Hypotension (Low Blood Pressure) is generally defined as a blood pressure reading below 90/60 mm Hg, although this can vary based on individual factors such as age and overall health. Some people with naturally low blood pressure may not experience any symptoms of hypotension, while others may experience symptoms such as:
- Dizziness or lightheadedness
- Fainting or near-fainting
- Blurred vision
- Fatigue
- Rapid, shallow breathing
- Nausea or vomiting
- Cold, clammy skin
- Rapid, weak pulse
If the blood pressure drops too low, it can lead to a lack of oxygen and nutrients being delivered to the body's organs and tissues. This can cause serious complications such as shock, organ failure, or even death.
Causes of Low Blood Pressure
Dehydration can cause Hypotension
When the body loses too much fluid, such as from sweating, vomiting, or diarrhea, it can lead to a decrease in blood volume and low blood pressure. Dehydration can cause hypotension, or low blood pressure, because when the body loses too much water, the volume of blood decreases, causing the blood vessels to constrict, which can lead to a decrease in blood pressure.
When the body is dehydrated, the kidneys try to conserve water by reabsorbing more fluid and producing less urine. This leads to a decrease in the volume of fluid in the blood vessels, which can cause a drop in blood pressure.
In addition, dehydration can cause a decrease in the level of electrolytes in the blood, such as sodium and potassium. These electrolytes play an important role in maintaining the balance of fluids in the body, and when their levels are low, it can lead to a drop in blood pressure.
Dehydration can also cause an increase in heart rate, which can further contribute to low blood pressure. When the body is dehydrated, the heart has to work harder to pump blood through the constricted blood vessels, which can cause the heart rate to increase.
Medications:
Certain medications, such as diuretics, alpha-blockers, and beta-blockers, can cause hypotension as a side effect. These antihypertensives, or blood pressure medications, can cause hypotension because of their actions such as dilating blood vessels, slowing down the heart rate, or increasing the production of urine. The risk of hypotension varies depending on the type and dosage of the medication as well as individual factors such as age, overall health, and other medications being taken.
Adding other drugs or medications along with antihypertensives can cause hypotension as well. For example, drinking alcohol with a blood pressure medication may enhance the drugs effect, and significantly lower blood pressure, even more than intended and cause dizziness or even fainting. This is more apparent in the first few weeks of starting an antihypertensive, while your body adjusts to the medications.
Heart problems:
Conditions that affect the heart's ability to pump blood, such as heart failure or heart attack, can lead to low blood pressure.
Endocrine disorders
Endocrine disorders can cause hypotension, or low blood pressure, because hormones play an important role in regulating blood pressure and blood volume in the body. Here are some examples of endocrine disorders that can cause hypotension:
Addison's disease: This is a condition in which the adrenal glands do not produce enough cortisol and aldosterone hormones. Aldosterone helps regulate the balance of fluids and electrolytes in the body, and a deficiency can lead to a decrease in blood volume and hypotension.
Hypothyroidism: An underactive thyroid gland can lead to a decrease in metabolic rate and a decrease in the heart's pumping ability, which can lead to low blood pressure.
Diabetes: Uncontrolled diabetes can cause autonomic neuropathy, which affects the nerves that control involuntary functions such as blood pressure regulation. This can cause a decrease in blood pressure upon standing, known as orthostatic hypotension.
Pituitary gland disorders: The pituitary gland produces several hormones that can affect blood pressure, such as growth hormone and adrenocorticotropic hormone (ACTH). Disorders of the pituitary gland, such as Cushing's disease or acromegaly, can lead to abnormal hormone production and hypotension.
Blood loss causes Hypotension
Severe blood loss from an injury, surgery, or internal bleeding can cause hypotension. Bleeding can cause hypotension, or low blood pressure, because blood loss decreases the volume of blood in the circulatory system, reducing the amount of blood available to be pumped by the heart. As a result, the heart has to work harder to maintain blood flow to the body, leading to a drop in blood pressure, sometimes causing even profound hypotension.
There are several mechanisms by which bleeding can cause hypotension:
- Decrease in blood volume: When a significant amount of blood is lost, the body's blood volume decreases, leading to a decrease in blood pressure. The loss of volume can be rapid in cases of severe bleeding, such as in trauma or hemorrhage, or gradual in cases of chronic bleeding, such as with ulcers or cancer.
- Decrease in oxygen delivery: Blood carries oxygen to the body's tissues, and a decrease in blood volume due to bleeding can result in decreased oxygen delivery to the body's organs, leading to hypotension and organ dysfunction.
