Physics Exam 4: OR Electrical Safety
The electrosurgery unit (aka ESU/electrocautery device) generates very high-frequency currents (radiofrequency range) of anywhere from _______ to __________ Hz.
500,000 - 1 million Hz
What frequency does AC occur?
60 Hz
What is considered a fire source in the OR?
- diathermy / lasers / lights - alcohol-based prep - drapes / sponges - O2
What composes a simple circuit?
(+) side (-) side ground
What would lead to a shock from an isolated circuit?
- two point contact w/ isolated circuit + ground - poor insulation around wire - wires exposed to H2O and someone in contact w/ water
______ Amps will result in the recommended max ______ Hz leakage current.
0.00001 A; 60-Hz
When directly stimulating the heart, how many Amps will cause vFib?
0.0001 A
A current of _____ Amps will result in threshold of perception.
0.001 A
How many Amps is accepted as the maximum harmless current intensity?
0.005 A
What is considered the "let go" current? What does this cause?
0.01-0.02 Amps; sustained muscle contraction
Considering MACROshocks, how many Amps will cause vFib?
0.1-0.3 Amps RESPIRATORY CENTER INTACT
What composes a complete circuit?
voltage simple circuit
What is an isolation transformer?
Converts electrical power from the primary side (hospital) to the secondary side (OR) Helps prevent MACROshocks
T/F: electricity is able to flow in incomplete circuits.
FALSE - electricity is NOT able to flow a circuit must be complete
T/F: Bipolar electrocautery and monopolar electrocautery are equally likely to cause burns.
FALSE: bipolar is less likely to cause burns/injuries - bipolar does not require a return electrode
The line isolation monitor starts alarming. What does this tell you? How do you respond?
Faulty equipment is plugged into the isolated line system unplug the last piece of equipment plugged in
How does line isolation monitoring prevent shocks in the OR?
measures to see if current in = current out of a circuit if a difference exists - alarm will sound - automatically changes system to a conventional grounded system
The (-) side of a simple circuit is _____.
neutral
Your patient has a pacemaker. What must you know?
pacer dependent or not
What is the effect of 0.05 Amps?
pain / fainting / mechanical injury HEART + RESPIRATORY FUNCTIONS INTACT
What would happen if someone used faulty equipment in which the grounding wire was broken and the device was plugged into an isolated power system?
NO SHOCK WOULD OCCUR to the individual
What occurs if a hot wire gets disrupted?
No flow
What is AC electricity?
alternative current, where e- flow REVERSES at a set frequency
Define electrical current.
amount of charge flowing/unit time
What does the reading on a line isolation monitor tell you? What would result in a dangerous situation?
amount of current that would flow in the case of a first fault second fault --> dangerous
What types of anesthesia equipment must be on a battery back-up?
anesthesia machine + ventilator gas Non-desflurane vaporizer
Electricity is the change in ______________ caused by ___________________.
potential energy; movement of e- d/t a charge gradient (high charge density --> low)
How many amps difference will a line isolation monitor detect?
detect 2-5 amps --> ALARM! (depends on the age / brand of the system)
What does an line isolation monitor do?
detects isolated power system integrity
What is a ground fault circuit interrupter?
device that detects currents large enough to cause injury SHUTS OFF CURRENT FLOW TO LIMIT EXPOSURE
What does DC electricity indicate?
direct current - flow of e- in one direction
For a given resistance, voltage and current are inversely/directly related.
directly related higher voltage = higher current flow
What can a charge create? Why?
electrical current; they can move
What can static electricity cause in the OR?
fire + patient injury (lines have transducers)
Electricity is commonly thought of as ____________ through a conducting material.
flow of charge
What is considered a conductor of current?
fluids containing lytes medical wires - (pacer / bladder stimulator / pain pump) ICD
What safety measure reduces potential for getting shocked in the OR?
grounding (low resistance)
A (+) charge is considered high/low density.
high density
The (+) side of a simple circuit is ______.
hot / live
What is Coulomb's (electrostatic) Law?
magnitude of electrostatic force + distance relationship opposite charges are attracted to each other more with decreased distance between them
Where are electrical vectors directed if it is low density (-)?
towards the source charge opposite for (+)
Electricity must have ____________ for electrical flow to occur.
a complete circuit
Define circuit.
loop of e-
______% of all electrical injuries in a hospital happen in the OR.
40%
When a shock occurs, which is affected first as current increases - cardiac or respiratory system?
1. Cardiac 2. Respirations
What is a risk of electrocautery to OR personnel? What can you do to reduce this risk?
