Electric & Fire Safety PDF

ELECTRIC & FIRE SAFETY KATHLEEN MINOTT, DNAP, CRNA OUTLINE Principles of Electricity Electrical Shock Hazards Electrical Power: Grounded Electrical Power: Ungrounded Line Isolation Monitor Ground Fault Circuit Interrupter Double Insulation Microshock Electorsurgery Environmental Hazards Electromagne...

ELECTRIC & FIRE SAFETY KATHLEEN MINOTT, DNAP, CRNA OUTLINE Principles of Electricity Electrical Shock Hazards Electrical Power: Grounded Electrical Power: Ungrounded Line Isolation Monitor Ground Fault Circuit Interrupter Double Insulation Microshock Electorsurgery Environmental Hazards Electromagnetic Interference Construction of New Operating Rooms Fire Safety PRINCIPLES OF ELECTRICITY Ohm’s Law - Basic principle of electricity E= I x R E=electromagnetic force (volts) I=current (amperes) R=resistance (ohms) P= E x I P=power (watts) Joule = watt-second Amount of electrical work done PRINCIPLES OF ELECTRICITY Power = work done, or heat produced in electrical circuit P = (I x R) x I 1 V EMF applied across a 1-ohm resistance = 1 A of current flow 1 A of current induced by 1 V of EMF = 1 W of power DIRECT & ALTERNATING CURRENTS Conductor – any substance that permits the flow of electrons Current – electrons flowing through a conductor Direct current – if the electrons always flow in the same direction Alternating current – if the electron flow reverses direction at a regular interval Involves Impedance IMPEDANCE E=IxZ Z = impedance Insulator – substance that opposes electron flow Impedance is directly proportional to frequency X inductance Z ∝ (f x IND) Impedance is inversely proportional to product of frequency & capacitance Z ∝ 1/(f x CAP) As AC current increases in frequency, capacitance & inductance increase As frequency increases, impedance falls & more current is allowed to flow CAPACITANCE Capacitor – 2 parallel conductors separated by an insulator Ability to store charge Capacitance – measure of substance’s ability to store charge DC – charged by voltage source (battery) – momentary current flow Circuit not completed unless resistance is connected b/t 2 plates & capacitor discharged AC – capacitor permits current flow even when circuit not complete by resistance Electrosurgical units – 0.5 to 2 million Hz – high-frequency causes decrease in impedance Stray capacitance – not designed into system INDUCTANCE Property of AC circuits in which an opposing electromagnetic field can be generated in the circuit To increase impedance ELECTRICAL SHOCK HAZARDS Electric shock can occur when a person contacts source of electricity Load - mount of current flowing through a given device is frequently Pacemakers, defibrillators Can inure/death Takes 3x as much DC as AC to cause Vfib Depends on impedance very high impedance circuit allows only small current to flow and thus has a small load very low impedance circuit will draw large current and is said to be a large load Short circuit - occurs when there is a zero-impedance load with a very large current flow SOURCE OF SHOCKS one must contact electrical circuit at 2 points; there must be a voltage source that causes current to flow through individual current can cause muscle contractions, alter brain function, paralyze respiration, arrhythmias Dissipation of energy thru tissues; as current passes through resistance , temperature increases, possibly causing burn severity of shock is determined by amount of current (amps) and duration of current flow ELECTRICAL OR SAFETY OR is a wet location A lot of electronic equipment & devices Ground – physical electrical connection to the earth OR electrical equipment is usually grounded OR electricity is usually not Varying amounts of shock with varying degrees of injury & damage ELECTRICAL OR SAFETY OR electrical current – hot wire, neutral wire & source of voltage to drive flow through impedance (equipment, patient, personnel) Hot wire – high voltage, conducts electricity to equipment Neutral wire – low voltage – ground wire that returns current back to power source, completing circuit Touching hot wire can lead to shock MICROSHOCK/MACROSHOCK Severity of shock is determined by location, duration, frequency, & magnitude Macroshock - large amounts of current flowing through a person, which can cause harm or death. Microshock - very small amounts of current applied to myocardium, and applies only to the electrically susceptible patient. This is an individual who has an external conduit that is in direct contact with the heart. EFFECTS OF SHOCK AT INCREASING CURRENT Current 1 s contact Effect Macroshock 1 mA Minimum perceptible 5 mA Maximum “harmless” current 10-20 mA “let go” current before sustained muscle contraction 50 mA Pain & possible mechanical injury 100-300 mA Vfib Microshock 20 – 100 µA Vfib 10 µA Recommended maximum leakage current ISOLATED POWER SOURCE Isolation transformer - Uses electromagnetic induction to induce current in ungrounded or secondary winding of transformer from energy supplied to primary winding No direct connection between