Electrocution

Electrocution Daeaths and its MLI

1. ELECTROCUTION The passage of electric current through the body is capable of producing wide range of effects, varying from insignificant localized muscular spasm with little or no contact burns to instantaneous death with little or no burns or extremely severe burning. FATAL ELECTROCUTION IS DIVIDED INTO THREE GROUPS (ACC. TO VOLTAGE) Domestic- the voltage of domestic supply is usually 220-240 volts AC with 50 cycles per second. Industrial - very high voltages are involved in driving heavy machinery and the voltages employed by different industries may vary. Lightning flashes are also electrical discharges.

2. FACTORS INVOLVED IN ELECTROCUTION FACTORS RELATED TO NATURE OF ELECTRIC SUPPLY INCLUDE 1) VOLTAGE (TENSION) - a volt is a unit of electromotive force. It is the force which is required to produce 1 ampere of intensity when passed through a conductor having resistance of 1 ohm. LOW TENSIONS- below 50 volts are not fatal. Most fatalities follow shock from currents at 220-240 volts which is the range of household supply. At such voltages the usual visible damage to body occurs in form of small electric marks and death is due to internal derangements of functions.

3. MEDIUM VOLTAGE- i.e. under 500 volts- predispose to prolonged contact due to induction of spasm of muscles and therefore the victim grips and holds on to the conductor. Under these conditions the shock may become lethal. HIGH VOLTAGE- the victim may be thrown of the source by violent muscular contractions or the body may be extensively damaged with severe and deep burns.

4. 2) AMPERAGE (INTENSITY)- It is the unit of electric current and is calculated by dividing voltage by resistance in ohms. I= V/R. On receiving a current of 1mA, a person experiences a tingling sensation. At 8-20mA current- the person holds on to the source of current. At higher currents the person may be thrown off the source.

5. 3) FORM OF CURRENT (WHETHER AC/DC). An AC current is one which reverses its direction at regular intervals. DC is one where current flows constantly in same direction. AC is more dangerous than DC.

6. FACTORS RELATING TO VICTIMS INCLUDE 1)RESISTANCE OF BODY TISSUES- the major barrier to the electric current is the skin. Once the skin has been overpowered by the electric current, the vascular system filled with electrolyte rich fluid serves as favorable medium for the passage of current. Skin on soles, finger pads and palms offer more resistance and dry skin offers more resistance than wet skin . Sweating reduces resistance. Vascular areas like cheeks offer less resistance

7. 2)AREA OF CONTACT OF BODY- smaller the area of contact between the skin and electric supply will exert more resistance than larger area. For e.g. tip of finger offers more resistance than palm of hand. This may occur when one grasps a hot wire with a wet/ sweated hand. Hence, the entire skin surface being bathed in salt water becomes a conductor and not enough current passes through any localized portion of hand to generate sufficient heat to burn the skin, hence electrocution may occur with no visible skin burning. Similarly electrocution may occur in bath without any external mark.

8. SECONDLY- part/site of the body and route of current through body has a considerable bearing. The passage of current through the region of heart is most dangerous. Heart is usually involved when path is from left arm to right leg. When head of worker may come in contact with conductor, brain stem may be directly involved leading to paralysis of cardiac or respiratory centre.

9. 3)DURATION OF CONTACT- longer the contact, greater will be the damage. 4)EARTHING/INSULATION- the current enters at one point and then leaves the body at some exit point, usually to earth. The better the contact between the person and the earth at the time of sustaining electric shock the more dangerous will be its effects. A person standing with dry shoes on a dry surface may rarely notice a shock which could prove fatal to some one standing bare foot on a wet surface.

10. MECHANISM OF DEATH 1) VENTRICULAR FIBRILLATION- most deaths from electric shock are due to cardiac arrythimas usually venticular fibrillation terminating in arrest. (abnormal electrical activity in heart causes uncoordinated contraction of muscles of ventricles). 2)SPASM OF RESPIRATORY MUSCLES- electric current passing through thorax may lead to tetanic contraction (muscular contraction without relaxation ) of muscles of respiration and ultimately produces respiratory arrest.

