Week 8 - Electrical and Fire Safety in OR Flashcards
What is Coulomb’s law?
Like charges repel each other while opposites attract
Electricity results from _________ __________
mobile charges
Electrical charge is measured in ____________ and a e (electron) has a magnitude of ___________
Coulombs, - 1.602^-19 C
How does electricity flow?
Movement of electrons from an area of high concentration to and area of low concentration
Stationary electrical charges vs electrical potential
Different!
SEC –> Measured in Joules, holding energy “still” (Cardioversion)
EP –> Measured in Volts, Volts = Joules / Coulombs
What is Ohm’s Law?
The potential of flow of electricity is proportional to the actual current, AFTER accounting for resistance
Measures resistance → V (potential difference) = I (current) x R (resistance). V = IR
What are good conductors of electricity?
Good conductors → Allow electrons to freely move through material with LITTLE resistance → Copper, METALS are generally good conductors. Exception → Graphite which is a non metal but conducts electricity fairly well
Metals are good conductors because their outer electron shells are mostly empty, allowing for electrons to freely flow through with little resistance
What are good insulators of electricity?
Good insulators → RESIST flow of electrons, they cannot freely move around → NON-METALS, can be charged, Silicon
Resistance → All materials offer some level of resistance, even conductors. The energy required to push electrons through a material is a measure of the resistance of the material
What is resistance in electricity?
Resistance is simply a ratio of voltage to current → How hard is it pushing to move these electrons. R = V / I
Materials that obey Ohm’s law are termed?
Materials that obey are termed ohmic, materials that do not (which there are a lot) are termed non-ohmic (diodes)
How does the ground play a role in electrical flow?
Ground is a conductor, connected to the earth’s ground → provides an alternate path for electricity to flow in a power surge
What is a DC circuit?
DC circuit → Electricity ALWAYS flows in one direction, generally how battery powered devices function (flashlight)
What is the Law of Conservation of Electrical Charge?
The total amount of electrical charge in the universe is constant!
Charge is simply transferred
Charges that move are _________
negatively charged
Coulomb’s law can be used to calculate what?
The force or attraction or repulsion between two charges
All electrical charges posses a force field, what is this?
This is what exerts the electrical force on a test charge located at any point around a central charge
This is a vector → SI units are Newtons per Coulomb (N/C)
An electrical current is _______ and is measured in __________
Moving electrons (negatively charged), amperes (amps).
This is the amount of charge flowing per unit of time –> 1 amp = coulombs / time (seconds)
What is an electrical circuit?
A circuit exists when a charge is able to flow through a closed path
2 types –> DC and AC circuits
What is an AC circuit?
Current can periodically change direction
Derive their energy from wall outlets or AC generators
What is a series circuit?
One pathway for current flow, voltages and resistances are additive
3 2 V batteries = 6 V
Car batteries work this way → 12 V battery from 6 2-V batteries
Resistors work by adding sum together as well
50 ohms and 25 ohms resistors = 75 ohms
What is a parallel circuit?
Current has more than one path it can take and resistors are connected in each pathway (household circuits)
Allows for electricity to run through separate circuits → Can turn on the microwave without everything else turning on
Each current runs through a resistor independently → Total resistance is found by adding inversely
Real circuits consist of both parallel and series circuits
What is electrical power?
Power is the rate at which energy is expended or consumed. P = I x V → Watts = amps x volts
Current x Potential energy
What is electrical energy?
Power x Time
Kilowatt hour is generally the unit used
What are the two types of semi-conductors?
P-type (positive type) → Silicon doped in boron. Boron atoms have one less valence electron than silicon atoms. More “positive holes”
N-type (negative type) → Silicon doped in arsenic. Arsenic atoms have one additional valence electron compared to silicon atoms.
What are semiconductors primarily made of?
Silicon, semiconductors are primarily used in computers
What are triodes?
Triodes → Known as transistors. Made from two closely situated pn junctions. Used for amplifying or switching currents
Two examples of where spectroscopy is used
Used for analysis of blood work and a pulse oximeter
What is spectroscopy?
The study of the absorption and emission of light and other radiation by matter
When white light passes through a colored substance, certain wavelengths are absorbed
In regard to spectroscopy, a substance __________ its _____________ color
absorbs, complementary
Ex –> Red things absorb green light
What is a monochromator?
