Electrical Safety In The Or

Front 1

Two major hazards from electrical appliances in the OR:

Back 1

Burns and arrhythmias

Front 2

Three types of electrical currents involved in OR fires:

Back 2

Macroshock
Microshock
Radiofrequency (Bovie) currents

Front 3

For a shock hazard to exist, the current must be able to flow in what direction?

Back 3

A path must exist from the electrical source to the patient, and another path must exist from the patient back to the electric source.

Front 4

The large amounts of current conducted through the patient's skin and other tissues.

Back 4

Macroshock

Front 5

The delivery of small amounts of current directly to the heart

Back 5

Microshock.

Front 6

Macroshock can cause one of two problems

Back 6

Burns

Cardiac Arrythmias

Front 7

How do currents get to the heart?

Back 7

Macroshock travels up the arms/ legs through the muscles to the thorax.

In the thorax the current is split b/n the chest wall and the great vessels, which deliver the current directly to the myocardium.

Front 8

With macroshock, currents pass through the extremities mostly through the _______.

Back 8

muscles.

Front 9

Ohm's Law

Back 9

V = I*R (chg P = QR)

V = Voltage difference = (MAP - CVP)

I = Current = Cardiac Output

R = Resistance = SVR

Therefore

(MAP - CVP) * 80 = CO * SVR

Front 10

The amount of current flowing per unit area is referred to as

Back 10

current density.

If the current density is great, even a small amount of current can cause burns or arrythmias to a small area.

Front 11

What risk factors in the OR place the pt at risk for electrocution.

Back 11

* The patient is unclothed and frequently wet.

* The pt is on a large metal table, frequently electrically operated, to which he or she may be connected by large wet towels.

* The pt is surrounded by electrical devices, and is directly connected to several of them.

*These electrical devices are exposed to spilled fluids and operator abuses that increase the potential for short circuits.

* The anesthetized pt is unable to respond to or withdraw from an electric shock.

Front 12

The main resistance to flow of current is....

Back 12

The main resistance to flow of current is the SKIN.

Front 13

The resistance of dry skin is about...

The current through dry skin is ....

Back 13

The resistance of dry skin is about 50,000 ohms.

The current through dry skin is 150V / 50,000 ohms, which is 0.003 A or 3 mA.

Front 14

The current required producing ventricular fibrillation across an arm-arm or arm-leg circuit is ...

Back 14

80mA

Dry skin produces a current of 3 mA and will not cause fibrillation.

Wet skin can produce a current of 300 mA and CAN cause fibrillation!!

Front 15

The resistance of wet skin is.....

The current of wet skin is.....

Back 15

The resistance of wet skin is 1/100th that of dry skin, about 500-1000 ohms.

The current of wet skin is 150V/500 ohms = 300 mA

Front 16

One of the best ways of preventing macroshocks is use of....

Back 16

One of the best ways of preventing microshocks is the line isolation transformer.

Front 17

Describe the line isolation transformer.

Back 17

The line isolation transformer is a device that prevents a circuit from being completed by connection to the ground.

A line isolation monitor is placed b/n the live wires and ground to measure impedance to flow.

If a live wire has contact to the ground, the line isolation monitor will alarm.

Line Isolation monitors are usually set to alarm at 2-5 mA potential leak.

If the line isolation monitor alarms, the LAST equipment plugged in should be disconnected and inspected to verify it is the offending piece of equipment.

They can also be activated if there is a cumulative effect of minor leakages of many piece of properly functioning electrical equipment.

Front 18

True or false

CVP catheters pose a high risk of microshock to the heart.

Back 18

False.

CVP catheters pose a low risk of microshock to the heart as long as they are not floated into the RV.

Front 19

Describe Electrocautery Devices

Back 19

Electrocautery (Bovie) devices use high-frequencies of 500,000 - 2,000,000 Hz to cut, cauterize, or destroy tissue.

These frequencies are too high to fibrillate the heart.

They only pose the risk of BURNS!!

Bovie units can be UNIPOLAR OR BIPOLAR

Front 20

Describe Bipolar Bovie Units

Back 20

Bipolar Bovie unit

* have 2 tips: one to supply the electrical current and the other to return the current.
* They do not have/ need a return electrode and are therfore less likely to cause burn or injury.

Front 21

Describe Unipolar Bovie Units

Back 21

* Have one tip to deliver an electric current

* Require a return electrode/ grounding plate called a "bovie pad".

Front 22

True or false

The "grounding plate" on unipolar bovie cauterizing machines grounds the patient to the ground.

Back 22

False

The patient should never be grounded. The grounding plate simply returns the current back to the electrocautery unit after it is used.

Front 23

Why does the patient not get burned by the grounding plate?

Back 23

The plate covers a very large surface. The current density is low.

Make sure that the gel of the plate has not dried and that the plate is applied properly prevent forcing the current through a much smaller area and causing a burn.

Front 24

What is the most important aspect of using/ setting up an electrocautery unit?

Back 24

Be certain that the ground plate is properly positioned and that the wires are intact b/n the plate and the electrocautery unit.

Front 25

Ground plates should never be placed over...

Back 25

Ground plates should never be placed over metallic prostheses.

If the current travels through a screw in someone's hip...it will be concentrated over a small area and will cause an internal burn!!!

Front 26

What danger is posed by electrocautery during laproscopic surgery?

Back 26

Cauterizer sparks could ignite bowel gas, causing a fire/ explosion.

Current could accidentally burn the bowel and cause perforation.

Front 27

How can you minimize sparking of electrocautery units?

Back 27

Use low power units.

Use Bipolar units to keep the current confined to the narrow gap b/n electrodes, helping to reduce the channel of current flowing through the bowel.

Front 28

Fuel for fires in the OR includes:

Back 28

Bowel Gas
Alcohol based prep solutions
Drapes

Front 29

The minimal amount of current that can produce ventricular fibrillation when applied directly to the myocardium via intracardiac electrodes.

Back 29

10 microamperes

The small amount of current is effective because it is applied to a small area. (high CURRENT DENSITY)

Front 30

What is the minimum amperage of macroshock/shock across skin that can cause ventricular fibrillaton?

Back 30

80 mA