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23.
HYPOXIA DURING ANESTHESIA
MACHINE AND MONITORISSUES
NatachaZamor
CASE
pressure gauges, and pressure regulators. e PISS prevents
the attachment of an incorrect cylinder to the yoke (see
A 65- year- old septic female is undergoing emergent bowel
resection for ischemic colitis. In the middle of the case the
oxygen low- pressure alarm sounds and the oxygen ow
drops. e hospital engineers announce that central oxygen
supply has been compromised because of hospital construction eorts. What are the next steps to keep this patient safe
and avoid hypoxia?
Hypoxia results from inadequate oxygen tension at the
cellular level characterized by tachycardia, hypertension,
peripheral vasoconstriction, dizziness, and mental confusion. Hypoxia has various etiologies including anemia,
histotoxic, metabolic, and hypoxic (meaning inadequate
delivery of oxygen to the patient). is chapter discusses
how hypoxic hypoxia can occur through the anesthesia
machine interface and the safety features within the modern anesthesia machine to help prevent its occurrence.
e anesthesia ventilator comprises three systems:highpressure, intermediate- pressure and low- pressure systems (see
Figure 23.1). Within each of these three frameworks there
Figure 23.2). Each gas cylinder has a pin conguration to
t its respective gas yoke. e positions of the holes on the
cylinder valve correspond with the pins tted to the yoke.
e pin positions for each medical gas are unique. ere are
six possible targets for each of the two pins to be inserted.
ese targets are measured in millimeters from the edge of
the yoke. For oxygen tanks, the pins are inserted at the 2-
and 5- mm position and for the nitrous oxide tanks, the pins
are inserted at the 3- and 5- mm positions.
2– 4
If an attempt is
made to t the wrong gas cylinder to the wrong yoke, a tight
seal will not be made. Furthermore, the incorporation of a
color code scheme used on caps, hoses, connectors, knobs,
and pressure gauges also helps to improve safety and prevent cross- linking.
2,4
An inherent weakness of the PISS is if
the wrong pin pulls out or breaks, it can lead to misconnections.5 Several case reports have been published regarding
misconnections from eroded or shortened pins.
6– 12
ere
have also been manufacturer errors where the cylinder content and yoke pins were mismatched.
13– 16
are safety features to help prevent the delivery of a hypoxic
gas mixture to the patient. ey include the pin index safety
system (PISS), diameter index safety system (DISS), failsafe
valve, oxygen- nitrous oxide proportioning system, oxygen
supply failure alarm, owmeter sequence, and, most distally,
the oxygen analyzer. If any of these components are absent,
then the anesthesia machine is obsolete by American Society
of Anesthesiologists (ASA) standards.1 Even with all these
safety checks, mechanical malfunctions and technical errors
can and do occur. None of these features can replace the vigilance of the anesthesiologist administering the anesthetic.
THE INTERMEDIATE- PRESSURESYSTEM
e intermediate system receives gas from the pipeline or
pressure regulators and extends to the ow control valves.
It includes the pipeline connections, oxygen failsafe valve,
oxygen ush, ventilator gas outlets, pressure gauge, and
ow control valves. Safety features in this system to prevent
hypoxic gas delivery include the DISS, the failsafe valve,
and the low- pressurealarm.
THE HIGH- PRESSURESYSTEM
e high- pressure system is composed of E cylinders down
to the pressure regulators. It includes the hanger yoke,
176
DIAMETER INDEX SAFETYSYSTEM
e anesthesia workstation has pipeline inlet connections of
oxygen, nitrous oxide, and air. ese inlets are threaded using
High-Pressure system
Intermediate-
e
s
outlet)
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177
Figure23.1 The high- ,
intermediate- , and low- pressure
systems of the anesthesia
machine. SOURCE:Reprinted with
permission from Subrahmanyam M,
Mohan S.Safety features in anesthesia.
Indian J Anaesth. 2013;57(5):472– 80.
DISS ttings.17 e Compressed Gas Association developed
the DISS to establish a standard for noninterchangeable,
movable connections for use with medical gases.18 e noninterchangeable indexing is achieved by a series of increasing and decreasing diameters of the connecting components
that act in a key- like fashion so that the ttings within the
gas service group will connect only with their own kind.
central pipeline crossings. ere have been multiple
incidences of patient asphyxiation because a non- lifesustaining gas is substituted for oxygen or an oxygen line
is poisoned with a toxic gas line contaminant.
