Autonomic dysreflexia
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Autonomic dysreflexia (AD) is a potential
medical emergency A medical emergency is an acute injury or illness that poses an immediate risk to a person's life or long-term health, sometimes referred to as a situation risking "life or limb". These emergencies may require assistance from another, qualified ...
classically characterized by uncontrolled
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
and
bradycardia Bradycardia (also sinus bradycardia) is a slow resting heart rate, commonly under 60 beats per minute (BPM) as determined by an electrocardiogram. It is considered to be a normal heart rate during sleep, in young and healthy or elderly adults, a ...
, although
tachycardia Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal (su ...
is known to commonly occur. AD occurs most often in individuals with
spinal cord injuries A spinal cord injury (SCI) is damage to the spinal cord that causes temporary or permanent changes in its function. Symptoms may include loss of muscle function, sensation, or autonomic function in the parts of the body served by the spinal cor ...
with lesions at or above the T6 spinal cord level, although it has been reported in patients with lesions as low as T10.
Guillain–Barré syndrome Guillain–Barré syndrome (GBS) is a rapid-onset muscle weakness caused by the immune system damaging the peripheral nervous system. Typically, both sides of the body are involved, and the initial symptoms are changes in sensation or pain oft ...
may also cause autonomic dysreflexia. The uncontrolled hypertension in AD may result in mild symptoms, such as sweating above the lesion level, goosebumps, blurred vision, or headache; However, severe hypertension may result in potentially life-threatening complications including
seizure An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with los ...
,
intracranial bleed Intracranial hemorrhage (ICH), also known as intracranial bleed, is bleeding within the skull. Subtypes are intracerebral bleeds (intraventricular bleeds and intraparenchymal bleeds), subarachnoid bleeds, epidural bleeds, and subdural bleeds. ...
, or
retinal detachment Retinal detachment is a disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blin ...
. AD is triggered by either noxious or non-noxious stimuli, resulting in sympathetic stimulation and hyperactivity. The most common causes include bladder or bowel over-distension, from
urinary retention Urinary retention is an inability to completely empty the bladder. Onset can be sudden or gradual. When of sudden onset, symptoms include an inability to urinate and lower abdominal pain. When of gradual onset, symptoms may include loss of bladd ...
and fecal compaction, respectively. The resulting sympathetic surge transmits through intact
peripheral nerves The peripheral nervous system (PNS) is one of two components that make up the nervous system of bilateral animals, with the other part being the central nervous system (CNS). The PNS consists of nerves and ganglia, which lie outside the brain an ...
, resulting in systemic
vasoconstriction Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vessel ...
below the level of the spinal cord lesion. The peripheral arterial vasoconstriction and hypertension activates the baroreceptors, resulting in a
parasympathetic The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of t ...
surge originating in the
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...
to inhibit the sympathetic outflow; however, the parasympathetic signal is unable to transmit below the level of the spinal cord lesion. This results in bradycardia,
vasodilation Vasodilation is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstriction, ...
,
flushing Flushing may refer to: Places * Flushing, Cornwall, a village in the United Kingdom * Flushing, Queens, New York City ** Flushing Bay, a bay off the north shore of Queens ** Flushing Chinatown (法拉盛華埠), a community in Queens ** Flushing ...
, pupillary constriction and nasal stuffiness above the spinal lesion, while there is
piloerection Goose bumps, goosebumps or goose-pimples are the bumps on a person's skin at the base of body hairs which may involuntarily develop when a person is tickled, cold or experiencing strong emotions such as fear, euphoria or sexual arousal. The f ...
, pale and cool skin below the lesion due to the prevailing sympathetic outflow. Initial treatment involves sitting the patient upright, removing any constrictive clothing (including abdominal binders and support stockings), rechecking blood pressure frequently, and then checking for and removing the inciting issue, which may require
urinary catheterization In urinary catheterization a latex, polyurethane, or silicone tube known as a urinary catheter is inserted into the bladder through the urethra to allow urine to drain from the bladder for collection. It may also be used to inject liquids used ...
or bowel disimpaction. If systolic blood pressure remains elevated (over 150 mm Hg) after initial steps, fast-acting short-duration
antihypertensives Antihypertensives are a class of drugs that are used to treat hypertension (high blood pressure). Antihypertensive therapy seeks to prevent the complications of high blood pressure, such as stroke and myocardial infarction. Evidence suggests that r ...
are considered, while other inciting causes must be investigated for the symptoms to resolve. Prevention of AD involves educating the patient, family and caregivers of the precipitating cause, if known, and how to avoid it, as well as other triggers. Since bladder and bowel are common causes, prevention involves routine bladder and bowel programs and urological follow-up for
cystoscopy Cystoscopy is endoscopy of the urinary bladder via the urethra. It is carried out with a cystoscope. The urethra is the tube that carries urine from the bladder to the outside of the body. The cystoscope has lenses like a telescope or microscope ...
/
urodynamic Urodynamic testing or urodynamics is a study that assesses how the bladder and urethra are performing their job of storing and releasing urine. Urodynamic tests can help explain symptoms such as: * incontinence * frequent urination * sudden, s ...
studies.


