What is Low Blood Pressure?

April 16, 2019

What is blood pressure?
Blood pressure is one of the body’s vital signs and refers to the force exerted by the blood on the walls of blood vessels during contraction and relaxation of the heart muscle. It refers to the force exerted by the blood on the walls of the blood vessels during contraction and relaxation of the heart muscle. Blood pressure measures the pressure of the arteries, which are the blood vessels that carry blood away from the heart. The ability of the arteries to respond to blood flow determines the blood pressure.

What is low blood pressure?
Low blood pressure causes insufficient blood flow, so oxygen and nutrients are not adequately delivered to the heart, brain, kidneys and other organs. This can cause damage and lead to permanent injury.

What is healthy blood pressure?
With each beat of the heart, blood is circulated throughout the body. The pressure exerted on the arteries when the heart beats is called the systolic pressure. It is the first or highest number in a blood pressure measurement. The pressure exerted on the arteries between heartbeats is called the diastolic pressure. A blood pressure reading of 120/80 millimeters (mm) or mercury (Hg) is considered normal. A reading above this is considered high blood pressure.

How does blood pressure occur?
The heart’s lower left chamber (ventricle) receives oxygenated blood from the lungs and pumps it throughout the body. The heart fills with blood between heartbeats. This phase of the heart cycle is called diastole. When the heart pumps blood throughout the arteries, this phase is called systole. You can check your heartbeat by placing your finger around your neck or on the inside of your wrist. The pulse you feel is the contraction of the left ventricle of the heart.

How is blood pressure determined?
There are several factors that affect blood pressure, and blood volume and blood vessel wall behavior are two important factors in determining blood pressure. Blood volume and blood vessel wall behavior are two important factors in determining blood pressure. The more blood is pumped out with each heartbeat, the higher the blood pressure. The presence of stiff or narrowed artery walls that resist blood flow also increases blood pressure. Having a lower blood volume and open, elastic arteries lowers blood pressure.

How does the body maintain normal blood pressure?
Baroreceptors are small nerve cells in the arteries near the heart that help regulate blood pressure.Baroreceptors communicate with the kidneys, arteries, veins, and heart to increase, decrease, or maintain blood pressure as needed. The function of the aortic receptors is to ensure that enough blood reaches the organs and tissues of the body.

Baroreceptor signals are sent to the heart.
If blood pressure is too low, the Baroreceptors send a signal to the heart telling it to beat faster and pump out more blood per minute. The result is an increase in blood flow and a rise in blood pressure.

Baroreceptor signals are sent to the veins.
If the blood pressure is too high, the Baroreceptors send signals to the veins instructing them to expand and store more blood and to return less blood to the heart. The result is reduced blood flow and lower blood pressure. Conversely, the veins become narrower and return more blood to the heart, thereby increasing blood pressure.

Baroreceptor signals are sent to the arteries.
When blood pressure is too high or too low, the Baroreceptors communicate directly with the artery to bring it to a more appropriate level. When blood pressure is too low, the Baroreceptors tell the artery to contract to help raise blood pressure. When blood pressure is too high, the Baroreceptors tell the artery to relax to help lower blood pressure.

Baroreceptor signals are sent to the kidneys.
The kidneys are involved in blood pressure control by regulating urine production. When the kidneys pump more water out of the blood, blood pressure decreases. When the kidneys reduce the amount of urine, water remains in the blood and blood pressure rises. The effect of the kidneys on blood pressure is slow — acting over hours to days — whereas the effect of baroreceptor control and other systems on blood pressure is very rapid.

Is low blood pressure bad for your health?
Low blood pressure is associated with a lower risk of heart disease, stroke and kidney disease. Those who exercise regularly, athletes, non-smokers and those who maintain an optimal body weight experience lower blood pressure. Lower blood pressure is a good thing as long as it doesn’t cause symptoms that could damage body organs and tissues.

