hypertension, e-medicine article

Author: Kamran Riaz, MD; Chief Editor: Vecihi Batuman, MD, FACP, FASN more...

Updated: Aug 10, 2011

Background

Hypertension is one of the most common worldwide diseases afflicting humans. Because of the associated morbidityand mortality and the cost to society, hypertension is an important public health challenge. Over the past severaldecades, extensive research, widespread patient education, and a concerted effort on the part of health careprofessionals have led to decreased mortality and morbidity rates from the multiple organ damage arising from yearsof untreated hypertension.

Approximately 50 million people in the United States are affected by hypertension.[1, 2] Substantial improvements havebeen made with regard to improving awareness and treatment of hypertension. However, approximately 30% of adultsare still unaware of their hypertension; up to 40% of people with hypertension are not receiving treatment; and, of those

treated, up to 67% do not have their blood pressure (BP) controlled to less than 140/90 mm Hg.[1] (SeeEpidemiology.)

Hypertension is the most important modifiable risk factor for coronary heart disease (the leading cause of death inNorth America), stroke (the third leading cause), congestive heart failure, end-stage renal disease, and peripheralvascular disease. Therefore, health care professionals must not only identify and treat patients with hypertension butalso promote a healthy lifestyle and preventive strategies to decrease the prevalence of hypertension in the generalpopulation. (See Treatment and Management.)

Definition and classification

Defining abnormally high blood pressure is extremely difficult and arbitrary. Furthermore, the relationship betweensystemic arterial pressure and morbidity appears to be quantitative rather than qualitative. A level for high BP must beagreed upon in clinical practice for screening patients with hypertension and for instituting diagnostic evaluation andinitiating therapy. Because the risk to an individual patient may correlate with the severity of hypertension, aclassification system is essential for making decisions about aggressiveness of treatment or therapeutic interventions.(See Clinical Presentation.)

Based on recommendations of the Seventh Report of the Joint National Committee of Prevention, Detection,Evaluation, and Treatment of High Blood Pressure (JNC VII), the classification of BP (expressed in mm Hg) for adults

aged 18 years or older is as follows[1] :

Normal - Systolic lower than 120, diastolic lower than 80Prehypertension - Systolic 120-139, diastolic 80-90Stage 1 - Systolic 140-159, diastolic 90-99Stage 2 - Systolic equal to or more than 160, diastolic equal to or more than 100

The classification above is based on the average of 2 or more readings taken at each of 2 or more visits after initialscreening. Normal BP with respect to cardiovascular risk is less than 120/80 mm Hg. However, unusually low readingsshould be evaluated for clinical significance.

Prehypertension, a new category designated in the JNC VII report, emphasizes that patients with prehypertension areat risk for progression to hypertension and that lifestyle modifications are important preventive strategies.

From another perspective, hypertension may be categorized as either essential or secondary. Essential hypertensionis diagnosed in the absence of an identifiable secondary cause. Approximately 95% of the 50 million American adultswith hypertension have essential hypertension, while secondary hypertension accounts for fewer than 5% of the cases.However, secondary forms of hypertension, such as primary hyperaldosteronism, account for 20% of resistanthypertension (hypertension that requires 4 or more medications to control).

Hypertension http://emedicine.medscape.com/article/241381-overview

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Especially severe cases of hypertension may be further categorized. Severe hypertension is defined by a bloodpressure above 180/110 without symptoms. Hypertensive urgency is defined as a BP above 180/110 with mild endorgan effects, such as headache and dyspnea. Hypertensive emergency is a BP of 220/140 or greater withlife-threatening end-organ dysfunction.

Hypertensive emergencies encompass a spectrum of clinical presentations in which uncontrolled BPs lead toprogressive or impending end-organ dysfunction; in these conditions, the BP should be lowered aggressively over

minutes to hours. Acute end-organ damage in the setting of a hypertensive emergency may include the following[3] :

Neurologic - Hypertensive encephalopathy, cerebral vascular accident/cerebral infarction. subarachnoidhemorrhage, intracranial hemorrhageCardiovascular - Myocardial ischemia/infarction, acute left ventricular dysfunction, acute pulmonary edema,aortic dissectionOther - Acute renal failure/insufficiency, retinopathy, eclampsia, microangiopathic hemolytic anemia

With the advent of antihypertensives, the incidence of hypertensive emergencies has declined from 7% to

approximately 1%.[4] In addition, the 1-year survival rate associated with this condition has increased from only 20%

(prior to 1950) to a survival rate of more than 90% with appropriate medical treatment.[5] (See Medication.)

