Low blood pressure (see HYPERTENSION for raised blood pressure). Some healthy individuals with a normal cardiovascular system have a permanently low arterial blood pressure for their age. What blood-pressure reading constitutes hypotension is arguable, but a healthy young person with figures below 100 mm Hg systolic and 65 mm Hg diastolic could be described as hypotensive. For a healthy 60 year old, comparative figures might be 120/80. The most common type is postural hypotension, when symptoms occur if the person suddenly stands, particularly after a period of rest or a hot bath. It results from the muscular tone of blood vessels becoming relaxed and thus unable to respond quickly enough to the change in posture, the consequence being a temporary shortage of arterial blood to the brain. Symptoms of dizziness, occasional fainting, and nausea may occur. Older people are especially vulnerable and may fall as a result of the sudden hypotension. Some drugs – anti-hypertensives and antidepressants – can cause hypotension. People with DIABETES MELLITUS occasionally develop hypotension because of nerve damage that affects the reflex impulses controlling blood pressure. Any severe injury or burn that results in serious loss of blood or body fluid will cause hypotension and SHOCK. Myocardial infarction (see HEART, DISEASES OF) or failure of the ADRENAL GLANDS can also cause these symptoms, as can a severe emotional event that causes shock.

Hypotension in healthy people does not require treatment, although affected individuals should be advised not to stand up suddenly or get out of a bath quickly. Someone who faints as a result of a hypotensive incident should be laid down for a few minutes to allow the circulation to return to normal. Hypotension resulting from burns, blood loss, heart attack or adrenal failure (shock) requires intensive care and attention to the causative condition.