Autonomic dysreflexia
Encyclopedia
Autonomic dysreflexia, "AD" also known as "autonomic hyperreflexia or Hyperreflexia
, is a potentially life threatening condition which can be considered a medical emergency
requiring immediate attention. AD occurs most often in spinal cord-injured individuals with spinal lesions above the T6 spinal cord level. Acute AD is a reaction of the autonomic (involuntary) nervous system to overstimulation. It is characterised by severe paroxysmal hypertension
(episodic high blood pressure) associated with throbbing headaches, profuse sweating, nasal stuffiness, flushing of the skin above the level of the lesion, bradycardia
, apprehension and anxiety, which is sometimes accompanied by cognitive impairment. The sympathetic
discharge that occurs is usually in association with spinal cord injury
(SCI) or disease (e.g. multiple sclerosis
). AD is believed to be triggered by afferent
stimuli (nerve signals that send messages back to the spinal cord and brain) which originate below the level of the spinal cord lesion. It is believed that these afferent stimuli trigger and maintain an increase in blood pressure via a sympathetically mediated vasoconstriction
in muscle, skin and splanchnic (gut) vascular beds.
in patients with spinal cord injury are loss of bowel and bladder function, resulting in impaction in the case of the bowels and distention in case of the bladder. These are generally found in patients with a spinal cord injury above the T6 (6th Thoracic Vertebral) level, but can occur in patients with a transection as low as T10 (10th Thoracic Vertebral) level. When a painful stimulus occurs, as when voiding is interrupted or a bowel obstruction occurs, nerve impulses are sent to the brain via the spinal cord. However, in spinal cord transection, these impulses are unable to travel past the injury. This results in a spinal cord reflex to the autonomic nervous system in response to pain. In patients with spinal cord transection, types of stimulation that are tolerated by healthy people create an excessive response from the person's nervous system.
Other causes include medication side effects and various disease processes. The use of stimulants such as cocaine and amphetamines which can result in urinary retention, and the use of CNS depressants and other psychotropic and psychoactive drugs can also lead to urinary retention and constipation thus leading to autonomic dysreflexia when in use over an extended period of time. Guillain-Barre syndrome
a demyelinating disease that can result in peripheral paralysis can progress to encompass autonomic functions leading to a loss of normal respiratory, bladder and bowel function, thus resulting in autonomic dysreflexia. Severe head trauma, and other brain injuries can instigate autonomic dysreflexia at the Central Nervous System
by interfering with the reception of the signal that brings the urge to void the bladder and bowels and with the volutary abiliity to micturate and defecate.
Other causal theories for Autonomic Dysreflexia include Noxious Stimuli or painful stimuli arising from the peripheral sensory neurons. These stimuli are interrupted in their journey to the brain due to a transection of the spine result in a paradoxical stimulation of autonomic pathways of the Autonomic Nervous System
.
Controversy Over Peripherally Noxious Causes of Autonomic Dysreflexia
Current scientific literature suggests that noxious (painful) stimuli are the primary initiators of AD. However, different studies have found that 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. They concluded that when deducing the potential causes of AD it is important to consider non-noxious sources of stimulation in addition to noxious triggers. Current Assessment of Autonomic Dysreflexia in patients with known causitive factors include palpation of the bladder and bowel and can also include bladder scan.
, orthostatic hypotension
, and ambient temperature intolerance. In autonomic dysreflexia, patients will experience hypertension, sweating, and erythema
(more likely in upper extremities) and may suffer from 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
without symptoms are usually experiencing essential hypertension, not autonomic dysreflexia. Aggressive treatment of these elderly patients with rapidly acting antihypertensive
medications can have disastrous results.
. It has rarely been reported in spinal cord lesions as low as T10. The first episode may occur weeks to years after spinal cord injury takes place, but most people at risk (80%) develop their first episode within the first year after injury.
readings over 200 mm. Hg), intense headaches, profuse sweating, facial erythema
, goosebumps, nasal stuffiness, and a "feeling of doom". An elevation of 40 mm. Hg. over baseline systolic should be suspicious for dysreflexia.
Drug treatment includes the rapidly acting vasodilators, including sublingual nitrate
s or oral clonidine
. Topical nitropaste is a convenient and safe treatment—an inch or two can be applied to the chest wall, and wiped off when blood pressures begin to normalize. Autonomic dysreflexia is abolished temporarily by spinal
or general anaesthesia
. These treatment are used during obstetric delivery of a woman with autonomic dysreflexia.
s or calcium channel blocker
s.
Complications of severe acute hypertension
can include seizures, pulmonary edema
, myocardial infarction
or cerebral hemorrhage.
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.