Pathophysiology

The pathogenesis of essential hypertension is multifactorial and highly complex. Multiple factors modulate the bloodpressure (BP) for adequate tissue perfusion and include humoral mediators, vascular reactivity, circulating bloodvolume, vascular caliber, blood viscosity, cardiac output, blood vessel elasticity, and neural stimulation. A possiblepathogenesis of essential hypertension has been proposed in which multiple factors, including genetic predisposition,excess dietary salt intake, and adrenergic tone, may interact to produce hypertension. Although genetics appears tocontribute to essential hypertension, the exact mechanism has not been established.

The natural history of essential hypertension evolves from occasional to established hypertension. After a longinvariable asymptomatic period, persistent hypertension develops into complicated hypertension, in which target organdamage to the aorta and small arteries, heart, kidneys, retina, and central nervous system is evident. The progressionbegins with prehypertension in persons aged 10-30 years (by increased cardiac output) to early hypertension inpersons aged 20-40 years (in which increased peripheral resistance is prominent) to established hypertension inpersons aged 30-50 years, and, finally, to complicated hypertension in persons aged 40-60 years.

One mechanism of hypertension has been described as high-output hypertension. High-output hypertension resultsfrom decreased peripheral vascular resistance and concomitant cardiac stimulation by adrenergic hyperactivity andaltered calcium homeostasis. A second mechanism manifests with normal or reduced cardiac output and elevatedsystemic vascular resistance due to increased vasoreactivity. Another (and overlapping) mechanism is increased saltand water reabsorption (salt sensitivity) by the kidney, which increases circulating blood volume.

Etiology

Hypertension may be primary, which may develop as a result of environmental or genetic causes, or secondary, whichhas multiple etiologies, including renal, vascular, and endocrine causes. Hypertensive emergencies are most oftenprecipitated by inadequate medication or poor compliance.

Environmental and genetic causes

Hypertension develops secondary to environmental factors, as well as to multiple genes, whose inheritance appears to

be complex.[6, 7] Very rare secondary causes are related to single genes and include Liddle syndrome, glucocorticoid-remediable hyperaldosteronism, 11 beta-hydroxylase and 17 alpha-hydroxylase deficiencies, the syndrome ofapparent mineralocorticoid excess, and pseudohypoaldosteronism type II.

Primary or essential hypertension accounts for 90-95% of adult cases, and a small percentage of patients (2-10%)have a secondary cause.

Causes of secondary hypertension

Renal causes (2.5-6%) include the renal parenchymal diseases and renal vascular diseases, as follows:


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Polycystic kidney diseaseChronic kidney diseaseUrinary tract obstructionRenin-producing tumorLiddle syndrome

Renovascular hypertension (RVHT) causes 0.2-4% of cases. Since Goldblatt’s seminal experiment in 1934, RVHThas become increasingly recognized as an important cause of clinically atypical hypertension and chronic kidneydisease, the latter by virtue of renal ischemia. The coexistence of renal arterial vascular (ie, renovascular) disease andhypertension roughly defines this type of nonessential hypertension. More specific diagnoses are maderetrospectively when hypertension is improved after intravascular intervention.

Vascular causes include the following:

Coarctation of aortaVasculitisCollagen-vascular disease

Endocrine causes account for 1-2% and include exogenous or endogenous hormonal imbalances. Exogenous causesinclude administration of steroids. The most common form of secondary hypertension is an endocrine cause: oralcontraceptive use. Activation of the renin-angiotensin-aldosterone system is the likely mechanism because hepaticsynthesis of angiotensinogen is induced by the estrogen component of oral contraceptives. Approximately 5% ofwomen prescribed oral contraceptives may develop hypertension, which abates within 6 months of discontinuation.The risk factors for oral contraceptive–associated hypertension include mild renal disease, familial history of essentialhypertension, age older than 35 years, and obesity.

