Review Article Electrical Safety in Operating Room. Abstract

Transcription

1 Review Article Electrical Safety in Operating Room Dipasri Bhattacharya 1 M.D., MNAMS, Professor and H.O.D., Dept of Anaesthesiology, R.G.Kar Medical College, Kolkata, West Bengal, India dipasribhattacharya123@gmail.com Ela Bhattacharya 2 B TECH in Electronics and Communication Engineering, TCS Consultant, Kolkata, West Bengal, India ela.bhattacharya007@gmail.com Abstract Unexpected loss of electrical power or system failure in the operating room can result in serious consequences. Safety codes require all hospitals to have an emergency electrical system. Special electrical power and safety systems protect personnel and patients in the operating room. These systems provide a high level of protection, however still require attention. Perioperative personnel need to be knowledgeable about electrical safety and emergency electrical power systems and hazards which might occur from electric shock in operating room. Electrical hazards may occur in the operating room in the form of macroshock, microshock, fire, explotion, diathermy hazards. Key words : Electrical safety, macroshock, microshock, fire, explotion, diathermy hazards 1. INTRODUCTION Electrical safety in the operating room is of paramount importance in the practice of anesthesia.when an individual contacts a source of electricity, damage usually occurs in one of two ways: 1,2 1) electrical current disrupt normal electrical function of cells : can contract muscles, paralyze respiration, cause seizures, or lead to ventricular fibrillation 2) dissipation of electrical energy throughout the tissues, thermal energy burn and cellular death. The hazards associated with electrical equipments are: Electric shock- Macro shock Electric shock-micro shock Burns Fire and explosions Diathermy hazards 2. DISCUSSION Electric Shock (Macro Shock) 1,2,3 Occurs with external application of a voltage to the skin, causing an electric current to pass through the body tissues. Commonly electric shock occurs from the AC mains supply. 38

2 How does electric shock occur? Electric shock occurs from the mains supply, when the body forms a circuit between the line and a local earth connection or the neural mains line. Earthed circuit- The local earth connection may occur via the floor or ground. Alternatively earthing may take place by inadvertent contact with earthed metal work such as an anesthetic machine or operating table. Isolated circuit- In the absence of an earth connection, an individual or a circuit, is said to be electrically isolated or floating. However current can still flow if contact with an alternative return path such as the neutral supply line is made. The effects of electric current flowing through body tissues depend on the following factors: whether the current is AC or DC the magnitude of the current the tissues current that passes through current density duration of current passage pre-existing disease of the patient Type of current: AC or DC DC produce single muscle spasm on contact may produce arrhythmia and chemical burn on prolonged exposure.ac will cause muscle spasm due to titanic effect which are maximal at mains frequency (50 Hz). AC current also causes arrhythmias. AC shock is 3 times more dangerous than DC shock for the same magnitude of current. Physiological effects at different current levels in AC mains Current (ma)) Effects 0-5 Tingling sensation 5-10 Pain severe pain, muscle spasm Respiratory muscle spasm, ventricular fibrillation, myocardial failure Factors determining magnitude are: voltage applied to the skin, impedance of the skin contact,impedance of the earth connection, tissue impedance. The tissue or organ through which the current passes disrupt normal physiological function. Electric burn depend on the current density (total current flowing by the cross sectional area that the current flows through). The longer the duration the more is the damage. Presence of ischemic heart disease increases the chance of developing arrhythmias. Prevention of macro shock:1) Equipment should be designed to suitable specifications. 2) Earth circuits: reduce the risk of electric shock by maintaining exposed metal to zero potential. 3) Isolated patient current 4) Leakage current should be < 500Ma 5) Isolated transformer6) Circuit breaker 7) Suitable foot wear with impedance of 100 kω to 1MΩ Micro Shock 1,2,3,4 Usually micro shock is caused by leakage current. Some potential sources of micro shock are: central venous catheter 39