Airway disorders Chemical exposure Viral exposure Wear proper airway protection
What does a hot wire do?
Brings electricity to something
What should never be used in an emergent case?
CHLORAPREP!!! - have to wait 3 minutes for dry time - fire risk!! (DON'T USE AROUND AIRWAY)
Describe monopolar electrocautery (aka diathermy).
High frequency current w/ low tissue penetration - delivered by a single tip - requires a grounding pad
Describe the isolation transformer in the OR.
Hospital current (primary) --> OR isolation transformer (secondary) - neutral line is ungrounded - ground is grounded
Does wall suction have a battery back-up?
LIMITED TO NONE - rely more on portable suction
A large return plate for monopolar cautery results in a high/low current density. What does this result in?
LOW; very little heat development
What is the fire algorithm for the OR?
Spark DREaM, Rapid Alert 1. STOP VENTILATION (O2 source) + ignition (surgeon) 2. Disconnect pt from circuit 3. Remove airway support device - (LMA / NC / ETT) 4. Extinguish - Use NS for airway fire 5. Mask ventilate - until safe to use O2 again 6. Re-intubate 7. Assess airway Spark DREaM, Rapid Alert ¯\_(ツ)_/¯ (spark - fire / dream - OR nightmare / rapid alert - respond quickly)
T/F: When using a short-circuited, faulty piece of equipment with an isolated power system will not usually trip the circuit breaker.
TRUE safety measure for life-support equipment so it doesn't shut down
What is bipolar cautery?
Two tips - current supply - current return separated by insulation no grounding pad required
What is Ohm's Law?
V = IR V: Voltage in volts I: Current in amperes R: Resistance in ohms
The OR is considered what type of area?
WET
What type of electrocautery is most optimal for a patient with a pacer? Why? What precaution should you take?
bipolar - no risk of passing current over pacer --> senses false electrical activity --> no pacing occurs Contact rep to see if a magnet does or does not need to be used --> automatic mode
Where do we see AC electricity?
both sides of isolation transformer from the OR side
What does a neutral wire do?
brings current back to its source to form a completed loop
What is a risk of diathermy? Why does this occur?
burns improperly applied grounding pad / faulty wires - current finds alternate route of grounding (ECG pads)
Why don't we use ground fault circuit interrupters in the OR?
can shut off equipment without warning
How does the use of an isolation transformer in the OR help prevent shocks?
circuits of electrical OR equipment become electrically isolated from ground
Define electricity.
combination of (+)/(-) charges
What is the standard unit of electricity?
coulombs
What is a MICROshock?
current --> heart directly
What is a MACROshock?
current --> skin before reaching destination
What causes heat to be created by electrocautery?
current passing through resistance
Why is bipolar diathermy is perceived to be safer than unipolar diathermy?
current pathway is shorter + in a small radius of the forceps No return plate needed
The magnitude of a charge is increased/decreased with distance.
decreased inversely related
What are preventative measures you can take to reduce risk of OR fire?
identify risks during time out assess O2 requirements - not required --> administer room air for comfort - required --> secure airway (no NC use) if pt requires O2, but must be able to talk (exceptional case): - NC w/ air + lowest possible O2 combo via blender/common gas outlet/Wye - "wash out" O2 w/ 5+ L of RA - open draping - consider options outside of cautery From video in lecture: https://www.apsf.org/wp-content/uploads/collateral/videos/APSF-OR-Fire-Safety-Video.mp4
Heat from electrocautery is directly/indirectly proportional to surface area through which the current passes.
indirectly proportional
What does the meter on a line isolation monitor continuously monitor?
integrity of the system
What is a risk of bipolar electrocautery?
internal injuries
Line isolation monitors continuously monitor the isolated power to ensure that it is ____________________.
isolated from ground
What is static electricity caused by?
lack of ground
If metal casings around a piece of equipment start to become charged, ____________ comes into play. What created this charge?
line isolation monitor; bad neutral wire
Define electrical circuit.
loop formed by wire that has a voltage source attached to it like a battery
What happens if a neutral wire is disrupted?
shock can occur
What would cause a shock if an isolation transformer is being used?
someone has to have contact with BOTH isolated circuits + ground
Describe how an OR fire will most likely present.
subtle blue flame
What is the effect of a 6 Amp MACROshock?
sustained myocardial contraction --> normal rhythm temporary respiratory paralysis burns (if high density)
In a properly functioning monopolar cautery system the only tissue effect is located at __________________.
the active electrode site (held by the surgeon)
When using monopolar electrocautery, the grounding pad should not cross _______.
the heart