11. 3)PARALYSIS OF RESPIRATORY CENTRE- it occurs when current passes through head 4)SECONDARY CAUSES- death may occur due to sustaining of mechanical injuries. It may happen when a worker working on a high voltage supply system gets electrocuted and falls from a height and receives head injury or some other injuries.

12. AUTOPSY FINDINGS FINDINGS IN DEATH DUE TO LOW OR MEDIUM TENSION CURRENTS- the point where the current enters the body is characterized by presence of electric mark or electric burn (JOULE BURN OR ENDOGENOUS BURN). Fatal electrocution can occur without any visible marks (deaths occurring in bath tubs).

13. SOME IMP FEATURES OF MARK INCLUDES 1)If the contact of skin with conductor is good and firm, the passage of current heats up tissue fluid and the skin offering resistance gets split and blister may be raised. 2)The blister may get ruptured if the contact is for long period.

14. 3) If the contact is not good the current jumps the gap in form of a spark between the source and skin and causes outer skin keratin to melt over a small area. On cooling the keratin gets condensed into hard brown nodule and this is termed as ‘ SPARK LESION’. A well developed electric mark is round or oval shallow crater , bordered by raised areola of pale skin around apart or whole of its circumference. The floor of crater is lined by pale flattened skin and ridge pattern may or may not be preserved.

15. These electric marks are produced by conversion of electricity into heat within tissues and therefore they are termed as endogenous burns. EXIT MARK - they are seen as split in the skin or sometimes even lacerations. Burns and perforations of clothings or shoes may be seen over the sight of exit. If the current enters and leaves the body at a wide area of low resistance (wet hand/ wet body) no marks are seen.

16. FINDINGS IN DEATHS DUE TO HIGH TENSION CURRENTS - (Exogenous burns) Injury occurs either by direct contact or by indirect results arching or flash over. The high tension injuries are usually seen in lineman working on grid system and occasionally in thieves stealing wires from high voltage over head lines.

17. In high voltages the current may spread to a few cm distance and the person may be knocked down without coming in contact with the source. There may be charring of tissues but depending on the degree they may be 1)Brownish discoloration of large areas of skin apart from actual burning. 2) Arborescent pattern resembling lightning burns. 3) Crocodile skin effect comprising of confluent multiple spark burns over large areas of body.

18. INTERNAL FINDINGS- gross findings in internal organs may be absent because the tissues are mainly aqueous and contain electrolytes for the passage of current. Mostly death is due to cardiac arrythimas leading to venticular fibrillation and arrest. If death is due to spasm of respiratory muscles- cyanosis of face, petechial haemorrhages in skin of face and beneath pleura and epicardium , congestion of viscera and oedema of lungs. Suspended animation is common in electrocution.

19. MEDICOLEGAL IMPORTANCE MOSTLY ACCIDENTAL. SUICIDAL AND HOMICIDAL RARE.

20. LIGHTNING In lightning the discharge may be from cloud to cloud or from cloud to earth through some object usually the tallest in contact with the earth. Lightning chooses the easiest path (not the shortest)i.e. path of least resistance. The electric current is direct of about 20,000 A and a million volts operating over an average period of 30 sec.

21. The effects of lightning are due to Passage of very high potential electricity which liberates tremendous amount of energy in form of heat and the burns are superficial owing to short duration of flash.

22. Lightning produces 1) Surface burns –which are tissue burns and usually travel through metallic objects carried or worn by the victim. 2) Arborescent burns or filigree burns or feathering which appears like branches of a tree. These are due to rupture of small blood vessels at several places. 3) Blast effects- may be observed in form of tearing of clothings or shoes or effects may also be seen on trees showing areas of scorched leaves and vegetation.

23. DIAGNOSIS OF DEATH May be achieved by considering the following 1) History of thunderstorm in the locality 2) Evidence of effects of lightning in the vicinity of scene of death i.e. damage to trees, houses or animals. 3) Tearing of clothings . 4) Characterstic nature and distribution of burns which are superficial due to brief duration of flash. 5) Sudden death may occur due to involvement of CNS causing paralysis of cardiac or respiratory centre.

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