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Hypotension is low blood pressure.
Blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motio ...

Blood pressure
is the force of blood pushing against the walls of the arteries as the heart pumps out blood. Blood pressure is indicated by two numbers, the
systolic to supply all body systems; 2) oxygen-depleted blood (blue arrow) in the right ventricle begins pulsing through the pulmonic (pulmonary) valve en route to the lungs for reoxygenation. depolarization is the start-point of the atrial stage of syst ...
blood pressure (the top number) and the
diastolic Image:Heart diastole.png, upright=1.5, Heart performance during ventricular diastole: early diastole is a suction mechanism that draws blood 'down' from the left atrium (pink) and right atrium (blue) into each of the two ventricles. Then, in late ve ...
blood pressure (the bottom number), which are the maximum and minimum blood pressures, respectively. A
systolic to supply all body systems; 2) oxygen-depleted blood (blue arrow) in the right ventricle begins pulsing through the pulmonic (pulmonary) valve en route to the lungs for reoxygenation. depolarization is the start-point of the atrial stage of syst ...
blood pressure of less than 90 millimeters of mercury (mm Hg) or
diastolic Image:Heart diastole.png, upright=1.5, Heart performance during ventricular diastole: early diastole is a suction mechanism that draws blood 'down' from the left atrium (pink) and right atrium (blue) into each of the two ventricles. Then, in late ve ...
of less than 60 mm Hg is generally considered to be hypotension. Different numbers apply to children. However, in practice, blood pressure is considered too low only if noticeable symptoms are present. Hypotension is the opposite of
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a Chronic condition, long-term Disease, medical condition in which the blood pressure in the artery, arteries is persistently elevated. High blood pressure usually does not ...

hypertension
, which is high blood pressure. It is best understood as a physiological state rather than a disease. Severely low blood pressure can deprive the brain and other vital organs of oxygen and nutrients, leading to a life-threatening condition called shock. Shock is classified based on the underlying cause, including
hypovolemic shock Hypovolemic shock is a medical emergency and an advanced form of hypovolemia due to insufficient amounts of blood and/or fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shea ...
,
cardiogenic shock Cardiogenic shock (CS) is a medical emergency resulting from inadequate blood flow due to the dysfunction of the ventricles of the heart.Textbooks of Internal MedicinHarrison's Principles of Internal Medicine 16th Edition, The McGraw-Hill McG ...
,
distributive shock Distributive shock is a medical Medicine is the art, science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes knowledge in the form ...
, and obstructive shock. Hypotension can be caused by excessive
exercise Exercise is any bodily activity that enhances or maintains physical fitness Physical fitness is a state of health Health is a state of physical, mental and social well-being Well-being, also known as ''wellness'', ''prudential value ...

exercise
, excessive heat, low
blood volume Blood volume is the volume Volume is a scalar quantity expressing the amount Quantity or amount is a property that can exist as a multitude Multitude is a term for a group of people who cannot be classed under any other distinct category, ex ...
(
hypovolemia Hypovolemia, also known as volume depletion or volume contraction, is a state of abnormally low extracellular fluid in the body. This may be due to either a loss of both salt and water or a decrease in blood volume. Hypovolemia refers to the loss ...
), hormonal changes, ,
anemia Anemia (American and British English spelling differences#ae and oe, also spelled anaemia) is a decrease in the total amount of red blood cells (RBCs) or hemoglobin in the blood, or a lowered ability of the blood to carry oxygen. When anemia c ...

anemia
, a lack of vitamin B12 and
folic acid Folate, also known as vitamin B9 and folacin, is one of the B vitamins B vitamins are a class of water-soluble vitamin A vitamin is an organic molecule , CH4; is among the simplest organic compounds. In chemistry, organic compounds ar ...
,
anaphylaxis Anaphylaxis is a serious allergic reaction Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity Hypersensitivity (also called hypersensitivity reaction or intolerance) refers to undesirable rea ...
,
heart The heart is a muscular MUSCULAR (DS-200B), located in the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use ...

