Common Symptoms of Low Blood Pressure

How to Recognize if Your Blood Pressure is Too Low

Dizziness is a sign of low blood pressure.
What are the symptoms of low blood pressure?. Hitoshi Nishimura/Taxi Japan/Getty Images

We hear a lot about high blood pressure, and what can happen if it isn't controlled, but problems can occur if your blood pressure drops too low as well. What symptoms might you expect, and what can happen if you are hypotensive (have low blood pressure)?

Low Blood Pressure (Hypotension)

Unlike high blood pressure symptoms, which are poorly defined and often totally absent, low blood pressure symptoms tend to be more classic and easily recognizable.

The development of symptoms is often a warning signs that you should be evaluated to discover the cause of the low blood pressure, and to rule out any underlying problems. In general, however, blood pressure must fall to a fairly low value before symptoms develop.

What Exactly is Low Blood Pressure?

Low blood pressure doesn't have an exact definition, though many physicians might say that a cut-off 90/60 often stands between normal blood pressure and low blood pressure. Instead of a number, the definition of low blood pressure is a blood pressure below which the heart cannot deliver adequate blood flow to all of the vitals tissues of the body. The number at which this occurs will be different for each person.

Without adequate blood flow, the tissues of the body are deprived both of oxygen and the nutrients required to fuel the function of the cells. An inadequate supply of oxygen to the tissues—referred to as tissue hypoxia—results in cell dysfunction and eventually cell death.

As we noted above, low blood pressure can carry a different definition for different people. Some people may have a blood pressure of 86/50 and not be hypotensive. For example, someone who is in excellent physical condition. This level of blood pressure may result in adequate perfusion of the vital organs of the body.

In contrast, a blood pressure of 120/70 may meet the definition of hypotension in some people. With some medical conditions, a higher blood pressure may be required to supply the tissues with ample oxygen, and even what appears to be normal blood pressure may be insufficient to adequately perfuse all of the tissues.

Causes of Low Blood Pressure

There are a number of conditions which can result in low blood pressure, yet one of the most common is when people take too high of a dose of blood pressure medication. There are a number of different mechanisms which can result in low blood pressure.

Dilation of blood vessels throughout the body (from medications) may result in a rapid drop of blood pressure. Inadequate blood volume, due to blood loss or dehydration may result in low blood pressure, which is also referred to as hypovolemic shock. In cardiogenic shock, blood pressure may be too low because the heart is not pumping strongly enough to circulate the blood or because an abnormal heart rhythm interferes with adequate circulation.

Other conditions which can result in low blood pressure (shock) may include an overwhelming infection (septic shock,) a severe allergic reaction (anaphylactic shock,) neurological disorders (neurogenic shock,) and more.

(Learn more about the different types of shock.)

There are a number of medical conditions which can result in low blood pressure. This may occur due to blood loss, the dilation of blood vessels, and other mechanisms.

Causes of low blood pressure may include:

  • Blood pressure medications
  • Dehydration (and causes of dehydration such as diuretics, vomiting, diarrhea, and more)
  • Heart problems (especially heart arrhythmias in which inadequate blood is circulated)
  • Bleeding (due to surgery, trauma, ulcers, and more)
  • Thyroid problems
  • Adrenal insufficiency
  • Anaphylaxis (severe allergic reaction)
  • Neurologic (neurogenic orthostatic hypotension)
  • Medications (such as narcotics, anesthetics
  • Surgery
  • Hypovolemic shock (blood loss from trauma, internal hemorrhage)

Common Symptoms of Low Blood Pressure

The symptoms of low blood pressure often depend on how rapidly low blood pressure develops. If blood pressure drops rapidly, there is little chance for your body to respond and symptoms may come on abruptly (you may pass out.) In contrast, if low blood pressure develops gradually, you may feel tired and weak, but otherwise unaware that your blood pressure is low.