Essentially a prism, a beam of light passes through and directs the light through a second silt before hitting the sample and then detector
How are spectrometers designed?
Spectrometers have the same basic design
Source of light goes through a silt to monochromator → this goes through the 2nd silt and then to the sample. Finally, the detector measures the intensity of the light
The source emits the desired wavelength of electromagnetic radiation.
What is this definition referring to in regard to spectroscopy?
Instrumentation
What is Beer’s law?
How light is absorbed by the sample (blood)
(A = abc)
What 3 things affect Beer’s law?
Absorptivity → Should be between 0.1 and 1 (a)
Increasing the Distance (b)
Concentration of the analyte (c)
What is transmittance in relation to Beer’s Law?
Fraction of light passing through a sample. Influenced by intensity of the light
The strength of a shock depends on what three things?
- Path of the current
- Magnitude of the current
- Duration of the contact
What two things can complete a path through which a current can flow?
Stray capacitances and Inductances
Macroshock is when _________
A relatively large amount of current flows through the body potentially resulting in injury or death
100 mA can initiate ventricular fibrillation
Microshock is when _________
A relatively small current is delivered externally directly to the heart via a low resistance pathway
100 microAmps or less can initiate ventricular fibrillation (book says 50 or less)
The longer an individual is in contact with a current, ____________
the greater the damage
How does a fuse work? What happens when this is burned out?
Fuses → If the current exceeds the rated value, the fuse will melt preventing further current from flowing
Needs to be replaced after burned out
What is the purpose of fuses and circuit breakers?
Designed to limit current flow in the event of a short circuit or circuit overload
How does a circuit breaker work?
Bimetallic strip → Will warp when heated too much which opens or “trips” the circuit. Once the strip cools it will return to its original shape allowing current to flow → The circuit will need to be reset with the flip of a switch.
What are three modern safety devices to help prevent circuit overload or a short?
Polarized plugs, three-pronged grounded plugs, and ground fault circuit interrupters (GFCIs)
What is a polarized plug?
One wide and one narrow prong → Narrow = high potential, wide = low potential
Casing is connected to the wide prong or low potential, this isolates the device case from the high potential
How does a three pronged grounded plug work?
The third prong provides a path to divert the high potential current directly to the ground thus protecting someone from touching the case of the appliance.
This is IF a high potential wire comes in contact with the appliance casing
How does a three pronged grounded plug look?
Two equal flat plugs with a third rounded ground prong wired directly to the case of the electrical device
Where would you expect to see a ground fault circuit interrupter?
A protective outlet used near water sources (sinks, tubs, and pools)
How does a ground fault circuit interrupter work?
Detects current imbalances between a high potential wire and a low potential wire
In a ground fault circuit interrupter, should the low and high potential wires be equal in current?
Yes
Designed to immediately shut off if there is an imbalance between the two currents
High potential and low potential wires should equal each other in current flow IF working correctly.
At what current difference does a ground fault circuit interrupter “trip”?
5 mA
What does a ground fault circuit interrupter look like?
Has two additional buttons on a normal looking outlet.
One button works to test the functionality
Second button is used to reset the circuit
Ground fault circuit interrupter placed upstream from additional outlets can do what?
Can protect the outlets downstream from the GFCI even though they are “normal” looking outlets
For circuit containing more than one outlet, this GFCI outlet can be placed at the first receptacle while the other outlets are “regular” but still protected by this outlet
Can also be placed in a circuit breaker with subsequent outlets looking regular but protected by this.
What type of system is primarily used in the OR?
Ungrounded systems
Why are ungrounded systems preferred in the OR?
Benefits are that when standing on the ground and touching a high potential wire, you won’t complete the circuit and receive a shock → Will receive a shock however if you touch TWO wires simultaneously
Why is there a high risk of macroshock in the OR?
Abundant electrical devices and conducting fluids (electrolytes)
What is an isolation transformer?
Works through electromagnetic induction
Outsources the secondary circuit (ungrounded) via an isolation transformer, which doesn’t physically touch the current, to the primary circuit (grounded) OUTSIDE of the OR
What is Faraday’s law of induction?
