Hypotension

Hypotension is the medical term for low blood pressure (under 90/60 mm Hg) 3.  Hypotension, which does not produce symptoms such as dizziness or faintness, is considered to be a sign of good cardiovascular health.  Low blood pressure without signs of hypoperfusion (decreased blood flow to tissue or organs) is healthy because it puts less strain on the blood vessels.  Typically athletes or a person who is very active may have hypotension without symptoms.  In other people, especially in the elderly, hypotension can be a sign of dysfunction in the cardiovascular system.  The best way to prevent hypotension is to identify and treat the cause.

Causes of hypotension (Medline plus)

• Wide, dilated blood vessels (as opposed to those that are blocked, narrowed or constricted)
• Weakened heart contraction
• Obstructed blood flow due to defective heart valves or other causes
• Overdosage of drugs taken to control high blood pressure (hypertension)
• Side effects of other prescription or over the counter medications  (Used for surgery, anti-hypertensives, heart medicines, antidepressants, anti-parkinsonians, alcohol, anti-anxiety agents, and narcotic analgesics)
• Pregnancy 
• Endocrine disorders such as under active thyroid (hypothyroidism), overactive thyroid (hyperthyroidism),diabetes, low blood sugar (hypoglycemia) or adrenal problems such as Addison disease
• Heat stroke or heat exhaustion
• Various types of heart disease (e.g.,congestive heart failure, atrial fibrillation or bradycardia)
• Various types of liver disease (e.g., cirrhosis of the liver, hepatitis or liver cancer)
• Crash diets
• Anemia (due to lack of iron, folic acid or vitamin B-12)
• Dehydration
• Shock

Orthostatic Hypotension is a drop in blood pressure due to a change in posture such as from lying to standing.  The general drop used to classify orthostatic hypotension is a drop in systolic blood pressure of 20 mm Hg, or 10 mm Hg in diastolic blood pressure 41.  This drop in blood pressure can lead to cerebral hypoperfusion, causing a decrease in the oxygen to the brain, resulting in dizziness and syncope (fainting) 41 .  Losing consciousness can cause a person to hit their head when they fall or result in broken hips and other bones and joints.  A couple of mechanisms that can cause an intolerance to gravity are an inadequate baroreceptor reflex and a lack of secondary veinous return through muscular movement. 8.  The baroreceptor reflex is a reflex in the baroreceptors of the aorta and carotid artery which senses the change in blood pressure and compensates to inhibit any pooling of blood in the lower extremities 6.  The baroreceptors compensate by inducing vasoconstriction and increasing the heart rate 8.  If the baroreceptors do not function properly, the body will not adjust to the gravitational stresses and cerebral hypoperfusion may occur 41. 

Veins are the blood vessels that bring blood back to the heart and contain one way valves to prevent backflow of blood.  Muscles in the legs and abdomen contract and with the help of the one way valves, they provide a pumping action to move blood back to the heart 8.  If the muscles do not contract properly, the pumping action of blood to the heart will be decreased, which will lead to increased risk of pooling of blood in the lower extremities. Some recommendations to reduce the risk of dropping blood pressure while rising up is to contract the muscles of the lower extremities; while sleeping have bed inclined at the head 5-20 degrees; wear compressive stockings; slow down while rising up; drink more water; and eat small frequent meals 41