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