recently as 2004, 2005, and 2006 there were six reported
incidences of intraoperative death from hypoxic asphyxiation when central pipeline gases were crossed in Europe.20
Pressure system
O Pipeline
N
Cylinder
Pressure
gauge
Pressure
regulator
2
Supply
2– 4
Fail-Safe
O
N
O Cylinder
2
Supply
Check
valve
O
N
2
N
O
2
O
2
O
2
O2Cylinder
Supply
is safety feature however, does not protect against
19– 31
As
Low-Pressure system
Calibrated
vaporizers
Check valv
Machine
outlet
(common ga
Pipeline
Pressure
gauge
valve
Oxygen
supply
failure
alarm
Pipeline Supply
2
Flow Meters
Second-stage
Pressure
O
2
regulator
Flow-control
valve
Oxygen
flush
valve
In the United States, pipeline- related deaths were reviewed
from 1972 to 1993. Forty- ve deaths resulted from 26
pipeline incidents. Of these, 13 were due to crossed pipelines and 5 involved a substitution of oxygen by another
gas in the bulk supply.8 In 1996 Moss and Evans reported
that trichloroethylene contamination was implicated
in four deaths in Texas.21 More recently, in 2002, two
additional hypoxic deaths were reported in New Haven,
Connecticut. ese deaths resulted from a medical gas
system failure in which an altered oxygen owmeter
was inadvertently connected to a wall supply source for
nitrous oxide.22 Additional problems arose when pipelines
were shortened and connectors were attached improperly
within the operating room, allowing nitrous oxide lines to
be adapted to oxygen outlets.
3
PIN INDEX SYSTEM YOKE BLOCK CYLINDER VALVE
Figure23.2 The pin index system and its components. SOURCE:Reprinted with permission from Subrahmanyam M, Mohan S.Safety features in anesthesia. Indian J Anaesth.
2013;57(5):472– 80.
HYPOXIA DURING ANESTHESIA:MACHINE AND MONITORISSUES 177
PIN INDEX SYSTEM
NIPPLE
WASHER
INDEX PINS
GAS OUTLET
TAPERED SCREW
TABERED TO FIT
TO CYLINDER
BODY
PIN INDEX PORT
178
SPROCKET
LINK-25 CHAI
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OXYGEN SUPPLY FAILUREALARM
e oxygen supply failure alarm (or low pressure alarm) will
sound when there is a signicant decrease in oxygen supply pressures. is occurs when there is a sudden loss of cylinder or pipeline pressure or when the anesthesia machine
is turned o. Many anesthesia machines have a pneumatic
alarm device that sounds a warning when oxygen supply pressure decreases to a predetermined threshold value
such as 30 psig. e 2000 American Society for Testing
delivery to maintain an FiO2 > 25%. Only at extremely
low oxygen pressure is the nitrous oxide ow completely
stopped.
2– 4,33
e presence of a failsafe valve in the absence of a proportioning system can still deliver a hypoxic mixture to the
patient. In such a scenario, the oxygen ow control valve
is closed, but because there is normal oxygen pipeline pressure, 100% nitrous oxide or any inert gas can be delivered to
the patient, resulting in hypoxia.
and Materials (ASTM) standard mandates that a medium
priority alarm be activated within 5 seconds when oxygen
LOW- PRESSURESYSTEM
pressure deceases below a manufacture specic pressure
threshold.
2,3,32
e low- pressure system involves the owmeter to the
common gas outlet. It includes the owmeters, vaporiz-
FAILSAFEVALVE
ers, proportioning system, common gas outlet, and oxygen
ush valves.
is device is designed to prevent the delivery of a hypoxic
gas mixture when oxygen supply fails. is feature is incorporated at the level of the pressure regulators. A failsafe
valve is present in the gas line supplying each of the ow
meters except oxygen. As oxygen supply pressure decreases,
the valve shuts o or proportionately decreases the supply
of all other gases.2 In this conguration, when oxygen pressure falls, the ow of other gases will concurrently fall to
prevent the administration of a hypoxic gas mixture. is
feature is called the Pressure Sensor Shut O Valve in the
Ohmeda machine and the Oxygen Failure Protection
Device in the Dräger machine. In the Ohmeda machine,
once oxygen pressure drops below 30 psi the unopposed
force of a spring closes the valve and nitrous oxide cannot
be administered. In the Dräger interface, a decrease in oxygen pressure causes a proportional decrease in nitrous oxide
OXYGEN– NITROUS OXIDE
PROPORTIONINGSYSTEM
e proportioning system is a feature that joins the nitrous
oxide and oxygen ow rates together to prevent the delivery of a hypoxic mixture. e oxygen– nitrous oxide proportion system is also known as the hypoxic guard and
has diering nomenclature based on the machine manufacturer. Ohmeda calls its proportion system the “Link
25 Proportion Limiting Control” while Dräger calls its
proportion system the “Oxygen Ratio Monitor Control”
(ORMC) and the “Sensitive Oxygen Ratio Control”
(S- ORC) in its most recent models.
