BY DR.SANDEEP

TRACE ANESTHETIC EXPOSURE

INTRODUCTION •Waste anesthetic gases are small amounts of anesthetic gases that leak from the patient’s anesthetic breathing circuit into the air of operating rooms during delivery of anesthesia.• It is an occupational hazard

The purpose of this session is to:Increase awareness about the adverse health effects of waste anesthetic gases

Describe how workers are exposed to waste anesthetic gases

Recommend work practices to reduce these exposures Identify methods to minimize leakage of anesthetic gases into the work environment

TRACE ANESTHETICS / WASTE GASES

DEFINITION:A trace level of anesthetic gas is a

concentration far below than needed for clinical anesthesia or that can be detected by smell.

•Usually expressed in PPM, which is volume by volume (100% of a gas is 10,00,000 ppm ; 1% is 10,000 ppm).

WHO IS EXPOSED TO WASTE ANESTHETIC GASES?

The following hospital workers may be exposed to waste anesthetic gases:• Anesthesiologists• Dentists• Nurse anesthetists• Operating-room nurses• Operating-room technicians• Other operating-room personnel• Recovery-room nurses• Other recovery-room personnel• Surgeons

Where are workers most likely to be exposed to waste anesthetic gases?

Workers are most likely to be exposed to waste

anesthetic gases in

• Operating facilities with no automatic ventilation or

scavenging systems,

• Operating facilities where these systems are in poor

condition, or

• Recovery rooms where gases exhaled by recovering

patients are not properly vented or scavenged.

Even when scavenging and venting systems

are in place, workers may be exposed to these gases

under the following conditions:

• When leaks occur in the anesthetic breathing circuit (which may

leak gas if the connectors, tubing, and valves are not maintained

and tightly connected)

• When anesthetic gases escape during hookup and disconnection of

the system

• When anesthetic gas seeps over the lip of the patient’s mask or

from endotracheal coupling (particularly if the mask is poorly fitted

—for example, during pediatric anesthesia)

• During dental operations

• During induction of anesthesia

•WASTE GASES ARE USUALLY

•Nitrous oxide

•Halogenated volatile anesthetics

• Combination of both

Concentrations in operating rooms vary greatly and depends on

• The fresh gas flow,• The ventilation system, • The length of time that anesthesia has been administered,• The measurement site,• Anesthetic technique,• And other variables

higher with pediatric anesthesia, in dental operations , and in poorly ventilated PACU.

SITES OF LEAK• Mask

• Endotracheal tube

• Anesthetic gas machine

• Ventilator

• Pumps

• Scavenging devices

• All connecting tubing

• Other elements- depending on the type of anesthesia

delivery system.

CONSEQUENCES

CONSEQUENCES• Spontaneous abortion• Infertility• Birth defects• Impaired performance• Cancer - Melanoma• Mutagenicity• Renal diseases• Hematological diseases• Neurologic symptoms• Cardiac diseases

MISCELLANEOUS• Bone and joint disease ,• Ulcers ,• Ulcerative colitis , • Gallbladder disease ,• Migraine, and• Headache and fatigue • Ophthalmic hypersensitivity• Conjunctivitis • Exacerbation of Myasthenia

Gravis

• Skin eruptions

• Liver diseases:- Recurrent hepatitis (halothane) enhanced hepatic metabolism of some drugs . Elevated serum autoantibodies that react with specific hepatic proteins, especially females and pediatric anesthesiologists.

• Bone marrow abnormalities

• Nonspecific polyneuropathy

CONTROL MEASURES• Complete elimination is impossible.

• Goal is to reduce concentrations to the lowest level with

a reasonable expenditure of effort and money.

• To achieve this, attention should be focused on four

areas:

1. Scavenging,

2. Equipment leaks,

3. Work techniques, and

4. The room ventilation system.

SCAVENGING SYSTEMS• Scavenging is the collection of excess gases from

equipment used to administer anesthesia or exhaled by

the patient and the removal of these gases to an

appropriate place of discharge outside the work

environment.

