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Hypotension

Hypotension is defined as low blood pressure, specifically < 90/60 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Clinically significant complications may occur when blood pressure falls enough for crucial organs to become insufficiently perfused. Diagnostic studies and treatment depend on the clinical presentation Presentation The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck. Normal and Abnormal Labor and underlying conditions.

Last updated: 4 Apr, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Overview

Definition

Hypotension is defined as blood pressure below 90/60 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma Hg. If blood pressure decreases enough, shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock may develop. Shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock is most commonly defined as the life-threatening failure of adequate oxygen delivery to the tissues and may be due to decreased blood perfusion of vital organs (e.g., brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification, heart, kidneys Kidneys The kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine. Kidneys: Anatomy, lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy).

Etiology

  • Cardiovascular: 
    • Hypovolemia Hypovolemia Sepsis in Children:
    • Impaired cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) output:  
      • Myocardial infarction Myocardial infarction MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction
      • Heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR) 
      • Aortic stenosis Stenosis Hypoplastic Left Heart Syndrome (HLHS) 
      • Arrhythmias
      • Constrictive pericarditis Constrictive pericarditis Inflammation of the pericardium that is characterized by the fibrous scarring and adhesion of both serous layers, the visceral pericardium and the parietal pericardium leading to the loss of pericardial cavity. The thickened pericardium severely restricts cardiac filling. Clinical signs include fatigue, muscle wasting, and weight loss. Pericarditis, pericardial effusion Pericardial effusion Fluid accumulation within the pericardium. Serous effusions are associated with pericardial diseases. Hemopericardium is associated with trauma. Lipid-containing effusion (chylopericardium) results from leakage of thoracic duct. Severe cases can lead to cardiac tamponade. Pericardial Effusion and Cardiac Tamponade, or cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) tamponade Tamponade Pericardial effusion, usually of rapid onset, exceeding ventricular filling pressures and causing collapse of the heart with a markedly reduced cardiac output. Pericarditis
      • Aortic dissection Aortic dissection Aortic dissection occurs due to shearing stress from pulsatile pressure causing a tear in the tunica intima of the aortic wall. This tear allows blood to flow into the media, creating a “false lumen.” Aortic dissection is most commonly caused by uncontrolled hypertension. Aortic Dissection
  • Infectious Infectious Febrile Infant:  
    • Sepsis Sepsis Systemic inflammatory response syndrome with a proven or suspected infectious etiology. When sepsis is associated with organ dysfunction distant from the site of infection, it is called severe sepsis. When sepsis is accompanied by hypotension despite adequate fluid infusion, it is called septic shock. Sepsis and Septic Shock or septic shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock
    • Staphylococcal toxic shock syndrome Staphylococcal Toxic Shock Syndrome Toxic Shock Syndrome
  • Neurologic: 
    • Central: 
      • Multiple system atrophy Multiple System Atrophy A syndrome complex composed of three conditions which represent clinical variants of the same disease process: striatonigral degeneration; shy-drager syndrome; and the sporadic form of olivopontocerebellar atrophies. Clinical features include autonomic, cerebellar, and basal ganglia dysfunction. Pathologic examination reveals atrophy of the basal ganglia, cerebellum, pons, and medulla, with prominent loss of autonomic neurons in the brain stem and spinal cord. Atypical Parkinsonian Syndromes
      • Parkinson’s disease
      • Multiple strokes
      • Tabes dorsalis Tabes dorsalis Parenchymatous neurosyphilis marked by slowly progressive degeneration of the posterior columns, posterior roots, and ganglia of the spinal cord. The condition tends to present 15 to 20 years after the initial infection and is characterized by lightning-like pains in the lower extremities, urinary incontinence; ataxia; severely impaired position and vibratory sense, abnormal gait, optic atrophy; Argyll-Robertson pupils, hypotonia, hyperreflexia, and trophic joint degeneration. Syphilis
      • Transverse myelitis Transverse myelitis Inflammation which extends horizontally across the spinal cord, believed to be immune-mediated and triggered by infection; associated with signs and symptoms of motor, sensory, and/or autonomic dysfunction. Mononucleosis
    • Peripheral: 