Exogenous administration of the other steroids used for therapeutic purposes also increases blood pressure,especially in susceptible individuals, mainly by volume expansion. Nonsteroidal anti-inflammatory drugs (NSAIDs) mayalso have adverse effects on blood pressure. NSAIDs block both cyclooxygenase-1 (COX-1) and COX-2 enzymes.The inhibition of COX-2 can inhibit its natriuretic effect, which, in turn, increases sodium retention. NSAIDs also inhibitthe vasodilating effects of prostaglandins and the production of vasoconstricting factors, namely endothelin-1. Theseeffects can contribute to the induction of hypertension in a normotensive and/or controlled hypertensive patient

Endogenous hormonal causes include the following:

Primary hyperaldosteronismCushing syndromePheochromocytomaCongenital adrenal hyperplasia

Neurogenic causes include the following:

Brain tumorBulbar poliomyelitisIntracranial hypertension

Drugs and toxins that cause hypertension include the following:

AlcoholCocaineCyclosporine, tacrolimusNSAIDsErythropoietinAdrenergic medicationsDecongestants containing ephedrineHerbal remedies containing licorice or ephedrine

Other causes include the following:

Hyperthyroidism and hypothyroidismHypercalcemiaHyperparathyroidismAcromegalyObstructive sleep apnea


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Pregnancy-induced hypertension

Causes of hypertensive emergencies

The most common hypertensive emergency is a rapid unexplained rise in BP in a patient with chronic essentialhypertension. Most patients who develop hypertensive emergencies have a history of inadequate hypertensivetreatment or an abrupt discontinuation of their medications.

Other causes of hypertensive emergencies include the use of recreational drugs, abrupt clonidine withdrawal, postpheochromocytoma removal, and systemic sclerosis.

Other causes include the following:

Renal parenchymal disease - Chronic pyelonephritis, primary glomerulonephritis, tubulointerstitial nephritis(accounts for 80% of all secondary causes)Systemic disorders with renal involvement - Systemic lupus erythematosus, systemic sclerosis, vasculitidesRenovascular disease - Atherosclerotic disease, fibromuscular dysplasia, polyarteritis nodosaEndocrine disease - Pheochromocytoma, Cushing syndrome, primary hyperaldosteronismDrugs - Cocaine, amphetamines, cyclosporine, clonidine withdrawal, phencyclidine, diet pills, oral contraceptivepillsDrug interactions - Monoamine oxidase inhibitors with tricyclic antidepressants, antihistamines, or tyramine-containing foodCentral nervous system (CNS) factors - CNS trauma or spinal cord disorders, such as Guillain-Barré syndromeCoarctation of the aortaPreeclampsia/eclampsiaPostoperative hypertension

Epidemiology

Hypertension is a worldwide epidemic; accordingly, its epidemiology has been well studied.

A 2005 survey in the United States found that in the population aged 20 years or older, an estimated 41.9 million menand 27.8 million women have prehypertension, 12.8 million men and 12.2 million women have stage 1 hypertension,

and 4.1 million men and 6.9 million women have stage 2 hypertension.[8] In many countries, 50% of the populationolder than 60 years has hypertension. Overall, approximately 20% of the world’s adults are estimated to havehypertension. The 20% prevalence is for hypertension defined as BP in excess of 140/90 mm Hg. The prevalencedramatically increases in patients older than 60 years.

Prognosis

Most individuals diagnosed with hypertension will have increasing BP as they age. Untreated hypertension is notoriousfor increasing the risk of mortality and is often described as a silent killer. Mild-to-moderate hypertension, if leftuntreated, is associated with a risk of atherosclerotic disease in 30% of people and organ damage in 50% of peopleafter only 8-10 years of onset.

Death from both ischemic heart disease and stroke increase progressively as BP increases. For every 20 mm Hgsystolic or 10 mm Hg diastolic increase in BP above 115/75 mm Hg, the mortality rate for both ischemic heart diseaseand stroke doubles.

