) increase in congenital abnormalities in the ch ildren of the exposed group (NIOSH, 1977). Another analysis of the female anesthesiologists exposed group suggested a two-fold increase in congenital abnormalities in their children compared with the unexposed female physician anesthesiologists and female pediatricians (p=0.13 and 0.07, respectively) (NIOSH, 1977). The sa me study showed a 25% increase (p=0.04) in the incidence of congen ital abnormalities for the children of exposed physician anesthesiolo gists wives (NIOSH, 1977). The study did not collect data on ty pes of anesthetic agents or concentrations of exposures. In addition to the increased ri sk of abortions and congenital abnormalities, various epidemiologi cal studies reported evidence of increased risks for liver and kidney diseases among workers exposed to anesthetic agents (NIOSH, 1977). During the dental portion of the same study above, the incidence of liver disease among dentists increased 156% (p<0.01) in the exposed group compared to the unexposed group after excluding cases of serum hepatitis due to exposure to blood or blood products (NIOSH, 1977). A study in Czechoslovakia surveyed physicians, nurses, and technicians to determine occupational related health problems. The authors reported an increase in parenchymal damage in the liver, in

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6 kidney dysfunction, and in hematolo gic disorders in the respondents commensurate with the length of service. The study did not use control groups or identify anesth etic agents and concentrations (NIOSH, 1977). In addition to human epidemiologi c studies, animal studies have investigated the toxicities of wast e anesthetic gases. A study was performed to investigate the potential teratogenicity of nitrous oxide in female rats. The pregnant rats were exposed to 50% nitrous oxide and 21-25% oxygen on day eight, 2529% nitrogen for two, four, or six days, or for a single day to 70% nitrous oxide and 30% oxygen within five-11 days. The animals were euthanized on day 20 after exposure. The most common anomalie s from exposure to 50% nitrous oxide were death and resorption of embryos and abnormalities of vertebrae and ribs. The single 24 hour period exposures within day five through 11 indicated a peak incidence of malformation occurring after exposure on day nine (NIOSH, 1977). Another study found that short periods of anesthesia with halothane were teratogenic in pregnant mice. The mice were anesthetized with one or 1.5% ha lothane for three hours on day 12, 13, 14, or 15 of gestation or, altern atively, on three consecutive days in the same period. Upon examining the fetuses, an increase in cleft

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7 palate, limb hematomas, and ossifica tion defects in the limbs of the exposed animals were observed (NIOSH, 1977). A study to measure perceptual, cognitive, and motor skills was performed on 40 male volunteers be tween the ages of 20 and 30. These volunteers were exposed on two occasions to four hours of inhalation of either air (control) or 500 ppm nitrous oxide in air with or without 15 ppm halothane. The re sponses to exposure of nitrous oxide with halothane showed statisti cally significant decreases in the performance of tasks in which attention was divided between auditory and visual signals, a visual tachistoscopic test, and memory tests involving digit span (short term memory test using numbers) and recall word pairs (NIOSH, 1977). Another study with 100 male volunteers was performed to measure perceptual, cognitive, an d motor skills. The following tests were conducted in the study: vi sual perception, immediate memory, and a combination of perception, cognition, and motor responses required in a task of divided atte ntion to simultaneous visual and auditory stimuli. The tests were conducted two hours after exposure to the anesthetic gas and continue d throughout the testing period. Volunteers exposed solely to nitrous oxide scored significantly lower on the digit-span test only. Volunt eers exposed to 50 ppm nitrous oxide and one ppm halothane resulted in de crements of performance for four

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8 of the seven tests administered. Volunteers exposed to 25 ppm nitrous oxide with 0.5 ppm halothan e did not show similar effects. Volunteers exposed to 500 ppm of nitrous oxide alone resulted in decrements of performance in six of the seven tests administered (NIOSH, 1977). After reviewing the available ev idence in the studies, NIOSH determined that the primary conc ern for developing an REL for halogentated anesthetic agents was the adverse effects on reproduction (NIOSH, 1977). However, NIOSH was not able to identify a safe level of exposure to workers based on the studies. Therefore, NIOSH recommended that exposures to halogenated anesthetic agents be no greater than the lowest level detected by sampling and analysis techniques recommended by NIOSH in 1977. This resulted in a ceiling REL of two ppm for each halogenated anesthetic agent. Regarding nitrous oxide, NIOS H considered the agent when combined with volatile anestheti cs and when solely used as an anesthetic agent. NIOSH determin ed that the primary concern for developing an REL for exposure to nitrous oxide alone was decrements in performance, cognition, audiov isual ability, and dexterity (NIOSH, 1977). Based on the data presented in the studies, NIOSH recommends an REL of 25 ppm TWA fo r nitrous oxide when used as

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9 the sole agent for anesthesia (ove r the period of administration) (NIOSH, 1977). NIOSH recommends that the RELs be applied to all workers exposed to inhalation anesthetic ag ents that escape into locations associated with administration of, or recovery from, anesthesia (NIOSH, 1977). Although NIOSH issued the RELs, they maintain a safe level of exposure cannot be defined since information on adverse health effects is not completely definiti ve and many unknown factors still exist (NIOSH, 1977). NIOSH insi sts that the RELs should be considered as the upper boundry of exposure, and every effort should be made to keep exposures to th e lowest level possible by current technology (NIOSH, 1977). Controversy Surrounding the Development of NIOSH RELs Controversy surrounded the NI OSH RELs because many of the studies were questioned in rega rd to validity and reproducibility (Badgwell, 1996). The main concerns centered on how to account for the many positive outcomes that found a statistically significant association between occupational ex posure to waste anesthetic gases and adverse health consequences (Badgwell, 1996). In addition to the