      • Amyloidosis Amyloidosis Amyloidosis is a disease caused by abnormal extracellular tissue deposition of fibrils composed of various misfolded low-molecular-weight protein subunits. These proteins are frequently byproducts of other pathological processes (e.g., multiple myeloma). Amyloidosis
      • Diabetic, alcoholic Alcoholic Persons who have a history of physical or psychological dependence on ethanol. Mallory-Weiss Syndrome (Mallory-Weiss Tear), or nutritional neuropathy Neuropathy Leprosy
      • Familial dysautonomia (Riley-Day syndrome)
      • Guillain-Barré syndrome Guillain-Barré syndrome Guillain-Barré syndrome (GBS), once thought to be a single disease process, is a family of immune-mediated polyneuropathies that occur after infections (e.g., with Campylobacter jejuni). Guillain-Barré Syndrome
      • Paraneoplastic syndromes Paraneoplastic syndromes Paraneoplastic syndromes are a heterogeneous group of disorders caused by an abnormal immune response to a neoplasm. The substances produced are not due to the direct effect of the tumor, such as metastasis, mass effect, or invasion. Antibodies, hormones, cytokines, and other substances are generated and affect multiple organ systems. Paraneoplastic Syndromes
      • Pure autonomic failure
      • Surgical sympathectomy
  • Endocrine: 
    • Adrenal insufficiency Adrenal Insufficiency Conditions in which the production of adrenal corticosteroids falls below the requirement of the body. Adrenal insufficiency can be caused by defects in the adrenal glands, the pituitary gland, or the hypothalamus. Adrenal Insufficiency and Addison’s Disease 
    • Hyperaldosteronism Hyperaldosteronism Hyperaldosteronism is defined as the increased secretion of aldosterone from the zona glomerulosa of the adrenal cortex. Hyperaldosteronism may be primary (resulting from autonomous secretion), or secondary (resulting from physiological secretion due to stimulation of the RAAS). Classically, hyperaldosteronism presents with hypertension, hypokalemia, and metabolic alkalosis. Hyperaldosteronism
  • Drug induced:
    • Anti-hypertensives (especially alpha- and beta-blockers Beta-blockers Drugs that bind to but do not activate beta-adrenergic receptors thereby blocking the actions of beta-adrenergic agonists. Adrenergic beta-antagonists are used for treatment of hypertension, cardiac arrhythmias, angina pectoris, glaucoma, migraine headaches, and anxiety. Class 2 Antiarrhythmic Drugs (Beta Blockers), centrally acting agents)
    • Antipsychotics, tricyclic antidepressants Tricyclic antidepressants Tricyclic antidepressants (TCAs) are a class of medications used in the management of mood disorders, primarily depression. These agents, named after their 3-ring chemical structure, act via reuptake inhibition of neurotransmitters (particularly norepinephrine and serotonin) in the brain. Tricyclic Antidepressants, and monoamine oxidase Oxidase Neisseria inhibitors ( MAOIs MAOIs Monoamine oxidase inhibitors are a class of antidepressants that inhibit the activity of monoamine oxidase (MAO), thereby increasing the amount of monoamine neurotransmitters (particularly serotonin, norepinephrine, and dopamine). The increase of these neurotransmitters can help in alleviating the symptoms of depression. Monoamine Oxidase Inhibitors
    • Theophylline Theophylline A methyl xanthine derivative from tea with diuretic, smooth muscle relaxant, bronchial dilation, cardiac and central nervous system stimulant activities. Theophylline inhibits the 3. Asthma Drugs
  • Miscellaneous:
    • Anaphylaxis Anaphylaxis An acute hypersensitivity reaction due to exposure to a previously encountered antigen. The reaction may include rapidly progressing urticaria, respiratory distress, vascular collapse, systemic shock, and death. Type I Hypersensitivity Reaction caused by medications, food, and arthropod or animal bites
    • Pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care (physiologic)
    • Hypo- or hyperthermia
    • Air embolism Air embolism Blocking of a blood vessel by air bubbles that enter the circulatory system, usually after trauma; surgical procedures, or changes in atmospheric pressure. Nonthrombotic Embolism
    • Pneumothorax Pneumothorax A pneumothorax is a life-threatening condition in which air collects in the pleural space, causing partial or full collapse of the lung. A pneumothorax can be traumatic or spontaneous. Patients present with a sudden onset of sharp chest pain, dyspnea, and diminished breath sounds on exam. Pneumothorax
    • Intradialytic hypotension
    • Postprandial hypotension
    • Orthostatic hypotension: a fall of at least 20 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma Hg in systolic blood pressure or of at least 10 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma Hg in diastolic pressure within 2–5 minutes of standing
    • Postural orthostatic tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children syndrome (POTS): chronic orthostatic intolerance defined by a heart rate Heart rate The number of times the heart ventricles contract per unit of time, usually per minute. Cardiac Physiology of ≥ 120/min or an increase of ≥ 30/min when a patient stands up