Faraday’s law of induction → Changing magnetic flux in one coil produces a changing voltage, and hence a changing current in the second coil.
What additional safety feature is used in the OR in ungrounded systems?
Line isolation monitors (LIMs)
What does is mean if you line isolation monitor alarms of a greater than 5 mA leakage?
You have turned an ungrounded system into a grounded system
What types of circuits receive at least some type of leakage?
All AC circuits experience leakage current (small amounts of current, in mA, leak onto the ground)
What do line isolation monitors measure?
LIM’s measure “impedance” to ground. Usually alarm around 2 or 5 mA’s of leakage
Newer ones alarm at 5 mA due to normal constant leak of 2 mA’s or less
What should you do if the line isolation monitor alarms?
If LIM alarms → Unplug last item plugged in and inspect, it may still be functional and can be used if it is essential and cannot be replaced, but increases risk of shock. Keep unplugging items until LIM reading is normal
Line isolation monitors allow the circuit to ____________
remain functional (turned on)
What is the difference between bipolar and unipolar electrodes in electrosurgery (electrocautery)
Bipolar → Has two tips, one delivering current and one returning the current → Does not require a large surface area return electrode and are LESS LIKELY to cause burns or injuries, aside from the tissue being worked on
Unipolar → Only have one tip to deliver current and a large surface area return electrode. The path of current flow from unipolar devices to the return electrode should NOT CROSS the patient’s heart.
What is electrosurgery?
Same thing as electrocautery
High frequency electric currents to cauterize, cut, and destroy tissue.
At what frequency current does electrosurgery work under?
0.3 - 2 MHz
In electrosurgery, electric power is dissipated as _________
heat
When should the large area return electrode be allowed to pass through the patients heart when using a unipolar electrode?
NEVER!
What happens if you touch a high potential open wire in a grounded system?
Does electrosurgery use an alternating current?
Yes
Why would a person be termed electrically susceptible?
They have a low resistance electrical pathway within their body
Pacemaker wire or a PAC carrying a saline solution
Do all AC and DC circuits experience leakage?
NO, only AC circuits do
On the order of mA, acceptable levels are less than 5 mA
Can a normal leakage amount (less than 5 mA) be dangerous?
No, only if there is excessive leakage.
What device would alarm you that an ungrounded system has become grounded?
Line isolation monitor
Alarms at 2 or 5 mA of leakage
What contaminant is produced during ESU or laser surgeries?
Smoke plume –> 95% water, 5% particulate matter, volatile gases, and microorganisms
Why are the particulates in the smoke plume formed during ESU or laser surgery worrisome?
These fine particulates can be as small as 0.3 mcm and can deposit in the lower airways
What are the OSHA guidelines regarding smoke produced during ESU or laser surgeries?
NONE! Besides being aware it exists
National Institute (NIOSH) recommends a local exhaust ventilation system to clear this smoke plume
What is a local exhaust system comprised of for clearing out the smoke plume?
Local exhaust ventilation system → Should contain a HEPA filter (can filter 0.3 mcm particulate matter) and suction be kept within 2 inches of surgical site to capture smoke plume
Why is a three stage filter better than just a HEPA filter?
Three stage filters → HEPA filter (0.3 particulate matter), layer of activated charcoal (odor absorption), and an ULPA (ultra low penetration air filter for 0.1 particulate matter)
What type of mask should be used in the OR when using laser or ESU techniques?
OR staff should wear N95 to prevent inhalation of smoke plume
Who is at the highest risk in the health care community of electrical injury?
Laser repair technicians
What type of surgery causes the most surgical fires?
90% ESU, 10% lasers
85% of these fires occurred during high risk surgeries involving the airway, head, neck, and upper chest
Most common surgical fire site?
→ Airway (all day) at 34%
- Kristie Hoch
What 3 things make up the fire triangle?
Fuel source, ignition source, oxidizer
All present in the OR
A CO2 laser produces the equivalent of _________________ contaminants for every 1 g of tissue
3 - 6 cigarettes
Fire risk should be part of ___________
Time out
What two things should always be available during a laser or ESU procedure?
A basin of water or NS should be available to extinguish fire
2 syringes filled with NS should be readily available for the airway incase of an airway fire
What are some fuel sources contributing to a surgical fire?