The morbidity and mortality of hypertensive emergencies depend on the extent of end-organ dysfunction onpresentation and the degree to which BP is controlled subsequently. With BP control and medication compliance, the

10-year survival rate of patients with hypertensive crises approaches 70%.[9]

In the Framingham Heart Study, the age-adjusted risk of congestive heart failure was 2.3 times higher in men and 3

times higher in women when highest blood pressure was compared to the lowest.[10] Multiple Risk Factor InterventionTrial (MRFIT) data showed that the relative risk for coronary heart disease mortality varied from 2.3-6.9 times higher for

persons with mild to severe hypertension compared to persons with normal BP.[11] The relative risk for stroke rangedfrom 3.6-19.2. The population-attributable risk percentage for coronary artery disease varied from 2.3-25.6%, whereasthe population-attributable risk for stroke ranged from 6.8-40%.

The Framingham Heart Study found a 72% increase in the risk of all-cause death and a 57% increase in the risk of any

cardiovascular event in patients with hypertension who were also diagnosed with diabetes mellitus.[12]


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Nephrosclerosis is one of the possible complications of long-standing hypertension. The risk of hypertension-inducedend-stage renal disease is higher in black patients, even when blood pressure is under good control. Furthermore,patients with diabetic nephropathy who are hypertensive are also at high risk for developing end-stage renal disease.

Comparative data from NHANES I and III showed a decrease in mortality over time among hypertensive adults, but the

mortality gap between hypertensive and normotensive adults remains high.[13]

Patient Education

Hypertension is a lifelong disorder. For optimal control, a long-term commitment to lifestyle modifications andpharmacological therapy is required. Therefore, repeated in-depth patient education and counseling not only improvecompliance with medical therapy but also reduce cardiovascular risk factors.

Various strategies to decrease cardiovascular disease risk include the following:

Prevention and treatment of obesityAppropriate amounts of aerobic physical activityDiets low in salt, total fat, and cholesterolAdequate dietary intakes of potassium, calcium, and magnesiumLimited alcohol consumptionAvoidance of cigarette smokingAvoidance of the use of illicit drugs, such as cocaine

For excellent patient education resources, visit eMedicine's Diabetes Center and Cholesterol Center. Also, seeeMedicine's patient education articles High Blood Pressure, High Cholesterol, Chest Pain, Coronary Heart Disease,and Heart Attack.

Contributor Information and DisclosuresAuthorKamran Riaz, MD Clinical Assistant Professor, Department of Internal Medicine, Section of Cardiology, WrightState University School of Medicine

Kamran Riaz, MD is a member of the following medical societies: American College of Cardiology, AmericanCollege of Physicians, American Society of Echocardiography, Ohio State Medical Association, and Royal Collegeof Physicians

Disclosure: Nothing to disclose.

Coauthor(s)Zina Semenovskaya, MD Resident Physician, Department of Emergency Medicine, Kings County Hospital, StateUniversity of New York Downstate Medical Center College of Medicine


Albert W Dreisbach, MD Associate Professor of Medicine, Division of Nephrology, University of MississippiMedical Center


Allysia M Guy, MD Staff Physician, Department of Emergency Medicine, State University of New York DownstateMedical Center


Kee-Hak Lim, MD Associate Professor, Department of Obstetrics and Gynecology, Harvard Medical School;Consulting Staff, Harvard Medical Faculty Physicians and Beth Israel Deaconess Medical Center


Guy Steinberg, MD, MPH, MSc Fellow in Maternal-Fetal Medicine, Beth Israel Deaconess MedicalCenter/Harvard Medical School



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Kean Theng Oh, MD Consulting Staff, Associated Retinal Consultants, PC

Kean Theng Oh, MD is a member of the following medical societies: American Academy of Ophthalmology,American Society of Retina Specialists, and Association for Research in Vision and Ophthalmology


Gary Setnik, MD Chair, Department of Emergency Medicine, Mount Auburn Hospital; Assistant Professor, Divisionof Emergency Medicine, Harvard Medical School

Gary Setnik, MD is a member of the following medical societies: American College of Emergency Physicians,National Association of EMS Physicians, and Society for Academic Emergency Medicine