Signs and symptoms

This condition is distinct and usually episodic, with the people potentially experiencing remarkably high blood pressure, intense headaches, profuse sweating, facial
erythema Erythema (from the Greek , meaning red) is redness of the skin or mucous membranes, caused by hyperemia (increased blood flow) in superficial capillaries. It occurs with any skin injury, infection, or inflammation. Examples of erythema not assoc ...
, goosebumps, nasal stuffiness, a "feeling of doom" or apprehension, and blurred vision. An elevation of 20 mm Hg over baseline systolic blood pressure, with a potential source below the neurological level of injury, meets the current definition of dysreflexia.


Complications

Autonomic dysreflexia can become chronic and recurrent, often in response to longstanding medical problems like soft tissue pressure injuries or hemorrhoids. Long term therapy may include alpha blockers or
calcium channel blocker Calcium channel blockers (CCB), calcium channel antagonists or calcium antagonists are a group of medications that disrupt the movement of calcium () through calcium channels. Calcium channel blockers are used as antihypertensive drugs, i.e., as ...
s. Complications of severe acute
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
can include seizures,
pulmonary edema Pulmonary edema, also known as pulmonary congestion, is excessive edema, liquid accumulation in the parenchyma, tissue and pulmonary alveolus, air spaces (usually alveoli) of the lungs. It leads to impaired gas exchange and may cause hypoxemia an ...
,
myocardial infarction A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may ...
, or
cerebral hemorrhage Intracerebral hemorrhage (ICH), also known as cerebral bleed, intraparenchymal bleed, and hemorrhagic stroke, or haemorrhagic stroke, is a sudden bleeding into the tissues of the brain, into its ventricles, or into both. It is one kind of bleed ...
. Additional organs that may be affected include the
kidneys The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; bloo ...
and
retinas The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...
of the eyes.


Causes

The first episode of autonomic dysreflexia may occur weeks to years after spinal cord injury takes place, but most people at risk (92%) develop their first episode within the first year after injury. The most common causative factor is bladder distention (responsible for approximately 85% of cases).https://www.ncbi.nlm.nih.gov/books/NBK482434/ Other common causes include a
urinary tract infection A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis) and when it affects the upper urinary tract it is known as a kidney ...
s, pressure ulcers, medication side effects and various disease processes.


Pain

Current scientific literature suggests that noxious (painful) stimuli below the level of the lesion are the primary initiators of AD. The most common such stimuli are distension of a hollow viscous such as the bladder or the rectum. Thus, assessment of autonomic dysreflexia in patients with known causative factors may include palpation of the bladder and bowel and can also include bladder scan. Not all noxious stimuli will cause AD. Some otherwise severe noxious stimuli, e.g. broken bones, may not result in AD, and may in fact even go unnoticed. Activation of pain receptors in muscle and skin below the lesion in spinal cord injured individuals did not trigger AD. These studies suggests that not all noxious stimuli are reliable triggers of AD, and because non-noxious stimuli can also trigger AD, attribution of an episode of AD to noxious stimuli may cause clinicians to overlook underlying non-noxious triggers. As a result, non-noxious trigger factors remain undetected, prolonging an episode of AD.


Mechanism

Supraspinal vasomotor neurons send projections to the intermediolateral cell column, which is composed of sympathetic
preganglionic neurons A ganglion is a group of neuron cell bodies in the peripheral nervous system. In the somatic nervous system this includes dorsal root ganglia and trigeminal ganglia among a few others. In the autonomic nervous system there are both sympatheti ...
(SPN) through the T1-L2 segments. The supraspinal neurons act on the SPN and its tonic firing, modulating its action on the peripheral sympathetic chain ganglia and the
adrenal medulla The adrenal medulla ( la, medulla glandulae suprarenalis) is part of the adrenal gland. It is located at the center of the gland, being surrounded by the adrenal cortex. It is the innermost part of the adrenal gland, consisting of chromaffin cel ...
. The sympathetic ganglia act directly on the blood vessels they innervate throughout the body, controlling vessel diameter and resistance, while the adrenal medulla indirectly controls the same action through the release of
epinephrine Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands and ...
and
norepinephrine Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter. The name "noradrenaline" (from Latin '' ad'', ...
. The descending autonomic pathways, which are responsible for the supraspinal communication with the SPN, are interrupted resulting in decreased sympathetic outflow below the level of the injury. In this circumstance, the SPN is controlled only by spinal influences. The first couple of weeks after a spinal injury, the decreased sympathetic outflow causes reduced blood pressure and sympathetic reflex. Eventually, synaptic reorganization and plasticity of SPN develops into an overly sensitive state, which results in abnormal reflex activation of SPN due to afferent stimuli, such as bowel or bladder distension. Reflex activation results in systemic vasoconstriction below the spinal cord disruption. The peripheral arterial vasoconstriction and hypertension activates the baroreceptors, resulting in a
parasympathetic The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of t ...
surge originating in the
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...
, which inhibits the sympathetic outflow; however, the parasympathetic signal is unable to transmit below the level of the spinal cord lesion. This results in
vasodilation Vasodilation is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstriction, ...
,
flushing Flushing may refer to: Places * Flushing, Cornwall, a village in the United Kingdom * Flushing, Queens, New York City ** Flushing Bay, a bay off the north shore of Queens ** Flushing Chinatown (法拉盛華埠), a community in Queens ** Flushing ...
, pupillary constriction and nasal stuffiness above the spinal lesion, while there's
piloerection Goose bumps, goosebumps or goose-pimples are the bumps on a person's skin at the base of body hairs which may involuntarily develop when a person is tickled, cold or experiencing strong emotions such as fear, euphoria or sexual arousal. The f ...
, pale and cool skin below the lesion due to the prevailing sympathetic outflow. The reason this issue is much more prominent for lesions at or above the T6 level is because the Splanchnic nerves emerge from the T5 level and below. Loss of brain's control over T6 and below causes splanchnic arteries to reflexively vasoconstrict and since the Splanchnic arteries are the body's largest reservoir for circulating blood, their vasoconstriction dramatically affects the blood pressure of the body.