Surgical prep solutions, facial hair, gloves, surgical drapes, ET tubes…
What should be considered when using alcohol based prepping solutions prior to surgery?
Alcohol/alcohol based solutions pose an increased risk to fire if adequate drying time isn’t provided → Make sure it doesn’t pool under the patient or saturates the drapes
Which fire extinguisher should be used during an OR fire and why?
Only initially use class BC! This is a CO2 extinguisher appropriate for surgical fires because it doesn’t leave residue or damage tissue.
Class ABC (dry powder) will contaminate all surfaces, cause respiratory irritation, and cause visual disturbances
What can happen during airway laser surgery to the ET tube?
Can catch on fire via different methods
Rupture of cuff → Can lead to fire due to increased risk of ignition via anesthetic gas
Inner tube fire → Can turn ET tube into a blow torch from the distal end causing lower airway trauma
What are some ignition sources aiding in a surgical fire?
Surgeon mainly controls this via laser or ESU
Desiccated soda lime, fiber optics, high speed drills, monitors, defibrillators
Who controls the oxidizer source contributing to a potential fire? What are the oxidizers?
Under control of YOU, the anesthetist
Air, O2, and N2O aid in this
O2 is the oxidizer responsible for 95% of surgical fires!
Because O2 is heavier than air, it accumulates around and under the surgical drapes
What should be done if supplemental O2 is needed during laser or ESU surgery?
SpO2 of 90 or less is undesirable and warrants supplemental O2 use → airway should be secured with an LMA or ET tube and FiO2 should not exceed 30%
What actions should be taken during laser or ESU surgery if your patients SpO2 deteriorates to 92% but maintains?
Mild respiratory depression with SpO2 at 92 or higher DOESN’T warrant use of supplemental O2 → continue with RA
How can O2 accumulation be minimized during surgery?
Minimize buildup of O2 with suctioning system → Even if patient’s airway is secured with an LMA or ET tube, continual suction of the oropharynx should be implemented
Why should TIVA sedation be used during ESU or laser surgeries?
Volatile anesthetic gases are NOT flammable, but shouldn’t be used during laser/ESU surgeries due to the ability to deteriorate in the presence of fire to toxic compounds
What should occur prior to initiation of ESU or laser surgery?
Turn off O2 for 1 minute before and DURING
To prevent surgical fires, what should be done with patient facial hair?
Coat with a water soluble lubricant
What type of ET tube should be used during laser surgery of the airway?
Laser resistant ET tube
Red rubber ET tube wrapped with fabric or a stainless steel double cuffed ET tube
What materials are most O2 devices made of that contribute to surgical fire ignition?
Polyvinyl chloride (PVC), ET tubes also have a radiopaque barium strip that ignite much faster than the PVC it is made of
O2 should be avoided in _____________ if patients can safely go without
MAC (monitored anesthesia care)
How can you prevent the smoke plume from reaching the lower airways when using an LMA?
Use 5 to 10 cm H20 of PEEP during laser surgery to prevent hot, toxic gases from entering the lower airways.
How should the cuff of the ET tube or LMA be filled and protected during laser surgery?
Fill ET cuff with NS and methylene blue –> This can alert the surgeon of a tear/leak.
Protect cuff with moistened gauze –> You will need to rewet throughout surgery
In the event of an airway fire, what steps should be performed in rapid succession?
Remove ET tube → remove flammable and burning materials from airway → stop gases → pour saline into patient’s airway
After an airway fire, how should the patients airway be examined?
Should be examined with a rigid bronchoscope for laryngeal edema and thermal trauma
What labs should be ordered after a patient experiences an airway fire?
ABG, CXR, and carboxyhemoglobin levels
What may need to occur if a patient needs to be reintubated after an airway fire?
A smaller ET tube may need to be used due to laryngeal edema –> Consider corticosteroids
After an airway fire, all patients, regardless of status, must be observed for a minimum of _____________
24 hours in the ICU
During laser surgery, what steps need to be taken when an ET needs to be repositioned or re-inflated?
Wait 1 minute before restarting surgery if ET tube needs to be repositioned or inflated
What steps should be taken for a non-airway fire?
