Scavenger System – Flashcards

The Occupational Safety and Health Act of 1970 emphasized the need for standards to protect workers from potential hazards in the workplace A "Recommended Standard for Occupational Exposure to Waste Anesthetic Gases and Vapors" was developed in 1977 by the National Institute for Occupational Safety and Health (NIOSH) In 1978, a waste gas scavenger interface valve was introduced to anesthesia practice

Cancer Females at a higher risk than males Liver disease Men at higher risk Renal Disease Increased risk only among women Adverse effects on DNA Teratogenicity Halothane? Neurobehavioral Function Occupational exposure can worsen psychomotor performance to an extent - volatile anesthetics more so than N2O

Epidemiological studies, primarily of operating room personnel, have shown increased risks of spontaneous abortion, premature delivery, and involuntary infertility among these occupationally exposed populations

Methodologically valid epidemiological studies with regard to health risks posed by volatile anesthetics do not exist Currently available data suggest that the potential harm is not significant provided that a efficient air conditioning and scavenging system is used The evidence that trace anesthetic gases are harmful is at present suggestive rather than conclusive Problems in women such as spontaneous abortion and fetal injury were the only health defects for which there was reasonably convincing evidence

Historically called 'laughing gas' for good reason Abusers know more than anesthetists Nerve damage similar to B12 deficiency Disrupts metabolic pathway of vitamin B12 Anemia due to folic acid deficiency Interference with DNA synthesis Inactivates methionine synthase Observed with as little as a 2 hour exposure Occasional 25 minute exposure OK Increased levels of homocysteine

Independent risk factor in cardiovascular disease Regulated by folate, vitamins B12 and B6 Cancer Decreased folate may damage DNA strands Dec. B12 traps folate into form unusable by body Dec. B12 -biomarker of chromosome breakage in WBC Breast cancer Risk doubled in women with dec. B12 Neural tube defects (encephaly or spina bifida) Defects occur between 21st-27th day after conception (when neural tube usually closes) Alzheimer's disease and dementia Dec. B12 in CSF May influence myelin sheath and neurotransmitters Depression 30% of patients hospitalized have dec. B12 B12 necessary for metabolism of neurotransmitters (dopamine and serotonin) Unclear relationship currently

folate, B6, B12 by reaction with methiane synthase

Depends on reactivity of compound & consequent capacity to alter DNA Inhalation agents "inert- do not spontaneously degrade" under normal circumstances & normal temperature Sevoflurane assessed using Ames test No mutagenicity for 0.1% to 30% Ethrane, Forane & Halothane Do not increase sister chromatid exchanges Desflurane results negative in 4 different tests DNA damage w/ Forane & Sevo 1-3 days after anesthesia...? ---- this only found in one study, after two weeks everything back to baseline

Breakage of both DNA strands Followed by an exchange of whole DNA duplexes Sensitive indicator of exposure to mutagens Anesthetists (Indian J Occup Med 2005) Control population SCE 5.78 inc. 1.23/cell Anesthetists SCE 7.68 2.03/cell No inc. SCE with Propofol in children (Mutat Res, 2003) Short-term Sevo no inc SCE in children (Br J Anes, 2003) Des inc. SCEs in females (Act Anes Scan, 2005) SS higher # at 1, 3 and 7th POD No difference between pre-op # SCEs & at POD 12 Iso & N2O inc. SCE (Occu Envir Med, 1999) Comparable to smoking 11 cigarettes

Decrease in cell-mediated immunity Modifies activity of immune mediators Oxidative burst response of neutrophils to bacteria important defense against infection Minimally influenced by Des, Iso and Sevo Depressed by Halothane Nitric oxide may mediate cytotoxic actions of macrophages against tumor cells and bacteria Des, Ethrane, Iso & Halothane time and dose-dependently inhibit production of NO May result from attenuation of intracellular calcium release

Des decreases febrile response to pyrogen interleukin-2 in dose related manner Controlled vent w/ 1.5 MAC Ethrane, Halothane, Iso or Sevo increases gene expression of proinflammatory cytokines N2O abuse Aplastic anemia, leukopenia & death B12 deficiency, perniciuos anemia-inactivation of methionine synthase-could influence DNA formation

Liver damage via metabolism or degradation Metabolism may lead to reactive intermediates that form adducts (chemical additions) to hepatic proteins "New" proteins may cause autoimmune reaction Antibodies attack altered hepatic proteins Mechanism of Halothane hepatitis? Autoimmune Acylated proteins (introduction of acid into compound) worst after Halo; Iso = Des = Oxygen; Ethrane least Compound A caused humoral immune response in guinea pigs...? antigenic adducts in liver also