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10 possibility that a direct causal relati onship existed, other explanations included the confounding effects of low response rates, variations in exposure, reporting errors, and recall bias (Badgwell, 1996). The American Dental Association highlights the fact that the investigator who performed the st udy upon which the NIOSH REL was based, stated in letters to the editor of Anesthesia Analgesia (1983) and Anesthesiology (1991), that he believed the conclusions of his study were no longer valid. In those letters, the investigator, Dr. Bruce states “there is no longer any need to refer to our conclusions as controversial. They were wrong, derived from data subject to inadvertent sampling bias and not applicable to the general population” (Anesthesiology, 1991). Dr. Bruce goes on to state the NIOSH RELs should be revised. In the 1990’s, new research was performed with new methodologies to correct the shortcomings of earlier work (Badgwell, 1996). In 1990, an epidemiological study was performed to compare reproductive outcomes for hospit al personnel exposed to waste anesthetic gases in operating and recovery rooms with outcomes of non-exposed personnel (Badgwell, 1996). The results of the study showed that women exposed to th e operating room environment for more than two hours a week had a 124% higher rate of spontaneous abortion (15.6% versus 12.6%) (Ba dgwell, 1996). When the data was

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11 analyzed to remove confounding factors by advanced statistical techniques (e.g. linear logistic regr ession), the study showed an even greater increased risk, 198% for spontaneous abortion (95% confidence interval (CI), 1.532.56) and 224% for congenital anomalies in offspring (95% CI, 1.69-2.97)(Badgwell, 1996). In 1995, a study by Rowland et al was published concerning occupational exposure to nitrous oxide and spontaneous abortion in female dental assistants (Badgwell, 1996). The study indicated that women working in unscavenged envi ronments with nitrous oxide for three hours or more a week had a 260% higher risk of spontaneous abortion (95% CI, 1.3-5.0, adjusted for age, smoking, and the number of mercury amalgams made each week) (Badgwell, 1996). After publication of the newer st udies highlighting the risks of exposure to waste anesthetic gases, NIOSH issued an alert bulletin in June 1994 for employers to control ex posures to nitrous oxide during anesthetic administration (N IOSH Publication No. 94-118). PACU Nurses Breathing Zo ne during Patient Care An observational study was cond ucted to determine the average distance between the breathing zo ne of nurses relative to the breathing zone of their patients, while in the PACU. This study

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12 involved nurses caring for 50 post operative patients. The distance from the nurse’s mouth to the mo uth of the patient was recorded during: admission procedures, drug administration, verbal communication, and airway manageme nt (Allen, et al, 1996). The study showed that nurses performed their duties within four to 36 inches from the patient’s mouth, wi th a majority of work performed within 18 to 24 inches (Allen, et al, 1996). The average and median distances were less than 21 and 20 in ches, respectively (Allen, et al, 1996). The conclusion of the inve stigator was that PACU nurses perform normal work duties an averag e of 21 inches from the patient’s mouth (Allen, et al, 1996). Anesthetic Agents The most commonly used inhalation anesthetic agents today include: nitrous oxide and the ha logenated anesthetic gases (i.e. isoflurane, sevoflurane, and desflurane) (Wenker, 1999). Nitrous Oxide N2O is a colorless, non-explosiv e, nonflammable gas at room temperature with a slightly sweet odor and taste (American

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13 Conference of Governmental Indust rial Hygienist (ACGIH), 2001). The molecular weight of N2O is 44.02, approximately 1.5 times the molecular weight of air. N2O was first introduced as an anesthetic agent in 1844 (ACGIH, 2001). During general anesthesia, nitrous oxide may be administered in co ncentrations up to 70% (700,000 ppm) over a time period of a few mi nutes to several hours (Allen et al, 1996). At the end of a surgery, pati ents exhale the anesthetic gases through the respiratory tract (A llen, et al, 1996). During the elimination process, the alveolar co ncentration of the anesthetic agent mirrors the delivery concentration of the anesthetic agent (Allen, et al, 1996). As the elimination process continues, the concentration of exhaled anesthetic gases decreases ex ponentially (Allen, et al, 1996). A study was performed that me asured the concentration of nitrous oxide during the elimination process. This study showed that after inhalation of 50% nitrous oxid e for five minutes, more than two hours were required for the end-tidal concentrations of nitrous oxide to decrease to the NIOSH REL of 25 ppm. Inhalation of 50% nitrous oxide for 30 minutes required fo ur hours before the end-tidal concentrations decreased to the NIOS H REL. The study also showed that patients who inhaled 50% ni trous oxide for 60 to 150 minutes, maintained end-tidal concentrations that exceeded 100 ppm for more than three hours (Allen, et al, 1996).

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14 Halogenated Anesthetic Gases (Isoflurane, Sevoflurane, and Desflurane) Isoflurane (Forane; C3H2ClF5O) is a colorless, nonflammable liquid with a slight pungent odor (Baxter, 2005). The molecular weight of C3H2ClF5O is 184.50, approximately 6.4 times the molecular weight of air. Isoflurane was involved in investigational studies in the 1970s (NIOSH, 1977). The Food and Drug Administration (FDA) approved the anesthetic agent in December of 1980 (OSHA, 2000). A study was performed to illustrate the rate of nitrous oxide and isoflurane gas elimination in patients undergoing elective pelvic, orthopedic, or abdominal surgeries (Allen, et al, 1996 ). Upon patient arrival at the PACU, end-tidal concentrations of nitrous oxide averaged 43,708 13,190 ppm, isoflurane concentrat ions averaged 1,638 518 ppm, and after 60 minutes end-tidal conc entrations were 14,077 9,213 ppm for nitrous oxide and 833 98 ppm for isoflurane (Allen, et al, 1996). Sevoflurane (Ultane; C4H3F7O) is a colorless, nonflammable liquid with a non-pungent odor (Abbott Laboratories, 2003). The molecular weight of C4H3F7O is 200.05, approximately 7 times the molecular weight of air. The FDA approved sevoflurane for use in the United States in January 1995 (Y oung, et al, 2005). Desflurane