equipment & utility company Power is isolated from ground – no hot, no neutral Very high impedance LINE ISOLATION MONITOR Protect against electrocution by turning a normal “grounded system” which only needs a single fault to cause electrocution into a protected system in which 2 faults are required to deliver a shock Continually detect whether electrical sys is isolated from ground Audible & visual alarms Usually alarms 2-5 mA between neutral & ground leads If hot wire short circuits, sys no longer isolated but should not deliver shock – less safe Neutral wire becomes grounded, then complete circuit exists for when device touched LINE ISOLATION MONITOR When alarms, unplug each device in the order it was most recently plugged in Replace faulty device immediately GROUND-FAULT CIRCUIT INTERRUPTERS (GFCI) Monitors both sides of circuit for equality of flow If difference of 5 mA, power shut off Better shock protection than LIM – shuts off power before second fault But will d/c power to any equipment immediately even if it interferes with patient safety Reset GFI. If it still triggers, start unplugging devices 1 at a time DOUBLE INSULATION Only instance when equipment is allowed to have 2 prongs instead of 3 Equipment has 2 layers of insulation & plastic exterior Only if OR has IPS Infusion pump MICROSHOCK Especially dangerous d/t direct path to heart Wire/catheter in heart can produce large density of current at heart Stray capacitance produced by AC circuits Intact ground wires most important factor in prevention Stray radiofrequency from ESU EQUIPMENT GROUND WIRES Provides low-resistance path for fault currents to reduce risk of macroshock Dissipates leakage currents that are potentially harmful to electrically susceptible patient Provides information to LIM on status of ungrounded sys If broken, IPS will appear safer than it actually is GREEN DOT ELECTROSURGERY UNIT (ESU) - MONOPOLAR Very high-frequency currents (500,000 to 1 million Hz) that pass thru tissue Heat is created by resistance of tissue to current Cut or coagulation Low tissue penetration & Do not excite contractile cells Energy should return through an electrode to ESU during use Interferes with everything! AICD needs magnet Can cause vfib d/t 50-60 Hz stray current on coagulation mode being used near heart and conductor Power supply isolated from ground BIPOLAR ESU Power passes between 2 blades Generates much less power than monpolar Don’t need dispersive electrode ENVIRONMENTAL HAZARDS Cords off floor; ceiling/wall plugs No multioutlet extension poor strips on the floor Modern monitoring cords isolate patient from power supply Generator power ELECTROMAGNETIC INTERFERENCE Cell phones, cordless phones, radios, wireless internet Pacemakers, monitoring devices, ventilators, infusion pumps At least 6 in away FIRE SAFETY FIRE SAFETY At least 90 – 100 fires/yr 5-10% associated with serious injury/death Burns Toxicants 2 types: IN or ON the patient; or remote PREPARATION FOR PREVENTION OF OR FIRE Train OR personnel in OR fire management Fire drills – practice Assure equipment is available & working Determine if high-risk situation exists Team decision-making for prevention Each person is assigned a task FIRE PREVENTION Allow skin preps to dry before draping (3 min) Place surgical drapes to prevent oxidizer build-up Communication to minimize oxidizer-rich environment near ignition source Keep oxygen concentration as low as possible Avoid nitrous Moisten gauzes/sponges near ignition source FIRE MANAGEMENT Look for early warning signs (pop, flash, smoke) Stop procedure; each member immediately carries out assigned task AIRWAY FIRE Simultaneously remove ETT, turn off gases, disconnect circuit Pour saline into airway Remove burning materials Mask ventilate patient, assess injury, consider bronchoscopy, reintubate FIRE ON THE PATIENT Turn off gases Remove drapes and burning material Extinguish flames with water, saline, or fire extinguisher Assess patient’s status, devise care plan, assess for smoke inhalation FAILURE TO EXTINGUISH Use CO2 fire extinguisher Activate fire alarm Consider evacuation of room; close door & don’t reopen Turn off medical gas supply to room FIRE RISK MANAGEMENT Preserve scene Notify hospital risk manager Follow local regulatory reporting requirements Treat fire as adverse event Conduct drills regularly INCREASED RISK PROCEDURES Head & neck, upper chest MAC cases with high flow oxygen Uncuffed tubes in airway procedures Laparoscopic LASER Light amplification by stimulated emission of radiation Nd:YAG (neodymium-doped YAG) – most powerful medical laser; 2-6 mm Energy source & material that energy excites to emit light (lasing medium) Argon – eye, dermatology; absorbed by hgb; tissue penetration 0.5 – 2 mm KTP (potassium titanyl phosphate) & YAG (frequency doubled yttrium aluminum garnet) CO2 laser – very little tissue penetration; absorbed by water tumor debulking; airway Oropharynx & vocal cords Helium-neon (He-Ne) – intense red light used for aiming CO2 & Nd:YAG Very low power