Ohmeda’s Link 25 System is a pneumatic and mechanical device (see Figure 23.3). e heart of the conguration
LINK-25 PROPORTIONING
SYSTEM
N2O
N
NITROUS OXIDE
SPROCKET
178 PART IV. PULMONARY CRISES
OXYGEN
O
2
Figure23.3 Mechanical linkage of oxygen and nitrous ow
meters, to prevent hypoxic mixture delivery. SOURCE:Reprinted
with permission from Subrahmanyam M, Mohan S.Safety features in
anesthesia. Indian J Anaesth. 2013;57(5):472– 80.
2
2
OO
2
CD
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179
is a mechanical integration of the nitrous oxide and oxygen ow control valves through a stainless steel chain. e
nitrous oxide control valve has a 24- tooth sprocket and is
connected to the 28- tooth sprocket of the oxygen control
valve. Normally both knobs can be operated independently.
At nitrous oxide to oxygen ratio 3:1 these valves become
linked. Any further increase in nitrous oxide proportionally
increases the oxygen ow to prevent a ratio greater than 3:1.
e nal 3:1 ow ratio results because the nitrous oxide ow
control valve is supplied by approximately 26 psig, whereas
the oxygen ow control valve is supplied by 14 psig. e
combination of the mechanical and pneumatic aspects of
the system yields the nal oxygen concentration.
2,5,17,19,33– 34
ere have been case reports of malfunctions in the Link25 proportioning system.
connecting the sprockets allowed nitrous oxide to increase
19,35– 37
In one case, a broken chain
to hypoxic concentrations.36 In another case, malposition of
the oxygen control knob on its stud caused failure of the
knob to engage, despite delivery of 100% nitrous oxide.19
In addition, loosening the stop screw on the collar of the
oxygen control knob has led to the delivery of a hypoxic
mixture in at least three cases.
19,37
e North American Dräger proportioning systems,
the ORMC and the S- ORC, are pneumatic oxygen–
nitrous oxide interlock systems designed to maintain the
fresh gas oxygen concentration at 25 ± 3. e ORMC
and S- ORC limit nitrous oxide ow to prevent delivery
of a hypoxic mixture. Supply oxygen and nitrous oxide are
modulated through respective resistors to exert a backpressure on the oxygen and nitrous oxide diaphragms. is
backpressure, in conjunction with the diering spring constants of the upper and lower springs, causes movement of
a piston attached to the proportioning valve. An increase
in nitrous oxide ow beyond 72% to 78% moves the piston, which raises the proportioning valve and limits further
nitrous oxide ow. Similarly, if the oxygen ow is reduced
to less than 22% from 28%, the nitrous oxide ow will be
reduced proportionally to maintain the oxygen percentage
required.
2,5,17,19,33– 34
e proportioning systems can permit a hypoxic mixture if the wrong gas is supplied though the oxygen pipeline or cylinder. Both the Ohmeda Link 25 system and the
Dräger ORMC/ S- ORC will be fooled if a gas other than
oxygen is present in the oxygen pipeline. Furthermore,
a hypoxic mixture can be delivered if there is a defective
pneumatic or mechanical component, leaks downstream of
ow control valves, or if a third inert gas is used.
2,4,5,17,19,33– 34
FLOWMETER SEQUENCE
Eger et al. in 1963 were the rst to point out that an
upstream oxygen owmeter can deliver a hypoxic mixture.38 If several owmeters are mounted together and a
leak develops in one ow tube, a higher proportion of the
gas coming from the upstream owmeter will tend to be
lost through the leak. If the oxygen owmeter is upstream,
this will tend to deliver a hypoxic mixture to the patient
(see Figure 23.4). Eger suggested that this danger could be
reduced if the oxygen owmeter were mounted in a downstream position.38 is has now become the convention
in modern anesthesia machines. is owmeter sequence,
however, is not foolproof. Regardless of the sequence of
owmeters, a break in the oxygen owmeter can lead to
a hypoxic mixture if nitrous oxide is being used.39 In this
scenario, oxygen escapes through the leak and nitrous oxide
continues to ow through the common gas outlet. is is
Figure23.4 Potential unsafe and safe arrangements of ow
meter tubes. SOURCE:Reprinted with per mission from Subrahmanyam
M, Mohan S.Safety features in anesthesia. Indian J Anaesth.
2013;57(5):472– 80.
HYPOXIA DURING ANESTHESIA:MACHINE AND MONITORISSUES 179
2
AIRN2OO
AIRN
OO
2
UNSAFE
SAFE
AIR
2
AIRN
N2OO
180
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particularly true at high ratios of nitrous oxide to oxygen
2,4,5,17,19,33– 34,39
ow.