• Also referred to as evacuation systems, waste anesthetic

gas disposal systems, anesthesia waste exhaust, and

excess anesthetic gas-scavenging systems.

SCAVENGING SYSTEMSConsists of five basic parts:

• A GAS-COLLECTING ASSEMBLY, which captures gases at the site of emission;• A TRANSFER TUBING, which conveys collected gases to the interface;• THE INTERFACE, which provides positive (and sometimes negative) pressure relief and may provide reservoir capacity• THE GAS-DISPOSAL TUBING, which conducts the gases from the interface to the gas-disposal system; and• THE GAS DISPOSAL SYSTEM, which conveys the gases to a point where they are discharged.

PASSIVE SYSTEMS

• Room Ventilation System – non-recirculating and

recirculating

• Piping Direct to Atmosphere-direct duct or vent,

specialized duct system, direct disposal line, or

through-the-wall system

• Adsorption Device-activated charcoal

• Catalytic Decomposition

ROOM VENTILATION SYSTEM

• A NONRECIRCULATING SYSTEM takes in exterior air and

processes it by filtering and adjusting the humidity and

temperature. The processed air is circulated through

the room and then all of it is exhausted to atmosphere

• A CIRCULATING SYSTEM takes a small amount of air is

taken in from the atmosphere, while the remaining air

is recirculated

VENTILATION SYSTEM

• Install a ventilation system that circulates and

replenishes the air in operating rooms (at least 15

air changes per hour, with a minimum of 3 air

changes of fresh air per hour).

• Install a ventilation system that circulates and

replenishes the air in recovery rooms (at least 6

air changes per hour, with a minimum of 2 air

changes of fresh air per hour) to prevent exposure

to waste anesthetic gases exhaled by patients.

PIPING DIRECT TO ATMOSPHERE

• The discharge point on the outside should be selected so that it is away from wind pressures, ignition hazards, windows, and the inlets for the ventilation system. It may be advantageous to attach a short T-piece as a terminal

• THE OPEN end should point downward to prevent water and dirt from entering and be fitted with netting to prevent insects, rodents, and foreign matter from entering the pipe.

•PROBLEMS include both positive and negative pressure caused by wind currents, obstruction from ice build up, and accumulation of foreign matter at the outlet

ADSORPTION • An adsorption device removes some or all excess anesthetic agents by adsorbing them or converting them to harmless substances

Eg: Canisters• The efficiency of adsorption also depends on the flow rate through the canister. Moisture may reduce the efficiency•ADV: Simple and portable, do not require expensive installation or maintenance, halogenated anesthetic vapors are not released to the ozone layer •DIS ADV : No adsorption device for nitrous oxide, expensive, effective for only short periods of time.

ACTIVE SYSTEMS

• Piped Vacuum Systems

• Active Duct System

PREVENTIVE MEASURES1. Checking equipment before use-check for irregularities

or breaks and circuit for negative pressure and positive

pressure relief as part of the daily machine checklist.

2. Turn on the local/ room ventilation system.

3. Using scavenging equipment-make sure the scavenging

equipment is properly connected & connect the gas

outlet to the hospital’s central scavenging system

4. Start the gas flow after the laryngeal mask or

endotracheal tube is installed

PREVENTIVE MEASURES5. Proper use of airway devices-Make sure that uncuffed

endotracheal tubes create a completely sealed airway

6. Using low fresh gas flows-Use the lowest anesthetic gas flow

rates possible for the proper functioning of the anesthesia

delivery system and for patient safety

7. Avoiding insufflation techniques AND HIGH FLOW Rates-rates

to prevent leaks: high flow rates generate more waste

anesthetic gases than low flow rates.

8. Preventing liquid agent spills-Fill vaporizers before or after the

anesthetic procedure [1 mL of a volatile liquid anesthetic = 200 mL

of vapour = 2ppm (closed room measuring 20 by 20 by 9 ft)]

PREVENTIVE MEASURES9. Proper mask fit

10.Washout of a Anesthetic gases at the end of the case-

Eliminate residual gases through the scavenging

system as much as possible before disconnecting a

patient from a breathing system

11.Preventing Anesthetic Gas Flow Directly into the Room-

Turn the gas off before turning off the breathing

system.