Disclosure: SironaHealth Salary Management position; South Middlesex EMS Consortium Salary Managementposition; ProceduresConsult.com Royalty Other

Michael G Ross, MD, MPH Professor of Obstetrics and Gynecology, University of California, Los Angeles, DavidGeffen School of Medicine; Professor, Department of Community Health Sciences, University of California at LosAngeles School of Public Health; Chair, Department of Obstetrics and Gynecology, Harbor-UCLA Medical Center

Michael G Ross, MD, MPH is a member of the following medical societies: American Association for theAdvancement of Science, American College of Obstetricians and Gynecologists, American Federation for ClinicalResearch, American Gynecological and Obstetrical Society, American Physiological Society, American PublicHealth Association, Association of Professors of Gynecology and Obstetrics, Perinatal Research Society, Phi BetaKappa, Society for Gynecologic Investigation, Society for Maternal-Fetal Medicine, and Society for Neuroscience


Carl V Smith, MD The Distinguished Chris J and Marie A Olson Chair of Obstetrics and Gynecology, Professor,Department of Obstetrics and Gynecology, University of Nebraska Medical Center

Carl V Smith, MD is a member of the following medical societies: American College of Obstetricians andGynecologists, American Institute of Ultrasound in Medicine, Association of Professors of Gynecology andObstetrics, Central Association of Obstetricians and Gynecologists, Council of University Chairs of Obstetrics andGynecology, Nebraska Medical Association, and Society for Maternal-Fetal Medicine


Paul Gibson, MD Associate Professor, Departments of Medicine and Obstetrics and Gynecology, Divisions ofGeneral Internal Medicine and Maternal-Fetal Medicine, University of Calgary

Paul Gibson, MD, is a member of the following medical societies: Alberta Medical Association, Canadian Society ofInternal Medicine, Royal College of Physicians and Surgeons of Canada, and Society of Obstetric Medicine


Nader Moinfar, MD Consulting Staff, Vitreoretinal Department, Magruder Eye Institute

Nader Moinfar, MD is a member of the following medical societies: American Academy of Ophthalmology,Association for Research in Vision and Ophthalmology, and Sigma Xi


David Chelmow, MD Leo J Dunn Distinguished Professor and Chair, Department of Obstetrics and Gynecology,Virginia Commonwealth University Medical Center

David Chelmow, MD is a member of the following medical societies: American College of Obstetricians andGynecologists, American Medical Association, Association of Professors of Gynecology and Obstetrics,Massachusetts Medical Society, Phi Beta Kappa, Sigma Xi, Society for Gynecologic Investigation, and Society forMedical Decision Making


Michel E Rivlin, MD Professor, Department of Obstetrics and Gynecology, University of Mississippi School of


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Medicine

Michel E Rivlin, MD is a member of the following medical societies: American College of Obstetricians andGynecologists, American Medical Association, Mississippi State Medical Association, and Royal College ofSurgeons of Edinburgh


Aqeel Ahmed, MD Staff Physician, Department of Pathology, University of Missouri at Kansas City

Aqeel Ahmed, MD is a member of the following medical societies: American Society for Clinical Pathology


Mert Erogul, MD Assistant Professor of Emergency Medicine, University Hospital of Brooklyn: Consulting Staff,Department of Emergency Medicine, Kings County Hospital Center

Mert Erogul, MD is a member of the following medical societies: American College of Emergency Physicians,American Medical Association, and Society for Academic Emergency Medicine


Christy Hopkins, MD, MPH Assistant Professor, Department of Surgery, University of Utah School of Medicine;Clinical Operations Director, Division of Emergency Medicine, University Health Care; Medical Director, UniversityHealth Care Transfer Center

Christy Hopkins, MD, MPH, is a member of the following medical societies: American College of EmergencyPhysicians


Simon K Law, MD, PharmD Associate Professor of Ophthalmology, Jules Stein Eye Institute, University ofCalifornia, Los Angeles, David Geffen School of Medicine

Simon K Law, MD, PharmD is a member of the following medical societies: American Academy of Ophthalmology,American Glaucoma Society, and Association for Research in Vision and Ophthalmology


