FAINTING is a sudden and brief loss of consciousness.
It is a symptom of an inadequate supply of oxygen and other nutrients to the brain, usually caused by a temporary decrease in blood volume or blood pressure.
Such decrease can occur whenever the body cannot quickly compensate for a drop in blood pressure.
For instance, in a person who has an abnormal heart rhythm the heart may be unable to increase the output of blood enough to compensate for a decrease in blood pressure.
People with such conditions may feel fine when resting but they faint when they are exercising because the body’s demand for oxygen increases suddenly.
This fainting is called exertional or effort syncope.
Blood volume decreases when a person bleeds and also when a person becomes dehydrated from diarrhoea, excessive sweating and excessive urination.
The body then finds methods to compensate for these volume losses in order to maintain blood pressure within the normal range.
Fainting can result when these compensatory mechanisms fail to take effect and there is inadequate blood supply to the brain.
Fainting from coughing (cough syncope) or urinating (micturation syncope) usually results when the amount of blood flowing back to the heart decreases during straining.
Fainting caused by urinating is particularly common in the elderly.
Swallowing syncope can accompany diseases of the oesophagus.
Fainting may also result from a decrease in the number of red blood cells (anaemia), a decrease in the level of blood sugar (hypoglycaemia), or a decrease in the level of carbon dioxide in the blood (hypocapnea) caused by over-breathing (hyperventilation).
Sometimes anxiety leads to hyperventilation.
When the carbon dioxide levels decrease the blood vessels in the brain contract and the person may feel faint but not actually lose consciousness.
Weight lifters’ syncope may result from hyperventilating before lifting.
In rare cases, typically in the elderly, fainting may be part of a mild stroke in which the blood flow to a part of the brain suddenly decreases.
Symptoms
Dizziness or light-headedness may precede fainting especially when a person is standing.
After a person falls the blood pressure increases partly because the person is lying down and often because the cause of the fainting has passed. Getting up too quickly may cause the person to faint again.
When the cause is abnormal heart rhythm fainting begins and ends suddenly.
Sometimes the person experiences palpitations just before fainting.
Orthostatic fainting occurs when a person sits up or stands too quickly.
A related form of fainting, called parade ground syncope, occurs when a person stands still for a long time on a hot day.
Because the leg muscles are not being used they do not push blood up toward the heart. Therefore blood pools in the leg veins and blood pressure falls.
Fainting that begins gradually with warning symptoms and also disappears gradually suggests changes in blood chemistry such as decreased blood sugar and carbon dioxide.
Low carbon dioxide (hypocapnea) is often preceded by a pins-and-needles sensation and chest discomfort.
Hysterical fainting, which is self-induced, is not a true faint. The person usually has some underlying psychological problems or intentions.
They only appear unconscious but do not have a heart rate or blood pressure abnormality and do not sweat or turn pale.
Diagnosis
A doctor will try to determine the underlying cause. Factors that help the doctor include the patient’s age when the fainting began, the circumstances under which it occurred, any warning signs, and the steps that help the person to recover such as lying down, holding the breath or drinking orange juice.
Descriptions from witnesses also help. The doctor also needs to know whether the person has any medical conditions and whether the person is taking any prescription or non-prescription drugs.
An electro-cardiogram (ECG) may indicate underlying heart or lung disease or even an echocardiogram (an imaging technique that uses ultrasound waves) can be done to investigate the cause.
Blood tests may show low blood sugar, low blood levels (anaemia) and other chemical imbalances.
Treatment
Usually, lying flat is all that is needed for a person to regain consciousness. Raising the legs may help to speed up recovery by increasing blood flow to the heart and brain.
If the person sits up too rapidly or is propped up or carried in an upright position, another fainting episode may occur.
Remember, the idea is to increase blood flow to the brain, and by standing up the blood is re-distributed by gravity to lower parts of the body.
In young people who do not have heart disease, fainting is not usually serious, and extensive diagnostic investigations and treatment are rarely necessary.
However, in older people, fainting may result from several inter-related problems that prevent the heart and blood vessels from adjusting appropriately to a decrease in blood pressure.
Treatment depends on the cause.
A slow heart beat can be corrected by drugs or surgically by implanting a pacemaker (an electronic device that stimulates heartbeats).
Other causes of fainting such as anaemia and low blood sugar can be treated appropriately.
It is important, especially for people who keep having faints again and again, to consult their doctors so that the cause can be determined.
