Hypotension

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Hypotension
Depiction of a hypotension (low blood pressure) patient getting her blood pressure checked Depiction of a hypotension (low blood pressure) patient getting her blood pressure checked.png
Depiction of a hypotension (low blood pressure) patient getting her blood pressure checked
Image showing patient having blood pressure checked. Systolic blood pressure less than 90 mmHg is considered hypotension (low blood pressure)
Specialty Critical care medicine, cardiology
Symptoms Dizziness, clumsiness, giddiness, headache, lightheadedness, fatigue, nausea, blurred vision, shakiness, breathlessness, increased thirst, irregular heartbeat, chest pain, fever, seizures
Complications Fainting, bleeding
Risk factors Older patient, Malnourishment
Diagnostic method Physical examination, based on symptoms
Treatment Intravenous fluid

Hypotension, also known as low blood pressure, is a cardiovascular condition characterized by abnormally reduced blood pressure. [1] Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood [2] and is indicated by two numbers, the systolic blood pressure (the top number) and the diastolic blood pressure (the bottom number), which are the maximum and minimum blood pressures within the cardiac cycle, respectively. [3] A systolic blood pressure of less than 90 millimeters of mercury (mmHg) or diastolic of less than 60 mmHg is generally considered to be hypotension. [4] [5] Different numbers apply to children. [6] However, in practice, blood pressure is considered too low only if noticeable symptoms are present. [7]

Contents

Symptoms may include dizziness, lightheadedness, confusion, feeling tired, weakness, headache, blurred vision, nausea, neck or back pain, an irregular heartbeat or feeling that the heart is skipping beats or fluttering, and fainting. [4] Hypotension is the opposite of hypertension, which is high blood pressure. [2] It is best understood as a physiological state rather than a disease. [2] Severely low blood pressure can deprive the brain and other vital organs of oxygen and nutrients, leading to a life-threatening condition called shock. [3] Shock is classified based on the underlying cause, including hypovolemic shock, cardiogenic shock, distributive shock, and obstructive shock. [8]

Hypotension can be caused by strenuous exercise, excessive heat, low blood volume (hypovolemia), [9] hormonal changes, [10] widening of blood vessels, [11] anemia, [12] vitamin B12 deficiency, [7] [13] anaphylaxis, [7] heart problems, [14] or endocrine problems. [15] Some medications can also lead to hypotension. [16] There are also syndromes that can cause hypotension in patients including orthostatic hypotension, [17] vasovagal syncope, [18] and other rarer conditions. [19] [20]

For many people, excessively low blood pressure can cause dizziness and fainting or indicate serious heart, endocrine or neurological disorders. [17]

For some people who exercise and are in top physical condition, low blood pressure could be normal. [21] [22] A single session of exercise can induce hypotension and water-based exercise can induce a hypotensive response. [23]

Treatment depends on what causes low blood pressure. [4] Treatment of hypotension may include the use of intravenous fluids or vasopressors. [24] When using vasopressors, trying to achieve a mean arterial pressure (MAP) of greater than 70 mmHg does not appear to result in better outcomes than trying to achieve an MAP of greater than 65 mmHg in adults. [25]

Signs and symptoms

For many people, low blood pressure goes unnoticed. [4] For some people, low blood pressure may be a sign of an underlying health condition, especially when it drops suddenly or occurs with symptoms. [5] Older adults also have a higher risk of symptoms of low blood pressure, such as falls, fainting, or dizziness when standing or after a meal. [4] If the blood pressure is sufficiently low, fainting (syncope) may occur. [17]

Low blood pressure is sometimes associated with certain symptoms, many of which are related to causes rather than effects of hypotension: [5]

Causes

Low blood pressure can be caused by low blood volume, [9] hormonal changes, [10] pregnancy, [26] widening of blood vessels, medicine side effects, [11] severe dehydration, [7] anemia, [12] vitamin B12 deficiency, [7] [13] anaphylaxis, [7] heart problems [14] or endocrine problems. [15]

Reduced blood volume, hypovolemia, is the most common cause of hypotension. [27] This can result from hemorrhage; insufficient fluid intake, as in starvation; or excessive fluid losses from diarrhea or vomiting. Hypovolemia can be induced by excessive use of diuretics. [16] Low blood pressure may also be attributed to heat stroke which can be indicated by absence of perspiration, light headedness and dark colored urine. [28]

Other medications can produce hypotension by different mechanisms. Chronic use of alpha blockers or beta blockers can lead to hypotension. [16] Beta blockers can cause hypotension both by slowing the heart rate and by decreasing the pumping ability of the heart muscle. [16]