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15 (Suprane; C3H2F6O) is a colorless, nonflammable liquid with a slight pungent odor (Baxter, 2005). The molecular weight of C4H3F7O is 168.04, approximately 6 times the mole cular weight of air. Desflurane was introduced for use in the Un ited States in 1992 (OSHA, 2000). Both sevoflurane and desflurane replaced isoflurane in the 1990s (Eger, 2005). These three anesthetic agents are halogenated with fluorine, making them nonflammable and decreasing their toxicity (compared with chloroform based anes thetics that are no longer used) (Eger, 2005). Since these anesthetic agents are relatively new, their toxicity has not been well characteri zed regarding chronic occupational exposure (Badgwell, 1996). A chemical and physical descriptio n of the anesthetic agents is provided in Table 1. Table 1. Chemical and Physical Descriptions of Anesthetic Agents (Merck, 2001). Anesthetic Agent CAS Number Physical State Molecular Weight Density Boiling Point (C) Nitrous Oxide10024-97-2Gas44.011.53 (gas)-88.46 Isoflurane26675-46-7Liquid184.491.4548.5 Sevoflurane28523-86-6Liquid200.051.5058.6 Desflurane57041-67-5Liquid168.041.4423.5

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16 Studies of PACU Nurse Exposure to Waste Anesthetic Gases Over the past several year s, there have been studies documenting compliance and noncompliance to the NIOSH RELs concerning nurse exposure to waste anesthetic gases in PACUs. In one particular study performed by Sessler, et al (1996), the breathing zone of PACU nurses was measured for concentrations of isoflurane, desflurane, and nitrous oxide for each individual patient (i.e. one set of exposure measurements per nurse for each patient that nurse attended). The results of this study were that breathing zone concentrations for isoflurane and de sflurane exceeded NIOSH RELs in 37% and 87% of the patients, respectively, and breathing zone concentrations for nitrous oxide exce eded RELs in 53% of patients. The investigators also mentioned in this study that the PACU averaged eight air changes per hour, and the majority of this air was recirculated. In another study performed by Krenzichek, et al (2002), the breathing zone of PACU nurses was measured for concentrations of waste anesthetic gases. The resu lts of the study indicated nurse exposure to nitrous oxide ranged from 2.9 ppm to 8.2 ppm (timeweighted average over the workshift ), and exposure to halogenated anesthetic gases were below dete ction limits. The investigators

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17 indicated the PACU was designed fo r six air changes per hour. These results were below the NIOSH RELs. A study performed by Bueck, et al (2001), measured exposures of nitrous oxide, isoflurane, desflu rane, and sevoflurane to intensive care unit (ICU) and PACU nurses. Th e results of this study indicated PACU nurses were exposed to desflurane and sevoflurane concentrations that exceeded the NIOSH RELs. The concentrations were 2.80 0.84 ppm for desflurane and 3.20 0.62 ppm for sevoflurane. PACU nurse exposure to isoflurane and nitrous oxide was within the NIOSH RELs. The concen trations were 1.30 0.54 ppm for isoflurane and 10.30 2.82 ppm for ni trous oxide. The investigators indicated the PACU ventilation system was designed for 15 air changes per hour, and 60% of the air was recirculated. Controlling Waste Anesthetic Ga s Concentrations in a PACU In a PACU, the source of waste an esthetic gases is the patient. An engineering control used to re duce the concentration of waste anesthetic gases in the ambient air of a PACU is ventilation. In the NIOSH Criteria for a Recommende d Standard to Occupational Exposures to Waste Anesthetic Gases and Vapors it states that PACUs must be provided with air exchan ge rates in compliance with those

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18 specified by the United States Department of Health, Education, and Welfare in Minimum Requirements of Construction and Equipment for Hospital and Medical Facilities (HEW Publication No. 74-4000, Rockville, Maryland, 1974). NIOSH recommends ventilation systems be maintained regularly and verifi ed by at least quarterly airflow measurements (NIOSH, 1977). More Recently, The American Institute of Architects and the National Inst itute of Health have recommended dilution ventilation. The dilution ventilation system should provide a minimum of six air changes per ho ur containing a minimum of 33% outside make-up air (OSHA, 2000). The Florida Building Code also recommends a minimum of 6 air ch anges per hour containing a minimum of 33% outside make-up air (International Code Council, Inc., 2004). The exhaust air from the ventilation system should not be re-circulated to other areas of the hospital. OSHA recommends two work practices to help define and reduce exposures to waste anesthetic gase s in the PACU, they include: periodic personnel exposure moni toring and a routine ventilation system maintenance program. Pers onnel exposure monitoring should include sampling for waste anesthetic gases in the breathing zone of PACU nurses during peak gas levels The sampling event should be performed every six months (OSHA, 2000).

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19 Purpose and Hypotheses of this Study The purpose of this thesis wa s to determine the occupational exposure of PACU nurses to nitrous oxide and halogenated anesthetic gases (isoflurane, desflurane, and se voflurane) in the PACU of a local Tampa hospital. The hypotheses were: 1. The levels of nitrous oxid e exposure are acceptable. 2. The levels of isoflurane exposure are acceptable. 3. The levels of desflurane exposure are acceptable. 4. The levels of sevoflurane exposure are acceptable. 5. There is no difference in th e results between active and passive sampling for the halo genated anesthetic gases. For the purpose of this study, “acceptable” exposures indicates concentrations of anesthetic agents below the NIOSH RELs.