Incorrect installation of scavenging system Inappropriate operation of interface valve Inadequate maintenance of machine Inappropriate work practices that alter the efficiency of the interface valve Flow rates of fresh gas used in the circuit Integrity and function of the facility's ventilation system Length of time anesthesia given in any work day Location where the waste gas is collected

Sources of leaks that may contribute to excess trace gas concentrations and how they can be detected and corrected Function and performance of the components in the anesthesia machine system that are designed to remove waste anesthetic gases from the machine and transfer them out of the work environment Methods for measuring and monitoring levels of waste gas in anesthetizing locations Work practices commonly known to help reduce the concentration of trace anesthetic gases Potential effects of prolonged exposure... Federal guidelines aimed at minimizing OR workers exposure

Nitrous Oxide 25ppm = 1/400th of 1% Halogenated agents 2ppm = 1/5000th of 1%

Anesthesia machines shall be inspected and tested on a quarterly basis to ensure leaks are minimized Recommended limits set by NIOSH should be considered a guide to the limits of exposure No worker should be exposed to more than an average of 2ppm over an 8 hour period of a halogenated agent No worker should be exposed to more than 25ppm of Nitrous Oxide over an 8 hour period Each facility should test and inspect its central vacuum system, ventilation and air conditioning system to ensure that complete room air exchanges are occur 15 times per hour or more Records of sampling and tests should be available to all workers Implementation of an information program that identifies the potential hazards of excessive exposure to waste anesthetic gases Training for workers to help them recognize, understand, and help them reduce the risk to unnecessary exposure

15 times per hour

The allowable leak for the entire breathing system is limited to less than 300ml/min to restrict the loss of gas volume intended to be delivered to the patient and to limit anesthetic gas pollution in anesthetizing locations Leakage in excess of 300ml/min from the patient circuit is considered excessive and is termed nonallowable ASTM limit 340ml/min

High pressure leaks In the cylinder gas supply Supply hose connections to the wall and machine Low pressure leaks Commonly occur in the breathing circuit CO2 absorber APL valve inhalation and exhalation check valves gas analysis sensor

Is to evacuate anesthetic waste gases from the anesthesia machine and out of the work environment Waste gas evacuation is required for every type of breathing circuit configuration because the anesthesia machine delivers more fresh gas flow than the patient needs Have been reported to reduce pollution tenfold

Active when a vacuum source is attached to the waste gas interface valve Passive when a vacuum is not used

To compensate for continuous flow and to minimize pollution, the waste gas interface valve must be visually monitored and adjusted on a regular basis whenever fresh gas flow is changed during the procedure or when the facility wide demand on the vacuum supply increases or decreases its capacity to provide suction

Collection and removal of waste gases Detection and correction of leaks Consideration in work practices An effective room ventilation system

A machine specific interface valve permits excess gas to be collected in a reservoir bag and regulates pressure within the bag Consists of a manifold with four ports and two relief valves When a bag is not used as the reservoir, a block of space is designed into the frame of the machine to serve as a reservoir for waste gases (AT UH, black part of machine on the side).

Uses the facilities air conditioning ducts instead of the vacuum system to dispose of waste gas, no need for adjustment Flow of gas is through the manifold is essentially the same as for active systems Pressure exerted by the gas is controlled by the positive and negative relief valves The adjustment knob must remain in down position to close the needle valve ----just vents out the system.

The rate at which gas flows through the interface valve in an active system is controlled by turning the adjustment knob of the needle valve Adjusting the needle valve alters the amount of vacuum coming in No calibration of knob Have to watch scavenger bag & adjust appropriately ****will often give two turns for adequate sx

Bag should be ½ empty then full If more empty than full, decrease the vacuum knob If more full than empty, increase the vacuum knob If using high flowrates from flowmeters, increase scavenger vacuum

If bag overdistended, the postive pressure relief valve opens If bag collapsed on itself, negative pressure relief valve opens In both active and passive systems, any obstruction in the hoses reduces flow through it If flow is insufficient and the reservoir bag becomes distended, the positive pressure relief valve opens and waste gas is intermittently discharged into anesthetizing area If the vacuum is insufficient in an active system and the reservoir bag distends, the positive pressure relief valve on the interface manifold opens to vent the accumulated exhaled gas into the room If flow of gas drawn out by the vacuum is too high and the bag collapses, the negative relief valve opens to draw room air into the manifold

