Hypertensive encephalopathy
Encyclopedia
Hypertensive encephalopathy is a neurological dysfunction induced by malignant hypertension
. The term "hypertensive encephalopathy" was introduced to describe this type of encephalopathy
by Oppenheimer and Fishberg in 1928. It describes cerebral conditions, typically reversible, caused by sudden and sustained severe elevation of blood pressure
. Hypertensive encephalopathy occurs in eclampsia
, acute nephritis
and crises in essential hypertension
. Symptoms of hypertensive encephalopathy include headache, restlessness, nausea, disturbances of consciousness, seizure
s, retina
l hemorrhage and papilledema
. Focal brain lesions may be associated with specific neurological symptoms. These neurological impairments may culminate in a coma
. The condition is treated by drugs that decrease blood pressure.
state. He described this condition a "pseudouremia". The term "hypertensive encephalopathy" was introduced by Oppenheimer and Fishberg in 1928 to describe the case of a patient with acute nephritis
, severe hypertension and cerebral symptoms.
In the past, the term "hypertensive encephalopathy" has been applied to a range of neurological problems occurring in hypertensive patients, such as headache, dizziness cerebral hemorrhage and transient ischemic attacks. However, currently this term is narrowed down to a clinical condition produced by elevated blood pressure and which can be reverted by blood pressure reduction.
. Overall, the condition is rare even among hypertensive patients. Different clinicians reported that from 0.5 to 15% of patients with malignant hypertension developed hypertensive encephalopathy. With the development of methods for detection and treatment of hypertension, hypertensive encephalopathy has been becoming more rare.
Symptoms of hypertensive encephalopathy typically start to occur 12–48 hours after a sudden and sustained increase in blood pressure
. The first manifestation of these symptoms is a severe headache
. Headache occurs in greater than 75% of patients. The patient becomes restless. Alterations in consciousness may follow several hours later, which include impaired judgement and memory, confusion
, somnolence
and stupor
. If the condition is not treated, these neurological symptoms may worsen and ultimately turn into a coma
. Other symptoms may include increased irritability
, vomiting
, seizures, twitching and myoclonus
of the limbs. Alterations in vision (vision blurring, hemivisual field defects, color blindness
, cortical blindness
) are common. They occur in 4 out of 11 cases (Jellinek et al. 1964). Hemiparesis
and aphasia
may also occur, but they are less common. Electroencephalographic examination detects the absence of alpha waves
, signifying impaired consciousness. In patients with visual disturbances, slow waves are detected in the occipital
areas.
, eclampsia
, crises in chronic essential hypertension
, sudden withdrawal of antihypertensive treatment. Additionally, hypertensive encephalopathy may occur in pheochromocytoma
, Cushing's syndrome, renal artery
thrombosis
.
The impairment of cerebral blood flow that underlies hypertensive encephalopathy is still controversial. Normally, cerebral blood flow is maintained by an autoregulation mechanism that dilate arterioles in response to blood pressure decreases and constricts arterioles in response to blood pressure increases. This autoregulation falters when hypertension becomes excessive. According to the over-regulation conception, brain vessels spasm in response to acute hypertension, which results in cerebral ischemia and cytotoxic edema. According to the autoregulation breakthrough conception, cerebral arterioles are forced to dilate, leading to vasogenic edema.
Cerebral edema
can be generalized or focal. Brain ventricles are compressed, cortical gyri flattened.
, chest X-ray
, urinalysis
, arterial blood gas analysis, cranial CAT scans and MRI
. Since decreasing the blood pressure is essential, anti-hypertensive medication is administered without awaiting the results of the laboratory tests.
s where vital signs and electroencephalographic characteristics can be monitored. The first measure is to lower blood pressure with drugs. Blood pressure reduction is monitored to avoid damage from excessive reduction. Excessively reduced blood pressure may result in cerebral infarction, blindness and cardiac ischemia.
Intravenously injected diazoxide
is effective in 80% of the patients with hypertensive encephalopathy. It normalizes blood pressure within 3-5 min, and the effect lasts 6–18 hours. One benefit of diazoxide is that it does not cause drowsiness and thus does not affect the patient’s state of consciousness. Reflex tachycardia caused by this drug is the major disadvantage which limits its use in patients with ischemic heart disease. Furosemide
injected simultaneously with diazoxide enhances both the antihypertensive effect and its duration.