heart
problems, or
endocrine The endocrine system is a messenger system comprising feedback loops of the hormone A hormone (from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Re ...

endocrine
problems. Some medications can also lead to hypotension. There are also syndromes that can cause hypotension in patients including
orthostatic hypotension Orthostatic hypotension, also known as postural hypotension, is a medical condition wherein a person's blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics (fr ...
,
vasovagal syncope 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 ...
, and other rarer conditions. For many people, excessively low blood pressure can cause dizziness and fainting or indicate serious heart, endocrine or
neurological disorders A neurological disorder is any disorder of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular ...
. For some people who exercise and are in top physical condition, low blood pressure could be normal. A single session of exercise can induce hypotension and water-based exercise can induce a hypotensive response. Treatment of hypotension may include the use of
intravenous fluids Intravenous therapy (abbreviated as IV therapy) is a medical technique that delivers fluids, medications and nutrition directly into a person's vein Veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood f ...
or
vasopressors An antihypotensive agent, also known as a vasopressor agent or simply vasopressor, or pressor, is any medication that tends to raise low blood pressure Hypotension is low blood pressure. Blood pressure is the force of blood pushing against the w ...
. When using vasopressors, trying to achieve a
mean arterial pressure In medicine, the mean arterial pressure (MAP) is an average blood pressure in an individual during a single cardiac cycle. Calculation The Systemic Vascular Resistance (SVR), denoted R is represented mathematically by the formula :R = \Delta P/ ...

mean arterial pressure
(MAP) of greater than 70 mm Hg does not appear to result in better outcomes than trying to achieve a MAP of greater than 65 mm Hg in adults.


Signs and symptoms

The primary symptoms of hypotension are
lightheadedness Lightheadedness is a common and typically unpleasant sensation of dizziness Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-speci ...
or
dizziness Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling such as giddiness or foolishness. Dizziness is a common medical c ...

dizziness
. If the blood pressure is sufficiently low, fainting (
syncope Syncope may refer to: * Syncope (medicine), also known as fainting * Syncope (phonology), the loss of one or more sounds, particularly an unstressed vowel, from the interior of a word * Syncopation, a musical effect caused by off-beat or otherwise ...
) may occur. Low blood pressure is sometimes associated with certain symptoms, many of which are related to causes rather than effects of hypotension: *
chest pain Chest pain is pain or discomfort in the chest, typically the front of the chest. It may be described as sharp, dull, pressure, heaviness or squeezing. Associated symptoms may include pain in the shoulder, arm, upper abdomen, or jaw, along with na ...
*
shortness of breath Shortness of breath (SOB), also known as dyspnea (BrE British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial codificat ...
*
irregular heartbeat Arrhythmia, also known as cardiac arrhythmia or heart arrhythmia, is a group of conditions in which the heartbeat is irregular, too fast, or too slow. The heart rateHeart rate is the speed of the heartbeat measured by the number of contraction ...
*
fever Fever, also referred to as pyrexia, is defined as having a temperature Temperature ( ) is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy Thermal radiation in visible light can be seen on th ...

fever
higher than 38.3 °C (101 °F) *
headache Headache is the symptom of pain Pain is a distressing feeling often caused by intense or damaging stimuli. The defines pain as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or ...

headache
* stiff neck * severe upper back pain *
cough A cough is a sudden expulsion of air through the large breathing passages that can help clear them of fluids, irritants, foreign particles and microbes A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, ...
with
sputum Sputum is mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body and covers the surface of internal organs. It consists o ...
* prolonged
diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery defecation, bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration of ...
or
vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach The stomach is a muscular, Organ (anatomy), hollow organ in the gastrointestinal tract of humans and many other anim ...

