Hypotension is low blood pressure, especially in the systemic circulatory artery. Blood pressure is the force of blood pushing the artery walls as the heart pumps blood out. Systolic blood pressure of less than 90 millimeters of mercury (mm Hg) or diastolic less than 60 mm Hg is generally considered to be hypotension. However, in practice, blood pressure is considered too low only if there are symptoms that are visible.
Hypotension is the opposite of hypertension, which is high blood pressure. It is best understood as a physiological state, not a disease. Very low blood pressure can deprive the brain and other vital organs of oxygen and nutrients, leading to a life-threatening condition called shock.
For some people who exercise and are in excellent physical condition, low blood pressure is a sign of good health and fitness. For many people, too low blood pressure can cause dizziness and fainting or show serious heart, endocrine or nerve disorders.
Treatment of hypotension may include the use of intravenous fluids or vasopressors. When using a vasopressor, trying to achieve a mean arterial pressure (MAP) greater than 70 mmHg does not seem to produce better results than trying to achieve a MAP greater than 65 mm Hg in adults.
Video Hypotension
Signs and symptoms
The main symptom of hypotension is the head feels light or dizzy.
If the blood pressure is low enough, fainting can occur.
Low blood pressure is sometimes associated with certain symptoms, many of which are related to causes rather than the effects of hypotension:
Maps Hypotension
Cause
Low blood pressure can be caused by low blood volume, hormonal changes, dilation of blood vessels, drug side effects, anemia, heart problems or endocrine problems.
Reduced blood volume, hypovolemia, is the most common cause of hypotension. This can happen due to bleeding; insufficient fluid intake, such as starvation; or excessive fluid loss from diarrhea or vomiting. Hypovolemia is often induced by excessive use of diuretics. Low blood pressure can also be associated with heat stroke. The body may have enough fluids but does not retain the electrolyte. The lack of perspiration, dizziness and dark urine are also indicators.
Other drugs can produce hypotension by different mechanisms. The chronic use of alpha blockers or beta blockers can lead to hypotension. Beta blockers can cause good hypotension by slowing the heart rate and by reducing the ability to pump the heart muscle.
Decreased cardiac output despite normal blood volume, due to severe congestive heart failure, large myocardial infarction, heart valve problems, or very low heart rate (bradycardia), often produce hypotension and can rapidly progress to cardiogenic shock. Arrhythmias often result in hypotension by this mechanism.
Some heart conditions can cause low blood pressure, including very low heart rate (bradycardia), heart valve problems, heart attacks and heart failure. This condition can cause low blood pressure because they prevent the body from being able to circulate enough blood.
Excessive vasodilation, or insufficient narrowing of the resistance vessels (mostly arterioles), causes hypotension. This may be due to decreased output of the sympathetic nervous system or increased parasympathetic activity that occurs as a result of injury to the brain or spinal cord or dysautonomia, an intrinsic abnormality in the functioning of the autonomic system. Excessive vasodilation may also occur due to sepsis, acidosis, or drugs, such as nitrate preparations, calcium channel blockers, or AT1 receptor antagonists (Angiotensin II acts on AT1 receptors). Many anesthetic agents and techniques, including spinal anesthesia and most inhalation agents, produce significant vasodilatation.
Meditation, yoga, or other mental-physiological discipline can reduce the effects of hypotension.
Lowering blood pressure is a side effect of certain herbal medicines, which can also interact with hypotensive drugs. An example is theobromine in Theobroma cacao , which lowers blood pressure through its actions as both a vasodilator and diuretic, and has been used to treat high blood pressure.
Syndrome
Orthostatic hypotension, also called postural hypotension , is a common form of low blood pressure. This happens after a change of body position, usually when a person stands from a sitting position or lies down. Usually transient and is a delay in the normal compensatory ability of the autonomic nervous system. Usually seen in hypovolemia and as a result of various drugs. In addition to blood pressure-lowering drugs, many psychiatric drugs, especially antidepressants, can have these side effects. Simple blood pressure and heart rate measurements when lying down, sitting, and standing (with a two minute delay between each change of position) can confirm the presence of orthostatic hypotension. Orthostatic hypotension is indicated if there is a drop in systolic pressure of 20 mmHg (and a decrease of 10 mmHg diastolic pressure in some facilities) and an increase in heart rate 20 times per minute.