The more closed ----- less to scavenger The more open ------ more to scavenger

In active scavenging systems, any unused port on the waste gas interface valve and manifold must be capped, or the vacuum will simultaneously draw in room air through the open port and/or discharge anesthetic gases into the room

When the anesthesia machine or another device is rolled onto the waste gas evacuation tubing and obstructs the flow of waste gas Blood, FFP, crystalloid solutions are unintentionally spilled on the interlace manifold - sealing the positive and negative relief valves Adhesive tape applied across the manifold unintentionally limiting the function of both relief valves Incorrect assembly of the gas disposal hose, impeding flow away from the patient circuit

If positive pressure relief valve is stuck closed, positive pressure may be transmitted to the patient circuit If the patient is unable to exhale, the airway pressure gauge and monitor will display a sudden elevated or sustained airway pressure If this happens immediately check the positive pressure relief valve on the interface manifold for occlusion Faster option, pull vacuum off so have no sx or remove scavenger bag is there is one.

If negative pressure relief valve stuck, negative pressure may develop in the patient circuit if there is too much vacuum Patient able to exhale just fine Gases sucked from expiratory side first....then the patient, but still have inspiratory flow Adjust the knob on the interface valve to match your flowrates Check those pressure relief valves!

Not as likely for pressure increase/decrease because there are holes present on scavenger system.

To verify that the waste gas interface valve Is functioning properly conduct the following inspection and testing before each case 1.Pressurize the breathing circuit using the O2 flush valve (to 30cm) 2.Occlude the patient end of the breathing circuit. Fill the rebreathing bag. Fully open the APL making sure that the breathing circuit pressure does not rise above 3cm of water after gas exits rebreathing bag (will check negative pressure valve--- should not be 0). 3. Place your index finger on the bottom of the negative pressure relief valve and push the valve stem up to physically verify that it moves freely 4. Inspect all surfaces for debris and clean them as recommended

The rate of air exchanges provided by the ventilation system in the room The integrity and capability of the facility central vacuum source Appropriate preventative maintenance procedures Frequency/efficacy of preuse leak testing of the machine and ventilator Ventilation systems designed to remove waste gas should be dedicated to waste gas only Systems should be nonrecirculating ie: they do not recirculate air from one location to another Guidelines established by the American Institute of Architecture identifies the standard minimum of 15 air exchanges per hour. New hospitals are required to have systems capable of 20 exchanges per hour

Preventative maintenance programs for anesthesia machines, patient ventilators, and equipment shall be performed by a factory trained technician on a quarterly or more frequent basis Clinical engineering department at UC performs preventative maintenance on anesthesia machines

Measurements are expressed in parts per million and represent a volume to volume relationship 100% of any gas is 1 million ppm; 1% of any gas is 10,000ppm Should always include regular sampling by a fully trained individual at peak times Repetitive sampling should occur on a prescribed schedule and at the least quarterly Complete records should be kept of all sampling methods, locations, dates, analytical methods, and concentrations of trace gases measured Results should be made available to employees

Simple deficiencies are the most overlooked causes of elevated trace gases in anesthetizing areas Lack of awareness and inattention to detail are often the most causative factors of OR pollution

Disconnect O2 and N2O pipeline hoses from wall outlets and close cylinder valves at the end of the day to conserve gas and limit N2O in the ambient air Never sniff an anesthetic agent! The odor threshold is approx 50ppm which is 25X more than the recommended exposure limit Conduct all leak test with oxygen only Avoid turning on N2O or any agent until the face mask is securely attached to the patients face Avoid unnecessary disconnection of the breathing circuit Turn off N2O and agent and empty the rebreathing bag into the waste gas scavenging system before disconnecting the breathing circuit from the patient Administer 100% O2 when possible before removing the mask or tracheal tube from the patient Avoid breathing anesthetic agents exhaled by the patients as they emerge from GA Avoid spilling agent when filling vaporizers Use the recommended key-filler adapter and attach it to the anesthetic agent bottle to minimize liquid agent from being vaporized into the ambient air during filling procedures Limit the use of N2O until airway established, always turn OFF when disconnecting ETT, special care when using LMA, mask for GA

Screened 413 articles (31 assessed) Genotoxic effects Neurobehavioral effects Immunology General health effects No evidence of being harmless or health risk Risk articles ignorant of modern scavengers Encourages proper use of scavenger

Some studies done: N2O - contribute to greenhouse effect Agents with chlorine (des, sevo, iso) - contribute to acid rain