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20 Methods Participants Participants for this study were PACU nurses. The manager of the PACU selected the nurses to particip ate in the study. The participants included six female nurses and one male nurse. Nurses were instructed to perform their normal work duties during the sampling event. Each nurse participating in the study sign ed an informed consent document that was approved by the University of South Florida Institutional Review Board. Sampling Protocol The anesthetic gases sampled for in this study were determined after meeting with the Chief of Anes thesiology to determine the most commonly used anesthesia agents in this particular PACU. These agents consisted of nitrous oxid e, isoflurane, sevoflurane, and desflurane.

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21 Nitrous Oxide was samp led using a ChemExpressTM Personal Monitor (Assay Technology Inc. Pleasanton, CA) attached to the nurse’s lapel for approximately three hours. A total of 15 samples were collected. The monitors were analyzed by Assa y Technology, Inc. at their American Industri al Hygiene Association (AIHA) accredited laboratory in Pleasanton, CA. The monitors were prepared for analysis by desorping the sorbent material (m olecular sieve pellets) in a vial containing deionized wa ter. The headspace was analyzed using a gas chromatograph/ electron capture detector. One field blank was sent for analysis. Isoflurane, desflurane, and se voflurane were sampled using a ChemExpressTM Personal Monitor (Assay Te chnology, Inc. Pleasanton, CA) attached to the nurse ’s lapel for approximatel y three hours. A total of 15 samples were collected. The monitors were analyzed by Assay Technology, Inc. at their AIHA accred ited laboratory in Pleasanton, CA. The monitors were prepared for an alysis by desorbing the sorbent material (coconut charcoal) in carb on disulfide, and analyzed using a gas chromatograph / flame ionization detector. One field blank was sent for analysis. Isoflurane, desflurane, and sevo flurane were also sampled using Anasorb 747 sorbent tubes (SKC, Inc. Eighty Four, PA). OSHA recommends sampling for desflura ne and sevoflurane using Anasorb

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22 747 sorbent tubes using a fl ow rate of 0.05 liters per minute (lpm) with a maximum air volu me of 3 liters. OSHA recommends sampling for isoflurane using Anasorb 747 sorbent tubes using a flow rate of 0.05 liters per minute (lpm) with a maximum air vo lume of 12 liters. Prior to sampling, Buck Basic-5TM personal air sampling pumps (AP Buck, Inc. Orlando, FL) and low-flow tube holder s (AP Buck, Inc. Orlando, FL) were calibrated using the Mini-BuckTM Model M-5 calibrato r (AP Buck, Inc. Orlando, FL). The air sampling pu mps and low-flow tube holders were calibrated to a flow rate of 0.05 lpm. During sampling, the personal sampling pump was attached to the nurse’s waist band The low-flow tube holders (containing the Anasorb 747 sorbent tubes) were attached to the nurse’s lapel and were connected to the pump by inch Tygon tubing. The sampling time for each sorbent tube was approximately one hour. A total of 15 samples were collected. The sorbent tubes were analyzed by Assa y Technology, Inc. at their AIHA accredited laboratory in Pleasanton CA. The monitors were prepared for analysis by desorping the coconut charcoal in carbon disulfide, and analyzed using a gas chromatograph / flame ionization detector. One field blank was se nt for analysis. At the conclusion of sampling, the air sampling pumps and lowflow tube holders were calibrated to ensure proper air flow rates. The pre-sampling and post-sampling flow rates were within 5%.

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23 Results Table 2-A below lists the nitrous ox ide exposure levels to nurses. The mass values list the amount of nitrous oxide found in the headspace of the sample during laboratory analysis. All of the mass values have been corrected for the bl ank sample listed at the bottom of the table. Table 2-A. PACU Nurse Exposu re Levels to Nitrous Oxide. Nurse Sample ID Mass N2O (g) Detection Limit (g) Sample Volume (L) Sample Time (min) Concentration1 (ppm) Adjusted Concentration2 (ppm) AFB02451.220.20.1351802.7 AFB04020.8550.20.1341791.2 AFB15320.720.20.1351800.7 BFB18750.4170.20.131175ND 0.6 BFB11830.8660.20.1371831.3 CFB0485ND0.20.136181ND 0.6 CFB08290.4740.20.139185ND 0.6 DFB11751.710.20.1361814.7 DFB21591.430.20.1391853.5 DFB15060.8590.20.1171561.4 EFB17310.9590.20.1381841.6 EFB16740.8080.20.1361811.0 EFB04301.10.20.1271692.4 F FFB17440.7690.20.1421890.8 G GFB03662.610.20.1311748.7 BLANK0.5540.2--n = 151 Values corrected for blank sample2 Adjusted concentration using formula (L/ v 2), where L is the detection limit. g Microgram; L Liter; min Minute; and ppm Parts Per Million. E A B C D

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24 Table 2-B lists the descriptive statistics and measures of variation including the upper and lo wer 95% confidence intervals for nurse exposures to nitrous oxide. Table 2-B. Summary of Nurse Exposures to Nitrous Oxide. StatisticsN2O (ppm) Maximum8.7 Minimum0.6 Range8.1 Mean2.12 Median1.3 Standard Deviation2.18 Lower Confidence Limit (95%)0.91 Upper Confidence Limit (95%)3.33 n = 15 ppm Parts Per Million Table 3-A lists the isoflurane exposu re levels to nurses measured by passive sampling. Table 3-B lists th e isolfurane exposure levels to nurses measured by ac tive sampling.