Hydralazine
is also administered intravenously or intramuscularly to reduce the blood pressure. Its action is similar to that of diazoxide, but less consistent.
Another drug which is used to reduce blood pressure is sodium nitroprusside
which is delivered continuously through intravenous infusion.
Nitroglycerine is also used to decrease blood pressure in patients with hypertensive encephalopathy.
Another class of drugs that are used to reduce blood pressure in hypertensive encephalopathy are ganglionic blocking agents: labetalol
, pentolinium
, phentolamine
and trimethaphan
. These agents have rapid effect, and they do not cause drowsiness. However, they may have side effects, such as bowel
and bladder
atony
. These drugs, with the exception of labetalol, are not used if hypertensive encephalopathy is associated with prepartal eclampsia
because they may harm the fetus.
Reserpine
, methyldopa
and clonidine
are less applicable to hypertensive emergency because their effect starts slowly (in 2–3 hours after administration) and they affect the patient's consciousness.
Oral antihypertensive drugs are administered after the patient recovers from the most severe symptoms, and
intravenous injections are no longer necessary.
In addition to antihypertensive drugs, anticonvulsant
drugs, such as phenytoin
, may be given to the patient with seizures. However, typically anti-hypertensive medication is sufficient for treatment of neurological symptoms.
Malignant hypertension
Malignant hypertension or hypertensive emergency is severe hypertension with acute impairment of an organ system and the possibility of irreversible organ-damage...
. The term "hypertensive encephalopathy" was introduced to describe this type of encephalopathy
Encephalopathy
Encephalopathy means disorder or disease of the brain. In modern usage, encephalopathy does not refer to a single disease, but rather to a syndrome of global brain dysfunction; this syndrome can be caused by many different illnesses.-Terminology:...
by Oppenheimer and Fishberg in 1928. It describes cerebral conditions, typically reversible, caused by sudden and sustained severe elevation of blood pressure
Blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
. Hypertensive encephalopathy occurs in eclampsia
Eclampsia
Eclampsia , an acute and life-threatening complication of pregnancy, is characterized by the appearance of tonic-clonic seizures, usually in a patient who had developed pre-eclampsia...
, acute nephritis
Nephritis
Nephritis is inflammation of the nephrons in the kidneys. The word "nephritis" was imported from Latin, which took it from Greek: νεφρίτιδα. The word comes from the Greek νεφρός - nephro- meaning "of the kidney" and -itis meaning "inflammation"....
and crises in essential hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
. Symptoms of hypertensive encephalopathy include headache, restlessness, nausea, disturbances of consciousness, seizure
Seizure
An epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...
s, retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
l hemorrhage and papilledema
Papilledema
Papilledema is optic disc swelling that is caused by increased intracranial pressure. The swelling is usually bilateral and can occur over a period of hours to weeks. Unilateral presentation is extremely rare....
. Focal brain lesions may be associated with specific neurological symptoms. These neurological impairments may culminate in a coma
Coma
In medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...
. The condition is treated by drugs that decrease blood pressure.
Historical note
The first descriptions of the condition date back to early 1900s. In 1914, Volhard and Fahr distinguished a neurological disorder caused by acute hypertension from a uremicUremia
Uremia or uraemia is a term used to loosely describe the illness accompanying kidney failure , in particular the nitrogenous waste products associated with the failure of this organ....
state. He described this condition a "pseudouremia". The term "hypertensive encephalopathy" was introduced by Oppenheimer and Fishberg in 1928 to describe the case of a patient with acute nephritis
Nephritis
Nephritis is inflammation of the nephrons in the kidneys. The word "nephritis" was imported from Latin, which took it from Greek: νεφρίτιδα. The word comes from the Greek νεφρός - nephro- meaning "of the kidney" and -itis meaning "inflammation"....
, severe hypertension and cerebral symptoms.
In the past, the term "hypertensive encephalopathy" has been applied to a range of neurological problems occurring in hypertensive patients, such as headache, dizziness cerebral hemorrhage and transient ischemic attacks. However, currently this term is narrowed down to a clinical condition produced by elevated blood pressure and which can be reverted by blood pressure reduction.