3 pulmonary artery catheter temporary external pacemaker oesophageal temperature probe in lower third of oesophagus static electricity development Prevention of micro shock : 1) Suitable footwear impedance 2) Antistatic flooring 3) Isolated patient current 4) Optimum design of earthing circuit for equipment 5) Correct humidity in theatre. Electric Burn 4 Burn may occur in different ways: Flash burn This is a high voltage (>1000) shock when electric arcing occur to the earth from the body. External burn Occur due to ignition of inflammable materials around the individual e.g. gas or vapor Tissue burn This may occur at the point of contact with the high voltage source or earthing point. Fire And Explosions 4 This occurs due to ignition of gas mixture which usually consists of a fuel with oxygen or nitrous oxide. The mixture either may simply burn or explode producing intense heat. For explosion to occur the things required are: a) an inflammable agent, b) an oxidizing agent, c) explosive concentration, d) source e.g. diathermy, electrostatic spark, surgical laser. Diathermy Hazards 4,5,6,7 In surgical diathermy a high frequency alternating current is passed through the body tissue and the concentration of current producing an area of high current density liberates heat. Temperature may rise to C or above. Current frequencies range from 400 khz to 10MHz. This is applied via a probe to produce coagulation and cutting effects. Most common risks are unwanted diathermy burn. Diathermy also interferes with monitoring systems and pacemakers. The circuits of diathermy Monopolar : The active electrode is the surgical site. The patient return electrode is elsewhere on patient body (the plate). The current passes through the patient as it completes the circuit from the active to the patient return electrode. Bipolar :The function of active and return electrode is performed at the surgical site. The two blades of forceps perform these two functions, thus only tissue grasped is included in electric circuit. No patient return electrode is needed. Safety measures 7 Use of isolated patient current The diathermy generator and accessories need to be serviced regularly with a full record being kept. Plugs, leads and sockets need to be checked regularly. The foot pedals to be checked to ensure that they are completely sealed and sensitive to light pressure. The alarm system should all be in order. Use of appropriate mode of diathermy whether it be monopolar or bipolar should be selected prior to use and correct setting should be checked. Make sure that the indifferent electrode in the monopolar system uses a flat surface which is dry. Ensure that the patient is protected from metal and the skin is checked after removal of plate. Ensure the line electrode is never kept on the drape or tray. 40

4 Insulation of the instrument should be checked regularly. Diathermy should never be used in presence of ether and should be kept at least 50cm away from anaesthetic machine. Alcohol disinfectants must be dried before diathermy use. The commonest cause of diathermy injury are : 6,7 a) incorrect application of patient plate b) the patient touching earth, metal objects such as part of table, c) careless technique (failure to put electrode back into the cover). ELECTRO CAUTERY Perfect application of monopolar diathermy, neutral plate has wider area of contact, less chance of diathermy burn ELECTRO CAUTERY WITH POOR CONTACT Wrong application of monopolar diathermy, neutral plate has small area of contact, chance of diathermy burn increased 41

5 3. MICRO SHOCK ELECTRICAL ISSUES WITH PACEMAKERS 6,7,8 1. Patients with an automated implanted cardioverter-defibrillator (AICD) need AICD turned off before surgery. This is done by magnet placement but can also be done by reprogramming. Thus, preoperative cardiac electrophysiology consultation is essential. 2. If possible, bipolar diathermy should be used instead of unipolar one. 3. All programmable pacemakers should be checked preoperatively to ensure proper function. 4. Pacemaker-dependent patients need to have asynchronous pacing programmed along with all ratesensing features disabled. A conventional defibrillator should be available. 5. Other pacemaker patients should have a pacing strategy established by preoperative cardiac electrophysiology consultation. 6. Pharmacologic treatment of complete heart block should be kept ready, particularly for pacemakerdependent patients, and isoprenaline should be available on the anesthesia drug cart. 7. If electrophysiological monitoring is being done, the anesthesiologist should review the locations of grounding pads that will be placed by the electro physiologist. Metallic Prosthesis With a monopolar circuit, the patient return electrode (plate) should be sited well away from the prosthetic site. How Can We Prevent Electrocution? 6,7,8 (i).general measures (ii).equipment design (iii).equipotentiality (iv).isolated circuits and (v).circuit breaker General measures: Adequate maintenance and regular testing of electrical equipment ensuring the patient is not in contact with earthed objects the wearing of antistatic shoes, whose high impedance will reduce any current flowing through the body proper grounding. Grounding: A ground is a conductive connection between electrical circuit or equipment and earth or to a conductive body which serves in place of earth grounding creates a low resistance path to earth. It is a method of protection from electrical shock Equipment design (International Electro-technical Committee Standard in IEC 601 ) Class I- accessible to the user, such as the metal casing, is connected to earth by an earth wire - third pin of the plug Class II - protected from the live supply by either double or re-inforced insulation Class III - use safety extra low voltage (SELV) Max leakage current not > 100uA Equipotentiality: terminals of each piece of equipment in a stack can be connected to each other bringing them all to the same potential. Isolated circuit: 42