Decreased cardiac output despite normal blood volume, due to severe congestive heart failure, large myocardial infarction, heart valve problems, or extremely low heart rate (bradycardia), often produces hypotension and can rapidly progress to cardiogenic shock. [14] Arrhythmias often result in hypotension by this mechanism. [14]

Excessive vasodilation, or insufficient constriction of the blood vessels (mostly arterioles), causes hypotension. [29] This can be due to decreased sympathetic nervous system output or to increased parasympathetic activity occurring as a consequence of injury to the brain or spinal cord. [30] Dysautonomia, an intrinsic abnormality in autonomic system functioning, can also lead to hypotension. [30] Excessive vasodilation can also result from sepsis, [29] acidosis, or medications, 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 inhalational agents, produce significant vasodilation. [31]

Lower blood pressure is a side effect of certain herbal medicines, [32] which can also interact with several medications. An example is the theobromine in Theobroma cacao , which lowers blood pressure [33] through its actions as both a vasodilator and a diuretic, [34] and has been used to treat high blood pressure. [35] [36]

Syndromes

Orthostatic hypotension

Orthostatic hypotension, also called postural hypotension, is a common form of low blood pressure. [17] It occurs after a change in body position, typically when a person stands up from either a seated or lying position. [37] It is usually transient and represents a delay in the normal compensatory ability of the autonomic nervous system. [38] It is commonly seen in hypovolemia and as a result of various medications. [17] In addition to blood pressure-lowering medications, many psychiatric medications, in particular antidepressants, can have this side effect. [39] Simple blood pressure and heart rate measurements while lying, seated, and standing (with a two-minute delay in between each position change) can confirm the presence of orthostatic hypotension. [40] Taking these measurements is known as orthostatic vitals. [17] Orthostatic hypotension is indicated if there is a drop of 20 mmHg in systolic pressure (and a 10 mmHg drop in diastolic pressure in some facilities) and a 20 beats per minute increase in heart rate. [40]

Vasovagal syncope

Vasovagal syncope is a form of dysautonomia characterized by an inappropriate drop in blood pressure while in the upright position. [18] Vasovagal syncope occurs as a result of increased activity of the vagus nerve, the mainstay of the parasympathetic nervous system. [18] Patients will feel sudden, unprovoked lightheadedness, sweating, changes in vision, and finally a loss of consciousness. [18] Consciousness will often return rapidly once patient is lying down and the blood pressure returns to normal. [41]

Other

Another, but rarer form, is postprandial hypotension, a drastic decline in blood pressure that occurs 30 to 75 minutes after eating substantial meals. [19] When a great deal of blood is diverted to the intestines (a kind of "splanchnic blood pooling") to facilitate digestion and absorption, the body must increase cardiac output and peripheral vasoconstriction to maintain enough blood pressure to perfuse vital organs, such as the brain. [42] Postprandial hypotension is believed to be caused by the autonomic nervous system not compensating appropriately, because of aging or a specific disorder. [42]

Hypotension is a feature of Flammer syndrome, which is characterized by cold hands and feet and predisposes to normal tension glaucoma. [20]

Hypotension can be a symptom of relative energy deficiency in sport, sometimes known as the female athlete triad, although it can also affect men. [43]

Pathophysiology

Blood pressure is continuously regulated by the autonomic nervous system, using an elaborate network of receptors, nerves, and hormones to balance the effects of the sympathetic nervous system, which tends to raise blood pressure, and the parasympathetic nervous system, which lowers it. [2] The vast and rapid compensation abilities of the autonomic nervous system allow normal individuals to maintain an acceptable blood pressure over a wide range of activities and in many disease states. [2] Even small alterations in these networks can lead to hypotension. [9]

Diagnosis

Hypotension thresholds (mmHg) [44]
Office Ambulatory
DaytimeNighttime24 hours
<110/70<105/65<90/50<100/60