Clinical features
Hypertensive encephalopathy is most commonly encountered in young and middle-aged people who suffer from hypertensionHypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
. Overall, the condition is rare even among hypertensive patients. Different clinicians reported that from 0.5 to 15% of patients with malignant hypertension developed hypertensive encephalopathy. With the development of methods for detection and treatment of hypertension, hypertensive encephalopathy has been becoming more rare.
Symptoms of hypertensive encephalopathy typically start to occur 12–48 hours after a sudden and sustained increase in blood pressure
Blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
. The first manifestation of these symptoms is a severe headache
Headache
A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...
. Headache occurs in greater than 75% of patients. The patient becomes restless. Alterations in consciousness may follow several hours later, which include impaired judgement and memory, confusion
ConFusion
ConFusion is an annual science fiction convention organized by the Stilyagi Air Corps and its parent organization, the Ann Arbor Science Fiction Association. Commonly, it is held the third weekend of January. It is the oldest science fiction convention in Michigan, a regional, general SF con...
, somnolence
Somnolence
Somnolence is a state of near-sleep, a strong desire for sleep, or sleeping for unusually long periods . It has two distinct meanings, referring both to the usual state preceding falling asleep, and the chronic condition referring to being in that state independent of a circadian rhythm...
and stupor
Stupor
Stupor is the lack of critical cognitive function and level of consciousness wherein a sufferer is almost entirely unresponsive and only responds to base stimuli such as pain. This is often mistaken for delirium and treated with Haldol and or other anti-psychotic drugs...
. If the condition is not treated, these neurological symptoms may worsen and ultimately turn into a coma
Coma
In medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...
. Other symptoms may include increased irritability
Irritability
Irritability is an excessive response to stimuli. The term is used for both the physiological reaction to stimuli and for the pathological, abnormal or excessive sensitivity to stimuli; It is usually used to refer to anger or frustration....
, vomiting
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
, seizures, twitching and myoclonus
Myoclonus
Myoclonus is brief, involuntary twitching of a muscle or a group of muscles. It describes a medical sign and, generally, is not a diagnosis of a disease. Brief twitches are perfectly normal. The myoclonic twitches are usually caused by sudden muscle contractions; they also can result from brief...
of the limbs. Alterations in vision (vision blurring, hemivisual field defects, color blindness
Color blindness
Color blindness or color vision deficiency is the inability or decreased ability to see color, or perceive color differences, under lighting conditions when color vision is not normally impaired...
, cortical blindness
Cortical blindness
Cortical blindness is the total or partial loss of vision in a normal-appearing eye caused by damage to the visual area in the brain's occipital cortex. This damage is most often caused by loss of blood flow to the occipital cortex from either unilateral or bilateral posterior cerebral artery...
) are common. They occur in 4 out of 11 cases (Jellinek et al. 1964). Hemiparesis
Hemiparesis
Hemiparesis is weakness on one side of the body. It is less severe than hemiplegia - the total paralysis of the arm, leg, and trunk on one side of the body. Thus, the patient can move the impaired side of his body, but with reduced muscular strength....
and aphasia
Aphasia
Aphasia is an impairment of language ability. This class of language disorder ranges from having difficulty remembering words to being completely unable to speak, read, or write....
may also occur, but they are less common. Electroencephalographic examination detects the absence of alpha waves
Alpha Waves
Alpha Waves is an early 3D game that combines labyrinthine exploration with platform gameplay. By most definitions of the genre it could be considered to be the first 3D platform game, released in 1990, 6 years before the genre's seminal classic Super Mario 64...
, signifying impaired consciousness. In patients with visual disturbances, slow waves are detected in the occipital
Occipital lobe
The occipital lobe is the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex. The primary visual cortex is Brodmann area 17, commonly called V1...
areas.
Pathogenesis
Hypertensive encephalopathy is caused by an increase in blood pressure. Several conditions may evoke blood pressure elevation: acute nephritisNephritis
Nephritis is inflammation of the nephrons in the kidneys. The word "nephritis" was imported from Latin, which took it from Greek: νεφρίτιδα. The word comes from the Greek νεφρός - nephro- meaning "of the kidney" and -itis meaning "inflammation"....