6 UNGROUNDED SAFETY, ISOLATED CIRCUIT ` Circuit breakers: designed to interrupt relatively large fault currents, protect property by preventing fires from starting, can be reset; fuses must be replaced, ineffective at preventing shocks. 4. KEY POINTS Fire Safety Issues 6,7,8,9 1.When preparing the anesthesia machine and drug cart before a case, following points to be kept in mind: Where is the nearest fire extinguisher? There should be one in every operating room. Where are the oxygen shut-off valves and how to operate them to stop oxygen flow to the operating room? Where is the nearest fire alarm? Where is the nearest escape passage? Where is the nearest defibrillator and code cart? 2.Recall that electrical fires, particularly those that involve the electric panel, require a special approach. If possible, quickly cut all electric power. Proper type of fire extinguisher must be used. The most common type of fire extinguisher sprays water. Water must not be thrown or sprayed onto an electrical fire or burning flammable liquids. Electrical fires require a dry chemical extinguisher, CO 2 extinguishers may also be sed. 3.Avoid use of high oxygen flow at the site of electro surgery and adequate air conditioning with 5-10 air changes per hour.. 4.Appropriate scavenging system. Use of noninflammable agents, use of antistatic equipments like foot wear, clothing and specialized equipments in the surgical field during laser surgery. 43

7 5. FINAL DO'S AND DON'TS FOR ELECTRICAL SAFETY 1. Do use only electrical devices with 3 -conductor power cords and 3-pin plugs. 2. Do unplug equipment by grasping the plug, not the cord. 3. Do check for frayed, cracked, or exposed wiring on equipment cords. 4. Do not use cheater plugs (3-wire to 2-wire adapters). They eliminate the ground connection, and result in possibility of serious shock hazards. 5. Do use diathermy properly. 6. Do follow use of diathermy guideline in patient s with pacemaker. 7. Do follow antistatic measures in operating room. 8. Do not plug equipment into defective receptacles. 9. Do plug equipment into wall receptacles with power switches in the OFF position. 10. Do not drape cords over hot or sharp objects. 11. Do not run cords where they cause a tripping hazard 12. Do not use extension cords unless authorized. The most important thing is to be remembered Electrical Safety Costs Little But Human Life Is Priceless. 5. REFERENCES 1. Bedford G, Bell K. Notes for a tutorial in the operating theatre. CPD Anaesth 2000; 2: Davies PD, Parbrook GD, Kenny GNC. Basic Physics and Measurement in Anaesthesia, 4th edn. Oxford: Butterworth- Heinmann, 1995; Hall CJ. Electrocution hazards in the operating theatre. Br J Anaesth 1978;50: Litt L. Electrical safety in the operating room. In: Miller RD ( 7 th ed) Anaesthesia. Edinburgh: Churchill Livingstone, 2010;chapter Moyle JTB, Davey A. Electrical hazards and their prevention. In:Ward C. (ed) Ward s Anaesthetic Equipment, 4th edn. London: WB Saunders, 1998; Barker SJ, Polson JS: Fire in the operating room: A case report and laboratory study. Anesth Analg 2001; 93: Barnes AM, Frantz RA: Do oxygen-enriched atmospheres exist beneath surgical drapes and contribute to fire hazard potential in the operating room?. AANA J 2000; 68: Aso Kanno T, Aso C, Saito S, et al: A combustive destruction of expiration valve in an anesthetic circuit. Anesthesiology 2003; 98: Wills JH, Ehrenwerth J, Rogers D. Electrical injury to a nurse due to conductive fluid in an operating room designated as a dry location. Anesth Analg 2010;110: AUTHOR S BRIEF BIOGRAPHY: Dr Dipasri Bhattacharya, aged 54yrs is a professor and H.O.D. of Dept of Anaesthesiology, R.G.KAR medical college, Kolkata, West Bengal, India, is an eminent teacher all over India, author of a book on Anaesthesiology, published many papers in the journal of international and state level, peer reviewer of many indexed journal, awarded medals for best postgraduate teacher in state level, Scientific secretary of Indian Society of Anaesthesiologist ( ISA) State level for last three years, vice president of ISA and Indian Society For Study of Pain. Ela Bhattacharya, aged 24yrs was a very good student of South Point School, Kolkata, West Bengal,has done B Tech In Electronics And Communication Engineering, very academic, ambitious, now working as TCS Consultant, preparing for higher studies in her field of interest. 44