vomiting
* shakiness (shivering) * loss of appetite *
dyspepsia Indigestion, also known as dyspepsia or upset stomach, is a condition of "impaired digestion". Symptoms may include upper abdominal fullness, heartburn, nausea Nausea is a diffuse sensation of unease and discomfort, often perceived as an ur ...
(indigestion) *
dysuria Dysuria refers to painful or urination Urination is the release of urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination r ...
(painful urination) * acute, life-threatening
allergic reaction Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity Hypersensitivity (also called hypersensitivity reaction or intolerance) refers to undesirable reactions produced by the normal immune system, i ...
*
seizures An epileptic seizure, formally known as a seizure, is a period of symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower tem ...
*
loss of consciousness Unconsciousness is a state which occurs when the ability to maintain an awareness of self and environment is lost. It involves a complete, or near-complete, lack of responsiveness to people and other environmental stimulus A stimulus is somethin ...
* profound
fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...
* temporary blurring or loss of vision * black tarry stools


Causes

Low blood pressure can be caused by low
blood volume Blood volume is the volume Volume is a scalar quantity expressing the amount Quantity or amount is a property that can exist as a multitude Multitude is a term for a group of people who cannot be classed under any other distinct category, ex ...
, hormonal changes, , medicine
side effects In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequences ...
, severe
dehydration In physiology, dehydration is a lack of total body water In physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the natural science that studie ...

dehydration
,
anemia Anemia (American and British English spelling differences#ae and oe, also spelled anaemia) is a decrease in the total amount of red blood cells (RBCs) or hemoglobin in the blood, or a lowered ability of the blood to carry oxygen. When anemia c ...

anemia
, vitamin b12 and
folic acid Folate, also known as vitamin B9 and folacin, is one of the B vitamins B vitamins are a class of water-soluble vitamin A vitamin is an organic molecule , CH4; is among the simplest organic compounds. In chemistry, organic compounds ar ...
deficiencies,
anaphylaxis Anaphylaxis is a serious allergic reaction Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity Hypersensitivity (also called hypersensitivity reaction or intolerance) refers to undesirable rea ...
, heart problems or endocrine problems. Reduced blood volume,
hypovolemia Hypovolemia, also known as volume depletion or volume contraction, is a state of abnormally low extracellular fluid in the body. This may be due to either a loss of both salt and water or a decrease in blood volume. Hypovolemia refers to the loss ...
, is the most common cause of hypotension. This can result from
hemorrhage Bleeding, also known as a hemorrhage, haemorrhage, or simply blood loss, is blood Blood is a body fluid in humans and other animals that delivers necessary substances such as nutrient A nutrient is a substance used by an organism to survi ...
; insufficient fluid intake, as in starvation; or excessive fluid losses from diarrhea or vomiting. Hypovolemia can be induced by excessive use of
diuretic A diuretic () is any substance that promotes diuresis Diuresis () is increased urination Urination is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretio ...
s. Low blood pressure may also be attributed to heat stroke which can be indicated by absence of perspiration, light headedness and dark colored urine. Other medications can produce hypotension by different mechanisms. Chronic use of
alpha blocker Alpha-blockers, also known as α-blockers or α-adrenoreceptor antagonists, are a class of pharmacological agents that act as antagonist An antagonist is a character in a story who is presented as the chief foe of the protagonist. Etymology ...
s or
beta blocker Beta blockers (beta-blockers, β-blockers, etc.) are a class of medications that are predominantly used to manage abnormal heart rhythms, and to protect the heart from a second heart attack (myocardial infarction A myocardial infarction (M ...
s can lead to hypotension. Beta blockers can cause hypotension both by slowing the heart rate and by decreasing the pumping ability of the heart muscle. Decreased
cardiac output Cardiac output (CO), also known as heart output denoted by the symbols Q, or \dot Q_ , is a term used in cardiac physiologyCardiac physiology or heart function is the study of healthy, unimpaired function of the heart: involving blood flow; Ca ...
despite normal blood volume, due to severe
congestive heart failure Heart failure (HF), also known as congestive heart failure (CHF) and (congestive) cardiac failure (CCF), is a set of manifestations caused by the failure of the heart The heart is a cardiac muscle, muscular Organ (biology), organ in mos ...
, large
myocardial infarction A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow Hemodynamics American and British English spelling differences#ae and oe, or haemodynamics are the Fluid dynamics, dynamics of blood flow. The circulatory sy ...