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25 Table 3-A. PACU Nurse Exposure Levels to Isoflurane (Passive Sampling). NurseSample ID Mass C3H2ClF50 (g) Detection Limit (g) Sample Volume (L) Sample Time (min) Concentration (ppm) Adjusted Concentration1 (pp m ) AFD0629ND20.677179ND0.39 AFD1532ND20.68180ND0.39 AFD0081ND20.684181ND0.39 BFD1173ND20.692183ND0.38 BFD0665ND20.692183ND0.38 CFD0935ND20.684181ND0.39 CFD1425ND20.688182ND0.39 DFD0608ND20.68180ND0.39 DFD1653ND20.711188ND0.37 DFD1244ND20.59156ND0.45 EFD1295ND20.696184ND0.38 EFD1559ND20.68180ND0.39 EFD0852ND20.631167ND0.42 FFFD0279ND20.699185ND0.38 GGFD1606ND20.662175ND0.40 BLANKND2---n = 15 g Microgram; L Liter; min Minute; and ppm Parts Per Million.1 Adjusted concentration using formula (L/ v 2), where L is the detection limit. E A B C D Table 3-B. PACU Nurse Exposure Levels to Isoflurane (Active Sampling). Nurse Sample ID Mass C3H2ClF5 (Front/Back)(g) Detection Limit (g) Sample Volume (L) Sample Time (min) Concentration (ppm) Adjusted Concentration1 (ppm) 2963AND/ND23.0462ND0.09 2957AND/ND23.0963ND0.09 2960AND/ND22.8458ND0.09 2954BND/ND22.9460ND0.09 2959BND/ND22.9961ND0.09 2421CND/ND23.0060ND0.09 2423CND/ND22.9559ND0.09 2419DND/ND23.0561ND0.09 2962DND/ND23.2565ND0.08 2414DND/ND23.0060ND0.09 2417END/ND23.0462ND0.09 2415END/ND22.9961ND0.09 2418END/ND22.9460ND0.09 F2955FND/ND22.9460ND0.09 G2958GND/ND22.8458ND0.09 BLANKND/ND2--n = 15 g Microgram; L Liter; min Minute; and ppm Parts Per Million. E1 Adjusted concentration using formula (L/v2), where L is the detection limit. A B C D

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26 Table 4-A lists the sevofluran e exposure levels to nurses measured by passive sampling. Table 4-B lists the sevoflurane exposure levels to nurses measured by active sampling. Table 4-C lists the descriptive statistics and me asures of variation including the upper and lower 95% confidence intervals for nurse exposures to sevoflurane. Table 4-A. PACU Nurse Exposure Levels to Sevoflurane (Passive Sampling). NurseSample ID Mass C4H3F7O (g) Detection Limit (g) Sample Volume (L) Sample Time (min) Concentration (ppm) Adjusted Concentration1 (pp m ) AFD0629ND20.628179ND0.39 AFD1532ND20.632180ND0.39 AFD0081ND20.635181ND0.38 BFD1173ND20.642183ND0.38 BFD0665ND20.642183ND0.38 CFD0935ND20.635181ND0.38 CFD1425ND20.639182ND0.38 DFD0608ND20.632180ND0.39 DFD1653ND20.66188ND0.37 DFD1244ND20.548156ND0.45 EFD1295ND20.646184ND0.38 EFD1559ND20.632180ND0.39 EFD0852ND20.586167ND0.42 FFFD0279ND20.649185ND0.38 GGFD1606ND20.614175ND0.40 BLANKND2---n = 15 g Microgram; L Liter; min Minute; and ppm Parts Per Million.1 Adjusted concentration using formula (L/ v 2), where L is the detection limit. C D E A B

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27 Table 4-B. PACU Nurse Exposure Levels to Sevoflurane (Active Sampling). Nurse Sample ID Mass C4H3F7O (Front/Back)(g) Detection Limit (g) Sample Volume (L) Sample Time (min) Exposure (ppm) Adjusted Concentration1 (ppm) 2963AND/ND23.0462ND0.08 2957A8.44/ND23.09630.332960A22.2/ND22.84580.942959BND/ND22.9961ND0.08 2954B9.48/ND22.94600.392421C5.15/ND23.00600.212423C24.1/ND22.95590.982419DND/ND23.0561ND0.08 2962D11.4/ND23.25650.0422414D9.28/ND23.00600.372417E4.49/ND23.04620.182415E8.81/ND22.99610.352418E7.57/ND22.94600.31F2955FND/ND22.9460ND0.08 G2958G8.95/ND22.84580.38BLANKND/ND2--n = 15 g Microgram; L Liter; min Minute; and ppm Parts Per Million.1 Adjusted concentration using formula (L/ v 2), where L is the detection limit. C D A B E Table 4-C. Summary of Nurse Ex posures to Sevoflurane (Active Sampling). StatisticsC4H3F7O (ppm) Maximum0.98 Minimum0.04 Range0.94 Mean0.32 Median0.31 Standard Deviation0.29 Lower Confidence Limit (95%)0.16 Upper Confidence Limit (95%)0.48 n = 15 ppm Parts Per Million Table 5-A lists the desflurane expo sure levels to nurses measured by passive sampling. Ta ble 5-B lists the desflura ne exposure levels to

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28 nurses measured by active sampling. Table 5-C lists the descriptive statistics and measures of variatio n including the upper and lower 95% confidence intervals for nurse exposures to desflurane. Table 5-A. PACU Nurse Exposure Levels to Desflu rane (Passive Sampling). NurseSample ID Mass C3H2OF6 (g) Detection Limit (g) Sample Volume (L) Sample Time (min) Concentration (ppm) Adjusted Concentration1 (pp m ) AFD0629ND20.716179ND0.41 AFD1532ND20.72180ND0.40 AFD0081ND20.724181ND0.40 BFD1173ND20.732183ND0.40 BFD0665ND20.732183ND0.40 CFD0935ND20.724181ND0.40 CFD1425ND20.728182ND0.40 DFD0608ND20.72180ND0.40 DFD1653ND20.752188ND0.39 DFD1244ND20.624156ND0.47 EFD1295ND20.736184ND0.40 EFD1559ND20.72180ND0.40 EFD0852ND20.668167ND0.44 FFFD0279ND20.74185ND0.39 GGFD1606ND20.7175ND0.42 BLANKND2---n = 15 g Microgram; L Liter; min Minute; and ppm Parts Per Million.1 Adjusted concentration using formula (L/ v 2), where L is the detection limit. D E A B C