For most adults, the optimal blood pressure is at or below 120/80 mmHg. [45] If the systolic blood pressure is <90 mmHg or the diastolic blood pressure is <60 mmHg, it would be classified as hypotension. [5] However, occasional blood pressure readings below 90/60 mmHg are not infrequent in the general population, [46] and, in the absence of some pathological cause, hypotension appears to be a relatively benign condition in most people. [46] The diagnosis of hypotension is usually made by measuring blood pressure, either non-invasively with a sphygmomanometer or invasively with an arterial catheter (mostly in an intensive care setting). Another way to diagnose low blood pressure is by using the mean arterial pressure (MAP) measured using an arterial catheter [47] or by continuous, non-invasive hemodynamic monitoring which measures intra-operative blood pressure beat-by-beat throughout surgery. A MAP <65 mmHg is considered hypotension. [47] Intra-operative hypotension <65 mmHg can lead to an increased risk of acute kidney injury, [48] myocardial injury [48] or post-operative stroke. [49] While an incidental finding of hypotension during a routine blood pressure measurement may not be particularly worrying, a substantial drop in blood pressure following standing, exercise or eating can be associated with symptoms and may have implications for future health. [45] A drop in blood pressure after standing, termed postural or orthostatic hypotension, is defined as a decrease in supine-to-standing BP >20 mm Hg systolic or >10 mm Hg diastolic within 3 minutes of standing. [50] [45] Orthostatic hypotension is associated with increased risk of future cardiovascular events and mortality. Orthostatic vitals are frequently measured to assist with the diagnosis of orthostatic hypotension, [40] and may involve the use of a tilt table test to evaluate vasovagal syncope. [41]

Treatment

Treatment depends on what causes low blood pressure. [4] Treatment may not be needed for asymptomatic low blood pressure. [51] Depending on symptoms, treatment may include drinking more fluids to prevent dehydration, taking medicines to raise blood pressure, or adjusting medicines that cause low blood pressure. [4] Adding electrolytes to a diet can relieve symptoms of mild hypotension, and a morning dose of caffeine can also be effective. [52] Chronic hypotension rarely exists as more than a symptom. In mild cases, where the patient is still responsive, laying the person on their back and lifting the legs increases venous return, thus making more blood available to critical organs in the chest and head. [52] The Trendelenburg position, though used historically, is no longer recommended. [53]

Hypotensive shock treatment always follows the first four following steps. Outcomes, in terms of mortality, are directly linked to the speed that hypotension is corrected. [9] Still-debated methods are in parentheses, as are benchmarks for evaluating progress in correcting hypotension. A study on septic shock provided the delineation of these general principles. [54] However, since it focuses on hypotension due to infection, it is not applicable to all forms of severe hypotension.

  1. Volume resuscitation (usually with crystalloid or blood products) [9]
  2. Blood pressure support with a vasopressor (all seem equivalent with respect to risk of death, with norepinephrine possibly better than dopamine). [55] Trying to achieve a mean arterial pressure (MAP) of greater than 70 mmHg does not appear to result in better outcomes than trying to achieve a MAP of greater than 65 mmHg in adults. [25]
  3. Ensure adequate tissue perfusion (maintain SvO2 >70 with use of blood or dobutamine) [9]
  4. Address the underlying problem (i.e., antibiotic for infection, stent or CABG (coronary artery bypass graft surgery) for infarction, steroids for adrenal insufficiency, etc...) [9]

The best way to determine if a person will benefit from fluids is by doing a passive leg raise followed by measuring the output from the heart. [56]

Medication

Chronic hypotension sometimes requires the use of medications. [57] Some medications that are commonly used include Fludrocortisone, Erythropoietin, and Sympathomimetics such as Midodrine and Noradrenaline and precursor (L-DOPS). [17]

Pediatrics

The definition of hypotension changes in the pediatric population depending on the child's age as seen in the table below.

Pediatric Hypotension [58]
AgeSystolic Pressure
Term Neonates<60 mmHg
Infants<70 mmHg
Children 1–10 years<70 + (age in years x 2) mmHg
Children >10 years<90 mmHg

The clinical history provided by the caretaker is the most important part in determining the cause of hypotension in pediatric patients. [59] Symptoms for children with hypotension include increased sleepiness, not using the restroom as much (or at all), having difficulty breathing or breathing rapidly, or syncope. [59] The treatment for hypotension in pediatric patients is similar to the treatment in adults by following the four first steps listed above (see Treatment). [9] Children are more likely to undergo intubation during the treatment of hypotension because their oxygen levels drop more rapidly than adults. [59] The closing of fetal shunts following birth can create instability in the "transitional circulation" of the fetus, and often creates a state of hypotension following birth; while many infants can overcome this hypotension through the closing of shunts, a mean blood pressure (MBP) of lower than 30 mmHg is correlated with severe cerebral injury and can be experienced by premature infants who have poor shunt closure. [60]

Etymology

Hypotension, from Ancient Greek hypo-, meaning "under" or "less" + English tension, meaning "'strain" or "tightness". [61] This refers to the under-constriction of the blood vessels and arteries which leads to low blood pressure. [62]