What are the symptoms of low blood pressure?
Many people live with low blood pressure, but they don’t have any symptoms. If this is the case, low blood pressure is of no consequence. Others with low blood pressure, however, experience dizziness and lightheadedness. This means that there is not enough blood flow to the brain. This in turn can lead to weakness, nausea, confusion and blurred vision. Low blood pressure affects other organs, causing shortness of breath, fainting, fainting, chest pain and cold, moist skin.

What is the cause of low blood pressure?
Hypotension may be caused by conditions that reduce arterial wall tension or reduce blood volume. Dehydration and bleeding are two examples of conditions that reduce blood volume. Conditions that reduce the amount of blood the heart pumps – such as cardiomyopathy and heart attacks – may be associated with low blood pressure. Spinal cord injuries and the side effects of certain medications can also lower blood pressure.

Low blood pressure caused by the nervous system.
The proper functioning of the central nervous system is necessary to maintain adequate blood pressure. The body’s vagus nerve and adrenaline system work together to influence blood pressure. When the vagus nerve is overstimulated, the veins dilate, not enough blood returns to the heart, and blood pressure decreases. Vasovagal syncope is a type of syncope that occurs when the vagus nerve is overstimulated. Vaso-vagal syncope can occur in people who are sensitive to pain or who cannot tolerate the sight of blood. In these cases, the vagus nerve is overstimulated and syncope occurs. This type of syncope may even occur during urination or defecation.

In some types of spinal cord injuries, the adrenaline leading to the arteries is blocked. When this happens, the artery remains wide open and is unable to maintain adequate blood pressure.

Low blood pressure from non-neurological causes.
Low blood pressure may be caused by conditions not related to the nervous system. Any condition that causes fluid loss, including dehydration due to diarrhea, vomiting, or bleeding, may cause low blood pressure. Adrenal dysfunction, pregnancy, and blood loss may also lower blood pressure.

Medications may cause low blood pressure.
Medications used to treat conditions other than low blood pressure may cause hypotension as a side effect. Erectile dysfunction medications such as sildenafil (Viagra), tricyclic antidepressants such as amitriptyline (Elavil), and Parkinson’s medications such as levodopa-carbidopa (Sinemet) are some of the medications whose side effects may include low blood pressure. Narcotic painkillers and alcohol can also lower blood pressure.

When antihypertensive drugs are too effective, they may cause low blood pressure. Angiotensin receptor blockers (ARBs), calcium channel blockers (CCBs), beta blockers, and diuretics (water pills) are some types of blood pressure medications.

What other conditions can cause low blood pressure?
Sometimes, bacterial or fungal infections from other parts of the body enter the bloodstream. This type of infection is called septicemia. It is potentially life-threatening and may cause severe low blood pressure called septic shock, which may damage organs. Sepsis may be caused by diverticulitis, pneumonia, urinary tract infections, or other infections.

What other conditions can cause low blood pressure? (continued)
Some people have severe and potentially life-threatening allergic reactions (anaphylaxis) to peanuts, intravenous contrast media, bee stings, antibiotics, or other foods and substances. An anaphylactic chain reaction results in the release of substances to “fight” the offending substance and causes a severe drop in blood pressure. Anaphylactic reactions are rare.

How is low blood pressure diagnosed?
To diagnose low blood pressure, your doctor may measure your blood pressure while the patient is lying down (lying on his or her back) and while he or she is standing up. Patients with low blood pressure may experience dizziness and vertigo when standing up. The heart rate usually increases to compensate for the low blood pressure. After a diagnosis of low blood pressure is made, the doctor will identify the cause of the problem. Sometimes the cause of low blood pressure may be easy to determine, such as bleeding from a wound, but most of the time the doctor may need to order other tests to discover the cause of the low blood pressure.

How is low blood pressure treated?
Anyone who has experienced low blood pressure or thinks they may have experienced low blood pressure should be evaluated by a physician. Patients should be evaluated even if the low blood pressure is not causing any symptoms. Treatment of low blood pressure varies depending on the cause of the condition. If a patient is already taking medication for high blood pressure, the dose of the medication may need to be adjusted. If fluid loss due to diarrhea or vomiting causes a drop in blood pressure, intravenous fluids may be administered to normalize the blood pressure.