Hypotension

Hypotension, also known as low blood pressure, is a cardiovascular condition characterized by abnormally reduced blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood and is indicated by two numbers, the systolic blood pressure (the top number) and the diastolic blood pressure (the bottom number), which are the maximum and minimum blood pressures within the cardiac cycle, respectively. A systolic blood pressure of less than 90 millimeters of mercury (mmHg) or diastolic of less than 60 mmHg is generally considered to be hypotension. Different numbers apply to children. However, in practice, blood pressure is considered too low only if noticeable symptoms are present.

Symptoms may include dizziness, lightheadedness, confusion, feeling tired, weakness, headache, blurred vision, nausea, neck or back pain, an irregular heartbeat or feeling that the heart is skipping beats or fluttering, and fainting. Hypotension is the opposite of hypertension, which is high blood pressure. It is best understood as a physiological state rather than a disease. Severely low blood pressure can deprive the brain and other vital organs of oxygen and nutrients, leading to a life-threatening condition called shock. Shock is classified based on the underlying cause, including hypovolemic shock, cardiogenic shock, distributive shock, and obstructive shock.

Hypotension can be caused by strenuous exercise, excessive heat, low blood volume (hypovolemia), hormonal changes, widening of blood vessels, anemia, vitamin B₁₂ deficiency, anaphylaxis, heart problems, or endocrine problems. Some medications can also lead to hypotension. There are also syndromes that can cause hypotension in patients including orthostatic hypotension, vasovagal syncope, and other rarer conditions.

For many people, excessively low blood pressure can cause dizziness and fainting or indicate serious heart, endocrine or neurological disorders.

For some people who exercise and are in top physical condition, low blood pressure could be normal. A single session of exercise can induce hypotension, and water-based exercise can induce a hypotensive response.

Treatment depends on the cause of the low blood pressure. Treatment of hypotension may include the use of intravenous fluids or vasopressors. When using vasopressors, trying to achieve a mean arterial pressure (MAP) of greater than 70 mmHg does not appear to result in better outcomes than trying to achieve an MAP of greater than 65 mmHg in adults.

For many people, low blood pressure goes unnoticed. For some people, low blood pressure may be a sign of an underlying health condition, especially when it drops suddenly or occurs with symptoms. Older adults also have a higher risk of symptoms of low blood pressure, such as falls, fainting, or dizziness when standing or after a meal. If the blood pressure is sufficiently low, fainting (syncope) may occur.

Low blood pressure is sometimes associated with certain symptoms, many of which are related to causes rather than effects of hypotension: