Technological Sciences for the Operating Room Electricity for the Surgical Technologist

Introduction W.T. Bovie developed first spark-gap tube generator Electrical burn is a serious risk to patients Patient Safety Depends on Knowing basic electrical terminology Principles of electricity Proper applications in O.R. Surgical technologists must learn theories of electricity and usage for 21st century medicine

Surgical Applications of Electricity Electrosurgical Unit (ESU) Generates current to cut tissue Direction of current flow: Generator → active electrode → dispersive (inactive) electrode → generator (Figure 6-6, Pg 115)

Surgical Applications of Electricity X-ray Machine Utilizes electromagnetic radiation Uses of X-rays View internal body structures Determine presence of foreign bodies Find retained sponges, sharps, or instruments Verify presence of fluid or air Assist in bone realignment

Surgical Applications of Electricity Endoscopes Instrument inserted in patient through abdomen, chest wall, or orifice Flexible or rigid Camera and light cord attached Used with ESU, laser or robotic arm Applications Diagnosis, obtain biopsy, repair, retrieve foreign object, hemorrhage control

Surgical Applications of Electricity Lasers Utilized in almost all surgical specialties Energy converted into light energy Laser light does not spread Choice of beam criteria Power, wavelength, color, duration of exposure, type of tissue Laser classification Gas, solid, liquid, semiconductor crystals

Surgical Applications of Electricity Robotics Extend and enhance human capabilities Components Robotic arm (manipulator), computers to operate the robotic arm and interpret commands, voicecard, video system and microphone Advantages Eliminates hand tremor (holding endoscope); promotes faster recovery, improves visualization of surgery site; enable telesurgery; reduces costs.

Principles of Electricity Electron Theory All electronic effects caused by movement of electrons Serves as basis for design of electrical equipment Atoms, Electrons, Matter Matter has mass and occupies space; consists of atoms

Principles of Electricity Atoms, Electrons, Matter Atoms Composed of protons, electrons, neutrons Nucleus is center; contains positive charged protons and neutral charged neutrons Negative charged electrons travel in orbits around nucleus Atoms held together by opposite charges of protons and electrons Different elements have varying numbers of protons and electrons

Principles of Electricity Atoms, Electrons, Matter Electrons Revolve in shells or orbits Close to nucleus – strong attraction; outer orbits – less attracted Free electrons located in outer orbits; movement creates electric current Electricity: term actually describes movement of free electrons moving from orbit of one atom to another (principle based on Bohr’s Theory)

Principles of Electricity Atoms, Electrons, Matter Electrons con’t. A conductor is a material that allows flow of free electrons The greater the number of electrons in a substance, the better the conductor Copper is the most commonly used material for a conductor. Silver, zinc and brass are also used. Devices in O.R. that use copper as a conductor: surgical lamps, ESU, power drills Water is a conductor; humidity in O.R. should be maintained at 50%-60%

Principles of Electricity Insulators Materials with small number of free electrons; inhibit flow of electrons Basically poor conductors Used to wrap conductors to preserve current and prevent leakage of electrons Types of insulators Rubber cord, plastic around ESU or X-ray machine

Principles of Electricity Electrical Charge Can be either positive or negative Defined as too many or too few electrons orbiting an atom Law of Electric Charge: like charges repel each other; unlike charges attract each other; opposites attract

Principles of Electricity Electrical Current Movement of electrical charge Current moves through conductors by movement of free electrons migrating from atom to atom inside conductor

Magnetism Magnetic Fields Electrons create a magnetic field or electric charge while orbiting the nucleus In some materials electrons travel in the same direction, combining magnetic fields Natural magnetic substances include iron, nickel, cobalt, even the earth Electrical generators depend on the close relationship of electricity and magnetism

Magnetism Magnetic Fields con’t. Two poles, north and south Earth Two poles, north and south Magnetic field is lines of magnetic force between poles Magnetic field causes metal objects to be attracted to the magnet; needle in a compass

Magnetism Electromagnets Metals that become magnetic when encircled by a conductor Magnetic field created by current traveling through conductor Magnetic field used to create electricity Electricity does not create power; only means for transporting it Interaction between wires and magnets produces power

Magnetism Electromagnets con’t. Example: Power plant Water from dam heated  forms steam  turns turbines (generators)  turbines spin magnets  electricity is created for use

Volts – Named after Alessandro Volta, a 17th Terminology Volt is electrical potential – Voltage is potential energy of electrons – Named after Alessandro Volta, a 17th century scientist who invented the battery Electric system: battery creates voltage to move electricity Circuit is the path electricity travels

Current Measured in amperes (amps) Rate of flow of electrons Current flow is the movement of free electrons Free electrons attracted from point of excess electrons to a point with fewer electrons