myocardial infarction
,
heart valve A heart valve is a one-way valve check valve Image:Check Valve.svg, 140px, Check valve symbol on piping and instrumentation diagrams. The arrow shows the flow direction. A check valve, non-return valve, reflux valve, retention valve, foot valv ...
problems, or extremely low heart rate (
bradycardia Bradycardia is a condition typically defined wherein an individual has a resting heart rateHeart rate is the speed of the heartbeat measured by the number of contractions (beats) of the heart The heart is a muscle, muscular Organ (anatom ...
), often produces hypotension and can rapidly progress to
cardiogenic shock Cardiogenic shock (CS) is a medical emergency resulting from inadequate blood flow due to the dysfunction of the ventricles of the heart.Textbooks of Internal MedicinHarrison's Principles of Internal Medicine 16th Edition, The McGraw-Hill McG ...
.
Arrhythmia Arrhythmia, also known as cardiac arrhythmia or heart arrhythmia, is a group of conditions in which the is irregular, too fast, or too slow. The that is too fast – above 100 beats per minute in adults – is called , and a heart rate that i ...
s often result in hypotension by this mechanism. Excessive
vasodilation Vasodilation is the widening of blood vessel The blood vessels are the components of the circulatory system The circulatory system, also called the cardiovascular system or the vascular system, is an organ system An organ system is ...

vasodilation
, or insufficient constriction of the blood vessels (mostly
arterioles An arteriole is a small-diameter blood vessel The blood vessels are the components of the circulatory system The circulatory system, also called the cardiovascular system or the vascular system, is an organ system that permits blood to c ...
), causes hypotension. This can be due to decreased
sympathetic nervous system The sympathetic nervous system (SNS) is one of two divisions of the autonomic nervous system The autonomic nervous system (ANS), formerly the vegetative nervous system, is a division of the peripheral nervous system that supplies smooth muscle ...
output or to increased
parasympathetic The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of t ...
activity occurring as a consequence of injury to the brain or spinal cord.
Dysautonomia Dysautonomia or autonomic dysfunction is a condition in which the autonomic nervous system The autonomic nervous system (ANS), formerly the vegetative nervous system, is a division of the peripheral nervous system that supplies smooth muscle an ...
, an intrinsic abnormality in autonomic system functioning, can also lead to hypotension. Excessive vasodilation can also result from
sepsis Sepsis is a life-threatening condition that arises when the body's response to infection An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction ...
,
acidosis Acidosis is a process causing increased acidity An acid is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is ...

acidosis
, or medications, such as nitrate preparations,
calcium channel blockers Calcium is a chemical element with the Symbol (chemistry), symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties a ...
, or AT1 receptor antagonists ( Angiotensin II acts on AT1 receptors). Many anesthetic agents and techniques, including
spinal anesthesia Spinal anaesthesia (or spinal anesthesia), also called spinal block, subarachnoid block, intradural block and intrathecal block, is a form of neuraxial regional anaesthesia involving the injection of a local anaesthetic or opioid into the subar ...
and most inhalational agents, produce significant
vasodilation Vasodilation is the widening of blood vessel The blood vessels are the components of the circulatory system The circulatory system, also called the cardiovascular system or the vascular system, is an organ system An organ system is ...

vasodilation
.
Meditation Meditation is a practice where an individual uses a technique – such as mindfulness Mindfulness is the practice of purposely bringing one's attention in the present moment without evaluation,Mindfulness Training as a Clinical Interventio ...