Diagnosis

The symptoms are usually not subtle, although asymptomatic events have been documented. Autonomic dysreflexia differs from
autonomic instability Dysautonomia or autonomic dysfunction is a condition in which the autonomic nervous system (ANS) does not work properly. This may affect the functioning of the heart, bladder, intestines, sweat glands, pupils, and blood vessels. Dysautonomia has ...
, the various modest cardiac and neurological changes that accompany a spinal cord injury, including
bradycardia Bradycardia (also sinus bradycardia) is a slow resting heart rate, commonly under 60 beats per minute (BPM) as determined by an electrocardiogram. It is considered to be a normal heart rate during sleep, in young and healthy or elderly adults, a ...
,
orthostatic hypotension Orthostatic hypotension, also known as postural hypotension, is a medical condition wherein a person's blood pressure drops when standing up or sitting down. Primary orthostatic hypertension is also often referred to as neurogenic orthostatic hyp ...
, and ambient temperature intolerance. In autonomic dysreflexia, patients will experience hypertension, sweating, spasms (sometimes severe spasms) and
erythema Erythema (from the Greek , meaning red) is redness of the skin or mucous membranes, caused by hyperemia (increased blood flow) in superficial capillaries. It occurs with any skin injury, infection, or inflammation. Examples of erythema not assoc ...
(more likely in upper extremities) and may experience headaches and blurred vision. Mortality is rare with AD, but morbidity such as stroke, retinal hemorrhage and pulmonary edema if left untreated can be quite severe. Older patients with very incomplete spinal cord injuries and systolic
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
without symptoms are usually experiencing essential hypertension, not autonomic dysreflexia. Aggressive treatment of these elderly patients with rapidly acting
antihypertensive Antihypertensives are a class of drugs that are used to treat hypertension (high blood pressure). Antihypertensive therapy seeks to prevent the complications of high blood pressure, such as stroke and myocardial infarction. Evidence suggests tha ...
medications can have disastrous results.


Treatment

Proper treatment of autonomic dysreflexia involves administration of anti-hypertensives along with immediate determination and removal of the triggering stimuli. Often, sitting the patient up and dangling legs over the bedside can reduce blood pressures below dangerous levels and provide partial symptom relief. Tight clothing and stockings should be removed.
Straight catheterization Straight may refer to: Slang * Straight, slang for heterosexual ** Straight-acting, an LGBT person who does not exhibit the appearance or mannerisms of the gay stereotype * Straight, a member of the straight edge subculture Sport and games * St ...
of the bladder or relief of a blocked urinary catheter tube may resolve the problem. The rectum should be cleared of stool impaction, using anaesthetic lubricating jelly. If the noxious precipitating trigger cannot be identified, drug treatment is needed to decrease elevating intracranial pressure until further studies can identify the cause. Drug treatment includes the rapidly acting vasodilators, including sublingual or topical
nitrate Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...
s or oral hydralazine or
clonidine Clonidine, sold under the brand name Catapres among others, is an α2-adrenergic agonist medication used to treat high blood pressure, ADHD, drug withdrawal ( alcohol, opioids, or nicotine), menopausal flushing, diarrhea, spasticity, and c ...
. Ganglionic blockers are also used to control
sympathetic nervous system The sympathetic nervous system (SNS) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of th ...
outflow. Topical nitroglycerin ointment is a convenient and safe treatment—an inch or two can be applied to the chest wall or forehead, and wiped off when blood pressures begin to normalize. Autonomic dysreflexia is abolished temporarily by spinal or
general anaesthesia General anaesthesia (UK) or general anesthesia (US) is a medically induced loss of consciousness that renders the patient unarousable even with painful stimuli. This effect is achieved by administering either intravenous or inhalational general ...
. These treatments are used during obstetric delivery of women with autonomic dysreflexia.


Prognosis

The cause of autonomic dysreflexia itself can be life-threatening, and must also be completely investigated and treated appropriately to prevent unnecessary morbidity and mortality. The Consortium for Spinal Cord Medicine has developed evidence-based clinical practice guidelines for the management of autonomic dysreflexia in adults, children, and pregnant women. There is also a consumer version of this guideline.


References


Further reading

* * * *


External links

{{Shock types Neurotrauma Medical emergencies Medical terminology Peripheral nervous system disorders