Exam 4: Lecture 3 Flashcards
Scavenging system
What did a NIOSH study as negative side effects for women working in the OR?
-spontaneous abortion
-liver/kidney disease
-cancer
-congenital abnormalities
NIOSH recommendation for halogenated agent exposure?
2 ppm
NIOSH recommendation for halogenated agent exposure if N2O is used?
0.5 ppm
NIOSH recommendations when N2O is the only anesthetic agent used?
25 ppm in the OR
50 ppm in dental offices
how much N2O and halogenated agent have been detected without scavenging system?
400-600 ppm N2O
5-10 ppm halogenated
how much can a scavenging system reduce exposure?
ten fold
how many air changes per hour do most ORs do?
20-25
air volume turned over in about 2.5 mins
what anesthetic circuit would increase the OR pollutant?
Mapleson circuits
semi-open?
sources of anesthetic gas contamination in high and intermediate pressure systems?
defective connectors, defective hanger yokes, bad seal
high pressure makes leaks more likely
sources of anesthetic gas contamination in the low pressure system?
N2O flowmeter, vaporizers, fresh gas delivery tubing, breathing circuit, CO2 absorber, unidirectional valves, ventilator, components of waste scavenging system
what is the relationship between peak pressures in the breathing circuit and the amount of gas the escapes through a leak in the low-pressure system?
direct linear
increased pressure
increased leak
how can the anesthesia ventilator leak anesthetic gas?
can leak internally and cause anesthetic gases to mix with the non=-scavenged driving gas of the ventilator
errors of anesthesia technique that can lead to anesthetic gas contamination?
changing absorbent mid case with high flows
how to prevent mask ventilation anesthetic gas contamination?
-don’t turn on the vaporizer or N2O until mask is on the patient
-turn flows as low as they go or pause while waiting for IV meds to take effect
-make sure mask fits well, good seal
how to decrease anesthetic gas contamination when you deep extubate a patient?
as the patient will continue to breathe anesthetic gases into the room, you should leave them attached to a well-fitting mask with 100% FiO2
how much N2O does cryosurgery leadk?
20-90 L/minute when used in surgery
do cardiopulmonary bypass machines have scavenging systems?
no
waste gas goes directly to the room
scavenging system may effect oxygen delivery?
what is the exhaled gas analyzer?
port on the vitals machine that draws gas directly from the patient circuit to analyze gas
-end tidal CO2
-delivered sevo
-most accurate measure of what is being administered
exhaled gas analyzers can draw how much gas if not scavenged?
100-300 mL/minute
what type of scavenging system does joint commission require?
active
when equipped with a properly functioning scavenging system, the trace concentration of anesthetic gases in an OR is reduced by how much?
90%
will scavenging system interfere with ventilation or oxygenation of anesthesia machine?
not if properly functioning
what must active scavenging systems have?
proper and adequate suction
how dos a passive scavenging system work?
driven by positive pressure from circuit and concentration system
two types of active scavenging system?
open and closed
what colors indicate waste scavenging coupler?
purple and yellow
what are the four parts of the waste gas scavenging system?
-relief valve through which gas leaves the breathing circuit
-conducting tubing to move the gas from the breathing circuit to the scavenging interface
-scavenging interface
-disposal line
potential complications of active open system?
suction could be in adequate and gas may leak back out into room
potential complications of active close system?
-increased pressure may backup into the circuit and back to patient leading to barotrauma
-may be caused by kink in system
how does waste anesthesia gas leave the circuit during spontaneous or manual ventilation?
the APL valve
-when open more gases will leave
-when closed less will leave
what does it mean to close the APL valve?
limit is usually 70 cm H2O
-would not allow patient to exhale as there would be too much pressure/resistance
what does it mean to open the APL valve?
to release pressure
there would be no resistance
0 cm H2O
what separates the manual and the ventilator circuits?
bypass switch
how do anesthesia waste gases leave the circuit when the anesthesia ventilator is in use?
through the ventilator pressure relief valve
-works in a similar way to APL just different location based on what you are using
what is a safe peak pressure?
below 35
on ventilation mode, where is excess gas routed?
through APL valve or ventilator spill valve, depending on ventilation mode
open scavenging interface system
how does an open interface scavenging system protect the patient?
from positive pressure associated with obstruction and negative pressure associated with waste disposal
-less likely for vent to become obstructed
closed scavenging interface system
less OR pollution, but less safe for patient
complications of inadequate suction in a closed scavenging interface system?
pressures can accumulate and put the patient at risk for barotrauma
-both positive and negative pressure relief valves
complications of too much suction in a closed scavenging interface system?
negative pressures can be transmitted to the patient
-could pull on the parenchyma, microvascular trauma
what does the reservoir bag on the closed scavenging interface system show?
