Two main types of effects of Electric shock :
Stimulation of muscles and nerves
- We've all felt that buzzing or tingling sensation without experiencing injury. A current as low as 0.25 milliamperes (mA) can cause this feeling.
- Starting at 10 mA, most people cannot let go of the shock source because their muscles contract.
- Above 50 mA, an electric current can trigger cardiac arrest if it passes through the heart.
Electric burns to tissue and organs
- Above 100 mA, electrical marks appear on the body at the points of contact.
- Above 10,000 mA (10 amperes), burns are severe and amputation is required.
Specific effects :
On the heart :
With every contraction, the heart pumps blood carrying oxygen throughout the body. The rhythm of the heartbeat is controlled by electrical impulses, which can be seen on an electrocardiogram. Current passing through the heart can cause an irregular heartbeat called arrhythmia, or even total disorganization of the rhythm, called ventricular fibrillation.
When ventricular fibrillation occurs, the heart stops pumping. The victim rapidly loses consciousness and dies if a healthy heartbeat is not restored by applying a second electric shock with a device called a defibrillator.
Heart rhythm disturbances can occur at the time of the shock or in the 24 hours following the accident.
On the muscles :
Muscles are stimulated by electricity. The effect of an electric shock depends on which muscles the current goes through. A current of more than 10 mA causes sustained contraction (tetanus) of the flexors, that is, the muscles that close the fingers and draw the limbs towards the body. The victim thus cannot let go of the source of current.
If the extensors (the muscles that open the figures and extend the limbs away from the body) are tetanized, the victim is propelled away from the current source, sometimes as much as ten metres!
Muscles, ligaments and tendons may tear as a result of the sudden contraction caused by an electric shock. Tissue can also be burned if the shock is lasting and the current is high.
On the nervous system :
Nerves are the tissue that offers the least resistance to the passage of an electric current. Some nerve damage caused by shock clears up with time, but some is permanent. The victim may feel pain, tingling, numbness, weakness or difficulty moving a limb.
When a shock occurs, the victim may be simply dazed or may experience amnesia, seizure or respiratory arrest.
Ultimate damage to the nerves and the brain will depend on the extent of the injuries caused by the heat along the path of the electric current and may develop up to three years after the shock. Nerve damage can also cause psychiatric disorders.
Electrical burns :
Electrical burns are not like burns caused by fire or by touching something hot. Electrical burns result from the heat generated by an electric current passing through the body, which literally cooks the tissue from within. Outward signs of electrical burns may be microscopic or nonexistent, and internal damage may be much more serious than the external injuries suggest. That's the iceberg effect.
Electrical marks appear at the body's point of contact with the current. They are typically tiny charred or hard craters that do not hurt because the nerves have been destroyed.
If a lot of tissue is destroyed, the waste generated can cause serious kidney or blood circulation disorders.
Electrical burns often have serious consequences: scarring, amputation, loss of function, loss of sensation and even death.
Elsewhere in the body :
Electric shock can also affect the eyes, causing cataracts to develop over time. Other disorders can appear in the weeks or months following the accident, depending on which organ the current passed through the body.
Source : Hydroquebec
Source : Hydroquebec
