Lecture 7.

Syncope

Unconsciousness is a state in which the casualty becomes insensible to commands because of an interruption to the normal functioning of the brain. A person has perhaps lost consciousness if he does not react to your action by opening his eyes or answering your questions.
There is no absolute dividing line between consciousness and un- consciousness. People can be fully conscious (aware and awake) or fully unconscious (no reaction to any stimulus) or at any level between these two extremes.

Loss of consciousness causes the muscles to relax. During the period of unconsciousness the tongue might fall backwards and block the breathing passage.

Fainting happens when  the casualty loses consciousness for a short amount of time because your brain isn’t getting enough oxygen. The medical term for fainting is syncope, but it’s more commonly known as “passing out.” A fainting spell generally lasts from a few seconds to a few minutes. A full recovery usually takes a few minutes. 

Syncope, commonly known as fainting, is a loss of consciousness and muscle strength characterized by a fast onset, short duration, and spontaneous recovery.

It is caused by a decrease in blood flow to the brain, typically from low blood pressure. There are sometimes symptoms before the loss of consciousness such as lightheadedness, sweating, pale skin, blurred vision, nausea, vomiting, or feeling warm. Syncope may also be associated with a short episode of muscle twitching. Psychiatric causes can also be determined when a patient experiences fear, anxiety, or panic; particularly before a stressful event usually medical in nature. When consciousness and muscle strength are not completely lost, it is called presyncope. It is recommended that presyncope be treated the same as syncope.

Causes range from non-serious to potentially fatal. There are three broad categories of causes:

1. heart or blood vessel related;
2. reflex, also known as neurally mediated; 
3. orthostatic hypotension.

Heart or blood vessel related syncope. Issues with the heart and blood vessels are the cause in about 10% and typically the most serious while neurally mediated is the most common. Heart related causes may include an abnormal heart rhythm, problems with the heart valves or heart muscle and blockages of blood vessels from a pulmonary embolism or aortic dissection among others.

Neurally mediated syncope occurs when blood vessels expand and heart rate decreases inappropriately. This may occur from either a triggering event such as exposure to blood, pain, strong feelings or a specific activity such as urination, vomiting, or coughing. Neurally mediated syncope may also occur when an area in the neck known as the carotid sinus is pressed.

Orthostatic hypotension syncope. The third type of syncope is due to a drop in blood pressure when changing position such as when standing up. This is often due to medications that a person is taking but may also be related to dehydration, significant bleeding or infection. Heat syncope occurs when heat exposure causes decreased blood volume and peripheral vasodilatation. Position changes, especially during vigorous exercise in the heat, may lead to decreased blood flow to the brain. Closely related to other causes of syncope related to hypotension (low blood pressure) such as orthostatic syncope.

Syncope affects about three to six out of every thousand people each year. It is more common in older people and females. It is the reason for one to three percent of visits to emergency departments and admissions to hospital. Up to half of women over the age of 80 and a third of medical students describe at least one event at some point in their lives. Of those presenting with syncope to an emergency department, about 4% died in the next 30 days. The risk of a poor outcome, however, depends very much on the underlying cause.

Differential diagnosis

Other diseases which mimic syncope include

• seizure,
• low blood sugar
• certain types of stroke
• intoxication of drugs or alcohol

While these may appear as "fainting", they do not fit the strict definition of syncope being a sudden reversible loss of consciousness due to decreased blood flow to the brain

What to do when someone faints

• Pass primery examination
• Position the person on his or her back. A cool, quiet place is best.
• If there are no injuries and the person is breathing, raise the person's legs above heart level — about 12 inches (30 centimeters) — if possible.
• Loosen belts, collars or other constrictive clothing.
• If the person doesn't regain consciousness within one minute, call 103 or your local emergency number.