Pathophysiology and Clinical Presentation

Pathophysiology

  • In the case of hypovolemia Hypovolemia Sepsis in Children, compensatory changes occur as a response to the decreased intravascular volume:
    • RAAS RAAS A blood pressure regulating system of interacting components that include renin; angiotensinogen; angiotensin converting enzyme; angiotensin i; angiotensin ii; and angiotensinase. Renin, an enzyme produced in the kidney, acts on angiotensinogen, an alpha-2 globulin produced by the liver, forming angiotensin I. Angiotensin-converting enzyme, contained in the lung, acts on angiotensin I in the plasma converting it to angiotensin II, an extremely powerful vasoconstrictor. Angiotensin II causes contraction of the arteriolar and renal vascular smooth muscle, leading to retention of salt and water in the kidney and increased arterial blood pressure. In addition, angiotensin II stimulates the release of aldosterone from the adrenal cortex, which in turn also increases salt and water retention in the kidney. Angiotensin-converting enzyme also breaks down bradykinin, a powerful vasodilator and component of the kallikrein-kinin system. Adrenal Hormones activation → fluid retention and vasoconstriction Vasoconstriction The physiological narrowing of blood vessels by contraction of the vascular smooth muscle. Vascular Resistance, Flow, and Mean Arterial Pressure
    • Sympathetic nervous system Nervous system The nervous system is a small and complex system that consists of an intricate network of neural cells (or neurons) and even more glial cells (for support and insulation). It is divided according to its anatomical components as well as its functional characteristics. The brain and spinal cord are referred to as the central nervous system, and the branches of nerves from these structures are referred to as the peripheral nervous system. Nervous System: Anatomy, Structure, and Classification activation → vasoconstriction Vasoconstriction The physiological narrowing of blood vessels by contraction of the vascular smooth muscle. Vascular Resistance, Flow, and Mean Arterial Pressure and increased heart rate Heart rate The number of times the heart ventricles contract per unit of time, usually per minute. Cardiac Physiology/contractility
    • B1 receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors activation → renin Renin A highly specific (leu-leu) endopeptidase that generates angiotensin I from its precursor angiotensinogen, leading to a cascade of reactions which elevate blood pressure and increase sodium retention by the kidney in the renin-angiotensin system. Renal Sodium and Water Regulation release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology
    • Increased antidiuretic hormone Antidiuretic hormone Antidiuretic hormones released by the neurohypophysis of all vertebrates (structure varies with species) to regulate water balance and osmolarity. In general, vasopressin is a nonapeptide consisting of a six-amino-acid ring with a cysteine 1 to cysteine 6 disulfide bridge or an octapeptide containing a cystine. All mammals have arginine vasopressin except the pig with a lysine at position 8. Vasopressin, a vasoconstrictor, acts on the kidney collecting ducts to increase water reabsorption, increase blood volume and blood pressure. Hypernatremia release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology → retention of free water and increased intravascular volume
    • When these compensatory mechanisms fail to maintain normal blood pressure, hypotension results in clinical manifestations.
  • In the case of septic shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock and anaphylaxis Anaphylaxis An acute hypersensitivity reaction due to exposure to a previously encountered antigen. The reaction may include rapidly progressing urticaria, respiratory distress, vascular collapse, systemic shock, and death. Type I Hypersensitivity Reaction, hypotension is caused by an increased release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology of cytokines Cytokines Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner. Adaptive Immune Response that produce vasodilation Vasodilation The physiological widening of blood vessels by relaxing the underlying vascular smooth muscle. Pulmonary Hypertension Drugs → decrease in peripheral vascular resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing → decrease in blood pressure
    • Massive inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation and release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology of cytokines Cytokines Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner. Adaptive Immune Response also cause contraction of endothelial cells → leakage of intravascular volume into the interstitium (“3rd spacing”) → lower circulating intravascular volume → hypotension
  • Heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR) and myocardial infarction Myocardial infarction MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction cause hypotension due to decreased cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) output → less circulating intravascular volume → hypotension
  • Medications can cause hypotension by:
    • Decreasing the peripheral vascular resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing (e.g., alpha-blockers Alpha-blockers Drugs that bind to but do not activate alpha-adrenergic receptors thereby blocking the actions of endogenous or exogenous adrenergic agonists. Adrenergic alpha-antagonists are used in the treatment of hypertension, vasospasm, peripheral vascular disease, shock, and pheochromocytoma. Antiadrenergic Drugs)
    • Causing volume depletion Volume depletion Volume status is a balance between water and solutes, the majority of which is Na. Volume depletion refers to a loss of both water and Na, whereas dehydration refers only to a loss of water. Volume depletion can be caused by GI losses, renal losses, bleeding, poor oral Na intake, or third spacing of fluids. Volume Depletion and Dehydration (e.g., thiazide Thiazide Heterocyclic compounds with sulfur and nitrogen in the ring. This term commonly refers to the benzothiadiazines that inhibit sodium-potassium-chloride symporters and are used as diuretics. Hyponatremia diuretics Diuretics Agents that promote the excretion of urine through their effects on kidney function. Heart Failure and Angina Medication)
  • Damage to the nervous system Nervous system The nervous system is a small and complex system that consists of an intricate network of neural cells (or neurons) and even more glial cells (for support and insulation). It is divided according to its anatomical components as well as its functional characteristics. The brain and spinal cord are referred to as the central nervous system, and the branches of nerves from these structures are referred to as the peripheral nervous system. Nervous System: Anatomy, Structure, and Classification can also cause hypotension by decreasing systemic vascular resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing due to the loss of sympathetic outflow and/or central control of blood pressure regulation.
  • Hypotension is common in pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care due to:

