Low blood pressure (hypertension) blood pressure is too low to cause symptoms such as dizziness and fainting.
The maintenance of blood pressure when it leaves the heart and circulates throughout the body is as essential as maintaining water pressure in the pipes of a home. The pressure should be high enough to carry oxygen and nutrients to body cells and extract from them the products of waste. However, if blood pressure is too high, it can burst a blood vessel and cause bleeding in the brain (cerebral hemorrhage) or other problems.
Conversely, if too low, can not supply enough oxygen and nutrients to cells, or remove debris from them. However, healthy individuals with normal blood pressure, rather low at rest, have a higher life expectancy.
Clearing
There are three factors that determine blood pressure: the amount of blood pumped from the heart, blood volume in blood vessels and their capacity.
The more blood from the heart (cardiac ejection volume) per minute, the higher the blood pressure. The amount of blood pumped may decrease if the heart beats more slowly or your contractions are weak, such as after a heart attack (myocardial infarction). A very fast heartbeat, as well as many other types of arrhythmias, may reduce the heart’s pumping efficiency and volume of expulsion.
The more blood that contains the circulatory system, the higher the blood pressure. If blood is lost from dehydration or bleeding, blood volume decreases and, consequently, lowers blood pressure.
The lower the ability of blood vessels, the higher the blood pressure. Therefore, the widening (dilation) of blood vessels leads to a drop in blood pressure, when they contract, blood pressure increases.
Some sensors, particularly those found in the neck and chest, constantly monitor blood pressure. When they detect a change caused by the action of one of these three factors, the sensors turn result in a change in any of the other factors to compensate for such change and, thus, maintain steady pressure. The nerves conduct signals from these sensors and from the centers of the brain to several of the key bodies:
The heart, to modify the frequency and strength of the pulse (in this way changes the amount of blood pumped).
Kidneys to regulate water excretion (and therefore to adjust the volume of blood in circulation).
Blood vessels to contract or dilate (ie, changing their capacity).
Therefore, if the blood vessels dilate and reduces blood pressure, immediately sensors send signals through the brain to the heart for it to increase the frequency of its pulsations, which will increase the removal of blood. Consequently, blood pressure, suffer little or no change. However, these compensatory mechanisms have limitations. For example, in case of bleeding, heart rate increases, increases the expulsion of blood and blood vessels constrict and reduce their capacity. However, if you lose a lot of blood quickly, clearing mechanisms are insufficient, and blood pressure decreases. If the bleeding stops, the rest of the body fluid tends to enter the bloodstream, it recovers the volume and the pressure rises. Finally, we produce new cells and blood volume is completely restored. Also, a blood transfusion can restore blood volume rapidly.
Hypotension can also be the result of a malfunction in the mechanisms that maintain blood pressure. For example, if a disruption in the ability of nerves to conduct signals, the control mechanisms of compensation may not work correctly.
Fainting
Fainting (syncope) is a sudden and brief loss of consciousness.
It is a symptom due to an inadequate supply of oxygen and other nutrients to the brain, usually caused by a temporary decrease in blood flow. This decrease can occur if the body can not quickly compensate for a sudden drop in blood pressure. For example, if a patient has an abnormal heartbeat, the heart may be unable to sufficiently increase the volume of blood removal to compensate for reduced blood pressure. These people have no symptoms at rest, but, instead, suffer fainting when they make some effort because the body’s oxygen demand increases abruptly is called syncope effort. Often, fainting occurs after making an effort because the heart is barely able to maintain adequate blood pressure during exercise, when exercise is stopped, the heart rate begins to decrease, but the blood vessels of the muscles remain dilated to remove metabolic waste products. The combination of reduced heart stroke volume with the increase in the capacity of the blood vessels causes the blood pressure falls and the person faints.
Obviously, blood volume decreases in case of bleeding. But this also happens when the person is dehydrated by situations such as diarrhea, excessive urination, excessive sweating, which often occurs in untreated diabetes or Addison’s disease.
Fainting can also occur when compensatory mechanisms are interfered with by signals sent through the nerves from other parts of the body. For example, an intestinal cramping can send a signal to the heart via the vagus nerve, which slows the heart rate enough to cause fainting. This type of fainting is called vasovagal syncope, or vasomotor. Many other signals (such as other pain, fear and the sight of blood) can cause this type of fainting.
