Low Blood Pressure Symptoms
Symptoms of low blood pressure or hypotension may include:
- Fainting (syncope)
- A feeling of lightheadedness
- Chest pain
- Blurred vision
- Increased thirst
Symptoms of low blood pressure or hypotension may include:
Blood pressure is the force exerted by circulating blood on the walls of blood vessels. It constitutes one of the critically important signs of life or vital signs which include heart rate, breathing, and temperature. Blood pressure is generated by the heart pumping blood into the arteries modified by the response of the arteries to the flow of blood.
An individual's blood pressure is expressed as systolic/diastolic blood pressure, for example, 120/80.
Blood pressure always is higher when the heart is pumping (squeezing) than when it is relaxing.
The range of systolic blood pressure for most healthy adults falls between 90 and 120 millimeters of mercury (mm Hg). Normal diastolic blood pressure ranges between 60 and 80 mm Hg. Current guidelines define normal blood pressure range as lower than 120/80. Blood pressures over 130/80 are considered high. High blood pressure increases the risk of damaging the arteries which leads to the development of:
Low blood pressure (hypotension) is pressure so low it causes symptoms or signs due to the low flow of blood through the arteries and veins. When the flow of blood is too low to deliver enough oxygen and nutrients to vital organs such as the brain, heart, and kidney, the organs do not function normally and may be temporarily or permanently damaged.
Unlike high blood pressure, low blood pressure is defined primarily by signs and symptoms of low blood flow and not by a specific blood pressure number. Some individuals routinely may have blood pressure numbers of 90/50 with no symptoms and therefore do not have low blood pressure. However, others who normally have higher blood pressures may develop symptoms of low blood pressure if their blood pressure drops to 100/60.
In pregnancy, blood pressure tends to decrease. Normal blood pressure during pregnancy may be lower than 100/60. Blood pressure should be monitored by the obstetrician during pregnancy.
During relaxation of the heart (diastole) the left ventricle of the heart fills with blood returning from the lungs. The left ventricle then contracts and pumps blood into the arteries (systole). The blood pressure in the arteries during contraction of the ventricle (systolic pressure) is higher because blood is being actively ejected into the arteries. It is lower during relaxation of the ventricle (diastolic pressure) when no blood is being ejected into the arteries. The pulse we feel when we place our fingers over an artery is caused by the contraction of the left ventricle and the ejection of blood.
Blood pressure is determined by two factors: 1) The amount of blood pumped by the left ventricle of the heart into the arteries, and 2) the resistance to the flow of blood caused by the walls of the arterioles (smaller arteries).
Generally, blood pressure tends to be higher if more blood is pumped into the arteries or if the arterioles are narrow and/or stiff. Narrow and/or stiff arterioles, by resisting the flow of blood, increase blood pressure. Arterioles may become narrower when the muscles surrounding them contract. Arterioles may become stiff and narrow when older patients develop atherosclerosis.
Blood pressure tends to be lower if less blood is being pumped into the arteries or if the arterioles are larger and more flexible and, therefore, have less resistance to the flow of blood.
The body has mechanisms to alter or maintain blood pressure and blood flow. There are sensors that sense blood pressure in the walls of the arteries and send signals to the heart, the arterioles, the veins, and the kidneys that cause them to make changes that lower or increase blood pressure.
There are several ways in which blood pressure can be adjusted; by adjusting the amount of blood pumped by the heart into the arteries (cardiac output), the amount of blood contained in the veins, the arteriolar resistance, and the volume of blood.
For example, low blood volume due to bleeding (such as a bleeding ulcer in the stomach or from a severe laceration from an injury) can cause low blood pressure. The body quickly responds to the low blood volume and pressure by the following adjustments which all increase blood pressure:
The heart rate increases and the forcefulness of the heart's contractions increase, pumping more blood through the heart.
Athletes, people who exercise regularly, people who maintain ideal body weight, and nonsmokers tend to have lower blood pressures. Low blood pressure is desirable as long as it is not low enough to cause symptoms and damage to the organs in the body.
When blood pressure is not sufficient to deliver enough blood to the organs of the body, the organs do not work properly and can be temporarily or permanently damaged. Symptoms of low blood pressure caused by conditions or diseases depend upon the specific cause of the low blood pressure. For example, if insufficient blood flows to the brain, brain cells do not receive enough oxygen and nutrients, and a person can feel lightheaded, dizzy, or even faint.
The most common symptoms of low blood pressure include:
Symptoms of low blood pressure due to conditions or diseases include:
Conditions that reduce the volume of blood, reduce cardiac output (the amount of blood pumped by the heart), and medications are frequent reasons for low blood pressure.
Several common reasons for bradycardia include: 1) sick sinus syndrome, 2) heart block, and 3) drug toxicity. Many of these conditions occur in the elderly.
An abnormally fast heart rate (tachycardia) also can cause low blood pressure. The most common example of tachycardia causing low blood pressure is atrial fibrillation. Atrial fibrillation is a disorder of the heart characterized by rapid and irregular electrical discharges from the muscle of the heart causing the ventricles to contract irregularly and (usually) rapidly. The rapidly contracting ventricles do not have enough time to fill maximally with blood before each contraction, and the amount of blood that is pumped decreases in spite of the faster heart rate. Other abnormally rapid heart rhythms such as ventricular tachycardia also can produce low blood pressure, sometimes even life-threatening shock.
Medications that cause low blood pressure
In some individuals, particularly relatively healthy ones, symptoms of weakness, dizziness, and fainting raise the suspicion of low blood pressure. In others, an event often associated with low blood pressure, for example a heart attack, has occurred to cause the symptoms.
Measuring blood pressure, in both the lying (supine) and standing positions usually is the first step in diagnosing low blood pressure. In patients with symptomatic low blood pressure, there often is a marked drop in blood pressure upon standing, and patients may even develop orthostatic symptoms. The heart rate often increases. The goal is to identify the cause of the low blood pressure. Sometimes the causes are readily apparent (such as loss of blood due to trauma, or sudden shock after receiving X-ray dyes containing iodine). At other times, the cause may be identified by testing:
Low blood pressure readings in healthy subjects without symptoms or organ damage need no treatment. All patients with symptoms possibly due to low blood pressure should be evaluated by a doctor. Patients who have had a major drop in blood pressure from their usual levels even without the development of symptoms also should be evaluated. The doctor needs to identify the cause of the low blood pressure; remedies will depend on the cause. For example, if a medication is causing the low blood pressure, the dose of medication may have to be reduced or the medication stopped. Do not adjust medication dose on your own, and do not stop taking any medication without first consulting your doctor.
*Note: Increasing salt intake can lead to heart failure in patients with existing heart disease and should not be undertaken without consulting a doctor.
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