Hypotension 500475 222970860 2008-07-01T23:48:30Z Asouers 7406953 /* Indicators */ {{Infobox_Disease | Name = Hypotension | Image = | Caption = | DiseasesDB = 6539 | ICD10 = {{ICD10|I|95||i|95}} | ICD9 = {{ICD9|458}} | ICDO = | OMIM = | MedlinePlus = 007278 | eMedicineSubj = | eMedicineTopic = | MeshID = D007022 }} In [[physiology]] and [[medicine]], '''hypotension''' refers to an abnormally low [[blood pressure]]. This is best understood as a physiologic state, rather than a disease. It is often associated with [[Shock (medical)|shock]], though not necessarily indicative of it. Hypotension is the opposite of [[hypertension]], which is high blood pressure. Hypotension can be life-threatening. ==Normal physiology== Blood pressure is continuously regulated by the [[autonomic nervous system]], using an elaborate network of [[sensory receptors|receptors]], [[nerve]]s, and [[hormone]]s to balance the effects of the [[sympathetic nervous system]], which tends to raise blood pressure, and the [[parasympathetic nervous system]], 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. ==Mechanisms and causes== Reduced blood volume, called [[hypovolemia]], is the most common mechanism producing hypotension. This can result from [[hemorrhage]], or blood loss; insufficient fluid intake, as in starvation; or excessive fluid losses from diarrhea or vomiting. Hypovolemia is often induced by excessive use of [[diuretic]]s. Other medications can produce hypotension by different mechanisms. Decreased [[cardiac output]] despite normal blood volume, due to severe [[congestive heart failure]], large [[myocardial infarction]], or [[bradycardia]], often produces hypotension and can rapidly progress to [[cardiogenic shock]]. [[Arrhythmia]]s often result in hypotension by this mechanism. [[Beta blocker]]s can cause hypotension both by slowing the heart rate and by decreasing the pumping ability of the heart muscle. Varieties of meditation and/or other mental-physiological disciplines can create temporary hypotension effects, as well, and should not be considered unusual. Excessive [[vasodilation]], or insufficient constriction of the resistance blood vessels (mostly [[arterioles]]), causes hypotension. 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 or of [[dysautonomia]], an intrinsic abnormality in autonomic system functioning. Excessive vasodilation can also result from [[sepsis]], [[acidosis]], or medications, such as [[Glyceryl trinitrate (pharmacology)|nitrate preparations]], [[calcium channel blockers]], angiotensin II receptor inhibitors or [[ACE inhibitors]]. Many anesthetic agents and techniques, including [[spinal anesthesia]] and most [[Inhalational anaesthetic|inhalational agents]], produce significant vasodilation. ==Syndromes== [[Orthostatic hypotension]], 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 and as a result of various medications. In addition to blood pressure-lowering medications, many psychiatric medications, in particular [[antidepressant]]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. Orthostatic hypotension is indicated if there is a drop in 20 mmHg of systolic pressure (and a 10 mmHg drop in diastolic pressure in some facilities) and a 20 bpm increase in heart rate. [[Neurocardiogenic syncope]] is a form of dysautonomia characterized by an inappropriate drop in blood pressure while in the upright position. Neurocardiogenic syncope is related to [[vasovagal syncope]] in that both occur as a result of increased activity of the [[vagus nerve]], the mainstay of the parasympathetic nervous system. Another, but rarer form, is [[postprandial]] hypotension, which occurs 30&ndash;75&nbsp;minutes after eating substantial meals. When a great deal of blood is diverted to the [[intestines]] to facilitate [[digestion]] and [[absorption]], the body must increase [[cardiac output]] and peripheral [[vasoconstriction]] in order to maintain enough blood pressure to perfuse vital organs, such as the brain. It is believed that postprandial hypotension is caused by the [[autonomic nervous system]] not compensating appropriately, because of ageing or a specific disorder. ==Indicators== For most individuals, a healthy [[blood pressure]] ranges from 90/50&nbsp;[[torr|mmHg]] to 120/80&nbsp;mmHg. A small drop in blood pressure, even as little as 20&nbsp;mmHg, can result in transient hypotension.{{Fact|date=May 2008}} Evaluating [[neurocardiogenic syncope]] is done with a [[tilt table test]]. ==Symptoms== The cardinal [[symptom]] of hypotension is [[lightheadedness]] or [[dizziness]]. If the blood pressure is sufficiently low, [[fainting]] and often [[seizure]]s will occur. Low blood pressure is sometimes associated with certain symptoms, many of which are related to causes rather than effects of hypotension: <div class="references-small" style="-moz-column-count:3; column-count:3;"> * [[Chest pain]] * [[Shortness of breath]] * [[Irregular heartbeat]] * [[Fever]] higher than 101&nbsp;°[[Fahrenheit|F]] (38.3&nbsp;°[[Celsius|C]]) * [[Headache]] * Stiff neck * Severe [[upper back pain]] * [[Cough]] with [[phlegm]] * Prolonged [[diarrhea]] or [[vomiting]] * [[Dysphagia]] * [[Dysuria]] * Foul-smelling [[urine]] * Adverse effect of [[medications]] * Acute, life-threatening [[allergic reaction]] * [[Seizures]] * [[Loss of consciousness]] * Profound [[fatigue (physical)|fatigue]] </div> ==Treatment== The treatment for hypotension depends on its cause. Asymptomatic hypotension in healthy people usually does not require treatment. Severe hypotension needs to be aggressively treated because reduced [[blood]] flow to critical organs including the [[brain]], [[heart]] and [[kidneys]] may cause organ failure and can ultimately lead to [[death]]. Treatment options include [[systemic]] [[vasoconstrictors]] and other drugs. Adding [[sodium]] to a diet can also relieve symptoms of mild hypotension. In mild cases, where the patient is still responsible, laying the person in dorsal decubitus (laying over the back) position and lifting the legs will increase venous return, thus making more blood available to critical organs at chest and head. ==References== * [http://www.undiag.com/diseases/hypotension.php Hypotension details] * [http://my.webmd.com/content/article/54/61510.htm hypotension WebMD] * [http://www.medterms.com/script/main/srchcont.asp?src=hypotension&op=mm hypotension Medterms] {{Vascular diseases}} [[Category:Cardiology]] [[Category:Blood pressure]] [[bs:Hipotenzija]] [[cs:Hypotenze]] [[de:Hypotonie]] [[es:Hipotensión]] [[fr:Hypotension artérielle]] [[ko:저혈압]] [[it:Ipotensione]] [[nl:Hypotensie]] [[ja:低血圧]] [[no:Hypotensjon]] [[pl:Hipotonia]] [[pt:Hipotensão]] [[ru:Артериальная гипотензия]] [[sq:Hipotensioni]] [[sv:Hypotension]] [[tr:Düşük tansiyon]] [[zh:低血壓]]