See also

Related Research Articles

<span class="mw-page-title-main">Blood pressure</span> Pressure exerted by circulating blood upon the walls of arteries

Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" refers to the pressure in a brachial artery, where it is most commonly measured. Blood pressure is usually expressed in terms of the systolic pressure over diastolic pressure in the cardiac cycle. It is measured in millimeters of mercury (mmHg) above the surrounding atmospheric pressure, or in kilopascals (kPa). The difference between the systolic and diastolic pressures is known as pulse pressure, while the average pressure during a cardiac cycle is known as mean arterial pressure.

<span class="mw-page-title-main">Hypertension</span> Long-term high blood pressure in the arteries

Hypertension, also known as high blood pressure, is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms itself. It is, however, a major risk factor for stroke, coronary artery disease, heart failure, atrial fibrillation, peripheral arterial disease, vision loss, chronic kidney disease, and dementia. Hypertension is a major cause of premature death worldwide.

Orthostatic hypotension, also known as postural hypotension, is a medical condition wherein a person's blood pressure drops when they are standing up (orthostasis) or sitting down. Primary orthostatic hypotension is also often referred to as neurogenic orthostatic hypotension. The drop in blood pressure may be sudden, within 3 minutes or gradual. It is defined as a fall in systolic blood pressure of at least 20 mmHg or diastolic blood pressure of at least 10 mmHg after 3 minutes of standing. It occurs predominantly by delayed constriction of the lower body blood vessels, which is normally required to maintain adequate blood pressure when changing the position to standing. As a result, blood pools in the blood vessels of the legs for a longer period, and less is returned to the heart, thereby leading to a reduced cardiac output and inadequate blood flow to the brain.

<span class="mw-page-title-main">Atenolol</span> Beta blocker medication

Atenolol is a beta blocker medication primarily used to treat high blood pressure and heart-associated chest pain. Although used to treat high blood pressure, it does not seem to improve mortality in those with the condition. Other uses include the prevention of migraines and treatment of certain irregular heart beats. It is taken orally or by intravenous injection. It can also be used with other blood pressure medications.

<span class="mw-page-title-main">Reflex syncope</span> Brief loss of consciousness due to a neurologically induced drop in blood pressure

Reflex syncope is a brief loss of consciousness due to a neurologically induced drop in blood pressure and/or a decrease in heart rate. Before an affected person passes out, there may be sweating, a decreased ability to see, or ringing in the ears. Occasionally, the person may twitch while unconscious. Complications of reflex syncope include injury due to a fall.

<span class="mw-page-title-main">Mean arterial pressure</span> Average blood pressure in an individual during a single cardiac cycle

In medicine, the mean arterial pressure (MAP) is an average calculated blood pressure in an individual during a single cardiac cycle. Although methods of estimating MAP vary, a common calculation is to take one-third of the pulse pressure, and add that amount to the diastolic pressure. A normal MAP is about 90 mmHg.

<span class="mw-page-title-main">Carotid sinus</span> Dilated area near internal carotid artery above bifurcation

In human anatomy, the carotid sinus is a dilated area at the base of the internal carotid artery just superior to the bifurcation of the internal carotid and external carotid at the level of the superior border of thyroid cartilage. The carotid sinus extends from the bifurcation to the "true" internal carotid artery. The carotid sinus is sensitive to pressure changes in the arterial blood at this level. It is the major baroreception site in humans and most mammals.

Orthostatic intolerance (OI) is the development of symptoms when standing upright that are relieved when reclining. There are many types of orthostatic intolerance. OI can be a subcategory of dysautonomia, a disorder of the autonomic nervous system occurring when an individual stands up. Some animal species with orthostatic hypotension have evolved to cope with orthostatic disturbances.

<span class="mw-page-title-main">Postural orthostatic tachycardia syndrome</span> Abnormally high heart rate after a postural change

Postural orthostatic tachycardia syndrome (POTS) is a condition characterized by an abnormally large increase in heart rate upon sitting up or standing. POTS is a disorder of the autonomic nervous system that can lead to a variety of symptoms, including lightheadedness, brain fog, blurred vision, weakness, fatigue, headaches, heart palpitations, exercise intolerance, nausea, diminished concentration, tremulousness (shaking), syncope (fainting), coldness or pain in the extremities, numbness or tingling in the extremities, chest pain, and shortness of breath. Other conditions associated with POTS include myalgic encephalomyelitis/chronic fatigue syndrome, migraine headaches, Ehlers–Danlos syndrome, asthma, autoimmune disease, vasovagal syncope, and mast cell activation syndrome. POTS symptoms may be treated with lifestyle changes such as increasing fluid, electrolyte, and salt intake, wearing compression stockings, gentle and slow postural changes, avoiding prolonged bedrest, medication, and physical therapy.

