Dr. Pallavi Dr. SanjayDr. SureshDr. SetuvarunDr. YaminiSeth G.S.M.C. & K.E.M.H.

ELETRICAL SAFETY IN OPEARTING ROOM

CURRENT (I) – amperes (A)VOLTAGE DIFFERENCE (V) - voltsRESISTANCE (R)- ohms

I

George Simon Ohm(1789-1854)- German Physicist

OHM’ LAW

CONDUCTOR AND INSULATOR

HOW CAN ELECTRICITY FLOW THROUGH BODY?

Two ways: Resistive coupling Capacitive coupling

RESISTIVE COUPLING

When the body makes a direct physical connection with the electrical circuit, its due to resistive coupling.

• Faulty equipments• Leakage current

CAPACITIVE COUPLING

Body acts like a capacitor, which stores the electrical charge.

In case of direct current, current flows for a brief period until the source and receiver are at same potential.

In case of alternating current, body would continuously charge and discharge, and current will continuously flow.

ELECTRICAL CURRENT EXISTS IN 2 FORMS :

Direct Current (DC)- Electrons flow in only one direction.

Used in certain medical equipment: defibrillators, pacemakers, electrical scalpels.

Alternating Current (AC)- Electrons flow back and forth through a conductor in a cyclic fashion

It is used in household and offices and is standardized to a frequency of 60 cycles/sec (60 Hz)

AC is far more efficient and also more dangerous than DC (~ 3 times): tetanic muscle contractions that prolong the contact of victim with source

DETERMINANTS OF ELECTRICAL INJURIES

Current density Current intensity Tissue resistance

The pathway that current takes through the body will determine which tissues are damaged.

The effect of the size of current and current pathway can be considered together as current density. This is the amount of current flowing per unit area.

Macroshock current is distributed somewhat evenly through body parts.

Microshock current path is through a single point, usually the heartTerm used to describe the very low level shocks that go undetected

For example, a 50 Hz alternating current flowing between each hand

the current has passed through the whole of the trunk with only a

small part of it passing through the heart, i.e. the myocardial current density is relatively low. However, if the current flows directly into the myocardium (or in very close proximity to it), for any given current, the current density will be much greater. In these circumstances, a substantially smaller current (50 μA at 50 Hz) can cause ventricular fibrillation.

MICROSHOCK Dangerous to an “electrically sensitive” patient - with breaks in skin like

abrasions, wet dressings, pacemakers, or monitoring lines connected to a

transducer.

Examples of equipment that may allowmicroshock include central venous catheters, intracardiacpacemakers with an external lead and, to a lesser extent, atemperature probe placed in the oesophagus immediatelybehind the left atrium.

Nerves and blood vessels are the best conductors: path of least resistance for current after it enters the body

The least resistance is found in nerves, blood, mucous membranes and muscles

The highest resistance is found in bones, fat and tendons

Skin’s resistance ranging between 40,000 and 100,000 Ω depending on thickness

Moist mucus membranes: significant orofacial injury to infants and toddlers

Exposure of different parts of the body to the same voltage >> same current >> different degree of damage because resistance varies.

ELECTRICAL INJURY TO SPECIFIC TISSUES & ORGANS

Cardiovascular System- Direct necrosis of the myocardium- Focal or diffuse Widespread, discrete, patchy contraction band necrosis involving the

myocardium, nodal tissue, conduction pathways and coronary arteries

Cardiac dysrhythmias- AC > 50-100 mA with hand-to-hand or hand-to-foot transmission >

ventricular fibrillation

High-voltage current (AC or DC) > ventricular asystole

Possible mechanisms:

1) Arrythmogenic foci due to myocardial necrosis (esp. SA Node injury)

2) Alterations in the Na+ - K+ adenosine triphosphatase concentration

3) Changes in the permeability of myocyte membranes

4) Anoxic injury (respiratory arrest precedes the injury to the heart)

Large arteries not acutely affected because their rapid flow dissipate heat.