Other safety features include ow control knob conguration. e ow control knob for oxygen
is the largest and most protruding and has tactile dierentiating features like a uted prole for additional and easy
identication.
MANDATORY MINIMUM OXYGEN FLOWALARM
2,4,5,17,19,33– 34
Some anesthesia machines require a minimum (50 to 250
cc/ min) ow of oxygen before other gases will ow.
OXYGENSENSOR
17
e oxygen sensor is the only monitor that analyzes gas
composition, making it the most important safeguard
against hypoxic gas delivery. Modern anesthesia ventilators
use infrared analysis, paramagnetic oxygen analysis, and
electrochemical oxygen analysis to measure oxygen con-
2. You were administering an oxygen and nitrous oxide
anesthetic. What do you expect to happen to your ratios
of oxygen and nitrous oxide during a central pipeline
failure? What safety feature in the modern anesthesia
machine facilitatesthis?
3. You open your oxygen cylinder to provide oxygen to
your patient. Can you keep your pipeline connected?
Why or whynot?
4. Is there a role for manual ventilation now that you are
working o the oxygen cylinder?
5. You are told that it is now safe to reconnect to the
pipeline source. You do so and place your patient
on 100% oxygen. Your patient who was previously
saturating 100% now desaturates and appears cyanotic.
What is your dierential? If there were a central
pipeline crossing, what safety feature in your machine
would detect it and what safety features mightnot?
centration delivered to the patients. None of the monitors
upstream of the oxygen analyzer are able to decipher gas
REFERENCES
composition. Hence, if there were a pipeline crossover, as
long as the pressure in the “oxygen” line was maintained,
it would pass the oxygen supply failure alarm, the failsafe
valve, and the O2- N2O proportioning system, but would be
detected at the level of the oxygen analyzer. Use of an oxygen analyzer with a low concentration alarm limit during
the administration of general anesthesia is required in the
ASA monitoring standards.40 Both the international and
US standards on respiratory gas monitors analyzers published in 2004 and 2005 require that a high- priority alarm
be used for inspired oxygen concentration below 18% and
that it not be possible to set the low oxygen alarm below
17,32,41
18%.
is monitor is also unfortunately not foolproof. ere have been reports in the literature of oxygen
analyzer malfunction.
42,43
ere are multiple systems built into the modern anesthesia machine to help prevent the delivery of a hypoxic
mixture to the patient. ere are documented malfunctions and failures within each of these safety features.
Ultimately, nothing replaces the attentiveness of a vigilant
anestheticteam.
CASE- BASED LEARNING DISCUSSION
1. In the context of a recognized pipeline failure, what
are the necessary steps you need to take to manage the
patient and keep her safe? Order them by importance.
1. American Society of Anesthesiologists Guidelines for Determining
Anesthesia Machine Obsolescence. Available at http:// www.asahq.
org/ Search.aspx?q=gu idel ines+determining+anesthesia+machine
+obsolescence.2004.
2. Miller RD, et al., eds., Miller’s Anesthesia. 7th ed. Philadelphia,
PA:Churchill Livingstone/ Elsevier;2010.
3. Donaldson M, et al. Nitrous oxide- oxygen administration: when
safety features no longer are safe. Journal of the American Dental
Association. 2012;143(2):134– 43.
4. Subrahmanyam M, Mohan S. Safety features in anesthesia. Indian
Journal of Anaesthesia. 2013;57(5):472– 80.
5. Dryo JF. Clinical Engineering Handbook. 1st ed. Burlington, MA:
Academic Press;2004.
6. Hogg CE. Pin- indexing failures. Anesthesiology. 1973;38(1):
85– 87.
7. Goebel WM. Failure of nitrous oxide and oxygen pin- indexing.
Anesthesia Progress. 1980;27(6):188– 91.
8. Petty W. AANA journal course: update for nurse anesthetists—
medical gases, hospital pipelines, and medical gas cylinders: how
safe are they? American Association of Nurse Anesthetists Journal.
1995;63(4):307– 24.
9. Mead P. Hazard with cylinder yoke. Anaesthesia and Intensive Care.
1981;9(1):79– 80.
10. omas AN, et al. Interchangeable oxygen and air connectors.
Anaesthesia. 2001;56(12):1295– 6.
11. Saha B, etal. Interchangeable oxygen and carbon dioxide cylinders.
Anaesthesia. 2005;60(8):827– 8.
12. Chamley D, Trethowen L. Pin index failure. Anaesthesia and
Intensive Care. 1993;21(1):128– 9.