Hyperreflexia
Hyperreflexia is defined as overactive or overresponsive reflexes. Examples of this can include twitching or spastic tendencies, which are indicative of upper motor neuron disease as well as the lessening or loss of control ordinarily exerted by higher brain centers of lower neural pathways...
, is a potentially life threatening condition which can be considered a medical emergency
Medical emergency
A medical emergency is an injury or illness that is acute and poses an immediate risk to a person's life or long term health. These emergencies may require assistance from another person, who should ideally be suitably qualified to do so, although some of these emergencies can be dealt with by the...
requiring immediate attention. AD occurs most often in spinal cord-injured individuals with spinal lesions above the T6 spinal cord level. Acute AD is a reaction of the autonomic (involuntary) nervous system to overstimulation. It is characterised by severe paroxysmal hypertension
Paroxysmal hypertension
Paroxysmal hypertension is episodic high blood pressure, which may be due to stress of any sort or from phaeochromocytoma, a type of tumor involving the adrenal medulla. Patients with paroxysmal hypertension who test negative for phaeochromocytoma are said to be suffering from...
(episodic high blood pressure) associated with throbbing headaches, profuse sweating, nasal stuffiness, flushing of the skin above the level of the lesion, bradycardia
Bradycardia
Bradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart...
, apprehension and anxiety, which is sometimes accompanied by cognitive impairment. The sympathetic
Sympathetic nervous system
The sympathetic nervous system is one of the three parts of the autonomic nervous system, along with the enteric and parasympathetic systems. Its general action is to mobilize the body's nervous system fight-or-flight response...
discharge that occurs is usually in association with spinal cord injury
Spinal cord injury
A spinal cord injury refers to any injury to the spinal cord that is caused by trauma instead of disease. Depending on where the spinal cord and nerve roots are damaged, the symptoms can vary widely, from pain to paralysis to incontinence...
(SCI) or disease (e.g. multiple sclerosis
Multiple sclerosis
Multiple sclerosis is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms...
). AD is believed to be triggered by afferent
Afferent
Afferent is an anatomical term with the following meanings:*Conveying towards a center, for example the afferent arterioles conveying blood towards the Bowman's capsule in the Kidney. Opposite to Efferent.*Something that so conducts, see Afferent nerve fiber...
stimuli (nerve signals that send messages back to the spinal cord and brain) which originate below the level of the spinal cord lesion. It is believed that these afferent stimuli trigger and maintain an increase in blood pressure via a sympathetically mediated vasoconstriction
Vasoconstriction
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...
in muscle, skin and splanchnic (gut) vascular beds.
Causes
The most common causes hyperreflexiaHyperreflexia
Hyperreflexia is defined as overactive or overresponsive reflexes. Examples of this can include twitching or spastic tendencies, which are indicative of upper motor neuron disease as well as the lessening or loss of control ordinarily exerted by higher brain centers of lower neural pathways...
in patients with spinal cord injury are loss of bowel and bladder function, resulting in impaction in the case of the bowels and distention in case of the bladder. These are generally found in patients with a spinal cord injury above the T6 (6th Thoracic Vertebral) level, but can occur in patients with a transection as low as T10 (10th Thoracic Vertebral) level. When a painful stimulus occurs, as when voiding is interrupted or a bowel obstruction occurs, nerve impulses are sent to the brain via the spinal cord. However, in spinal cord transection, these impulses are unable to travel past the injury. This results in a spinal cord reflex to the autonomic nervous system in response to pain. In patients with spinal cord transection, types of stimulation that are tolerated by healthy people create an excessive response from the person's nervous system.
Other causes include medication side effects and various disease processes. The use of stimulants such as cocaine and amphetamines which can result in urinary retention, and the use of CNS depressants and other psychotropic and psychoactive drugs can also lead to urinary retention and constipation thus leading to autonomic dysreflexia when in use over an extended period of time. Guillain-Barre syndrome
Guillain-Barré syndrome
Guillain–Barré syndrome , sometimes called Landry's paralysis, is an acute inflammatory demyelinating polyneuropathy , a disorder affecting the peripheral nervous system. Ascending paralysis, weakness beginning in the feet and hands and migrating towards the trunk, is the most typical symptom...
a demyelinating disease that can result in peripheral paralysis can progress to encompass autonomic functions leading to a loss of normal respiratory, bladder and bowel function, thus resulting in autonomic dysreflexia. Severe head trauma, and other brain injuries can instigate autonomic dysreflexia at the Central Nervous System
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
by interfering with the reception of the signal that brings the urge to void the bladder and bowels and with the volutary abiliity to micturate and defecate.
Other causal theories for Autonomic Dysreflexia include Noxious Stimuli or painful stimuli arising from the peripheral sensory neurons. These stimuli are interrupted in their journey to the brain due to a transection of the spine result in a paradoxical stimulation of autonomic pathways of the Autonomic Nervous System
Autonomic nervous system
The autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils,...