Medial necrosis: aneurysm formation and rupture

Smaller vessels acutely affected due to coagulation necrosis compartment syndrome

NERVOUS SYSTEM Loss of conciousness, confusion & impaired recall

Peripheral motor & sensory nerves > motor & sensory deficits

Seizures, visual disturbances & deafness

Hemiplegia, quadriplegia, spinal cord injury

Transient paralysis, autonomic instability > hypertension, peripheral vasospasm due to lightning from massive release of catecholamines

RESPIRATORY SYSTEM

Direct injury to the respiratory control center >> cessation of respiration or suffocation secondary to tetanic contractions of the respiratory muscles

Acute respiratory dysfunction syndrome secondary to ischemia, aggressive fluid resuscitation, ventilator-associated pneumonia

OTHER SYSTEMS

Kidneys susceptible to anoxic/ischemic injury

Release of myoglobin & creatinine phosphokinase > renal tubular damage > renal failure

Fractures

Transient autonomic disturbances > fixed pupils may be perceived as severe brain injury or even death

Temporary sensorineural hearing loss

Better Safe Than Sorry

PREVENTION OF ELECTRICAL HAZARDS

PREVENTING ELECTRICAL HAZARDS

Electrical accidents appear to be caused by a combination of three possible factors:

1. unsafe equipment and/or installation,

2.unsafe by environment,

3. and unsafe work practices.

PREVENTING ELECTRICAL HAZARDS

These include: Insulation

Guarding

Grounding

Electrical protective devices: Fuses & circuit breakers Ground fault circuit interrupter Isolation transformer & Line isolation monitor Safe work practices

INSULATION

One way to safeguard individuals from electrically energized wires and parts is through insulation.

An insulator is any material with high resistance to electric current.

Insulators such as glass, mica, rubber, and plastic,

Before you prepare to work with electric equipment, it is imperative to check the insulation

The insulation of flexible cords, such as extension cords, is particularly vulnerable to damage.

Electrical Power can exist in two forms-

GROUNDED

UNGROUNDED

GROUNDING

The "ground" refers to a conductive body, usually the earth, and means a conductive connection, whether intentional or accidental, by which an electric circuit or equipment is connected to earth or the ground plane.

Method of protecting from electric shock.

Secondary protective measure.

By "grounding" a tool or electrical system, a low-resistance path to the earth is intentionally created.

UNGROUNDED

GROUNDED

GROUNDING Think about your house:

2 prong outlets = no ground 3 prong outlets = grounded

Modern homes have a ground to reduce amount of shock

TWO PRONGED PLUG

THREE PRONGED PLUG

Low resistance and has sufficient current carrying capacity to prevent the buildup of voltages that may result in a personnel hazard.

This does not guarantee that no one will receive a shock, be injured, or be killed.

It will, however, substantially reduce the possibility of such accidents.

One of these is called the "service or system ground."

This type of ground is primarily designed to protect machines, tools, and insulation against damage.

There are 2 types of grounding required -

To offer enhanced protection, an additional ground, called the "equipment ground"

This additional ground safeguards the electric equipment operator in the event that a malfunction causes any metal on the tool to become accidentally energized.

The resulting heavy surge of current will then activate the circuit protection devices and open the circuit.

EXTREMELY IMPORTANT

Never remove a grounding device from any electrical source, tool, or equipment.

Never remove the ground prong from an electrical cord or device of any kind.

Never by-pass grounding or circuit breaker protection as any time.

If you find any of the above have occurred, repair and / or report immediately.

CIRCUIT PROTECTION DEVICES

Circuit protection devices are designed to automatically limit or shut off the flow of electricity in the event of a ground-fault,overload, or short circuit in the wiring system.

Fuses, circuit breakers, ground-fault circuit interrupters, isolation transformer and line isolation monitor

CIRCUIT PROTECTION DEVICES

Fuses & circuit breakers-monitor the amount of current that the circuit will carry.

Fuses are designed to melt when too much current flows through them.

Circuit breakers, on the other

hand, are designed to trip open the circuit by electro-mechanical means.

They prevent over-heating of wires and components that might otherwise create hazards for operators.

They also open the circuit under certain hazardous ground-fault conditions.

Fuses & circuit breakers-

GUARDING

Live parts of electric equipment operating at 50 volts or more must be guarded against accidental contact. This is accomplished by:

Location in a room, vault, or similar enclosure accessible only to qualified persons

Use of permanent, substantial partitions or screens to exclude unqualified persons

Elevation of 8 feet (2.44 meters) or more above the floor.

GROUND FAULT CIRCUIT INTERRUPTER

The ground-fault circuit interrupter, or GFCI, is designed to shutoff electric power within as little as 1/40 of a second.