Fainting motivated by coughing (cough syncope) or urination (micturition syncope) usually occurs when the amount of blood returning to the heart decreases during exercise. Micturition syncope is particularly common in the elderly. Syncope during swallowing can occur in people with diseases of the esophagus.
The cause of fainting can also be a decrease in the number of red blood cells (anemia), a decrease in the concentration of blood sugar (hypoglycemia) or a decrease in levels of carbon dioxide in the blood (hypocapnia) by breathing fast (hyperventilating). Sometimes, anxiety is accompanied by hyperventilation. When the concentration of carbon dioxide decreases, the brain’s blood vessels constrict and you may receive a feeling of faintness without reaching to lose consciousness. The weightlifter syncope is the result of hyperventilation before exercise.
In rare cases, especially in the elderly, fainting can be part of a mild stroke in which blood flow to a part of the brain decreases abruptly.
Symptoms
When the person is standing, prior to fainting, you may notice slight dizziness. When dropped, blood pressure rises in part because the person is lying and often, because the cause of syncope is over. Getting up too quickly can cause a new fainting.
When the cause is an arrhythmia, fainting appears and disappears suddenly. Sometimes they experience palpitations (awareness of heartbeat) just before fainting.
Orthostatic syncope occurs when a person sits or stands too quickly. A similar form of fainting, called syncope “military parades,” occurs when a person stands still for a long time on a hot day. As in this situation, the leg muscles are not being used, do not push blood to the heart and, consequently, it stagnates in the veins of the legs and the blood pressure drops repentinamente.El vasovagal syncope occurs when a person sitting or standing and is often preceded by nausea, weakness, yawning, blurred vision and sweating. Extreme pallor is observed, the pulse becomes very slow and the person faints.
Fainting begins gradually, which is preceded by warning symptoms which gradually disappears, suggests changes in blood chemicals, such as a decrease in the concentration of sugar (hypoglycemia) or the rate of carbon dioxide (hypocapnia ) caused by hyperventilation. Hypocapnia often preceded by a tingling sensation and discomfort in the chest.
Hysterical fainting is not a true syncope. The person only appears to be unconscious, but no abnormalities in heart rate or blood pressure and does not sweat or become pale.
Diagnosis
First, it is necessary to determine the underlying cause of fainting because some causes are more serious than others. Heart disease, such as abnormal heart rhythms or aortic stenosis, can be deadly; other disorders are much less worrisome.
The factors that facilitate the diagnosis are the age of onset of episodes of fainting, the circumstances in which they occur, the warning signs before the episode and maneuvers that help the person recover (like lying down, holding your breath or drink orange juice). The descriptions that bring the witnesses about the episode can be helpful. The doctor also needs to know if you have any other medical condition or taking any drugs, whether prescription or not.
You can play a fainting episode in safe conditions, for example, telling the patient to breathe quickly and deeply. Or, while monitoring the heartbeat with an electrocardiogram (ECG), the doctor may press gently on the carotid sinus (a part of the internal carotid artery that contains sensors that monitor blood pressure).
An electrocardiogram may indicate an underlying heart or lung disease. To find the cause of syncope, uses a Holter monitor, a small device that records heart rhythms for 24 hours while the patient performs normal daily activities. If the arrhythmia coincides with an episode of fainting, it is likely (but not certain) to be the cause.
Other tests such as echocardiography (a technique that produces images using ultrasound), can reveal structural or functional cardiac abnormalities. In addition, blood tests can detect a low concentration of blood sugar (hypoglycemia) or too few red blood cells (anemia). To diagnose epilepsy (which is sometimes confused with fainting), can be an electroencephalogram, a test that shows patterns of electrical brain waves.
Treatment
Usually, the fact is enough to lie to regain consciousness. The elevation of the legs can speed recovery by increasing blood flow to the heart and brain. If you stand up too quickly or is held or carried in an upright position, there may be another episode of fainting.
In young people who do not have heart disease, fainting spells are generally not serious and requires no extensive diagnostic tests or treatment. However, in the elderly, syncope can be caused by several interrelated problems that prevent the heart and blood vessels react to a decrease in blood pressure.