Meditation
,
yoga Yoga (; sa, योग, lit=yoke' or 'union ) is a group of Asana, physical, mind, mental, and Spirituality#Asian traditions, spiritual practices or disciplines that originated in History of India, ancient India, aimed at controlling ('y ...

yoga
, or other mental-physiological disciplines may produce hypotensive effects. Lower blood pressure is a side effect of certain herbal medicines, which can also interact with several medications. An example is the
theobromine Theobromine, also known as xantheose, is a bitter alkaloid Alkaloids are a class of base (chemistry), basic, natural product, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some relat ...

theobromine
in ''
Theobroma cacao ''Theobroma cacao'', also called the cacao tree and the cocoa tree, is a small ( tall) evergreen In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scie ...

Theobroma cacao
'', which lowers blood pressure through its actions as both a
vasodilator Vasodilation is the widening of blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. ...
and a
diuretic A diuretic () is any substance that promotes diuresis Diuresis () is increased urination Urination is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretio ...
, and has been used to treat high blood pressure.


Syndromes


Orthostatic hypotension

Orthostatic hypotension Orthostatic hypotension, also known as postural hypotension, is a medical condition wherein a person's blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics (fr ...
, also called ''postural hypotension'', is a common form of low blood pressure. It occurs after a change in body position, typically when a person stands up from either a seated or lying position. It is usually transient and represents a delay in the normal compensatory ability of the autonomic nervous system. It is commonly seen in
hypovolemia Hypovolemia, also known as volume depletion or volume contraction, is a state of abnormally low extracellular fluid in the body. This may be due to either a loss of both salt and water or a decrease in blood volume. Hypovolemia refers to the loss ...
and as a result of various medications. In addition to blood pressure-lowering medications, many psychiatric medications, in particular
antidepressant Antidepressants are medications used to treat major depressive disorder, some anxiety disorders, some chronic pain conditions, and to help manage some addictions. Common Side effect, side-effects of antidepressants include Xerostomia, dry mouth, ...
s, can have this side effect. 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. Taking these measurements is known as orthostatic vitals. 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.


Vasovagal syncope

Vasovagal syncope 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 ...
is a form of
dysautonomia Dysautonomia or autonomic dysfunction is a condition in which the autonomic nervous system The autonomic nervous system (ANS), formerly the vegetative nervous system, is a division of the peripheral nervous system that supplies smooth muscle an ...
characterized by an inappropriate drop in blood pressure while in the upright position. Vasovagal syncope occurs as a result of increased activity of the
vagus nerve The vagus nerve, historically cited as the pneumogastric nerve, is the tenth cranial nerve Cranial nerves are the nerve A nerve is an enclosed, cable-like bundle of nerve fibers called axon An axon (from Greek ἄξων ''áxōn'', axi ...
, the mainstay of the
parasympathetic nervous system The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system The autonomic nervous system (ANS), formerly the vegetative nervous system, is a division of the peripheral nervous system that supplies s ...
. Patients will feel sudden, unprovoked lightheadedness, sweating, changes in vision, and finally a loss of consciousness. Consciousness will often return rapidly once patient is lying down and the blood pressure returns to normal.