, eclampsia
Eclampsia
Eclampsia , an acute and life-threatening complication of pregnancy, is characterized by the appearance of tonic-clonic seizures, usually in a patient who had developed pre-eclampsia...
, crises in chronic essential hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
, sudden withdrawal of antihypertensive treatment. Additionally, hypertensive encephalopathy may occur in pheochromocytoma
Pheochromocytoma
A pheochromocytoma or phaeochromocytoma is a neuroendocrine tumor of the medulla of the adrenal glands , or extra-adrenal chromaffin tissue that failed to involute after birth and secretes excessive amounts of catecholamines, usually noradrenaline , and adrenaline to a lesser extent...
, Cushing's syndrome, renal artery
Renal artery
The renal arteries normally arise off the side of the abdominal aorta, immediately below the superior mesenteric artery, and supply the kidneys with blood. Each is directed across the crus of the diaphragm, so as to form nearly a right angle with the aorta....
thrombosis
Thrombosis
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...
.
The impairment of cerebral blood flow that underlies hypertensive encephalopathy is still controversial. Normally, cerebral blood flow is maintained by an autoregulation mechanism that dilate arterioles in response to blood pressure decreases and constricts arterioles in response to blood pressure increases. This autoregulation falters when hypertension becomes excessive. According to the over-regulation conception, brain vessels spasm in response to acute hypertension, which results in cerebral ischemia and cytotoxic edema. According to the autoregulation breakthrough conception, cerebral arterioles are forced to dilate, leading to vasogenic edema.
Cerebral edema
Cerebral edema
Cerebral edema or cerebral œdema is an excess accumulation of water in the intracellular or extracellular spaces of the brain.-Vasogenic:Due to a breakdown of tight endothelial junctions which make up the blood-brain barrier...
can be generalized or focal. Brain ventricles are compressed, cortical gyri flattened.
Diagnostics
Diagnostic methods for hypertensive encephalopathy include physical examination, blood pressure measurement, blood sampling, ECG, EEGEEG
EEG commonly refers to electroencephalography, a measurement of the electrical activity of the brain.EEG may also refer to:* Emperor Entertainment Group, a Hong Kong-based entertainment company...
, chest X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
, urinalysis
Urinalysis
A urinalysis , also known as Routine and Microscopy , is an array of tests performed on urine, and one of the most common methods of medical diagnosis...
, arterial blood gas analysis, cranial CAT scans and MRI
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
. Since decreasing the blood pressure is essential, anti-hypertensive medication is administered without awaiting the results of the laboratory tests.
Treatment
Acute cases of hypertensive encephalopathy require urgent treatment, preferably in intensive care unitIntensive Care Unit
thumb|220px|ICU roomAn intensive-care unit , critical-care unit , intensive-therapy unit/intensive-treatment unit is a specialized department in a hospital that provides intensive-care medicine...
s where vital signs and electroencephalographic characteristics can be monitored. The first measure is to lower blood pressure with drugs. Blood pressure reduction is monitored to avoid damage from excessive reduction. Excessively reduced blood pressure may result in cerebral infarction, blindness and cardiac ischemia.
Intravenously injected diazoxide
Diazoxide
Diazoxide is a potassium channel activator, which causes local relaxation in smooth muscle by increasing membrane permeability to potassium ions...
is effective in 80% of the patients with hypertensive encephalopathy. It normalizes blood pressure within 3-5 min, and the effect lasts 6–18 hours. One benefit of diazoxide is that it does not cause drowsiness and thus does not affect the patient’s state of consciousness. Reflex tachycardia caused by this drug is the major disadvantage which limits its use in patients with ischemic heart disease. Furosemide
Furosemide
Furosemide or frusemide is a loop diuretic used in the treatment of congestive heart failure and edema. It is most commonly marketed by Sanofi-Aventis under the brand name Lasix...
injected simultaneously with diazoxide enhances both the antihypertensive effect and its duration.
Hydralazine
Hydralazine
Hydralazine is a direct-acting smooth muscle relaxant used to treat hypertension by acting as a vasodilator primarily in arteries and arterioles...
is also administered intravenously or intramuscularly to reduce the blood pressure. Its action is similar to that of diazoxide, but less consistent.