-distended: suction is too low
-flat: suction is too high
what protects the patient and ventilator from excessive positive or negative pressure?
relief valves interposed between the breathing circuit and the hospital’s vacuum
what does a closed scavenging system include?
-reservoir bag
-spring loaded valves that prevent the hospital evacuation system from exerting too high or low pressure
what happens if there is insufficient suction in a closed scavenging interface system?
-excessive pressure build up in the reservoir
-pop off valve opens
-waste gas will be vented into the room
in a closed scavenging interface system, how will the reservoir bag behave normally?
bag will distend during exhalation and empty during inhalation
what will an over pressurized, overfilled reservoir bag on a closed system predict?
a block somewhere
can open waste scavenging systems be active or passive?
active
can we adjust the relief valve in an active closed scavenging system?
no, we can only adjust the suction
in an active scavenging disposal system, how much air should wall suction be capable of drawing?
> 30 L/min
what should active waste scavenging disposal interfaces be equipped with?
at least one negative pressure relief valve (closed) or ports open to atmosphere (open)
why is it preferable to have a dedicated separate vacuum system for waste anesthetic gases?
distributes suction to other sources, diluting it
for general anesthesia what is required for dental offices?
waste gas disposal and medical vacuum separate from dental vacuum
hazards of scavenging?
-excessive negative or positive pressure applied to pulmonary tract
-errors in assembly of the scavenging system
-open systems can become blocked
-hoses can become kinked
how to test the low-pressure system for leaks?
-remove breathing hoses and bags from anesthesia manual circuit
-connect the two unidirectional valves with short piece of corrugated hose
-close APL valve, occlude the bag mount opening
-slowly turn on the oxygen flowmeter until the breathing circuit reaches a pressure of 40 cm H2O
-titrate oxygen flow down to find minimum flow necessary to maintain this pressure for 30 seconds
what should your low pressure leak be?
less than 200 mL/min
-this would contribute no more than 4 ppm of N2O
why is PACU an anesthesia gas exposure zone?
patients are still breathing out some residual gas for a short time, but there is no active filtration in PACU like in the OR
where should you sample from to test OR safety?
measuring N2O at the level of the anesthesia workstation correlates well with personal sampling
what is time weighted average and how to sample?
TWA sample may be obtained by continuously pumping ambient air into an inert bag at a constant low rate of flow (4L/hour) with a bag capacity of 20-30L
-this concentration represents the average exposure over the collection period
what is the time weighted average of nitrous?
25 ppm
you can go over temporarily, but you must compensate with less exposure
is it bad if you can smell sevo?
yes
olfactory thresholds for N2O and halothane are 10-30%
how much do inhaled anesthetics account for of the carbon footprint of an average surgical procedure?
1/3
5% of hospitals total greenhouse gases
decay times of anesthetic gases?
-sevo: 1.1 year
-iso: 3.2 years
-desflurane: 14 years
global warming potential measure of anesthetic gases?
-sevo: 130
-iso: 510
-des: 2540
-N2O: 289
on a MAC-hour basis, nitrous and desflurane are how much greater in global warming potentials than sevo and iso?
20x
greenhouse gas effects of propofol are how much smaller than desflurane or nitrous?
4 orders of magnitude smaller
environmental concern recommendation
-avoid N2O as a carrier gas
-avoid unnecessarily high FGF
-reserve des and N2O only for cases they could reduce mortality
-use sevo or iso
-reconsider N20 for labor patients
-use IV and regional when appropriate
-low flow techniques
what is the physiologic requirement of oxygen under anesthesia?
250 mL/min
meaning you could run .3 to .5 mL/min of O2 during the case
do your metabolic requirements increase or decrease under anesthesia?
decrease
what can climate change lead to?
primary cause of disease
-asthma
-cardiopulmonary complications
-infectious disease
-food and water supply instability