12.Alteratons in work practices

PREVENTIVE MEASURES

13.Using intravenous and regional anesthesia

14.Keeping scavenging hoses off the floor

15.Leak control

MONITORING Develop a monitoring program supervised by a

knowledgeable person in every operating facility. Such a program should include

•Quantitatively evaluating the effectiveness of a

waste-gas control system and

• Repeatedly measuring concentrations of anesthetic

gas in the breathing zones of the most heavily

exposed workers while they perform their usual

procedures.

• Keep good records of all collected air sample results

for at least 30 years.

MONITORING • Keep medical records of a worker’s exposure for 30

years after his or her employment has ended

•Obtain baseline liver and kidney data for operating-

room personnel and monitor their liver and kidney

functions periodically.

• Record medical histories for workers and their

families, including occupational histories and

outcomes of all pregnancies of female workers and

wives of male workers (if possible

MONITORNG TRACE GASES

• Air monitoring

•EQUIPMENT:-

• Infrared analyzers

• Proton transfer reaction mass spectrometry

•Dosimeters

• Ionizing leak detectors

•Oxygen analyzer

• Carbon dioxide analyzer

SAMPLING METHODS

• Instantaneous sampling

• Sampling at the air conditioning exhaust

• Time weighted average sampling

• Continuous sampling

• Personnel sampling

AGENTS TO BE MONITERED

• Nitrous oxide

• Volatile agents

SITES TO BE MONITORED

• Monitoring should be scheduled so that the work of each

anesthesia provider and of each operating room is

checked while using a mask, supraglottic device, and

tracheal tube.

• Monitoring should be performed during spontaneous,

manually assisted, and manually controlled and

automatic ventilation.

• The results of the monitoring should be analyzed and

discussed with all parties concerned

OTHER ASPECTS

• Personal Monitoring

• Area (room) sampling

• Monitoring frequency

MONITORING FREQUENCYThe following schedule has been suggested :

• An annual comprehensive survey in which exposure levels are measured, leaks detected and corrected, and TWA exposure levels are calculated or measured. • Quarterly follow-up with a less-detailed survey; if there appears to be a problem, a comprehensive survey should be performed to determine causes and assess corrective actions. • A repeat comprehensive survey in the event of major changes to the ventilation system, anesthesia equipment, or scavenging systems.• TWA monitoring of each member of the staff for a short period, such as a week, repeated on a 6-month basis also has been suggested

MEDICOLEGAL ASPECTS

OCCUPATIONAL SAFETY AND HEALTH ACT(OSHA)

Agencies

The national institute of OSHA

safety and health (NIOSH)

• NIOSH under the department of Health and human services

• OSHA under the department of Labour

•NIOSH- conducting and funding research and

education and for preparing criteria documents to

be used to develop standards.

• OSHA - enacting job safety and health standards,

establishing reporting and recordkeeping

procedures, inspecting workplaces, and enforcing

the requirements of the act by using citations and

fines.

ARBITRARY SAFETY LIMITS• For Nitrous Oxide alone-exposure limit of 25 ppm

• For halogenated agents used alone, the limit was 2 ppm

.

• When halogenated agents are used in combination with

Nitrous Oxide, the recommended limits were 25 ppm

nitrous oxide and 0.5 ppm of the halogenated agent

• For dental facilities, a level of 50 ppm Nitrous Oxide was

recommended.

• During mask induction, the level of Sevoflurane should

be less than 2 ppm.

• The 1970 act gives each employee the right to request an OSHA inspection if an employee believes that he or she is in imminent danger from a hazard or if OSHA standards are being violated.

• The American Society of Anesthesiologists (ASA) legal counsel has advised that it is within the right of an employer to refuse to permit an OSHA representative to enter the facility unless that individual has either a search warrant or a court order compelling the inspection. • All states have workers' compensation laws so that individuals suffering from occupational diseases can collect benefits, irrespective of whether or not the employer's negligence caused the disease

THANK YOU