Another drug which is used to reduce blood pressure is sodium nitroprusside
Sodium nitroprusside
Sodium nitroprusside is the inorganic compound with the formula Na2[Fe5NO]·2H2O. This red-coloured salt, which is often abbreviated SNP, is a potent vasodilator...
which is delivered continuously through intravenous infusion.
Nitroglycerine is also used to decrease blood pressure in patients with hypertensive encephalopathy.
Another class of drugs that are used to reduce blood pressure in hypertensive encephalopathy are ganglionic blocking agents: labetalol
Labetalol
Labetalol is a mixed alpha/beta adrenergic antagonist, which is used to treat high blood pressure.-Indications:...
, pentolinium
Pentolinium
Pentolinium is a ganglionic blocking agent which acts as a nicotinic acetylcholine receptor antagonist. It can be used as an antihypertensive drug during surgery or to control hypertensive crises. It works by binding to the acetylcholine receptor of adrenergic nerves and thereby inhibiting the...
, phentolamine
Phentolamine
Phentolamine is a reversible nonselective alpha-adrenergic antagonist. -Mechanism:Its primary action is vasodilation due to α1 blockade....
and trimethaphan
Trimethaphan
Trimetaphan camsilate or trimethaphan camsylate , trade name Arfonad, is a drug that counteracts cholinergic transmission at the ganglion type of nicotinic receptors of the autonomic ganglia and therefore blocks both the sympathetic nervous system and the parasympathetic nervous system...
. These agents have rapid effect, and they do not cause drowsiness. However, they may have side effects, such as bowel
Ileus
Ileus is a disruption of the normal propulsive ability of the gastrointestinal tract.Ileus is commonly defined simply as bowel obstruction. However, authoritative sources define it as decreased motor activity of the GI tract due to non-mechanical causes...
and bladder
Bladder
Bladder usually refers to an anatomical hollow organBladder may also refer to:-Biology:* Urinary bladder in humans** Urinary bladder ** Bladder control; see Urinary incontinence** Artificial urinary bladder, in humans...
atony
Atony
Pronounced In medicine, atony refers to a muscle that has lost its strength. It is frequently associated with the conditions Atonic seizure, atonic colon, uterine atony, gastrointestinal atony and choreatic atonia.Atony can also refer to the paralyzed or extremely relaxed state of skeletal...
. These drugs, with the exception of labetalol, are not used if hypertensive encephalopathy is associated with prepartal eclampsia
Eclampsia
Eclampsia , an acute and life-threatening complication of pregnancy, is characterized by the appearance of tonic-clonic seizures, usually in a patient who had developed pre-eclampsia...
because they may harm the fetus.
Reserpine
Reserpine
Reserpine is an indole alkaloid antipsychotic and antihypertensive drug that has been used for the control of high blood pressure and for the relief of psychotic symptoms, although because of the development of better drugs for these purposes and because of its numerous side-effects, it is rarely...
, methyldopa
Methyldopa
Methyldopa is an alpha-adrenergic agonist psychoactive drug used as a sympatholytic or antihypertensive. Its use is now mostly deprecated following the introduction of alternative safer classes of agents...
and clonidine
Clonidine
Clonidine is a sympatholytic medication used to treat medical conditions, such as high blood pressure, some pain conditions, ADHD and anxiety/panic disorder...
are less applicable to hypertensive emergency because their effect starts slowly (in 2–3 hours after administration) and they affect the patient's consciousness.
Oral antihypertensive drugs are administered after the patient recovers from the most severe symptoms, and
intravenous injections are no longer necessary.
In addition to antihypertensive drugs, anticonvulsant
Anticonvulsant
The anticonvulsants are a diverse group of pharmaceuticals used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of bipolar disorder, since many seem to act as mood stabilizers, and in the treatment of neuropathic pain. The goal of an...
drugs, such as phenytoin
Phenytoin
Phenytoin sodium is a commonly used antiepileptic. Phenytoin acts to suppress the abnormal brain activity seen in seizure by reducing electrical conductance among brain cells by stabilizing the inactive state of voltage-gated sodium channels...
, may be given to the patient with seizures. However, typically anti-hypertensive medication is sufficient for treatment of neurological symptoms.