Vasovagal syncope is a form of dysautonomia characterized by improperly decreasing blood pressure when in an upright position. Vasovagal syncope occurs as a result of increased activity of the vagus nerve, the mainstay of the parasympathetic nervous system.
Other forms, but more rarely, are postprandial hypotension, a drastic decrease in blood pressure that occurs 30 to 75 minutes after eating substantial food. When a lot of blood is transferred to the intestine (a kind of "splanchnic blood collection") to facilitate digestion and absorption, the body must increase cardiac output and peripheral vasoconstriction to maintain enough blood pressure to tidy up vital organs, such as the brain.. Postprandial hypotension is believed to be caused by an autonomic nervous system that does not compensate appropriately, due to aging or certain disorders.
Hypotension is a feature of Flammer syndrome characterized by cold hands and feet and predisposes to normal tension glaucoma.
Pathophysiology
Blood pressure is constantly regulated by the autonomic nervous system, using complex tissue receptors, nerves and hormones to balance the effects of the sympathetic nervous system, which tends to increase blood pressure, and the parasympathetic nervous system, which lowers it. The wide and rapid compensatory capabilities of the autonomic nervous system allow normal individuals to maintain acceptable blood pressure for various activities and in many disease states.
Diagnosis
The diagnosis of hypotension is done by first obtaining blood pressure, either non-invasively with sphygmomanometer or invasive with arterial catheters (mostly in intensive care settings). If MAP (Mean Arterial Pressure) is & lt; 65mmHg, this is generally considered hypotension.
For most adults, healthy blood pressure is at or below 120/80 mmHg. A small drop in blood pressure, even as small as 20 mmHg, can cause temporary hypotension.
Evaluation of vasovagal syncope was done by tilt table test.
Treatment
Treatment for hypotension depends on the cause. Chronic hypotension rarely exists as more than symptoms. Untreated hypotension in healthy people usually does not require treatment. Adding electrolytes to the diet can ease symptoms of mild hypotension. The morning caffeine dose can also be effective. In mild cases, where the patient is still responsive, putting the person in a dorsal decubitus position (lying on the back) and raising the legs increases venous return, thus making more blood available for vital organs in the chest and head. Trendelenburg's position, although used historically, is no longer recommended.
Hypotensive shock treatment always follows the following four steps. The results, in terms of death, are directly related to the speed of corrected hypotension. The method is still debated in parentheses, as are benchmarks to evaluate progress in correcting hypotension. A study of septic shock provides an overview of these general principles. However, since it focuses on hypotension due to infection, it does not apply to all forms of severe hypotension.
- Volume resuscitation (usually with crystalloid)
- Support blood pressure with a vasopressor (all appear to be equivalent with respect to the risk of death, with norepinephrine probably better than dopamine). Trying to achieve a mean arterial pressure (MAP) of more than 70 mmHg does not seem to produce better results than trying to reach a MAP greater than 65 mm Hg in adults.
- Ensure adequate tissue perfusion (keep SvO2 & gt; 70 by using blood or dobutamine)
- Address the underlying problem (ie, antibiotics for infection, stents, or CABG (coronary artery transplant surgery) for infarcts, steroids for adrenal insufficiency, etc...)
The best way to determine if a person will benefit from the fluids is by doing passive leg lift followed by measuring the output of the heart.
More
Treatment of medium-term (and less well-planned) hypotension includes:
- Blood sugar control (80-150 by one study)
- Early nutrition (by mouth or tube to prevent ileus)
- Steroid support
Etymology
Hypotension , from Ancient Greek hypo - , which means "under" or "less" English tension , meaning "tension" or "stiffness". This refers to the narrowing of the underlying blood vessels and arteries leading to low blood pressure.
See also
- Dysautonomia
- The hypotensive transfusion reaction
- orthostatic intolerance
References
External links
- Understanding Low Blood Pressure - WebMD Basics
- Hypotension Health PubMed
Source of the article : Wikipedia
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