Electric Shock-mechanism And Effects
(dr jayaprakash)
CHANGES DUE TO ELECTRICAL BURNAlternating current injuries are the commonest,mostly in men and hand being the area affected.Most injuries are due to low voltage burns[<1000v].Low voltage carry a significant risk of electrocution due to cardiac arrest because they may cause muscle spasm.High voltage burns produce extensive tissue damage.Tissue damage from low voltage needs direct contact at any frequency from DC to ionizing radiation.Commercial electrical power ranges from DC to 150 hz in the low frequency range .On direct contact the electron flow in metal conductor or arc is converted at skin surface to electrolyte ions that carry the current through the body.The electrochemical process generates heat and toxic chemical byproducts that contribute to local tissue injuryLow frequency electricity causes injury by permeabilizing cell membranes, electroconformational denaturation of cell membrane proteins and thermal denaturation of tissue proteins. When current of >50 mA is passed hand to hand or hand to foot that is enough to induce depolarization of myocardial membrane to produce cardiac arrythmias,particulary if induced depolarization is at early myocardial repolarisation .Early repolarisation is the most vulnerable period of cardiac electrical activity.Peripheral nerves and skeletal muscle tissue are the most vulnerable to membrane damage by electrical currents.the ?not let go? phenomenon results from passage of more than 14 to 16 mA longitudinally through the forearm that induces tetanic contractions of muscles controlling handgrip. Disruption of extremity skeletal muscle and nerve cell membrane by the process of electroporation results when more than .5 to 1mA is passed through the extremity.Extensive tissue injury leads to release of hemoglobin and myoglobin to circulation ,which may crystallize in kidney leading to renal failure
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