13. S erlin S. Check your tanks. Anesthesia & Analgesia. 2004;98(3):870.
14. Menon MR, Lett Z. Incorrectly lled cylinders. Anesthesia.
1991;46(2):155– 6.
15. Taylor NJ, Davison M. Inaccurate color coding of medical gas
cylinders. Anaesthesia. 2009;64(6):690.
16. Crombie N. Confusing and ambiguous labeling of an oxygen
cylinder. Anesthesia. 2009;64(1):98.
180 PART IV. PULMONARY CRISES
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181
17. Dorsch JA. Understanding Anesthesia Equipment. Philadelphia,
PA: Wolters Kluwer Health/ Lippincott Williams & Wilkins;
2008.
18. Compressed Gas Association. Standard for Medical Gas Supply
Systems at Health Care Facilities. Chantilly, VA:CGA;2013.
19. Atlee JL. Complication in Anesthesia. 2nd ed. Philadelphia, PA:
Saunders;2006.
20. Her H, etal. Fatal errors in nitrous oxide delivery. Anaesthesia.
2007;62(12):1202– 6.
21. Moss E. Hospital Deaths. Anesthesia Patient Safety Foundation
Newsletter. Summer 1996.http:// www.apsf.org/ newsletters/ html/
1996/ summer/ apsfmoss.html
22. Worth RF. Hospital says two died in nitrous oxide mistake. NewYork
Times. January 17, 2002. http:// www.nytimes.com/ 2002/ 01/ 17/
nyregion/ hospital- says- two- died- in- nitrous- oxide- mistake.html.
23. Sprague DH, Archer GW Jr. Intraoperative hypoxia from an
erroneously lled liquid oxygen reservoir. Anesthesiology. 1975;42:
360– 2.
24. Lye A, Patrick R. Oxygen contamination of the nitrous oxide
pipelines supply. Anaesthesia and Intensive Care. 1998;26(2):
207– 9.
25. Schumacher S, etal. Bulk liquid oxygen supply failure. Anesthesiology. 2004;100(1):186– 9.
26. Bernstein DB, Rosenberg AD. Intraoperative hypoxia from nitrogen tanks with oxygen ttings. Anesthesia & Analgesia. 1997;
84(1):225– 7.
27. DiPaolo V. Hospital’s failure to analyze gases made crossing of gas
lines deadly. Mod Healthcare. 1977;Sep:116– 17.
28. Crossed oxygen and nitrous oxide gas lines claim yet another victim.
Biomed Safety Standards. 1978;8:141– 2.
29. Another case of crossed oxygen and nitrous oxide gas lines. Biomed
Safety Standards. 1978;8:117– 8.
30. Mazze RI. erapeutic misadventures with oxygen delivery systems:
the need for continuous in- line oxygen monitors. Anesthesia &
Analgesia. 1972;51(5):790– 2.
31. Weller J etal. Anesthetists’ management of oxygen pipeline failure:
room for improvement. Anesthesia. 2007;62(2):122– 6.
32. ASTM:Standard specication for particular requirements for anesthesia workstations and their components. (ASTM F1850- 00). In
Medical devices and services, vol. 13.01. Conshohocken, PA;2005.
33. Baheti DK, et al. Understanding Anesthetic Equipment &
Procedures: APractical Approach. New Delhi, India: JP Medical
Ltd;2014.
34. Rose G. Anesthesia Equipment Simplied. New York, NY:
McGraw Hill Professional;2014.
35. Ishikawa S, etal. Hypoxic gas ow caused by malfunction of the proportioning system of anesthesia machines. Anesthesia & Analgesia.
2002;94(6):1672.
36. Gordon PC, et al. Failure of the proportioning system to prevent hypoxic mixture on a Modulus II Plus anesthesia machine.
Anesthesiology. 1995;82(2):598– 9.
37. Cheng CJ, Garewal DS. A failure of the chain- link mechanism on
the Ohmeda Excel 210 anesthetic machine. Anesthesia & Analgesia.
2001;92(4):913– 4.
38. Eger EI, etal. Anesthetic ow meter sequence:a cause for hypoxia.
Anesthesiology. 1963;24(3):396– 7.
39. Chung DC, et al. Hypoxic gas mixtures delivered by anesthetic
machines equipped with a downstream oxygen owmeter. Canadian
Anaesthetists’ Society Journal. 1980;27(6):527– 30.
40. American Society of Anesthesiologists. Standards for basic anesthesia monitoring. ASA 2011. https:// www.asahq.org/ ~/ .../ standards.../ standards- for- basic- anesthetic- monitoring.pdf
41. International Standards Organization. Medical electrical equipment-
participation requirements for the basic safety and essential performance of respiratory gas monitors. Geneva, Switzerland; 2004.