Symptoms of low blood pressure may include:

  • Dizziness or feeling like you are standing on a rocking boat
  • Lightheadedness
  • Blurry vision
  • Fainting
  • Fatigue
  • Weakness
  • Confusion and other changes in mental status or a sense of "impending doom"
  • Changes in breathing patterns (fast, shallow breathing is common during an episode of low blood pressure)
  • Rapid heart rate (heart rate often speeds up in compensation for a drop in blood pressure)
  • Palpitations
  • Pallor
  • Nausea
  • Suddenly feeling cold or clammy
  • Coma and death (when severe)

Complications of Low Blood Pressure

Whether low blood pressure is dangerous or not depends on many factors. If your blood pressure is 88/50 and you are adequately delivering oxygen to the tissues of your body, it would not be dangerous. On the other hand, your blood pressure could be 120/80 and still be considered "dangerous low blood pressure" if your body requires a higher blood pressure than this to perfuse your tissues.

A sudden drop in blood pressure when standing (orthostatic hypotension) can be very dangerous if you lose consciousness and fall. In this case a large part of the danger lies in where and how you fall rather than what is happening in your body.

Low blood pressure is usually most serious when it results in a prolonged reduction in the blood flow to critical organs of the body. Within minutes, low blood flow to the heart or brain can result in irreversible damage to these tissues. Chronically low to low-normal blood pressure is often most serious with regard to the effect on the kidneys.

The effect of low blood pressure on the body also depends on how well the body's compensatory mechanisms are working. For example, when the systolic (top number) blood pressure drops 15 to 20 points, the heart rate usually increases by around 15 beats per minute in order to deliver the same amount of blood to the tissues. If your heart rate cannot speed up to compensate (due to heart disease or abnormal heart rhythm's for instance) the effect will be more severe than if your body can adequately compensate. The body compensates in other ways as well, such as by increasing the pump force of your heart, and constricting blood vessels in the periphery (your arms and legs) to maintain a normal blood pressure in the core of the body.

These compensatory mechanisms, however, can result in further problems when they are used by the body for prolonged periods of time, such as when the extremities are deprived of adequate blood flow (due to vasoconstriction) for an extended period of time (which can result in gangrene and more.) Blood flow to the intestines may also be diverted in the event in a drop in core blood pressure, which can result in damage to the intestines and other abdominal organs.

Treatment of Low Blood Pressure (Hypotension)

As with any emergency, it is important to first establish "ABC" which stands for airway, breathing, and circulation. If the airways are obstructed, the obstruction needs to be removed. If a person is not breathing, artificial respiration is needed. If the heart is not beating (or is beating inadequately such as with a severe arrhythmia) CPR will be needed to restore circulation.

Further steps will depend on the initial diagnosis of what is causing low blood pressure. For example, if low blood pressure is thought to be due to low blood volume, intravenous fluids or blood may be given. If low blood pressure is due to a severe allergic reaction, adrenaline (epinephrine) will be given.

If low blood pressure is more of a chronic issue, further work-up will be needed to determine the exact cause. If blood pressure medications are the cause, these will be discontinued.

"Iatrogenic" Low Blood Pressure

The term "iatrogenic" refers to a medical treatment which causes a problem. It's not uncommon for people prescribed high blood pressure medications to end up with blood pressure which is too low. Some people have higher blood pressure when they are in the clinic (something that is called white coat hypertension) due to anxiety. When this occurs, medications may end up being prescribed which result in blood pressure that is too low outside the clinic. Ambulatory blood pressure monitoring (checking blood pressure outside the stressful setting of the clinic) may be needed to know how aggressive to be in treating high blood pressure to avoid inadvertently causing low blood pressure.

Bottom Line on Low Blood Pressure (Hypotension)

Low blood pressure can cause serious problems due to inadequate perfusion of vital organs of the body. Recognizing the symptoms and getting appropriate medical care is mandatory to avoid long term problems. There are a wide variety of causes, though the initial treatment—stabilizing a patient's airway, breathing, and circulation are the same. If you are concerned that you or a loved one are suffering from low blood pressure, call your doctor or call for emergency assistance right away.

Sources:

Kasper, Dennis L.., Anthony S. Fauci, and Stephen L.. Hauser. Harrison's Principles of Internal Medicine. New York: Mc Graw Hill education, 2015. Print.

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