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29 Table 5-B. PACU Nurse Exposure Levels to Desflurane (Active Sampling). Nurse Sample ID Mass C3H2OF6 (Front/Back)(g) Detection Limit (g) Sample Volume (L) Sample Time (min) Exposure (ppm) Adjusted Concentration1 (ppm) 2963AND/ND33.0462ND0.14 2957A9.68/ND33.09630.452960AND/ND32.8458ND0.15 2959BND/ND32.9961ND0.15 2954BND/ND32.9460ND0.15 2421C4.76/ND33.00600.232423C10.7/ND32.95590.522419D12.2/ND33.05610.572962D13.0/ND33.25650.0572414D6.01/ND33.00600.292417END/ND33.0462ND0.14 2415E12.8/ND32.99610.612418E9.46/ND32.94600.46F2955F16.5/ND32.94600.8G2958G8.02/ND32.84580.41BLANKND/ND3---n = 15 g Microgram; L Liter; min Minute; and ppm Parts Per Million. A B C D E1 Adjusted concentration using formula (L/v2), where L is the detection limit. Table 5-C. Summary of Nurse Ex posures to Desflurane (Active Sampling). StatisticsC3H2F6O (ppm) Maximum0.80 Minimum0.06 Range0.74 Mean0.34 Median0.29 Standard Deviation0.22 Lower Confidence Limit (95%)0.18 Upper Confidence Limit (95%)0.50 n = 15 ppm Parts Per Million

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30 Table 6 lists the exposures for nitrous oxide, desflurane, and sevoflurane to nurses. The haloge nated exposure co lumn represents the combined effect of the halo genated exposures using the ACGIH Additive Mixture Formula.

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31 Table 6. PACU Nurse Exposure Levels to Nitrous Oxide used in Combination with a Halogenated Anesthetic. Nurse Sample ID (Nitrous Oxide) Sample Time (Nitrous Oxide) N i trous O x id e Exposure1 (ppm) Sample ID (Halogenated) Sample Time (Halogenated) Desflurane Exposure (ppm) Sevoflurane Exposure (ppm) Halogenated2 Exposure AFB02451802.72963A62NDNDAFB04021791.22957A630.450.330.4 AFB15321800.72960A58ND0.94BFB1875175ND2954B61NDNDBFB11831831.32959B60ND0.39CFB0485181ND2421C600.230.210.2 CFB0829185ND2423C590.520.980.8 DFB11751814.72419D610.57NDDFB21591853.52962D650.0570.0420.05 DFB15061561.42414D600.290.370.3 EFB17311841.62417E62ND0.18EFB16741811.02415E610.610.350.5 EFB04301692.42418E600.460.310.4 F FFB17441890.82955F600.8NDG GFB03661748.72958G580.410.380.4 n = 151 Values corrected for blank sample2 Combined effect of Exposures (C1/T1) + (C2/T2) = 1, then the threshold of the mixture is not exceeded. E A B C D

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32 In this study, a comparison of the passive and active sampling methods was performed. A single factor ANOVA was used to compare the methods and the results are presented in Table 7. Table 7. Comparison of Active and Passive Sampling Methods for Halogenated Anesthetic Gases. Anova: Sin g le Factoralpha = 0.05 SUMMARY GroupsCountSumAverageVariance Passive4517.8500.3970.00041 A ctive4511.2600.2500.056 A NOVA Source of VariationSSdfMSFP-valueF crit Between Groups0.48310.48317.2340.0000763.949 Within Groups2.464880.028 Total2.94789

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33 Discussion Nurse Exposures to Waste Anesthetic Gases The levels of nurse exposure to nitrous oxide were below the NIOSH REL of 25 pp m. The mean exposure wa s 2.12 0.29 ppm. The maximum and minimum exposures were 8.7 and 0.6 ppm. In order to produce accurate descriptive statistics, censored data were adjusted by following formula: 2 L Equation 1 for each nondetectable value, where L is equal to the detection limit (Hornung et. al, 1990). This formula was chos en because it gives a better estimate of the me an and standard deviation when the data are not highly skewed (Hornung et. al, 1990). The 95 % confidence interval (CI) of the adjusted data was from 0.91 to 3.33 ppm, well below the NIOSH REL. The levels of nurse exposures to isoflurane, sevoflurane, and desflurane were below the NIOSH REL of 2 ppm. All of the exposure values for isoflurane, sevoflurane, and desflurane obta ined by passive

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34 sampling were non-detectable. The le vels of exposure for isoflurane obtained by active sampling were also non-detectab le. However, exposure values for sevoflurane an d desflurane obtained by active sampling were detectable. The mean exposure for sevoflurane was 0.32 0.29 ppm. The maximum an d minimum exposu res were 0.98 and 0.04 ppm. In determining the de scriptive statistics, the censored data were adjusted by equation 1. The 95% CI was fr om 0.16 to 0.48 ppm. The mean exposure for desflu rane was 0.34 0.22 ppm. The maximum and minimum exposures were 0.80 and 0.06 ppm. The 95% CI was from 0.18 to 0.50 ppm. The ACGIH Additive Mixture Formula was used to determine if the NIOSH REL was exceeded by simu ltaneous exposure to sevoflurane and desflurane. This formula app lies to the additive model. The additive model is when th e combined biological effect of the agents of the mixture is equal to the sum of each of the agents alone. The formula is: 1 ....2 2 11 n nT C T C T C Equation 2 If the sum of the equation exceeds one, then the thresold limit of the mixture should be consider ed as being exceeded (ACGIH, 2005). After applying this formul a, it should be considered that the NIOSH REL