42. Vinay B, Gopalakrishna KN. An unusual cause with a simple solution for failure of oxygen sensor in a Dräger Fabius GS ventilator.
Saudi J Anaesth. 2014;8(4):565– 6.
43. Harris B, etal. An insidious failure of an oxygen analyzer. Anesthesia
& Analgesia. 2006;102(5):1468– 72.
HYPOXIA DURING ANESTHESIA:MACHINE AND MONITORISSUES 181
182
Endotracheal tubes
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24.
AIRWAYFIRE
Ju- MeiNg
CLINICALCASE
intensive care with its accompanying morbidity.4 One or
two deaths per year are caused by airway res.
1,5
A 67- year- old male, intubated from the intensive care unit
(ICU), presents for tracheostomy. He has a history of
hypertension and was involved in a motor vehicle accident
1 week prior, sustaining a liver laceration (treated conservatively), right pneumothorax and 7th to 10th rib fractures
with lung contusion, and a fracture of his right femoral
sha (managed with internal xation). His arterial blood
gas showed PaO2 of 89 mmHg, PaCO2 42 mmHg on
assist- control ventilation with fractional inspired oxygen
concentration (FiO2) of 0.6, and PEEP 8 cmH2O. e
anesthetic plan is to advance his endotracheal tube (ETT)
until the tip is just above the carina (cu is below the tracheal incision) and to use a volatile anesthetic in 100%O2.
CONCEPT
ree elements have to be present for any re to start:(1)ignition source, (2)fuel, and (3) an oxidizer. is “re triad”
(Figure 24.1) is interdependent, and removing any one component eliminates the potential of a re outbreak altogether.
Oxygen- enriched environments lower the temperature at
which fuels ignite and cause res to burn more intensely and
spread more quickly. Nitrous oxide supports combustion
and OR res involving mixtures of nitrous oxide and oxygen are as easily ignited and as severe as res involving 100%
oxygen. In airway res, ignition sources include the electro-
BACKGROUND
surgical unit (ESU) and laser. e ETT is the most common
fuel, though the patient’s tissue is another potential fuel. e
oxidizer is usually oxygen. In order to reduce risks of airway
e true incidence of operating room (OR) res is dicult to ascertain; the Emergency Care Research Institute
(ECRI) estimates that 550 to 650 surgical res occur in the
re during airway surgery, oxygen concentration should ide-
ally be less than 30% before using electrocautery, and nitrous
oxide should not be inuse.
United States per year,1 and about 21% occur in the airway despite reductions in inspired oxygen concentration
to less than 30%. Operating room res can result in devastating morbidity and mortality, and are largely preventable. e American Society of Anesthesiologists (ASA)
IGNITION
SOURCE
Lasers
Electrocautery Units
has issued an updated Practice Advisory for the Prevention
and Management of Operating Room Fires,2 including the
updated operating room res algorithm. e emphasis is on
prevention (education, training, and proper surgical technique), surgical team communication, and management
of re when it occurs. An airway re refers to a re in the
airway or breathing circuit, and usually occurs during tracheostomy, endoscopic airway surgery, or oropharyngeal
FUEL
OXIDIZER
Oxygen
surgery. Historically, the estimated incidence of airway res
was between 0.4% and 0.57% in patients undergoing laser
airway surgery.3 Airway injuries can necessitate prolonged
Figure24.1 The elements in the “re triad.”
182
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183
CLINICAL SCENARIOS— OROPHARYNGEAL/
LARYNGEAL SURGERY
Electrocautery use during tonsillectomy or laser laryngeal
surgery can cause res when an oxygen- enriched environment is allowed to build up in the oropharynx. During tracheostomy, subcutaneous/ adipose tissues in the neck and/ or
the ETT have been reported to ignite when electrocautery
concentration to decrease to < 30% depending on the circuit
length, the fresh gas ow rate, and the starting circuit oxygen
concentration.7 e laser tip should be visible and clear of the
end of the bronchoscope or ETT during lower airway surgery. During tracheostomy, it is important to ensure a hemostatic surgical eld prior to tracheal incision. is avoids the
need for diathermy aer the airway isopen.
8
was utilized. Endoscopic laser surgery of the lower airways
can lead to airway burns; smoke coming from the patient’s
ANESTHETIC CONSIDERATIONS
mouth may indicate combustion of airway tissue and/ or the
ETT, as there is no possible route for venting. Aserious thermal or chemical injury from airway re is less likely when the
ame or smoke is vented out through a tracheostomy opening or the oropharynx before reaching the distal airway.