Other

Another, but rarer form, is
postprandial Prandial relates to a meal. Postprandial (from post prandium) means after eating a meal, while preprandial is before a meal. Usages of postprandial The term ''postprandial'' is used in many contexts. Gastronomic or social Refers to activities ...
hypotension, a drastic decline in blood pressure that occurs 30 to 75 minutes after eating substantial meals.Merck Manual Home Edition
"Postprandial Hypotension."
Last accessed October 26, 2011.
When a great deal of blood is diverted to the
intestines The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system The human digestive system consists of the gastrointestinal tract The gastrointestinal tract, (GI tract, GIT, d ...
(a kind of "
splanchnic Splanchnic is usually used to describe organs in the abdomen, abdominal cavity. It is used when describing: * Splanchnic tissue * Splanchnic organs - including the stomach, small intestine, large intestine, pancreas, spleen, liver, and may also i ...
blood pooling") to facilitate
digestion Digestion is the breakdown of large insoluble food Food is any substance consumed to provide Nutrient, nutritional support for an organism. Food is usually of plant, animal or Fungus, fungal origin, and contains essential nutrients, such a ...
and
absorption Absorption may refer to: Chemistry and biology *Absorption (chemistry), diffusion of particles of gas or liquid into liquid or solid materials *Absorption (skin), a route by which substances enter the body through the skin *Absorption (pharmacolo ...
, the body must increase
cardiac output Cardiac output (CO), also known as heart output denoted by the symbols Q, or \dot Q_ , is a term used in cardiac physiologyCardiac physiology or heart function is the study of healthy, unimpaired function of the heart: involving blood flow; Ca ...
and peripheral
vasoconstriction Vasoconstriction is the narrowing of the blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of th ...

vasoconstriction
to maintain enough blood pressure to perfuse vital organs, such as the brain. Postprandial hypotension is believed to be caused by the autonomic nervous system not compensating appropriately, because of aging or a specific disorder. Hypotension is a feature of Flammer syndrome, which is characterized by cold hands and feet and predisposes to normal tension
glaucoma Glaucoma is a group of eye diseases which result in damage to the optic nerve The optic nerve, also known as cranial nerve II, or simply as CN II, is a paired cranial nerve Cranial nerves are the nerve A nerve is an enclosed, cable-l ...

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


Pathophysiology

Blood pressure is continuously regulated by the
autonomic nervous system The autonomic nervous system (ANS), formerly the vegetative nervous system, is a division of the peripheral nervous system that supplies smooth muscle and glands, and thus influences the function of viscera, internal organs. The autonomic nervous ...

autonomic nervous system
, using an elaborate network of
receptors Receptor may refer to: *Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a ne ...
,
nerve A nerve is an enclosed, cable-like bundle of fibers (called axon An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences Despite the various English dialects Dialect The term diale ...

nerve
s, and
hormone A hormone (from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appr ...

hormone
s to balance the effects of the
sympathetic nervous system The sympathetic nervous system (SNS) is one of two divisions of the autonomic nervous system The autonomic nervous system (ANS), formerly the vegetative nervous system, is a division of the peripheral nervous system that supplies smooth muscle ...
, which tends to raise blood pressure, and the
parasympathetic nervous system The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system The autonomic nervous system (ANS), formerly the vegetative nervous system, is a division of the peripheral nervous system that supplies s ...
, which lowers it. 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. Even small alterations in these networks can lead to hypotension.


Diagnosis

The diagnosis of hypotension is made by first obtaining a blood pressure, either non-invasively with a
sphygmomanometer A sphygmomanometer ( ), also known as a blood pressure monitor, or blood pressure gauge, is a device used to measure blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics ...

sphygmomanometer
or invasively with an
arterial catheter An arterial line (also art-line or a-line) is a thin catheter inserted into an artery An artery (plural arteries) () is a blood vessel that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most ar ...
(mostly in an intensive care setting). If the systolic blood pressure is <90mmHg or the diastolic blood pressure is <60mmHg, it would be classified as hypotension. Another way to measure low blood pressure is the MAP (
Mean Arterial Pressure In medicine, the mean arterial pressure (MAP) is an average blood pressure in an individual during a single cardiac cycle. Calculation The Systemic Vascular Resistance (SVR), denoted R is represented mathematically by the formula :R = \Delta P/ ...