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35 for halogenated anesthetic s was not exceeded. However, it should be noted that in one case (Nurse C), the sum approached one (0.8). A summary of the statistical data is presented below in Table 8. Summary of Waste Anesethe tic Gas Exposure Data. Table 8. Summary of Waste An esthetic Gas Exposure Data. Mean Standard Deviation Minimum, Maximum 95% Confidence Interval Nitrous Oxide2.122.180.06, 8.70.91, 3.33 Isoflurane0.08*0.002*0.08*, 0.09*0.08*, 0.09* Sevoflurane0.320.290.04, 0.980.16, 0.48 Desflurane0.340.220.06, 0.800.18, 0.50 n = 15 for each anesthetic agent Non-detected values adjusted by equation 1. parts per million Anesthetic Agents Currently, there are no OSHA PELs for the waste anesthetic agents involved in this study. The NIOSH REL for ni trous oxide is 25 ppm TWA over the period of administration. ACGIH has a TLV for nitrous oxide of 50 ppm. The NIOS H REL for halogenated anesthetic agents is a ceiling limit of 2 ppm. ACGIH does not have TLVs for the halogenated anesthetic agents in volved in this study. A summary of the occupational exposure limits is presented in Table 9. Summary of Occupational Exposure Limits for Waste Anesthetic Gases.

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36 Table 9. Summary of Occupation al Exposure Limits for Waste Anesthetic Gases (ACGIH, 2005 and NIOSH, 1977). Anesthetic Agent NIOSH REL ACGIH TLV-TWA OSHA PEL-TWA Nitrous Oxide 25150None Isoflurane 22NoneNone Sevoflurane 22NoneNone Desflurane 22NoneNone1 TWA over the period of administration2 Ceiling Limit parts per million Comparison of Passive an d Active Sampling Methods In order to compare the passive and active sampling methods, an ANOVA was performed. The ANOVA allowed for a comparison of the mean values calculated among the ex posure levels of the passive and active sampling methods for haloge nted anesthetics. All of the censored data were applied to the formula in equation 1. For the purposes of this study, the significance level was = 0.05. A p-value less than 0.05 suggests that ther e is a statistically significant difference among the means, wherea s, a p-value greater than 0.05 suggests there is no statistically significant difference among the means.

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37 The results of the ANOVA indica ted a statistically significant difference (p < 0.05) among the mean values of the analytical data from passive and active sampling methods. Three variables that may explain the difference among mean values related to passive sampling are sampling time, back diffusion and variability of anesthetic gas concentrations. The sampling time for measuring halogenated anesthetic agents using the passive sampling method was three hours. This sampling time yielded detection limits of 0.4 ppm for isoflurane and sevoflurane, and 0.6 ppm for desflurane. The sampling time for measuring halogenated anesthetic agents usin g the active sampling method was one hour. This sampling time yi elded detection limits of 0.09 ppm, 0.08 ppm, and 0.1 ppm for isoflurane, sevoflurane, and desflurane, respectively. The detection limit s for the passive sampling method were in the same range as the measured concentrations of halogenated anesthetic agents in the PACU. According to the laboratory, a sample time of ei ght hours for the passive sampling method would have yielded a detection limit of 0.1 ppm for isoflurane and sevoflurane, and 0.2 ppm for de sflurane. These detection limits would have been similar to the active sampling method detection limits, therefore, allowing a better comparison. However, a disadvantage of the eight hour sample time from a regulatory

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38 perspective is the NIOSH ceiling limit REL of 2 ppm. This ceiling limit cannot be exceeded at any time during the workshift. Therefore, it is required to keep the sample time as short as possible to determine peak exposure concentrations. Once sampling has started, back diffusion may have occurred if the vapor pressure of the analyte at the sorbent surface was greater than the external concentration. Theoretically, the patient exhales the greatest concentration of anesthetic gases upon arrival to the PACU. As the patient’s length of time in the PACU increases, the concentration of gases exhaled will decrease. The variability of anesthetic gas concentrations may also explain the differences between the means of the exposure levels. The passive sampler may not have the ab ility to collect the “short-lived” analyte in the sorbent material (i.e. coconut charcoal). However, this may not be a problem if the sampling time is in excess of the time constant of the passive sampler (Cohen, et al, 2001). The time constant (i.e. the time it takes a molecule to diffuse into the sampler under steady-state conditions) for most commercial passive samplers is between one and ten seconds (Cohen, et al, 2001). There could also be differences in adsorption efficiencies in the sorbent materials. The Anasorb 747 tubes used during active sampling contained a synthetic carbon with a low ash content. The

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39 ChemExpressTM monitors used during passive sampling contained coconut charcoal. According to SK C, Inc., dynamic uptake studies demonstrated that Anasorb sorbent material collected less water vapor than the coconut charcoal, thereby increasing desorption efficiencies (SKC Inc, 2001). PACU Ventilation NIOSH recommends the following to reduce exposures to anesthetic gases: monitor air in the personal breathing zone of the affected worker; monitor the room air; determine HVAC system performance in removing anesthetic gases from the room, if exposures are above the RELs increase the amou nt of make-up air into the room; and institute a worker education program. The primary engineering contro l to reduce exposures to anesthetic gases within a PACU is the HVAC system. Hospitals must be constructed to the design and co nstruction standards described in Chapter 59A-3 of the Florida Admini strative Code. The requirements for PACU HVAC systems are a mini mum of six room air changes per hour with a minimum of 33% fresh air. The relative pressure within a

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40 PACU is required to be neutral to the adjacent areas (International Code Council, Inc., 2004). According to hospital engineerin g personnel, the HVAC system in the PACU where the study was perfor med is maintained regularly. They also stated the sy stem is operating at si x room air changes per hour with 33% fresh air, and the pr essure is neutral to the adjacent areas.