Clinical presentation Presentation The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck. Normal and Abnormal Labor

  • Lightheadedness or dizziness Dizziness An imprecise term which may refer to a sense of spatial disorientation, motion of the environment, or lightheadedness. Lateral Medullary Syndrome (Wallenberg Syndrome)
  • Syncope Syncope Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation. The condition is caused by transient interruption of cerebral blood flow that may be benign or related to a underlying life-threatening condition. Syncope (temporary loss of consciousness)
  • Nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics
  • Fatigue Fatigue The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli. Fibromyalgia
  • Diaphoresis (excessive sweating) or clammy skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions
  • Confusion
  • Blurred vision Vision Ophthalmic Exam

Diagnosis

Urgent/emergent evaluation

History: 

  • Bleeding  
  • Trauma 
  • Medications
  • Chest pain Chest Pain Chest pain is one of the most common and challenging complaints that may present in an inpatient and outpatient setting. The differential diagnosis of chest pain is large and includes cardiac, gastrointestinal, pulmonary, musculoskeletal, and psychiatric etiologies. Chest Pain 
  • Insect or animal bites
  • Respiratory distress  
  • Pregnant or possible pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care 
  • Other history relating to presentation Presentation The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck. Normal and Abnormal Labor

Physical examination:

Laboratory tests:

  • CBC
  • CMP: glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance, electrolytes Electrolytes Electrolytes are mineral salts that dissolve in water and dissociate into charged particles called ions, which can be either be positively (cations) or negatively (anions) charged. Electrolytes are distributed in the extracellular and intracellular compartments in different concentrations. Electrolytes are essential for various basic life-sustaining functions. Electrolytes, BUN/creatinine
  • Urinalysis Urinalysis Examination of urine by chemical, physical, or microscopic means. Routine urinalysis usually includes performing chemical screening tests, determining specific gravity, observing any unusual color or odor, screening for bacteriuria, and examining the sediment microscopically. Urinary Tract Infections (UTIs) in Children 
  • Blood and urine Urine Liquid by-product of excretion produced in the kidneys, temporarily stored in the bladder until discharge through the urethra. Bowen Disease and Erythroplasia of Queyrat cultures Cultures Klebsiella
  • Cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes

Additional tests:

  • ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG)
  • Imaging of the suspected organ/region (e.g., brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification, abdomen, kidneys Kidneys The kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine. Kidneys: Anatomy)
  • Endoscopy Endoscopy Procedures of applying endoscopes for disease diagnosis and treatment. Endoscopy involves passing an optical instrument through a small incision in the skin i.e., percutaneous; or through a natural orifice and along natural body pathways such as the digestive tract; and/or through an incision in the wall of a tubular structure or organ, i.e. Transluminal, to examine or perform surgery on the interior parts of the body. Gastroesophageal Reflux Disease (GERD) or colonoscopy Colonoscopy Endoscopic examination, therapy or surgery of the luminal surface of the colon. Colorectal Cancer Screening if GI bleed is suspected

Outpatient/non-urgent evaluation

  • Detailed history
  • Pertinent physical examination
  • Laboratory tests as indicated
  • Additional tests as necessary/according to clinical suspicion:
  • Referral to cardiologist, neurologist, gastroenterologist, or other specialists as applicable

Management

The main goal of the management of hypotension is to reverse the etiology. Thus, identifying and treating the cause appropriately, either medically or surgically, is most important.

Cause-specific therapy

Table: Cause-specific therapy
Cause of hypotension Specific management
Acute hemorrhage with hypovolemia Hypovolemia Sepsis in Children Blood transfusion
Infection with hypovolemia Hypovolemia Sepsis in Children IV fluids IV fluids Intravenous fluids are one of the most common interventions administered in medicine to approximate physiologic bodily fluids. Intravenous fluids are divided into 2 categories: crystalloid and colloid solutions. Intravenous fluids have a wide variety of indications, including intravascular volume expansion, electrolyte manipulation, and maintenance fluids. Intravenous Fluids or plasma Plasma The residual portion of blood that is left after removal of blood cells by centrifugation without prior blood coagulation. Transfusion Products
Cardiogenic shock Cardiogenic shock Shock resulting from diminution of cardiac output in heart disease. Types of Shock Intra-aortic balloon pump Pump ACES and RUSH: Resuscitation Ultrasound Protocols (IABP)
Sepsis Sepsis Systemic inflammatory response syndrome with a proven or suspected infectious etiology. When sepsis is associated with organ dysfunction distant from the site of infection, it is called severe sepsis. When sepsis is accompanied by hypotension despite adequate fluid infusion, it is called septic shock. Sepsis and Septic Shock or septic shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock IV antibiotics
Vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia combined with hypotension Hospitalization Hospitalization The confinement of a patient in a hospital. Delirium and IV fluids IV fluids Intravenous fluids are one of the most common interventions administered in medicine to approximate physiologic bodily fluids. Intravenous fluids are divided into 2 categories: crystalloid and colloid solutions. Intravenous fluids have a wide variety of indications, including intravascular volume expansion, electrolyte manipulation, and maintenance fluids. Intravenous Fluids
Ruptured artery Emergency surgical repair
Drug-induced hypotension Discontinue or decrease the dose of the offending medications.
Heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR)
Inferior vena cava Inferior vena cava The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy ( IVC IVC The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy) compression Compression Blunt Chest Trauma by gravid uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Uterus, Cervix, and Fallopian Tubes: Anatomy in pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care Left lateral repositioning and avoidance of supine position
Acute myocardial infarction Myocardial infarction MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction
  • Depends on many factors (e.g., time from onset, comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus, symptoms)
  • IV fluids IV fluids Intravenous fluids are one of the most common interventions administered in medicine to approximate physiologic bodily fluids. Intravenous fluids are divided into 2 categories: crystalloid and colloid solutions. Intravenous fluids have a wide variety of indications, including intravascular volume expansion, electrolyte manipulation, and maintenance fluids. Intravenous Fluids are often used to increase preload Preload Cardiac Mechanics and maintain cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) output.