Ohm’s Law Scientific law of electricity – Mathematical equation showing how voltage, current, and resistance interrelate – Ohm’s Law: V = I x R Resistance Restricting flow of current; measured in ohms Ohm’s Law – More voltage will increase current if resistance is constant; higher resistance causes decreased current if voltage is constant

Power Rate at which work is completed Measured in watts (W) Rate of movement of electrons or current flow Product of voltage & current is power P = I x V Measured in watts (W) Converted to kilowatts (KW): 1 KW = 1,000 W Example: DC Circuit is 12V & 20A, Power is P = 20 x 12 = 240W or 0.24KW

Load Device that uses electricity to perform a function Can change amount of energy from power source Examples: surgical lamps, ESU, power drills, video monitors Resistive energy loads: conductor has high resistance to flow of electricity Example: filament (conductor) in light bulb; electricity has to force way thru resistance to cause filament to glow

Switch Device used to open or close circuit Example: Flashlight Controls flow of electricity Example: Flashlight Batteries (power) Wires (conductors) connected to battery that is connected to switch activated by user Bulb (load) must have voltage Voltage carried by conductors and switch controls flow of current to load; open switch – no flow, closed switch bulb lights up

Wires Hot Wire Neutral Wire Ground Wire Wire that connects to switch; colored red Neutral Wire Pathway for electrons to return to energy source; complete the circuit; colored green Ground Wire Sends leaking electrons to ground to prevent shock; colored black

Resistors Devices made of materials that are purposely resistive Designated with letter R

Direct Current (DC) Electrical current flows in one direction – negative to positive pole Example: Batteries Serve as storage device; keep electricity until needed Negative (-) and positive (+) terminals When switch is closed, current flows from one terminal to the other

Direct Current (DC) Batteries con’t. Four components of DC circuit Battery: source of electricity Wire (battery to load): conductor Switch: control device Load: bulb

Alternating Current Current that periodically reverses direction Complete cycle is current that moves in one direction, then reverses direction Hertz (Hz): one AC cycle Frequency: number of AC cycles in a second; symbol ƒ Most common AC in U.S. is 60 cycle AC Typical voltage is 110V or 120V

Alternating Current AC Can Change Voltage AC delivered as high voltage, then “stepped down” Example: Transformers “step up” exiting voltage Power lines (transformer) deliver electricity at high voltage Voltage is stepped down before use

Radio Frequency (RF) Frequency is number of wave cycles (one cycle is a hertz) per second Radio and TV signals are electromagnetic waves Radio transmitter delivers signal to antennae system Electromagnetic signals travel through cable, air or optical fiber to receiving antennae RF spectrum begins at 9 kHz (or less) to over 3 GHz

Isolated Circuit Cause of electrical shock Secondary circuit contains hazardous current due to isolated circuit Transformer insulation isolates secondary circuit Person touches both poles of non-insulated isolated circuit and experiences an electrical shock and/or burn

Isolated Circuit Secondary Circuit con’t. Two methods of prevention: Solid insulation placed as total barrier to prevent complete access to circuit Conductive barrier of insulation between isolated circuit and conductive barrier

Electrosurgery Application of electrical current through tissue to coagulate bleeding or cut tissue Electrosurgical Unit (ESU): Device that provides power for electric current Electrosurgery: Electrical currents applied directly to tissue; utilizes AC current Electrocautery: Uses heated wire to burn tissue; no electricity enters body; utilizes DC current

Electrosurgery ESU Circuit: Current Flow Generator  thru conductor cord  active electrode (Bovie tip)  surgical site (energy converted to thermal energy to cut or coagulate)  thru patient  dispersive electrode (grounding pad)  conductor cord  generator

Bipolar Electrosurgery Used for delicate procedures, presence of moisture, prevent nerve damage Two prongs of forceps: active and inactive electrodes Current travels through one tip, passes thru tissue, disperses to other tip No dispersive electrode required

Monopolar Electrosurgery Flow of current is as described. Dispersive Electrode (grounding pad) Placement is critical to avoid electrical burns to patient Pad must be in complete contact with patient’s skin Pad pulled up or portion not in contact, may result in second or third degree burns to patient

Electrosurgery Shock and Burn Patient Burns usually deep; tissue necrosis; thrombosis Debridement Sterile Surgery Team Members RF Capacitive Coupling: AC travels from active electrode, through intact insulation, burns skin; apply active electrode beneath Crile held by surgeon to prevent burns

Electrosurgery Shock & Burn con’t. Sterile Surgery Team Members Dielectric Breakdown: High voltage breaks down insulating material, such as sterile glove; produces hole in glove – surgical team member sustains small burn

Electrosurgery Vaporized Tissue Plume Occurs during procedures involving electrosurgery, lasers, power drills Plume is vaporized tissue Contains hazardous bioparticles that are carcinogenic, mutagenic, and they may carry bloodborne pathogens Surgical technologists utilize suction to “suck smoke” from wound when using electrosurgery or smoke evacuators for lasers

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