A David Barnes, MD, PhD, MPH, FACOG Consulting Staff, Department of Obstetrics and Gynecology, MammothHospital (Mammoth Lakes, California), Pioneer Valley Hospital (Salt Lake City, Utah), Warren General Hospital(Warren, Pennsylvania), and Mountain West Hospital (Tooele, Utah)

A David Barnes, MD, PhD, MPH, FACOG is a member of the following medical societies: American College ofForensic Examiners, American College of Obstetricians and Gynecologists, American Medical Association,Association of Military Surgeons of the US, and Utah Medical Association


Assaad J Sayah, MD Chief, Department of Emergency Medicine, Cambridge Health Alliance

Assaad J Sayah, MD is a member of the following medical societies: National Association of EMS Physicians


Michael S Beeson, MD, MBA, FACEP Professor of Emergency Medicine, Northeastern Ohio UniversitiesCollege of Medicine and Pharmacy; Attending Faculty, Akron General Medical Center

Michael S Beeson, MD, MBA, FACEP is a member of the following medical societies: American College ofEmergency Physicians, Council of Emergency Medicine Residency Directors, National Association of EMSPhysicians, and Society for Academic Emergency Medicine



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John D Bisognano, MD, PhD, FACP, FACC, Professor of Medicine, Director of Outpatient Cardiology,Department of Medicine, Cardiology Division, University of Rochester Medical Center

John D Bisognano, MD, PhD, FACP, FACC, is a member of the following medical societies: American College ofCardiology and American College of Physicians-American Society of Internal Medicine


Bruce A Meyer, MD, MBA Executive Vice President for Health System Affairs, Chief Clinical Officer, InterimCEO, University Hospitals; Professor, Department of Obstetrics and Gynecology, University of Texas SouthwesternMedical School

Bruce A Meyer, MD, MBA is a member of the following medical societies: American College of Obstetricians andGynecologists, American College of Physician Executives, American Institute of Ultrasound in Medicine,Association of Professors of Gynecology and Obstetrics, Massachusetts Medical Society, Medical GroupManagement Association, and Society for Maternal-Fetal Medicine


David FM Brown, MD Associate Professor, Division of Emergency Medicine, Harvard Medical School; ViceChair, Department of Emergency Medicine, Massachusetts General Hospital

David FM Brown, MD is a member of the following medical societies: American College of Emergency Physiciansand Society for Academic Emergency Medicine


Hampton Roy Sr, MD Associate Clinical Professor, Department of Ophthalmology, University of Arkansas forMedical Sciences

Hampton Roy Sr, MD is a member of the following medical societies: American Academy of Ophthalmology,American College of Surgeons, and Pan-American Association of Ophthalmology


John J Kavanagh Jr MD, Chief, Professor, Department of Internal Medicine, Section of Gynecological andMedical Therapeutics, MD Anderson Cancer Center, University of Texas Medical School at Houston

John J Kavanagh Jr is a member of the following medical societies: American Association for Cancer Research,American Association for the Advancement of Science, American Association for the History of Medicine,American College of Physicians, American Federation for Medical Research, American Medical Association,Society of Gynecologist Oncologists, Southern Medical Association, and Texas Medical Association


Mark Zwanger, MD, MBA Assistant Professor, Department of Emergency Medicine, Jefferson Medical Collegeof Thomas Jefferson University

Mark Zwanger, MD, MBA is a member of the following medical societies: American Academy of EmergencyMedicine, American College of Emergency Physicians, and American Medical Association


Michael P Carson, MD Clinical Associate Professor, Department of Medicine, Clinical Associate Professor,Department of Obstetrics/Gynecology and Reproductive Sciences, University of Medicine and Dentistry of NewJersey, Robert Wood Johnson Medical School; Director of Research/Outcomes, Department of Medicine, JerseyShore University Medical Center

Michael P Carson, MD is a member of the following medical societies: American College of Physicians, Society ofGeneral Internal Medicine, and Society of Obstetric Medicine


Pamela L Dyne, MD Professor of Clinical Medicine/Emergency Medicine, University of California, Los Angeles,


