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The heart pumps blood around the body through the blood vessels. Blood pressure is the amount of force exerted on the artery walls by the pumping blood.
Blood pressure varies according to environmental demands
For example, it rises during physical exertion and drops in extreme heat. Hypotension, or low blood pressure, means that the pressure of blood circulating around the body is lower than normal, or lower than expected given the environmental conditions.
However, ‘hypotension’ is a relative term – one person may have low blood pressure compared to others of similar physical characteristics, but may be perfectly healthy.
Low blood pressure is only a problem if it has a negative impact on the body.
For example, vital organs (particularly the brain) may be starved of oxygen and nutrients if the blood pressure is too low for that particular person. Substantial blood loss can cause a sudden drop in blood pressure (shock).
The most dramatic symptom of sudden hypotension is unconsciousness. Usually, low blood pressure develops over time.
Symptoms include: Fainting
Blood pressure is measured using a device known as a sphygmomanometer.
If the measurement drops 30mmHg below the person’s usual blood pressure, this is considered to be hypotension. Low blood pressure has many different causes including: The body’s reaction to heat, which is to shunt blood into the vessels of the skin, leading to dehydration Addison’s disease (where the adrenal glands fail to produce sufficient blood-pressure-maintaining hormones).
Generally, when you stand upright from a sitting or lying position, the blood vessels in your body respond to gravity by constricting.
This increases blood pressure
Orthostatic hypotension means that the blood vessels don’t adjust to a standing position and, instead, allow the blood pressure to drop, resulting in a feeling of light-headedness. Causes include: Irregular heart beat (heart arrhythmia).
Treatment depends on the cause
For example, the dosages of existing medications may need to be altered or a bleeding stomach ulcer surgically repaired.
If no particular cause can be found, drugs may be used to raise blood pressure. In extreme cases, a lower body pressure suit may be required.
Hypotension, or low blood pressure, means that the pressure of blood circulating around the body is lower than normal or lower than expected. Low blood pressure is only a problem if it has a negative impact on the body and produces symptoms. Some causes of hypotension include blood loss, dehydration and certain medications, such as antihypertensive drugs.
Symptoms of hypotension Light-headedness, when standing from a sitting or lying position Unsteadiness Dizziness Weakness Blurred vision Fatigue Causes of hypotension Emotional stress, fear, insecurity or pain (the most common causes of fainting) Dehydration, which reduces blood volume Blood donation Internal bleeding, such as a perforated stomach ulcer Blood loss from trauma, such as a road accident or deep cut Pregnancy Medications for high blood pressure Diuretics, which produce fluid loss Medications for depression Medications for certain heart conditions Allergic reaction to certain drugs or chemicals Some forms of infection, such as toxic shock syndrome Heart disease, which can hamper the pumping action of the heart muscle Some nervous system disorders, such as Parkinson’s disease Orthostatic hypotension Nervous system diseases, such as neuropathy Prolonged bed rest Dehydration Treatment for hypotension Where to get help Your doctor Things to remember.
Key Points
- Substantial blood loss can cause a sudden drop in blood pressure (shock)
- most dramatic symptom of sudden hypotension is unconsciousness
- Symptoms include: Fainting
- Causes include: Irregular heart beat (heart arrhythmia)
- Treatment depends on the cause