It works by comparing the amount of current going to electric equipment against the amount of current returning from the equipment along the circuit conductors.

If the current difference exceeds 6 milliamperes, the GFCI interrupts the current quickly enough to prevent electrocution.

GROUND FAULT CIRCUIT INTERRUPTER

UNGROUNDING

The OR has many perils that make grounding impracticle.

Saline puddles

Power cords with tears in their insulation (colored part of cord)

Numerous electronic devices that risk

UNGROUNDING – ISOLATED POWER

Isolated Power System provides protection from Macroshock.

Faulty equipment plugged into an isolated power system does not present a shock hazard.

ISOLATION TRANSFORMER

An isolation transformer is a transformer used to transfer electrical power from a source of alternating current (AC) power to some equipment or device while isolating the powered device from the power source, usually for safety.

ISOLATED AND UNGROUNDED

LINE ISOLATION MONITOR

Continuously monitors the potential for current flow fromthe isolated power supply to ground.

Determines the degree of isolation b\w 2 power wires and the ground.

Predicts the current flow

Alarm is activated if 2mA-5mA of current is detected.

Line isolation monitor

STANDARDS OF SAFETY OF MEDICAL EQUIPMENTS

British Standard symbols used on medical equipments-

SAFE WORK PRACTICES

While working with electric equipment need to use safe work practices.

These include:

Switch off electric equipment before inspecting or making repairs

Using electric tools that are in good condition

Using appropriate protective equipment

CARE OF CORDS & EQUIPMENTS

Power tools and extension cords must be inspected each time they are used.

They must be taken out of service immediately upon discovery of worn or broken insulation.

DON’T Don’t plug in equipment with wet hands

Don’t plug in equipment when cord is wet

Don’t drape cords over hot or sharp objects

Don’t run cords where they cause tripping hazard

Don’t use extension cords unless authorized

MANAGEMENT OF ELECTRICAL HAZARDS

PERSONS AT RISK -o PATIENT

o DOCTORS

o NURSING STAFF

o OTHER PERSONES PRESENT IN OPERATING ROOM

PATIENT MOST IMPORTANT BECAUSE- Wet surface

Metal tables

Can’t move

Direct contact with electrosurgical equipments

GUPTA K, PREM KUMAR GV, BANSAL A, MEHTA Y BURN INJURY BY DISPLACEMENT OF ELECTROCAUTERY PLATE.

INDIAN J ANAESTH [SERIAL ONLINE] 2011 [CITED 2013 FEB 2];55:634-5. AVAILABLE FROM: HTTP://WWW.IJAWEB.ORG/TEXT.ASP?2011/55/6/634/90636

ELECTROCAUTERY

PRINCIPLE

High current enters body through small surface area electrode i.e. cutting tool producing high resistance R, small area, causes local tissue heating which leads to cutting and coagulation.

Operate at frequency approximately 300 kHz to 2 MHz, to prevent cardiac arrhythmias.

UNIPOLAR VS BIPOLAR

UNIPOLAR- Electric current that enters in body travels

through the body and collected outside surgical field by grounding pad.

BIPOLAR- Current enters in body through one electrode

collected millimeters away from second identical electrode .

PRECAUTIONS

GROUNDING PAD - Wide area, well jelled and with good contact with body.

Unipolar cautery should be avoided in

neurosurgery patient and patient with AICD.

Remove all metal ornaments such as ear rings and bangles.

IF present, keep the grounding pad on same side of surgery NOT on OPPOSITE side.

RECONCENTRATION

ELECTRO-QUATERY WITH LARGE CONTACT

ELECTRO-QUATERY WITH POOR CONTACT

ELECTROCAUTERY WITH AICD-

RESPONSE TO CAUTERY— Inhibition of pacing. Asynchronous pacing. Reset to backup mode. Ventricular fibrillation . Myocardial burns rare.

PRECAUTIONS TO BE TAKEN-

Use bipolar cautery.

Limit use to minimal.

Use grounding pad close to operative site and away from pacemaker site.

Do not use cautery within 15 cm of pacemaker site .

Frequency of cautery should be limited for 1 sec burst every 10 sec.

Pacemaker should be changed to asynchronous mode by magnet or by programmer before using cautery.

Provision of alternate temporary pacing should be there in operative room.

Drugs like ISOPROTERENOL , ATROPINE should be available.