6
Dierent anesthetic techniques have been used during
laser surgery of the airway.9 e FiO2 should be kept at the
minimum tolerated by the patient during critical periods,
and ventilation may be held if necessary. Depending on the
nature and location of the lesion, patient comorbidities,
PREVENTION STRATEGIES
and the availability of equipment and expertise, the mode
of ventilation and/ or method of securing airway may be
modied. e possibility of complete airway collapse or
Primary prevention should be accomplished through
education and training of all OR personnel. Steps should
include credentialing of surgeons for laser operation, safety
checklists, and protocols for airway res. Periodic checks
of both the availability and functional status of re safety
equipment, as well as re drills, will help to ensure that high
standards are maintained.
Secondary prevention includes preoperative discussion
among the surgical team prior to high- risk procedures, preassigned tasks in the event of a re, and closed- loop communication before use of the laser or ESU. Communication
should help to ensure that inspired oxygen concentration
is below 30% and that the ow of oxygen is stopped when
possible during periods of laser or ESU within the airway.
an inability to ventilate must be taken into consideration
when deciding between spontaneous or positive- pressure
ventilation. “Tubeless” techniques (jet ventilation, intermittent apneic ventilation) omit the ETT as fuel source,
however laser- safe ETTs are commonly used when ventilation through an ETT is necessary. To reduce the risk of a
re when a laser safe ETT is not available, the tube sha
may be covered with metal foil or laser- protective coatings,
and saline added to the tube cu (Figure 24.2).
9
During elective tracheostomy, the patient usually
arrives to the OR with a cued ETT (generally made of
PVC that can ignite in an O2- rich environment) in situ.
Communication between the surgeon and anesthesiologist
regarding the patient’s respiratory status (tolerance of apnea,
loss of recruitment, FiO2 requirements) and coordination
ENVIRONMENTAL CONSIDERATIONS
of tube exchange (endotracheal tube- for- tracheostomy cannula) are critical. Airway re is prevented by minimizing
FiO2 (<0.3) and eliminating the use of electrocautery aer
Warning signs should be posted at OR entry points. Water/
saline and wet sponges should be immediately available to
extinguish the re. All equipment should be tested prior to
use; the laser should be placed in a standby mode when not
in activeuse.
entering the trachea. When decreasing the FiO2, use high
fresh gas ows and monitor the expired oxygen concentration. is ensures that both the FiO2 and expired oxygen
concentrations are reduced.7 For patients who do not tolerate low FiO2 or prolonged apnea, the ETT may be advanced
such that the cu is distal to the surgical entry point. is
SURGICAL CONSIDERATIONS
allows continued ventilation and use of higherFiO2.
Clear warning should be given by the operator as to when
the laser is activated and avoidance of laser or electrocautery
use for hemostasis when O2 concentrations are high. It may
take minutes for both the inspired and expired circuit oxygen
AIRWAYFIRE 183
ACUTE MANAGEMENT
Should a re occur, immediate and concurrent steps should
include the following as shown in Box 24.1.
10
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Figure24.2 Laser- resistent tubes. Mallinckrodt Laser oral tracheal
tube (Covidien, Boulder, CO) is a metal tube with a very high
ignition temperature and double cuffs designed to be lled with
saline so that a laser strike to the proximal cuff will extinguish
the re, and distal cuff will prevent backow of oxygen. LaserShield II Endotracheal tube (Medtronic Xomed, Inc., Jacksonville,
FL) has a reective aluminium wrap with smooth uoroplastic
overwrap to reduce trauma, and methylene blue in the ination
valve for immediate detection of cuff rupture.
e anesthesiologist should immediately disconnect
the anesthesia circuit and/ or turn o the oxygen ow as
the surgeon stops lasering/ electrocautery and oods the
eld with saline. Saline ush down the ETT can help extinguish intraluminal re. If the re is not extinguished by
these maneuvers, the CO2 re extinguisher should be used.2
Depending on the amount of damage to the ETT and/ or
airways, the ETT may be removed or changed. is is oen
indicated if the tube has been melted in order to remove an
ignition source and prevent further tissue damage. e clinician must weigh the risk- benet ratio of minimizing the
inhalation of toxic combustion products and the spread of
re into the tracheobronchial tree against losing the airway
(especially if this was a previously dicult airway or one
that has since become edematous). In certain circumstances,
the benets of leaving the ETT in may outweigh the risks
of leaving it in place aer the airway re is extinguished.
e damaged ETT may still allow for acceptable ventilation of the lungs with oxygen, or serve as a conduit for a
tube exchanger.6 If in doubt, the ETT should be removed to
limit damage, and an alternate means of securing the airway
established.
antibiotics, based on the degree of damage and patient
comorbidities, this might warrant individual discussion.