Medical therapy

Table: Medical therapy
Indication Medical therapy
Hypotensive emergencies for anaphylaxis Anaphylaxis An acute hypersensitivity reaction due to exposure to a previously encountered antigen. The reaction may include rapidly progressing urticaria, respiratory distress, vascular collapse, systemic shock, and death. Type I Hypersensitivity Reaction or shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock IM or IV epinephrine Epinephrine The active sympathomimetic hormone from the adrenal medulla. It stimulates both the alpha- and beta- adrenergic systems, causes systemic vasoconstriction and gastrointestinal relaxation, stimulates the heart, and dilates bronchi and cerebral vessels. Sympathomimetic Drugs (nonselective beta-agonist), dobutamine Dobutamine A catecholamine derivative with specificity for beta-1 adrenergic receptors. Sympathomimetic Drugs (beta-1 adrenergic receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors agonist), or dopamine Dopamine One of the catecholamine neurotransmitters in the brain. It is derived from tyrosine and is the precursor to norepinephrine and epinephrine. Dopamine is a major transmitter in the extrapyramidal system of the brain, and important in regulating movement. Receptors and Neurotransmitters of the CNS
Severe cases of arrhythmia Antiarrhythmics and/or cardioversion Cardioversion Atrial Fibrillation (management depends on the specific subtype)
Orthostatic hypotension Fludrocortisone Fludrocortisone A synthetic mineralocorticoid with anti-inflammatory activity. Mineralocorticoids to promote fluid and salt retention
Adrenal insufficiency Adrenal Insufficiency Conditions in which the production of adrenal corticosteroids falls below the requirement of the body. Adrenal insufficiency can be caused by defects in the adrenal glands, the pituitary gland, or the hypothalamus. Adrenal Insufficiency and Addison’s Disease Replacement of mineralocorticoids Mineralocorticoids Mineralocorticoids are a drug class within the corticosteroid family and fludrocortisone is the primary medication within this class. Fludrocortisone is a fluorinated analog of cortisone. The fluorine moiety protects the drug from isoenzyme inactivation in the kidney, allowing it to exert its mineralocorticoid effect. Mineralocorticoids and glucocorticoids Glucocorticoids Glucocorticoids are a class within the corticosteroid family. Glucocorticoids are chemically and functionally similar to endogenous cortisol. There are a wide array of indications, which primarily benefit from the antiinflammatory and immunosuppressive effects of this class of drugs. Glucocorticoids

Clinical Relevance

The following conditions are the most common causes of hypotension: 

  • Heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR): the inability of the heart to supply the body with normal cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) output to meet its metabolic needs and to provide sufficient oxygenation to the organs. Echocardiography Echocardiography Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic. Tricuspid Valve Atresia (TVA) can confirm the diagnosis and give information about the ejection fraction Ejection fraction Cardiac Cycle. Treatment is directed at the removal of excess fluid and decreasing oxygen demand of the heart. 
  • Tachyarrhythmias: a rhythm in which the heart rate Heart rate The number of times the heart ventricles contract per unit of time, usually per minute. Cardiac Physiology exceeds 100/min, which may result in poor perfusion. Can be physiologic, without symptoms of hemodynamic change, or pathologic, resulting in hemodynamic instability and possibly related to intrinsic cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) abnormalities, systemic diseases, or medication toxicity Toxicity Dosage Calculation
  • Bradyarrhythmias Bradyarrhythmias Bradyarrhythmia is a rhythm in which the heart rate is less than 60/min. Bradyarrhythmia can be physiologic, without symptoms or hemodynamic change. Pathologic bradyarrhythmia results in reduced cardiac output and hemodynamic instability causing syncope, dizziness, or dyspnea. Bradyarrhythmias: a rhythm in which the heart rate Heart rate The number of times the heart ventricles contract per unit of time, usually per minute. Cardiac Physiology is < 60/min. Can be physiologic, without symptoms or hemodynamic change, or pathologic, resulting in reduced cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) output and hemodynamic instability. May present as syncope Syncope Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation. The condition is caused by transient interruption of cerebral blood flow that may be benign or related to a underlying life-threatening condition. Syncope, dizziness Dizziness An imprecise term which may refer to a sense of spatial disorientation, motion of the environment, or lightheadedness. Lateral Medullary Syndrome (Wallenberg Syndrome), or dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea.
  • Sepsis Sepsis Systemic inflammatory response syndrome with a proven or suspected infectious etiology. When sepsis is associated with organ dysfunction distant from the site of infection, it is called severe sepsis. When sepsis is accompanied by hypotension despite adequate fluid infusion, it is called septic shock. Sepsis and Septic Shock: an organ dysfunction resulting from a dysregulated systemic host response to infection. The etiology is mainly bacterial and pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia is the most commonly known source. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship commonly present with fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children, tachypnea Tachypnea Increased respiratory rate. Pulmonary Examination, hypotension, and/or altered mentation.
  • Adrenal insufficiency Adrenal Insufficiency Conditions in which the production of adrenal corticosteroids falls below the requirement of the body. Adrenal insufficiency can be caused by defects in the adrenal glands, the pituitary gland, or the hypothalamus. Adrenal Insufficiency and Addison’s Disease: the inadequate production of adrenocortical hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types ( glucocorticoids Glucocorticoids Glucocorticoids are a class within the corticosteroid family. Glucocorticoids are chemically and functionally similar to endogenous cortisol. There are a wide array of indications, which primarily benefit from the antiinflammatory and immunosuppressive effects of this class of drugs. Glucocorticoids, mineralocorticoids Mineralocorticoids Mineralocorticoids are a drug class within the corticosteroid family and fludrocortisone is the primary medication within this class. Fludrocortisone is a fluorinated analog of cortisone. The fluorine moiety protects the drug from isoenzyme inactivation in the kidney, allowing it to exert its mineralocorticoid effect. Mineralocorticoids, and adrenal androgens Androgens Androgens are naturally occurring steroid hormones responsible for development and maintenance of the male sex characteristics, including penile, scrotal, and clitoral growth, development of sexual hair, deepening of the voice, and musculoskeletal growth. Androgens and Antiandrogens). The condition can be primary or secondary. Primary adrenal insufficiency Primary adrenal insufficiency An adrenal disease characterized by the progressive destruction of the adrenal cortex, resulting in insufficient production of aldosterone and hydrocortisone. Clinical symptoms include anorexia; nausea; weight loss; muscle weakness; and hyperpigmentation of the skin due to increase in circulating levels of acth precursor hormone which stimulates melanocytes. Adrenal Insufficiency and Addison’s Disease (Addison’s disease) is related to disease in the gland itself; the most common cause is autoimmune adrenalitis. Secondary adrenal insufficiency Adrenal Insufficiency Conditions in which the production of adrenal corticosteroids falls below the requirement of the body. Adrenal insufficiency can be caused by defects in the adrenal glands, the pituitary gland, or the hypothalamus. Adrenal Insufficiency and Addison’s Disease occurs due to decreased production of adrenocorticotropic hormone Adrenocorticotropic hormone An anterior pituitary hormone that stimulates the adrenal cortex and its production of corticosteroids. Acth is a 39-amino acid polypeptide of which the n-terminal 24-amino acid segment is identical in all species and contains the adrenocorticotropic activity. Upon further tissue-specific processing, acth can yield alpha-msh and corticotropin-like intermediate lobe peptide (clip). Adrenal Hormones (ACTH) either from prolonged glucocorticoid therapy or disease in the pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types or hypothalamic glands.
