Electrical Safety in the OR PDF

Electrical Safety in the OR Dr. Joseph Curione 1 2 Outline Principles of Electricity Electrical Shock Hazards Grounding Line Isolation Monitor Electrocautery } } } } } 3 Definitions Electricity is the flow of electrons Conductors – Any substance that permits the flow of electrons (or current) Insula...

Electrical Safety in the OR Dr. Joseph Curione 1 2 Outline Principles of Electricity Electrical Shock Hazards Grounding Line Isolation Monitor Electrocautery } } } } } 3 Definitions Electricity is the flow of electrons Conductors – Any substance that permits the flow of electrons (or current) Insulators – Any substance that prevents the flow of electrons } } } 4 Definitions } Current: Flow of electrically charged particles (electrons) } Circuit: Electrons flow around a closed path. } There are two types of circuits: Direct Current (DC), and alternating current (AC) circuits. } DC circuits: } } 5 Parallel Series Definitions } Direct Current (DC) – The flow of electrons in one direction } Alternating Current (AC) – Electrons flow switches directions at regular intervals (120 times per second for 60 Hz wall current) 6 DC vs. AC Direct Current 7 Alternating Current Volts, Amps, Ohms (Ω) Voltage (V) = pressure behind electrons Amps (I) = current: number of electrons flowing past a given point per unit of time Ohms Ω (R) = resistance to the flow } } } Water Analogy: VOL. OF WATER 8 Ohm’s Law Voltage = Current x Resistance } 9 V=IxR Calculate Voltage } } } } What voltage is needed to drive a current of 3 Amps through a 100k Ω resistor? V=IxR = 3 x 100,000 = 3 x 105 V 10 Calculate Resistance } Example: What resistance across a 100 volt source would produce a current of 100 ma (0.1 amp)? } } } } Answer: R = V/I = 100 volts/0.1 amp = 1000 ohms Ohm’s Law in Fluids: Pressure = Flow x Resistance } 11 BP = CO x SVR Capacitance } } A capacitor stores charge (electrons) A capacitor consists of any two parallel conductors that are separated by an insulator. 12 Capacitance } Stray Capacitance / Capacitive Coupling } Capacitive coupling occurs in the presence of a capacitor and is created when two conductors are separated by an insulator. It can occur many times during a laparoscopic procedure, as tissue, trocar and instrument (itself consisting of active electrode and primary insulation) are in close proximity. Capacitive coupling can transfer current to non-target tissue through intact insulation, thereby causing stray electrosurgical burns. Inherent in all electrical equipment Undesirable 13 Probers cited a “communications failure between the surgeon and anesthesiologist,” who wasn’t aware a certain instrument would be used “in the presence of oxygen,” according to the state Health Department’s report on the 2014 blaze which was obtained by The NYPost under a Freedom of Information Law request. Beware of Nose rings & other jewelry (Bovie) 14 https://nypost.com/2016/05/01/hospital-probed-after-patient-catches-fire-during-surgery/ Electrical Shock } People become injured or death occurs when voltage pushes electrons through the human body, particularly through the heart. } } 15 Electrical burns V-Fib Electrical Shock } } } DC – less dangerous AC (at 60 Hz) – more dangerous, but high frequency current has low tissue penetration and does not excite contractile cells (but, can still cause burns) To get a shock, you have to become part of an electrical circuit between a high-voltage source—like a power line—and the ground (or a grounded object, like a ladder). Without coming into contact with both, you can't be electrocuted, which is why birds on power lines don’t normally get shocked. 16 17 18 19 20 Electrical Shock } Macroshock – large current flows that can cause harm } Microshock – small amounts of current flow only dangerous to susceptible individuals (ex. Pacing wires and central lines) } } 21 100 microamps à Ventricular Fibrillation. 10 microamps: is the maximum recommended leakage current. Effects of Macroshock and Microshock Macroshock (mA) Effect 1 Perception 5 Maximal harmless current 10 “Let-go” current 50 Pain, Possible Loss of consciousness, muscle lock 100 (0.1 A) V-Fib 6000 Complete physiological damage Microshock (µA) Effect 100 V-Fib in humans (direct contact w/ heart) -Direct contact with the heart at 100 micro Amps causes V-Fib - Interesting facts: A USB port on your computer runs at 100 milliamps -The “let-go” current is defined as that current above which sustained muscular contraction occurs and at which an individual would be unable to let go of an energized wire. 22 Leakage Current } } Occurs when current leaks out of an intended circuit, and flows through some alternate path. Undesirable because the current flowing through the alternate path can cause damage, fires, RF noise, or electrocution. 23 Electrical Shock } The maximum leakage current allowed in Operating Room equipment is 10 µA 24 Isolation Transformers } Used to supply sensitive equipment such as medical devices. } Not physically connected. Transfers electricity through a magnetic field (Induction). } Used to protect secondary circuits and individuals from electrical shocks between energized conductors and earth ground. 25 Example of Light bulb induction 26 27 Isolation Transformer in OR 28 Isolation Tansformer & Line Isolation Monitor 29 The Line Isolation Monitor } A safety device that monitors for Leakage current from internal faults } Continuously monitors the potential for current flow from the isolated power supply to the ground } Alarm between 2 – 5 mA potential leak (5 mA = maximal harmless current) } If the alarm sounds, the last piece of equipment should be disconnected and inspected. } Equipment that activates a line isolation monitor alarm may still be operational, but increases the potential risk of shock. 30 Electrocautery } } } } } } Electrocautery devices use low-voltage, high-amperage, direct or alternating high-frequency (0.1-3 Megahertz) electric currents to cauterize, cut, and destroy tissue. Either bipolar or monopolar The element in electrocautery is HOT Excellent for pinpoint hemostasis Can cause electrical interference with the monitors. Large surface area/ low-impedance return electrode avoids burns at the currents point of exit. 31 Bipolar Electrocautery } Two tips: } } } 32 1 supplies current 1 returns current Does not return a grounding pad Monopolar Electrocautery } The active electrode is in the wound. } The patient return electrode is attached somewhere else on the patient. } The current must flow through the patient to the patient return electrode. } Current flow should not cross the patient’s heart (typically grounding pad is placed on leg) } Patients with pacemakers and ICD’s are at risk. (disable w/ magnet) 33