Treatment depends on the cause.
To correct a heart beat too slow, a pacemaker can be implanted surgically, which consists of an electronic device that stimulates the heartbeat. To slow a heart rate too fast can be used drugs. If the problem is an abnormal rhythm (the heart beats irregularly from time to time), may be appealed to the implantation of a defibrillator. You can also treat other causes of fainting (such as hypoglycemia, anemia or low blood volume). Surgical intervention should be considered when syncope is due to valvular disease, irrespective of the age of the person.
Orthostatic Hypotension
Orthostatic hypotension is an excessive reduction of blood pressure by adopting the upright position, causing a decrease in cerebral blood flow and subsequent fainting.
Orthostatic hypotension is not a specific disease, but rather an inability to regulate blood pressure quickly. May be due to various causes.
When a person stands up suddenly, gravity causes a portion of the blood from pooling in the veins of the legs and lower body. The accumulation reduces the amount of blood returning to the heart and therefore the amount pumped. The result is a decrease in blood pressure. In this situation, the body responds quickly: the heart beats faster, the contractions are stronger, the blood vessels constrict and reduce its capacity. When these compensatory responses fail or are slow, orthostatic hypotension occurs.
Episodes of orthostatic hypotension usually occur due to side effects of drugs, especially those that are given to combat cardiovascular problems, especially in the elderly. For example, diuretics, especially strong in high doses, can reduce blood volume due to fluid removed from the body and therefore lower blood pressure. Drugs that dilate blood vessels (such as nitrates, calcium antagonists and inhibitors of angiotensin converting) increase the ability of the vessels and therefore also lower blood pressure. Bleeding or excessive fluid loss from vomiting, diarrhea, excessive sweating, untreated diabetes or Addison’s disease may cause a reduction of circulating blood volume. Arterial sensors that trigger compensatory responses are sometimes impaired by the action of certain drugs such as barbiturates, alcohol and drugs used to treat hypertension and depression. Diseases that damage the nerves that regulate the diameter of blood vessels can also cause orthostatic hypotension. These lesions are a common complication of diabetes, amyloidosis and spinal cord injuries.
Symptoms and Diagnosis
People with orthostatic hypotension usually experienced fainting, light dizziness, confusion or blurred vision when they get up from bed or incorporated abruptly after having been sitting a long time. Fatigue, exercise, alcohol or a heavy meal may exacerbate symptoms. A sharp reduction of blood flow to the brain can cause fainting or even seizures.
When these symptoms, your doctor can diagnose orthostatic hypotension. The diagnosis can be confirmed if blood pressure drops significantly when the patient gets up and returns to normal when lying down. The doctor must then try to determine the cause of orthostatic hypotension.
Prognosis and Treatment
A diabetic with hypertension have a worse prognosis if they also suffer from orthostatic hypotension. When the cause of orthostatic hypotension is a decrease in blood volume, a particular drug or a certain dose of a medication, the disorder can be corrected rápidamente.Cuando there is no treatment for the cause of orthostatic hypotension, it is often possible eliminate or reduce symptoms. People prone to this condition should not be moved or stand up suddenly or stand still for a long time. If hypotension is caused by an accumulation of blood in the legs, elastic compression stockings may be helpful. When orthostatic hypotension is the result of prolonged bed rest, it is possible to improve the situation if it gradually increases the time spent sitting.
To avoid a decrease in blood pressure can be administered ephedrine or phenylephrine. The blood volume can also be increased by increasing the intake of salt and, if necessary, ingesting hormones that cause the withholding of it, such as fludrocortisone. In people without heart failure or hypertension, is recommended to add salt to their meals free or taking salt tablets. Elderly patients with orthostatic hypotension should drink plenty of fluids and little or no alcohol. However, due to retention of salt and fluids, a person can increase rapidly from one to two kilograms in weight and developing heart failure because of the high-salt diet, especially the elderly. If these measures are not effective, other drugs (such as propranolol, dihydroergotamine, indomethacin and metoclopramide) may help prevent orthostatic hypotension, although at the expense of a high risk of side effects.
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