As shown in Box 24.1, further management depends
on the severity of injury and need for postoperative
BOX 24.1 RECOMMENDED INTERVENTIONS WHEN AIRWAY
FIREOCCURS
• Remove or minimize the oxygen delivered: disconnect the
patient from the source of oxygen if possible; if this is
not possible then lower to 21%FiO
• Extinguish the fire with saline or a saline- soakedcloth
• Assess injuries with beroptic bronchoscopy and direct
laryngoscopy and determine whether it is safe to remove
the damaged endotracheal tube and if the airway can
be safely secured. The benet of removing the damaged
endotracheal tube has to be weighed against the risks
of potential difculties of securing the airway; this has
to be judged on a case- by- casebasis
• Remove all external burning objects from patient
2
SUBSEQUENT MANAGEMENT
After the fire is extinguished and the patient stabilized
(mask, supraglottic airway, or ETT), the extent of airway damage should be assessed. The clinician should
perform bronchoscopy (flexible or rigid) of the tracheobronchial tree and lavage and/ or remove debris/ foreign
bodies if necessary. Although there is little evidence for
the routine administration of steroids and prophylactic
184 PART IV. PULMONARY CRISES
• Resume ventilation and oxygen delivery as soon as
safely possible
• Prevent reignition:
• Continue cooling the area ofre
• Resume ventilation with the lowest toleratedFiO
• Formulate alternateplans:
• If the procedure is a tracheostomy, then proceed with
tracheostomy expeditiously before removing the burned
endotracheal tube if it was onre
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185
vertically from the wound. What are the immediate
BOX 24.1 CONTINUED
steps totake?
• If the initial surgical procedure was not a tracheostomy,
after assessing the airway, consider prophylactic
tracheostomy
• Assess whether the patient needs to be kept intubated
after the procedure
• Monitor the patient for signs of lunginjury
3. e re is extinguished. Should the ETT be removed?
Should the surgeon then proceed with the procedure
once the re is extinguished?
4. ere is minimal damage to the tissues around
the tracheostomy and the procedure is completed
without further incident. What follow- up measures
are important?
ventilation. Ideally after an airway fire during tracheostomy, patients should return to the ICU (after reestablishing the airway with a tracheostomy), and be
monitored for evidence of lung injury.
ese events should be reported and analyzed in
order to identify prevention steps that need to be reinforced in order to decrease the likelihood of future airway
res occurring. Hospital risk management should also be
notied.
CASE- BASED LEARNING DISCUSSION
1. What do you think of the anesthesia plan? What are
some alternatives?
2. e case proceeds with the original plan. e
endotracheal tube is advanced under bronchoscopic
guidance until the tip is just above the carina, and
the patient is anesthetized with isourane 1% in
100% O2. e tracheal incision is made, and just
as the surgeon is attempting to control bleeding in
the adipose tissue with the diathermy (monopolar
coagulation), a 15- cm jet of ame was seen arising
REFERENCES
1. ERCI Institute. New clinical guide to surgical re prevention.
Health Devices. 2009;38:314– 32.
2. Apfelbaum JL, Caplan RA, Barker SJ, etal. Practice advisory for the
prevention and management of operating room res:an updated
report by the American Society of Anesthesiologists task force on
operating room res. Anesthesiology. 2013;118:271– 90.
3. Burgess GE III, LeJeune FE Jr. Endotracheal tube ignition during
laser surgery of the larynx. Archives of Otolaryngology. 1979;105:
561– 2.
4. Tykocinski M, omson P, Hooper R. Airway re during tracheotomy. ANZ Journal of Surgery. 2006;35:49– 57.
5. Wolf LG. Danger from OR res still a serious problem. Journal of
Clinical Monitoring and Computing. 2000;16:237– 8.
6. Chee WK, Benumof JL. Airway re during tracheostomy:extubation may be contraindicated. Anesthesiology. 1998;89:1576– 8.
7. Remz M, Luria I, Gravenstein M, etal. Prevention of airway res:do
not overlook the expired oxygen concentration. Anesthesia &
Analgesia. 2013;117:1172– 6.
8. Rogers ML, Nickalls RWD, Brackenbury ET, Salama FD, Beattie
MG, Perks AGB. Airway re during tracheostomy:prevention strategies for surgeons and anaesthetists. Annals of e Royal College of
Surgeons of England. 2001;83:376– 80.
9. Sheinbein DS, Loeb RG. Laser surgery and re hazards in ear, nose,
and throat surgeries. Anesthesiology Clin. 2010;28:485– 96.
10. Frendl G. Laser surgery of the airway and laser safety. In:Hartigan
PM, ed. Practical Handbook of oracic Anesthesia. NewYork,
NY:Springer; 2012:427– 44.
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