Remove all drapes, stop gases, and remove or extinguish materials with saline, water, or smothering
How should severe airway burns be treated?
Serve burns require continued intubation with 30-60% humidified O2 → Trach and PEEP may be required for long term
What does RACE stand for?
Rescue the patient
Alert staff and Activate the alarm
Confine the fire
Evacuate the room
After an airway fire has been extinguished, how should the patient be ventilated?
With AIR via BVM
Continuous use of laser safety eyewear (LSE) is required for _____________
OR personnel AND any awake patient
How should alarms be adjusted when wearing LSE?
Monitors should be at maximum brightness and alarms on the LOUDEST setting
Why should monitors be observed is tinted LSE prior to inducing the patient?
To ascertain the effect of the tinted eyewear on the monitors while the patient is stable
What LSE may affect perception?
Tinted or colored LSE
How are anesthetized pateints protected from ocular injury during laser surgery?
- Eyes should be covered with saline-moistened eye pads and laser shields
The most common hazards of medical lasers include:
- thermal trauma
- eye injury
- perforation of organs or vessels
- gas embolization
- electrical shock
- air contamination
- fire
Most medical lasers are class _____, and are potential ______ hazards
4
* fire
What are the advantages of surgical laser use (4)?
- precision
- access to remote sites in body
- reduced blood loss
- reduced damage to adjacent tissue
What is a disadvantage to surgical laser use?
- Delayed wound healing
Laser-tissue interactions include:
1. Photo_______
2. Photo_______
3. Photo________
4. Photo_________
- mechanical (“shock wave”)
- thermal (rapid temperature increase)
- chemical (breaks molecular bonds or excites molecules)
- dynamic (activation of photosensitizing medications)
Absorption of the light is necessary for the laser to be effective - absorption is dependent on _________ and ____________
- type of tissue
- wavelength of the light
The reaction of tissue to light absorption is dependent on the wavelength, ____________ and ______________
- intensity
- exposure time
True or false:
All laser types have the same effect on biological tissue?
False
* laser effect on tissue is dependent on wavelength of the laser
Laser is actually an acronym meaning:
- Light Amplification by the Stimulated Emission of Radiation
A collision between a photon and an excited atom stimulates ____________
The emission of a second photon = laser
What is the most commonly used medical grade laser?
CO2 Laser
Laser energy is measured in ________, while power is measured in __________
joules, watts
Absorption depth is achieved when the intensity of the laser in reduced by ___________
63%
Why is deoxygenated blood darker in color than oxygenated blood?
Deoxygenated blood absorbs more red wavelengths
Which laser melts anything in its path, including steel?
CO2 laser
Examples of class III lasers
Spectroscopy and light shows –> Can cause eye injury if viewed directly
What class of lasers does a laser safety officer (LSO) need to be appointed?
Class IIIB or IV
How does a laser safety interlock system work?
Surgical laser is disabled when the OR door is unexpectedly opened
Non-beam laser injuries include
Secondary injuries –> Due to air contaminants, fire, electrical shock, and noise
Longer laser wavelengths have ___________ skin penetration
deeper
Skin trauma is dependent on what two things regarding use of a laser?
Energy and wavelength (longer = deeper penetration)
What should be placed on the patient’s skin surrounding the path of a laser beam?
saline-soaked towels –> Prevents thermal trauma
Should petroleum based eye ointments be used to protect a patient from laser misdirections?
NO –> This can cause serve burns and fire if ignited
If cones are damaged by a green light laser, then the patient may experience difficulty discriminating between what colors?
Green and blue
Severe eye pain and sensation of sand in the eye can present later (not immediately) on from exposure to what
Ultraviolet radiation
Laser damage to the retina is _______
Permanent
Why do darkened OR’s place surgical personnel and awake patients at higher risk of laser exposure?
Dilates the pupils –> Bigger target for laser to strike
Why do patients undergoing Nd:YAG laser surgery of the airway need to be monitored for 24-48 hours?
Nd:YAG laser is associated with delayed tissue damage because of its increased tissue penetration –> perforation, bleeding, or edema may not be present until hours after.
What are diodes?
Large conductance in one direction, smaller conductance in another direction.
Can be used to control the direction of the current.
LED’s are an example. These are non ohmic
