Comprehensive Report: Engineering Controls for Post-Operatory Waste Anesthetic Gases – Baseline Data Collection

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• Personal Author:
  Feng, H. Amy ; Garcia, Alberto ; Garner, Sara ; Merk, Gabriel
• Corporate Authors:
  National Institute for Occupational Safety and Health. Division of Applied Research and Technology
• Description:
  Waste anesthetic gases (WAGs) are small releases of anesthetic gases that leak from the patient's anesthetic breathing circuit into the air of operating rooms (OR) during delivery of anesthesia as well as during recovery from anesthesia in the Post Anesthesia Care Unit (PACU). Waste anesthetic gases include nitrous oxide and halogenated anesthetics such as halothane, enflurane, isoflurane, desflurane, sevoflurane, and methoxyflurane. WAGs pose a significant health hazard in the hospital setting and must be controlled to protect health care workers in the OR, PACU, and other applications where anesthetic gases are used. Exposure to uncontrolled WAGs in health care environments has been associated with adverse health outcomes such as liver and kidney disease, fatigue, irritability, drowsiness, headaches, miscarriages, genetic damage, birth defects, and cancer. As a result, systems and work practices have been developed for hospital OR and dental treatment rooms to decrease occupational exposure by scavenging WAGs. However, few studies have addressed exposure to WAGs in the PACU. Between May 2019 and January 2020, National Institute for Occupational Safety and Health (NIOSH) investigators conducted field assessments of three different PACUs that included collecting baseline WAG's data along with physical descriptions and ventilation parameters. Two of the PACUs evaluated were considered open concept units, one had a 12-patient capacity and about 1500 ft2 of floor space and the other one had a 6-patient capacity and about 800 ft2 floor space. The third PACU unit evaluated was considered a closed concept PACU. It had a 7-patient capacity and an approximate floor space of 2800 ft2. A closed concept PACU is a room where each patient has an independent, three-sided recovery area with an open front. Area WAG concentrations were measured using a Fourier transform infrared (FTIR) spectrometer analyzer. The FTIR analyzer simultaneously collected real-time data for multiple gases, including sevoflurane, isoflurane, and nitrous oxide. Additionally, ventilation airflow measurements in the PACUs were collected. The number of air changes per hour (ACH) for each unit was calculated and compared to ANSI/ASHRAE Standards. ASHRAE Standard 170-2017 prescribes a minimum of 6 ACH of total ventilation air that includes a minimum of 2 ACH of outdoor air. PACUs 2 and 3 were above the ASHRAE recommendations. PACU 1 was slightly below ASHRAE recommendations at 5.75 ACH. The WAG concentration measurements collected were area samples and not exposure concentrations measured from workers' breathing zones, however comparison of the observed results with occupational exposure limits can provide some context. Measurements in a patient's breathing zone are expected to give higher values of WAG concentrations. The five halogenated anesthetics currently used in the United States are halothane, isoflurane, enflurane, desflurane, and sevoflurane. No NIOSH recommended exposure limit (REL) exists for the three most currently used anesthetics (isoflurane, desflurane, and sevoflurane). In 1977, NIOSH recommended that occupational exposure to halogenated anesthetic agents, when used as the sole anesthetic, should be controlled so that no worker would be exposed to time-weighted average concentrations greater than 2 ppm during anesthetic administration over a sampling period of less than 1-hour. When halogenated anesthetics are associated with nitrous oxide, NIOSH recommends that the limit value should not exceed 0.5 ppm over the same sampling period. This occupational exposure limit was recommended by NIOSH for the type of anesthetic gas to which isoflurane and sevoflurane belong, but before they effectively came into use. NIOSH also recommends that occupational exposure to nitrous oxide should not be greater than 25 ppm. Other standard setting bodies, like the Occupational Safety and Health Administration (OSHA) and the American Conference of Governmental Industrial Hygienists (ACGIH), don't have limits for many of the halogenated gases. However, ACGIH included a Threshold Limit Value (TLV) of 50 ppm for isoflurane over an 8-hour shift in the 2022 updates to its Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices. The 1-minute maximum concentration of nitrous oxide in PACU 1 was 2.6 ppm which was well below the NIOSH REL. The maximum 1-minute average concentration of isoflurane was 4.6 ppm, and for sevoflurane the maximum was 34 ppm. PACU 1 routinely extubated patients in the PACU. The maximum 1-minute average concentration of nitrous oxide in PACU 2 was 0.3 ppm which was well below the NIOSH REL. The maximum concentration of isoflurane and sevoflurane were recorded at 11.2 ppm and 10.2 ppm respectively. The maximum 1-minute concentration of nitrous oxide in PACU 3 was recorded at 17.5 ppm and was caused by an instantaneous spike that was quickly diluted and dissipated by the PACU ventilation system. The 1-hour average nitrous oxide concentration for PACU 3 was consistently below the NIOSH REL. For the same PACU unit, the maximum 1-minute average concentrations of isoflurane and sevoflurane were recorded at 6.1 ppm and 46.2 ppm respectively which were both above the NIOSH recommendations for halogenated gases. Collectively, these field assessment surveys reinforce the opportunity for engineering control approaches to reduce WAG concentrations within the PACU working environment. Although the observed concentrations were area samples and not worker breathing exposures, NIOSH recommendations were exceeded within all of the evaluated PACU units. Each PACU experienced at least 1-hour of cumulative time over the NIOSH recommendations for halogenated gases. These observations indicate that general dilution ventilation, at the current air exchange rates, was not enough to keep WAG concentrations near the patient below the NIOSH recommendations. Other engineering control techniques that control the emissions closer to the source might be required to reduce WAG emissions into the PACU environment. Additional research is needed to identify an effective approach to control WAG concentrations within the PACU.
• Subjects:
  Anesthesia Engineering Environmental Monitoring Health Care Facilities Workforce And Services Occupational Health Safety Ventilation
• Keywords:
  Air Sampling Breathing Zone Control Technology Engineering Controls Exposure Health Care Facilities Infrared Spectroscopy Operating Rooms OSHA Region 5 PACU Post Anesthesia Care Unit WAG Waste Anesthetic Gases

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• Series:
  Engineering and Physical Hazards Survey Reports
• DOI:
  https://doi.org/10.26616/NIOSHEPHB2022DFSE822
• Publisher:
  National Institute for Occupational Safety and Health
• Document Type:
  Text
• Name as Subject:
  Community Health Surgery Center North ; Community Surgery Center Hamilton
• Genre:
  Field Study
• Place as Subject:
  Indiana ; Indianapolis (IN) ; Noblesville (IN) ; OSHA Region 5
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  DFSE - Division of Field Studies and Engineering ; EPHB - Engineering and Physical Hazards Branch
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  1-21
• NIOSHTIC Number:
  nn:20064718
• NTIS Accession Number:
  PB2022-100405
• Citation:
  Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, EPHB Report No. 2022-DFSE-822, 2022 Mar ; :1-21
• Federal Fiscal Year:
  2022
• NORA Priority Area:
  Healthcare and Social Assistance
• Peer Reviewed:
  False
• NAICS and SIC Codes:
  622110 - General Medical and Surgical Hospitals - (NAICS)
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:88ec437de84cdc7ea4e5ec9477631305807d5c1400f4f9194072aa89fb75995db4c5c59557cba3bd969a0ff97c66b9936390c6c8febc42333a4a339de638989d
• Download URL:
  https://stacks.cdc.gov/view/cdc/174850/cdc_174850_DS1.pdf
• File Type:
  [PDF - 1.07 MB ]