Mean Arterial Pressure
) using the arterial catheter or continuous, non-invasive hemodynamic monitoring which measures intra-operative blood pressure beat-by-beat throughout surgery. A MAP <65mmHg is considered hypotension. Intra-operative hypotension <65 mmHg can lead to an increased risk of acute kidney injury,Walsh, M., Devereaux, P. et al. Relationship between Intraoperative Mean Arterial Pressure and Clinical Outcomes a er Noncardiac Surgery. Anaesthesiology. 2013;119:507-515. myocardial injury or post-operative stroke. For most adults, the ideal
blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics, a force is an influence that can change the motion (physics), motion of an Physical object, object. A force can cause an object with mas ...

blood pressure
is at or below 120/80 mmHg. A small drop in blood pressure, even as little as 20 mmHg, can result in transient hypotension. Orthostatic vitals are measured to diagnose orthostatic hypotension. Evaluation of vasovagal syncope is done with a
tilt table test A tilt table test (TTT), occasionally called upright tilt testing (UTT), is a medical procedureA medical procedure is a course of action intended to achieve a result in the delivery of healthcare. A medical procedure with the intention of determi ...
. Besides the definitive threshold, an abrupt fall in systolic blood pressure around 30 mmHg from one's ''typical average systolic pressure'' can also be diagnosed with hypotension.


Treatment

The treatment for hypotension depends on its cause. Chronic hypotension rarely exists as more than a symptom. Asymptomatic hypotension in healthy people usually does not require treatment. Adding electrolytes to a diet can relieve symptoms of mild hypotension. A morning dose of caffeine can also be effective. In mild cases, where the patient is still responsive, laying the person in dorsal decubitus (lying on the back) position and lifting the legs increases venous return, thus making more blood available to critical organs in the chest and head. The Trendelenburg position, though used historically, is no longer recommended. 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. 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. However, since it focuses on hypotension due to infection, it is not applicable to all forms of severe hypotension. # Volume resuscitation (usually with Iv colloid, crystalloid or blood products) # Blood pressure support with a vasopressor (all seem equivalent with respect to risk of death, with norepinephrine possibly better than dopamine). Trying to achieve a
mean arterial pressure In medicine, the mean arterial pressure (MAP) is an average blood pressure in an individual during a single cardiac cycle. Calculation The Systemic Vascular Resistance (SVR), denoted R is represented mathematically by the formula :R = \Delta P/ ...

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 mm Hg in adults. # Ensure adequate tissue perfusion (maintain SvO2 >70 with use of blood or dobutamine) # Address the underlying problem (i.e., antibiotic for septic shock, infection, stent or Coronary artery bypass surgery, CABG (coronary artery bypass graft surgery) for infarction, steroids for adrenal insufficiency, etc...) The best way to determine if a person will benefit from fluids is by doing a passive leg raise followed by measuring the cardiac output, output from the heart.


Medication

Chronic hypotension sometimes requires the use of medications. Some medications that are commonly used include Fludrocortisone, Erythropoietin, and Sympathomimetics such as Midodrine and Norepinephrine, Noradrenaline and precursor (L-DOPS). * Fludrocortisone is the first-line therapy (in the absence of heart failure) for patients with chronic hypotension or resistant orthostatic hypotension. It works by increasing the intravascular volume. * Midodrine is a therapy used for severe orthostatic hypotension, and works by increasing peripheral vascular resistance. * Norepinephrine, Noradrenaline and its precursor L-DOPS are used for primary autonomic dysfunction by increasing vascular tone. * Erythropoietin is given to patients with neurogenic orthostatic hypotension and it works through increasing vascular volume and viscosity.


Pediatrics

The definition of hypotension changes in the pediatric population depending on the child's age as seen in the table below. The clinical history provided by the caretaker is the most important part in determining the cause of hypotension in pediatric patients. 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 (medicine), syncope. The treatment for hypotension in pediatric patients is similar to the treatment in adults by following the four first steps listed above (see Treatment). Children are more likely to undergo intubation during the treatment of hypotension because their oxygen levels drop more rapidly than adults. 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.


Etymology

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


See also

* Hypertension


References


External links


Curlie.org: Hypotension
{{Subject bar , portal1= Medicine Hypotension, Vascular diseases