Defibrillation – paddles should be kept as far as possible from pulse generator , if possible antero posterior.

Pacemaker devise should be rechecked after procedure.

Abdelmalak B, Jagannathan N, Arain FD, Cymbor S, McLain R, Tetzlaff JEElectromagnetic interference in a pacemaker during cauterization with the coagulating, not cutting mode. J Anaesthesiol Clin Pharmacol [serial online] 2011 [cited 2013 Feb 2];27:527-30. Available from: http://www.joacp.org/text.asp?2011/27/4/527/86600

ABSTRACT  Electromagnetic interference in pacemakers has almost always been

reported in association with the cutting mode of monopolar electrocautery and rarely in association with the coagulation mode.

We report a case of electrocautery-induced electromagnetic interference with a DDDR pacemaker (dual-chamber paced, dual-chamber sensed, dual response to sensing, and rate modulated) in the coagulating and not cutting mode during a spine procedure. We also discuss the factors affecting intraoperative electromagnetic interference.

A 74-year-old man experienced intraoperative electromagnetic interference that resulted in asystole caused by surgical electrocautery in the coagulation mode while the electrodispersive pad was placed at different locations and distances from the operating site (This electromagnetic interference did not occur during the use of the cutting mode). However, because of careful management, the outcome was favorable. Clinicians should be aware that the coagulation mode of electrocautery can cause electromagnetic interference and hemodynamic instability. Heightened vigilance and preparedness can ensure a favorable outcome.

Figure 1: Patient's electrocardiogram (EKG) tracing and arterial line wave form showing normal sinus rhythm with good perfusion prior to the application of electrocautery

Patient's electrocardiogram (EKG) tracing and arterial line wave form showing bradycardia evolving to asystole as a result of EMI during electrocauterization with coagulation mode while the electrodispersive pad was on the opposite shoulder of the pacemaker. A similar response was seen when the electrodispersive pad was moved to the contralateral thigh

Patient's electrocardiogram (EKG) tracing and arterial line wave form showing minimal EMI not affecting arterial line tracing during electrocauterization with cutting mode while the electrodispersive pad was on the contralateral thigh

DEFIBRILLATORS- Defibrillators are one of the most important thing in operating room. If improperly used it may lead to electrical injuries

COMMON MISTAKES – Insufficient force is applied to paddles and contact is poor.

paddles applied to irregular surface or bony prominences.

Insufficient or wrong kind of jell is used.

Another conductive medium between paddles.

PREVENTION-

Defibrillator should be checked daily. Adequate jelly should be applied. Skin contact should be good as indicated by indicator on pads. Ensure there is no other conductive medium . Before delivering shock check and say clearly and loudly “ I CLEAR, YOU CLEAR, EVERYBODY CLEAR”.

MRI ROOM-

One of potential space for electrical accidents.

Routine equipments cant be used.

Magnetic field can induce changes in ECG along with heating and thermal injuries at the site of ECG electrode

and pulse oxymeter- ANTENNA EFFECT.

Cardio scope and pulse oxymeter wire should be kept straight , avoid loops and multiple contacts with patient.

Use MRI compatible pulse oxymeter with fiber optic signal linking between sensor and monitor.

Temperature probe with RF filter should be used.

Absolute exclusion of ferromagnetic material .

SAFETY MEASURES-

Regular check of all electrical equipments. Team work- Involvement of surgeon, anaesthetist,

nursing staff along with biomedical engineering department.

Proper checklist before every procedure. Proper grounding. Fire plans.

GENERAL PRECAUTIONS-

Multiple plugs extension boxes should not be placed on floors as they may come in contact with fluid and electrolyte solutions.

Ceiling mounted tracks can be used to bring electrical outlet close to operating table.

Power chords that come down the wall should not cross traffic lines.

Power taps in operating room should have water tight or flip covers so that water should not enter in it

Electrosurgical and laser units may interfere with operation of other equipments , so should be away from monitors.

Electrosurgical equipments and monitors should be attached in separate circuit.

Electrosurgical equipments and monitors should be periodically inspected by biomedical engineering department.

This equipments should be regularly calibrated.

Wear and tear of chords should be regularly checked and replaced.

Monitors should be handled with respect.

Infusion pump should be draped with watertight covers .

Care should be taken while moving equipments.

Shocking!

Work shouldn’t be

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