.
Controversy Over Peripherally Noxious Causes of Autonomic Dysreflexia
Current scientific literature suggests that noxious (painful) stimuli are the primary initiators of AD. However, different studies have found that 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. They concluded that when deducing the potential causes of AD it is important to consider non-noxious sources of stimulation in addition to noxious triggers. Current Assessment of Autonomic Dysreflexia in patients with known causitive factors include palpation of the bladder and bowel and can also include bladder scan.
Diagnosis
The diagnosis is usually not subtle, although asymptomatic events have been documented. Autonomic dysreflexia differs from autonomic instability, a term used to describe the variety of modest cardiac and neurological changes that accompany a spinal cord injury, including bradycardiaBradycardia
Bradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart...
, orthostatic hypotension
Orthostatic hypotension
Orthostatic hypotension, also known as postural hypotension, orthostasis, and colloquially as head rush or dizzy spell, is a form of hypotension in which a person's blood pressure suddenly falls when the person stands up or stretches. The decrease is typically greater than 20/10 mm Hg, and may be...
, and ambient temperature intolerance. In autonomic dysreflexia, patients will experience hypertension, sweating, and erythema
Erythema
Erythema is redness of the skin, caused by hyperemia of the capillaries in the lower layers of the skin. It occurs with any skin injury, infection, or inflammation...
(more likely in upper extremities) and may suffer from 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
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...
without symptoms are usually experiencing essential hypertension, not autonomic dysreflexia. Aggressive treatment of these elderly patients with rapidly acting antihypertensive
Antihypertensive
The antihypertensives are a class of drugs that are used to treat hypertension . Evidence suggests that reduction of the blood pressure by 5 mmHg can decrease the risk of stroke by 34%, of ischaemic heart disease by 21%, and reduce the likelihood of dementia, heart failure, and mortality from...
medications can have disastrous results.
Onset
The risk is greatest with cervical spinal cord lesions and is rare with lesions below T6 Thoracic vertebraeThoracic vertebrae
In human anatomy, twelve thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. They are intermediate in size between those of the cervical and lumbar regions; they increase in size as one proceeds down the spine, the upper...
. It has rarely been reported in spinal cord lesions as low as T10. The first episode may occur weeks to years after spinal cord injury takes place, but most people at risk (80%) develop their first episode within the first year after injury.
Symptoms
This condition is distinct and usually episodic, with the patient experiencing remarkably high blood pressure (often with systolicSystole (medicine)
Systole is the contraction of the heart. Used alone, it usually means the contraction of the left ventricle.In all mammals, the heart has 4 chambers. The left and right ventricles pump together. The atria and ventricles pump in sequence...
readings over 200 mm. Hg), intense headaches, profuse sweating, facial erythema
Erythema
Erythema is redness of the skin, caused by hyperemia of the capillaries in the lower layers of the skin. It occurs with any skin injury, infection, or inflammation...
, goosebumps, nasal stuffiness, and a "feeling of doom". An elevation of 40 mm. Hg. over baseline systolic should be suspicious for dysreflexia.
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. Catheterization 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 nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...
s or oral 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...
. Topical nitropaste is a convenient and safe treatment—an inch or two can be applied to the chest wall, and wiped off when blood pressures begin to normalize. Autonomic dysreflexia is abolished temporarily by spinal
Spinal anaesthesia
Spinal anaesthesia , also called spinal analgesia or sub-arachnoid block , is a form of regional anaesthesia involving injection of a local anaesthetic into the subarachnoid space, generally through a fine needle, usually 9 cm long...
or general anaesthesia
General anaesthesia
General anaesthesia is a state of unconsciousness and loss of protective reflexes resulting from the administration of one or more general anaesthetic agents...
. These treatment are used during obstetric delivery of a woman with autonomic dysreflexia.
Complications
Autonomic dysreflexia can become chronic and recurrent, often in response to longstanding medical problems like soft tissue ulcers or hemorrhoids. Long term therapy may include alpha blockerAlpha blocker
Alpha-1 blockers constitute a variety of drugs which block α1-adrenergic receptors in arteries and smooth muscles.-Pharmacology:...
s or calcium channel blocker
Calcium channel blocker
A calcium channel blocker is a chemical that disrupts the movement of calcium through calcium channels.CCB drugs devised to target neurons are used as antiepileptics. However, the most widespread clinical usage of calcium channel blockers is to decrease blood pressure in patients with...
s.
Complications of severe acute 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...
can include seizures, pulmonary edema
Pulmonary edema
Pulmonary edema , or oedema , is fluid accumulation in the air spaces and parenchyma of the lungs. It leads to impaired gas exchange and may cause respiratory failure...
, myocardial infarction
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
or cerebral hemorrhage.
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.