<span class="mw-page-title-main">Tilt table test</span> Medical procedure often used to diagnose dysautonomia or syncope

A tilt table test (TTT), occasionally called upright tilt testing (UTT), is a medical procedure often used to diagnose dysautonomia or syncope. Patients with symptoms of dizziness or lightheadedness, with or without a loss of consciousness (fainting), suspected to be associated with a drop in blood pressure or positional tachycardia are good candidates for this test.

Alpha-1 blockers constitute a variety of drugs that block the effect of catecholamines on alpha-1-adrenergic receptors. They are mainly used to treat benign prostatic hyperplasia (BPH), hypertension and post-traumatic stress disorder. Alpha-1-adrenergic receptors are present in vascular smooth muscle, the central nervous system, and other tissues. When alpha blockers bind to these receptors in vascular smooth muscle, they cause vasodilation.

<span class="mw-page-title-main">Hypertensive emergency</span> Very high blood pressure and signs of organ damage

A hypertensive emergency is very high blood pressure with potentially life-threatening symptoms and signs of acute damage to one or more organ systems. It is different from a hypertensive urgency by this additional evidence for impending irreversible hypertension-mediated organ damage (HMOD). Blood pressure is often above 200/120 mmHg, however there are no universally accepted cutoff values.

<span class="mw-page-title-main">Pure autonomic failure</span> Medical condition

Pure autonomic failure (PAF) is an uncommon, sporadic neurodegenerative condition marked by a steadily declining autonomic regulation. Bradbury and Eggleston originally described pure autonomic failure in 1925.

Hypertensive encephalopathy (HE) is general brain dysfunction due to significantly high blood pressure. Symptoms may include headache, vomiting, trouble with balance, and confusion. Onset is generally sudden. Complications can include seizures, posterior reversible encephalopathy syndrome, and bleeding in the back of the eye.

The Bezold–Jarisch reflex involves a variety of cardiovascular and neurological processes which cause hypopnea, hypotension and bradycardia in response to noxious stimuli detected in the cardiac ventricles. The reflex is named after Albert von Bezold and Adolf Jarisch Junior. The significance of the discovery is that it was the first recognition of a chemical (non-mechanical) reflex.

<span class="mw-page-title-main">Syncope (medicine)</span> Transient loss of consciousness and postural tone

Syncope, commonly known as fainting or passing out, is a loss of consciousness and muscle strength characterized by a fast onset, short duration, and spontaneous recovery. It is caused by a decrease in blood flow to the brain, typically from low blood pressure. There are sometimes symptoms before the loss of consciousness such as lightheadedness, sweating, pale skin, blurred vision, nausea, vomiting, or feeling warm. Syncope may also be associated with a short episode of muscle twitching. Psychiatric causes can also be determined when a patient experiences fear, anxiety, or panic; particularly before a stressful event, usually medical in nature. When consciousness and muscle strength are not completely lost, it is called presyncope. It is recommended that presyncope be treated the same as syncope.

<span class="mw-page-title-main">Dopamine beta hydroxylase deficiency</span> Medical condition

Dopamine beta (β)-hydroxylase deficiency is a human medical condition involving inadequate dopamine beta-hydroxylase. It is characterized by increased amounts of serum dopamine and the absence of norepinephrine (NE) and epinephrine.

Orthostatic syncope refers to syncope resulting from a postural decrease in blood pressure, termed orthostatic hypotension.

<span class="mw-page-title-main">Orthostatic hypertension</span> Medical condition

Orthostatic hypertension is a medical condition consisting of a sudden and abrupt increase in blood pressure (BP) when a person stands up. Orthostatic hypertension is diagnosed by a rise in systolic BP of 20 mmHg or more when standing. Orthostatic diastolic hypertension is a condition in which the diastolic BP raises to 98 mmHg or over in response to standing, but this definition currently lacks clear medical consensus, so is subject to change. Orthostatic hypertension involving the systolic BP is known as systolic orthostatic hypertension.

The Systolic Blood Pressure Intervention Trial (SPRINT) is a multi-center clinical trial that was performed from 2010 to 2015, and published in November 2015.

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