Causes of Low Blood Pressure
The pressure exerted on the walls of blood vessels as blood circulates through them is known as blood pressure. Blood pressure is well known as one of the vital signs of life, along with temperature, heartbeat, and respiration (breathing). An individual’s blood pressure is determined by both the force of the heart pumping blood throughout the circulatory system, and the response of the blood vessels to this force.
When blood pressure is measured, it is expressed as two numbers; systolic/diastolic. The top number, systolic, represents pressure in the arteries as the heart pumps blood, while the bottom number, diastolic, is a measure of the pressure in the arteries when the heart relaxes. The top number will always be higher, as pressure is greater when the heart is pumping. A normal blood pressure for most adults is somewhere in the range of 90 to 120 for the systolic measure, and 60 to 80 for the diastolic measure.
Most people think of problems with blood pressure in terms of it being too high. Any measure over 130/80 is considered high blood pressure, or hypertension. Low blood pressure (hypotension), on the other hand, is not determined by any specific measure, but by the appearance of symptoms. What constitutes “low” blood pressure will vary from one person to another. Low blood pressure means that the blood is not flowing adequately through the blood vessels, so that the appropriate, necessary levels of oxygen and nutrients are not being delivered to the body’s vital organs. This can cause either temporary or permanent damage to the organs.
Low blood pressure can be caused by a variety of different health conditions:
- Dehydration
- Inflammation of organs
- Bleeding, either internal or external
- Certain medications
- Various forms of heart disease, which inhibits the heart’s ability to pump blood efficiently
- Pulmonary embolism
- Abnormal heart rate, either fast or slow
- Vasovagal reaction
- Postural hypotension
- Adrenal insufficiency, such as with Addison’s disease
- Micturition syncope
- Anaphylaxis
- Septicemia
Obviously, there are a number of conditions which can cause low blood pressure. Understanding them can help to rule out some as potential causes, so that the cause of the problem can be found and treated quickly.
Dehydration can occur due to severe vomiting and diarrhea which typically accompany an intestinal illness, or from other sources such as heat stroke. Treatment for this condition is fairly obvious; the body must be re-hydrated. If the patient cannot drink fluids or keep them down, an IV can quickly introduce fluids to the system.
When an organ is inflamed through illness, blood enters the inflamed tissues leaving the normal blood supply in the vessels running low. If inflammation of an organ, such as pancreatitis, is the cause of low blood pressure, then treatment of that inflammation will correct the problem.
Bleeding, either internal or external, can be the cause of low blood pressure. This can result from trauma such as an accident, or due to complications that may arise during surgery. Bleeding may also occur due to a variety of gastrointestinal abnormalities or a ruptured aneurism.
Low blood pressure is sometimes a side effect of certain medications, such as those prescribed for depression, erectile dysfunction, high blood pressure, and Parkinson’s disease. Use of diuretics for weight loss can also cause low blood pressure. Alcohol and narcotics are another possible cause. Any time a patient presents with low blood pressure, the treating physician will ask for a complete drug history to rule out medications as the cause.
Heart disease in one very obvious cause of low blood pressure. When the heart suffers from disease, it is weakened and is unable to pump blood effectively, which lowers blood pressure. Other diseases of the heart, such as aortic stenosis, and infections in the organ can be the culprit.
A pulmonary embolism results when a blood clot in a vein dislodges and travels to the heart and then on to the lungs. The clot can block the flow of oxygenated blood from the lungs back into the heart. This condition is life-threatening and should be treated as an emergency.
An abnormally fast heart rate is called tachycardia, while a slow heart rate is referred to as bradycardia. Heart rate is easy to measure and can be therefore be quickly ruled in or out as the likely cause of low blood pressure.
Some of the possible causes of low blood pressure are relatively temporary. Vasovagal reaction, for example, is caused by temporary emotions of fear or pain. Postural hypotension is caused by standing up from a sitting or lying down position. Often this is simply caused by blood settling in the lower part of the body, but can also be due to diabetes, alcoholism, or rare neurological disorders. Micturition syncope occurs when the patient urinates, and usually seen in elderly people. The blood pressure drops when the bladder empties, and the patient may faint.
The adrenal glands produce a hormone called cortisol, which regulates blood pressure. If the adrenal glands are weakened from disease, they may not produce enough cortisol. When blood pressure is chronically low, adrenal disease such as Addison’s disease may be suspected.
Anaphylaxis is an allergic reaction and can be caused by the body’s reaction to bee stings, penicillin, peanuts, and more. Usually, other symptoms of allergic reaction, such as wheezing, hives, and a swollen throat will be present.
Septicemia is an infection of the blood, and usually originates from an illness such as pneumonia or bladder infection, among others. When bacteria from the infected area of the body enter the bloodstream, it can cause damage to other organs as well as life-threatening low blood pressure known as septic shock.
When a patient presents with low blood pressure, the doctor must quickly determine the cause. When blood pressure is extremely low, it can cause permanent organ damage or death. Once the cause of the hypotension is identified and treated, blood pressure should return to normal. In cases of permanent damage to the heart, blood pressure may remain chronically low and need to be monitored on a long-term basis.