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41 Conclusions The exposure levels of nitr ous oxide were below the NIOSH TWA-REL of 25 ppm. The exposure levels of nurse to isoflurane, sevoflurane, and desflurane were below the NIOSH ceiling limit REL of 2 ppm. There was a difference in the resu lts between active and passive sampling methods. The results of the ANOVA indicated a statistically significant difference (p < 0.05) among the mean values of the exposure data from active an d passive sampling methods. Future studies are warranted to further assess nurse exposure to waste anesthetic gases. Invest igators measuring exposures to halogenated anesthetic agents by passive sampling methodologies should pay close attention to th e sample time and corresponding detection limits. Future studies should also focus on variables associated with exposure to anesthet ic gases. These include: patient load in the PACU; the variability of nitrous oxide compared to halogenated gases used in patient anesthesia; the amount of post operative care needed; patient body size and minimum alveolar

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42 concentration (MAC) of the anesthet ic agent administered; examination of the procedure of scavenging anesth etic gases exhaled by the patient at the end of surgery before transf er to the PACU; and HVAC system operation and performance. Another variable to consid er includes the density of these agents compared with that of air. Since these agents are heavier than air, a few samples sh ould be obtained close to ground level to determine if excessive co ncentrations of these agents are accumulating. These studies will be helpful to further assess the level of exposure of PACU nurses to waste anesthetic gases.

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43 References Abbott Laborato ries. Ultane Sevoflurane Material Safety Data Sheet. Chicago, Illinoise. August 2003. Allen, A. and JM Badgwell. The Po st Anesthesia Care Unit: Unique Contribution, Unique Ri sk. Journal of PeriAnesthesia Nursing. 11(4):248-58, 1996 August. American Conference of Governmental Industrial Hygien ists (ACGIH). Documentation of Threshold Limit Value for Nitrous Oxide. 2001. Cinncinatti, Ohio. American Conference of Governmental Industrial Hygien ists (ACGIH). TLVs and BEIs Based on the Documentation of the Threshold Limit Values for Chemical Substances an d Physical Agents & Biological Exposure Indices. 2005. Cinncinatti, Ohio. Badgwell, JM. An Evaluation of Ai r Safety Source Co ntrol Technology for the Post Anesthesia Care Unit. Journal of PeriAnesthesia Nursing. 11(4):207-22, 1996 August. Bruce, DL, and Stanley, TH. Rese arch Application May be Subject Specific, Anesth. Analg. No. 62, p.617-621. 1983. Bruce, DL. Recantation Revisited, Anesthesiology, Vol. 74, No. 6, p.1160-1161. June 1991. Bueck, Matthias; Westphal, Klaus; Lischke, Volker; Eiden, Ulrich; Byhahn, Christian; et al. Occupati onal Exposure of Post Anesthesia Care Unit and Intensive Care Unit Staff to Nitrous Oxide and Volatile Anesthetics. Anesthesiology. 95:A1081, 2001.

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44 Cohen, Beverly and McCammon Jr, Charles. Eds. Air Sampling Instruments for Evaluation of Atmospheric Contaminants. 9th Edition. ACGIH. Cincinnati, Ohio. Eger, Edmond. The Pharmacology of Inhaled Anesthetics. Seminars in Anesthesia, Perioperative Medici ne and Pain, Volume 24, Issue 2, June 2005. Hornung, Richard W. and Laurence D. Reed. Estimation of Average Concentration in the Presence of Nondetectable Values. Applied Occupational and Environmental Hy giene. 5(1):46-51. 1990 Jan. International Code Council, Inc. 2004 Florida Building Code Section 419 Hospitals. ICC Publications, Illinois. 2004. Krenzischek DA. Schaefer J. Nolan M. Bukowski J. Twilley M. Bernacki E. Dorman T. Phase I collaborative pilot study: Waste anesthetic gas levels in the PACU. Journal of Pe riAnesthesia Nursing. 17(4):227-39, 2002 Aug. NIOSH. Criteria for a recommended standard: occupational exposure to anesthetic gases and vapors. Cincinnati, OH: United States Department of Health, Education, and Welfare, 1977. O’Neil, Maryadele, Smith, Ann, and Heckelman, Patricia. Eds. The Merck Index An Encyclopedia of Chem icals, Drugs, and Biologicals. Thirteenth Edition. Merck Research Laboratories, Merck & Company, Incorporated. Whitehouse Station, NJ. 2001. Sessler, Daniel I. MD; Badgwell, J. Michael MD Exposure of Postoperative Nurses to Exhaled Anesthetic Gases. Anesthesia & Analgesia. 87(5):1083-1088, November 1998. United States Department of Labor. Occupational Safety and Health Administration. Anesthetic Gases: Guidelines for Workplace Exposures. OSHA Directorate for Te chnical Support. Office of Science and Technical Assessment. May 18, 2000. Retrieved November 2005 from the World Wide Web: http://www.osha.gov/dts/osta /anestheticgases/index.html Wenker, Oliver. Review of Currently Used Inhalation Anesthetics Part I. The Internet Journal of Anesth esiology. 1999. Volume 3, Number 2.

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45 Wenker, Oliver. Review of Currently Used Inhalation Anesthetics Part II. The Internet Journal of Anes thesiology. 1999. Volume 3, Number 3. Young, Christopher; Apfelbaum, Jeffr ey. Inhalational Anesthetics: Desflurane and Sevoflurane. Journal of Clinical Anesthesia. Volume 7, Issue 7:564-577, 1995.

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46 Appendices

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47 Appendix A: Laboratory Analytical Report

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