- Activation of compensatory mechanisms: The body has several compensatory mechanisms to maintain blood pressure in response to bleeding, such as increasing heart rate and constricting blood vessels. However, these mechanisms may be insufficient to compensate for significant blood loss, leading to hypotension.
Septic shock
Septic shock is a life-threatening medical condition caused by a severe infection that triggers an overwhelming immune response, leading to widespread inflammation and tissue damage. Hypotension, or low blood pressure, is a common feature of septic shock and is a result of several mechanisms:
- Vasodilation: The immune response triggered by the infection causes the release of inflammatory mediators, such as cytokines, which can cause the blood vessels to dilate. This dilation results in a decrease in vascular resistance and blood pressure.
- Decreased cardiac output: The inflammation and tissue damage caused by sepsis can lead to a decrease in the heart's ability to pump blood, which can contribute to hypotension.
- Impaired oxygen delivery: The decreased blood pressure caused by septic shock can result in decreased oxygen delivery to the body's tissues, which can cause organ dysfunction and further contribute to hypotension.
- Fluid loss: Septic shock can also cause the blood vessels to become more permeable, resulting in fluid leakage from the bloodstream into the surrounding tissues. This can lead to a decrease in blood volume and contribute to hypotension.
Anaphylaxis Causes Hypotension
Anaphylaxis is a severe, life-threatening allergic reaction that can cause a sudden drop in blood pressure, or hypotension, among other symptoms. The hypotension in anaphylaxis is typically caused by two primary mechanisms:
- Vasodilation: When anaphylaxis occurs, the immune system releases large amounts of histamine and other inflammatory mediators that can cause blood vessels to dilate or widen. This results in a decrease in vascular resistance and a drop in blood pressure. The vasodilation also causes an increase in capillary permeability, which leads to fluid leakage from the blood vessels into the surrounding tissues, resulting in a decrease in blood volume and contributing to hypotension.
- Increased heart rate: The drop in blood pressure caused by vasodilation triggers a reflex response in the body that attempts to compensate by increasing heart rate. The increased heart rate, however, may not be enough to maintain adequate blood pressure, particularly if the hypotension is severe.
Neurological disorders
The autonomic nervous system plays a critical role in regulating blood pressure by controlling the constriction and dilation of blood vessels and the rate and strength of the heart's contractions. Neurological disorders that affect the autonomic nervous system, such as Parkinson's disease and multiple system atrophy, can lead to low blood pressure, or hypotension, through several mechanisms:
- Impaired blood vessel constriction: The autonomic nervous system is responsible for regulating the constriction and dilation of blood vessels. In Parkinson's disease and multiple system atrophy, the autonomic nervous system can become damaged or dysfunctional, resulting in a decreased ability to constrict blood vessels. This leads to a decrease in vascular resistance and blood pressure.
- Reduced heart rate and strength of contractions: The autonomic nervous system also controls the rate and strength of the heart's contractions. In neurological disorders such as Parkinson's disease and multiple system atrophy, the autonomic nervous system can become impaired, resulting in a decreased heart rate and a weaker force of heart contractions. This can lead to a decrease in cardiac output and blood pressure.
- Impaired baroreflex function: The baroreflex is a mechanism that helps to regulate blood pressure by detecting changes in blood pressure and adjusting the body's responses accordingly. In neurological disorders such as Parkinson's disease and multiple system atrophy, the baroreflex can become impaired, resulting in a decreased ability to respond to changes in blood pressure. This can contribute to hypotension.
Orthostatic Hypotension
Post Prandial Hypotension
Postprandial hypotension is a condition in which a person experiences a sudden drop in blood pressure after eating a meal. This can result in symptoms such as dizziness, lightheadedness, and even fainting.
- Aging: Postprandial hypotension is more common in older adults, as the body's ability to regulate blood pressure decreases with age.
- Autonomic nervous system disorders: The autonomic nervous system is responsible for regulating many bodily functions, including blood pressure. Disorders such as Parkinson's disease and multiple system atrophy can affect the autonomic nervous system, leading to postprandial hypotension.
- Diabetes: Diabetes can damage the nerves that control blood pressure, leading to postprandial hypotension.
- Medications: Certain medications, such as alpha-blockers, diuretics, and nitrates, can cause postprandial hypotension.
- Gastric bypass surgery: Gastric bypass surgery can alter the digestive process and lead to postprandial hypotension.
Vasovagal Hypotension
Medical Procedures with Hypotension as a Complication
Apheresis: Apheresis is a medical procedure that involves the removal of blood from a patient, separation of specific blood components, and then returning the remaining blood components back to the patient. During the apheresis procedure, the patient's blood is circulated through an extracorporeal machine, which can lead to a decrease in blood volume and subsequent hypotension.