- Published on Friday, 07 May 2010 14:34
- Written by Dr Ian Marshall
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Electrocution is an ever-present risk onboard a yacht, and it can even happen whilst swimming nearby. A doctor looks at risk factors, symptoms and treatment of electric shocks.
We might make fun of the effects of electrocution or electric shocks – think Itchy and Scratchy plugging each other into the mains on The Simpsons – but the reality is that electricity is dangerous stuff and can be fatal.
We receive an electric shock when our body is in contact with a source of voltage sufficiently high enough to cause a current through our tissues. The minimum current a human can feel is about 1 milliampere (mA). Relatively small currents of electricity (40–70mA) can cause death, usually by affecting the heart or brain.
The current may pass through the heart causing ventricular fibrillation, a condition in which there is uncoordinated contraction of the muscles of the ventricles, making them twitch or quiver. This results in there being no cardiac output or circulation of blood to the rest of the body. This is one cause of cardiac arrest.
If the current passes through the brain there is damage to the nervous tissue, especially the nerves controlling the heart and lungs. Cardiac and respiratory arrest may occur. Even if this does not happen, loss of consciousness will quickly occur.
During an electric shock, heat is generated from the passage of the current with consequent tissue damage. This can be seen on the skin where both entry and exit burns may be found. However, depending on the pathway taken by the current inside the body, other organs such as the liver, kidneys, bowel or lungs may be damaged due to heat effect or dissipation of energy as the current passes through. As can be seen, death may result from a number of causes.
Skin resistance plays a large part in how an electric shock will affect us. Dry, intact skin has the highest resistance. Dry skin is a poor conductor of electricity and will impede the current most. Wet or broken skin has the least resistance and allows the current to flow more easily across the body.
Touching live wires with dry hands may give a shock but the same wires touched by someone who is wet after getting out of the shower or bath may be fatal. Hence we are always warned about the use of electrical appliances in bathrooms. We have all seen movies where the victim is taking a bath and a live electric light (or something equally electrified) is thrown into the water by the murderer to cause death.
Most of us would think that electric shocks could only happen whilst onboard a yacht. However they may also occur when swimming near a boat and death can result from electric shock drowning. Faulty wiring on a yacht may cause the underwater hull metals to become energised. The same thing may happen when shore power leaks into a marina or dock. Someone swimming close to the hull may experience a low level current through the body that causes ventricular fibrillation or muscle spasm with loss of the ability to move, both of which may result in drowning. Because of the risk of electric shock drowning no one should swim in marinas.
If you come across someone who has collapsed onboard, always consider the possibility of electricity being involved and check the immediate area for signs of danger to yourself. Shout for help and your emergency medical equipment. Do not approach the victim until you are sure any power source has been switched off or disconnected.
Once it is safe to approach you should ascertain if the person is responding, and if not go through your cardio-pulmonary resuscitation (CPR) protocol. Remember that ventricular fibrillation can be determined and treated only by using a defibrillator. This is an important, life-saving piece of equipment to have onboard for emergency use.
When consciousness is lost after an electric shock it will always be necessary to get medical advice about further management. Monitoring of vital signs and conscious level will be needed for at least 24 hours and further investigation or a period of observation in hospital may be advised. Any burns will need immediate treatment, and if full thickness skin loss is present, skin grafting may be required.
A well-maintained boat that has had regular safety checks will reduce the chance of electrocution occurring but as a recent tragic incident onboard has shown, it will not eliminate all risk. A well-trained crew, with the right medical equipment to hand can make all the difference between life and death in the event of collapse due to electric shock.
WORDS Dr Ian Marshall
Dr Ian Marshall is Medical Director at Ocean Medical International.