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David Geffen School of Medicine; Attending Physician, Department of Emergency Medicine, Olive View-UCLAMedical Center

Pamela L Dyne, MD is a member of the following medical societies: American Academy of Emergency Medicine,American College of Emergency Physicians, and Society for Academic Emergency Medicine


Robin R Hemphill, MD, MPH Associate Professor, Director, Quality and Safety, Department of EmergencyMedicine, Emory University School of Medicine

Robin R Hemphill, MD, MPH is a member of the following medical societies: American College of EmergencyPhysicians and Society for Academic Emergency Medicine


Steve Charles, MD Director of Charles Retina Institute; Clinical Professor, Department of Ophthalmology,University of Tennessee College of Medicine; Adjunct Professor of Ophthalmology, Columbia College ofPhysicians and Surgeons; Clinical Professor Ophthalmology, Chinese University of Hong Kong

Steve Charles, MD is a member of the following medical societies: American Academy of Ophthalmology,American Society of Retina Specialists, Club Jules Gonin, Macula Society, and Retina Society

Disclosure: Alcon Laboratories Consulting fee Consulting; OptiMedica Ownership interest Other; Topcon MedicalLasers Consulting fee Consulting

Mark A Silverberg, MD, MMB, FACEP Assistant Professor, Associate Residency Director, Department ofEmergency Medicine, State University of New York Downstate College of Medicine; Consulting Staff, Department ofEmergency Medicine, Staten Island University Hospital, Kings County Hospital, University Hospital, State Universityof New York Downstate Medical Center

Mark A Silverberg, MD, MMB, FACEP is a member of the following medical societies: American College ofEmergency Physicians, American Medical Association, Council of Emergency Medicine Residency Directors, andSociety for Academic Emergency Medicine


Specialty Editor BoardL Michael Prisant, MD, FACC, FAHA Cardiologist, Emeritus Professor of Medicine, Medical College of Georgia

L Michael Prisant, MD, FACC, FAHA is a member of the following medical societies: American College ofCardiology, American College of Chest Physicians, American College of Clinical Pharmacology, American Collegeof Forensic Examiners, American College of Physicians, American Heart Association, and American MedicalAssociation

Disclosure: Boehringer-Ingelheim Honoraria Speaking and teaching

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center Collegeof Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

George R Aronoff, MD Director, Professor, Departments of Internal Medicine and Pharmacology, Section ofNephrology, Kidney Disease Program, University of Louisville School of Medicine

George R Aronoff, MD is a member of the following medical societies: American Federation for Medical Research,American Society of Nephrology, Kentucky Medical Association, and National Kidney Foundation


Yasmine Subhi Ali, MD, MSCI, FACC, FACP President, Nashville Preventive Cardiology, PLLC; Assistant ClinicalProfessor of Medicine, Vanderbilt University School of Medicine

Yasmine Subhi Ali, MD, MSCI, FACC, FACP is a member of the following medical societies: American College of


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Cardiology, American College of Physicians, American Heart Association, American Medical Association, NationalLipid Association, and Tennessee Medical Association

Disclosure: Pfizer I own a small number of shares of Pfizer stock. These were NOT given to me by Pfizer, butrather purchased by myself as a personal investor for my diversified investment portfolio. None

Chief EditorVecihi Batuman, MD, FACP, FASN Professor of Medicine, Section of Nephrology-Hypertension, TulaneUniversity School of Medicine; Chief, Medicine Service, Southeast Louisiana Veterans Health Care System

Vecihi Batuman, MD, FACP, FASN is a member of the following medical societies: American College of Physicians,American Society of Hypertension, American Society of Nephrology, and International Society of Nephrology


AcknowledgmentsThe authors and editors of eMedicine gratefully acknowledge the contributions of previous authors Gregory EChow, MD, Brian Euerle, MD, FACEP, Alan D Forker, MD, Stephanie R Fugate, DO, Bradley M Hughes, MD, DawnC Jung, MD, Claude Kortas, MD, MEd, FRCPC, Paul J Lee, MD, Stephen Morris, MD, Alexander N Orsini, MD, SatSharma, MD, FRCPC, Matthew Warden, MD, to the development and writing of the source articles.

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