  • Hypothermia Hypothermia Hypothermia can be defined as a drop in the core body temperature below 35°C (95°F) and is classified into mild, moderate, severe, and profound forms based on the degree of temperature decrease. Hypothermia: prolonged or severe cold exposure Exposure ABCDE Assessment that causes peripheral vasoconstriction Vasoconstriction The physiological narrowing of blood vessels by contraction of the vascular smooth muscle. Vascular Resistance, Flow, and Mean Arterial Pressure when the mean Mean Mean is the sum of all measurements in a data set divided by the number of measurements in that data set. Measures of Central Tendency and Dispersion body temperature Body Temperature The measure of the level of heat of a human or animal. Heatstroke drops below 34°C (93.2°F). Hypotension can result when compensatory mechanisms fail.
  • Heatstroke Heatstroke Heatstroke is an illness characterized as a core body temperature exceeding 40°C (104°F) with accompanying neurological symptoms including ataxia, seizures, and/or delirium. Heatstroke is usually due to the body’s inability to regulate its temperature when challenged with an elevated heat load. Heatstroke: an illness characterized as a core body temperature Body Temperature The measure of the level of heat of a human or animal. Heatstroke exceeding 40°C (104°F) with accompanying neurological symptoms including ataxia Ataxia Impairment of the ability to perform smoothly coordinated voluntary movements. This condition may affect the limbs, trunk, eyes, pharynx, larynx, and other structures. Ataxia may result from impaired sensory or motor function. Sensory ataxia may result from posterior column injury or peripheral nerve diseases. Motor ataxia may be associated with cerebellar diseases; cerebral cortex diseases; thalamic diseases; basal ganglia diseases; injury to the red nucleus; and other conditions. Ataxia-telangiectasia, seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures, and/or delirium Delirium Delirium is a medical condition characterized by acute disturbances in attention and awareness. Symptoms may fluctuate during the course of a day and involve memory deficits and disorientation. Delirium. Usually due to the body’s inability to regulate its temperature when challenged with an elevated heat Heat Inflammation load, causing peripheral vasodilatation and resultant hypotension.
  • Dehydration Dehydration The condition that results from excessive loss of water from a living organism. Volume Depletion and Dehydration: refers to a loss of water volume in the body. Dehydration Dehydration The condition that results from excessive loss of water from a living organism. Volume Depletion and Dehydration may be caused by GI losses (e.g., diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea), renal losses (e.g., diuretics Diuretics Agents that promote the excretion of urine through their effects on kidney function. Heart Failure and Angina Medication), bleeding, poor sodium Sodium A member of the alkali group of metals. It has the atomic symbol na, atomic number 11, and atomic weight 23. Hyponatremia intake, and/or 3rd spacing of fluids. The body also loses fluid through normal physiologic processes including respiration Respiration The act of breathing with the lungs, consisting of inhalation, or the taking into the lungs of the ambient air, and of exhalation, or the expelling of the modified air which contains more carbon dioxide than the air taken in. Nose and Nasal Cavity: Anatomy, urination, and sweating. Dehydration Dehydration The condition that results from excessive loss of water from a living organism. Volume Depletion and Dehydration occurs when fluid loss from the body exceeds fluid intake.
  • Myocardial infarction Myocardial infarction MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction: ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage of the myocardial tissue due to a complete obstruction or drastic constriction of the coronary arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology. This condition is usually accompanied by an increase in cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes, typical ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) changes, and chest pain Chest Pain Chest pain is one of the most common and challenging complaints that may present in an inpatient and outpatient setting. The differential diagnosis of chest pain is large and includes cardiac, gastrointestinal, pulmonary, musculoskeletal, and psychiatric etiologies. Chest Pain. The subsequent decreased cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) output often results in hypotension.

References

  1. Gaieski DF, Mikkelsen ME. (2021). Evaluation of and initial approach to the adult patient with undifferentiated hypotension and shock. UpToDate. Retrieved on March 20, 2021, from https://www.uptodate.com/contents/evaluation-of-and-initial-approach-to-the-adult-patient-with-undifferentiated-hypotension-and-shock
  2. Procter LD. (2020). Shock. Merck Manual Professional Version. https://www.merckmanuals.com/professional/critical-care-medicine/shock-and-fluid-resuscitation/shock
  3. Thompson AD, Shea MJ. (2020). Orthostatic Hypotension. Merck Manual Professional Version. https://www.merckmanuals.com/professional/cardiovascular-disorders/symptoms-of-cardiovascular-disorders/orthostatic-hypotension
  4. American Heart Association. (2021). Syncope. Retrieved on March 20, 2021, from https://www.heart.org/en/health-topics/arrhythmia/symptoms-diagnosis–monitoring-of-arrhythmia/syncope-fainting

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