Some Causes of Low Blood Pressure
What Happens in the Body |
Examples of Causes |
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The autonomic nervous system becomes impaired |
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Blood flow back to the heart is blocked |
During pregnancy, pressure on the inferior vena cava (the main vein that carries blood from the legs) from the uterus when women lie in certain positions Increased abdominal pressure when straining to move bowels or pass urine or when lifting heavy weights |
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Blood vessels become dilated (widened) |
Alcohol Some allergic reactions Some antidepressants, such as amitriptyline Antihypertensive drugs that dilate blood vessels (such as calcium channel blockers, angiotensin-converting enzyme inhibitors, and angiotensin II receptor blockers) Bacterial infections, if severe Exposure to heat Nerve damage (such as that due to diabetes, amyloidosis, or spinal cord injuries) Nitrates |
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Blood volume is decreased |
Diarrhea Diuretics (drugs that help the kidneys remove water from the body, such as furosemide and hydrochlorothiazide) Excessive bleeding Excessive sweating Excessive urination (a common symptom of untreated diabetes or Addison disease) |
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The brain centers that control blood pressure are inhibited |
Alcohol Antidepressants Antihypertensive drugs such as methyldopa and clonidine Barbiturates |
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Cardiac output is decreased |
Heart muscle damage or malfunction (such as that due to a heart attack or myocarditis) |