Last Updated: May 24, 2001
Background: Autonomic dysreflexia (AD) is a syndrome of massive imbalanced reflex sympathetic discharge occurring in patients with spinal cord injury (SCI) above the splanchnic sympathetic outflow (T5-T6). Anthony Bowlby first recognized this syndrome in 1890 when he described profuse sweating and erythematous rash of the head and neck initiated by bladder catheterization in an 18-year-old patient with SCI. Guttmann and Whitteridge completed a full description of the syndrome in 1947. This condition represents a medical emergency, so recognizing and treating the earliest signs and symptoms efficiently can avoid dangerous sequelae of elevated blood pressure. SCI patients, caregivers, and medical professionals must be knowledgeable about this syndrome and its management.
Pathophysiology: This phenomenon occurs after the phase of spinal shock in which reflexes return. Individuals with injury above the major splanchnic outflow may develop AD. Below the injury, intact peripheral sensory nerves transmit impulses that ascend in the spinothalamic and posterior columns to stimulate sympathetic neurons located in the intermediolateral gray matter of the spinal cord. The inhibitory outflow above the SCI from cerebral vasomotor centers is increased, but it is unable to pass below the block of the SCI. This large sympathetic outflow causes release of various neurotransmitters (norepinephrine, dopamine-b-hydroxylase, dopamine), causing piloerection, skin pallor, and severe vasoconstriction in arterial vasculature. The result is sudden elevation in blood pressure and vasodilation above the level of injury. Patients commonly have a headache caused by vasodilation of pain sensitive intracranial vessels.
Vasomotor brainstem reflexes attempt to lower blood pressure by increasing parasympathetic stimulation to the heart through the vagus nerve to cause compensatory bradycardia. This reflex action cannot compensate for severe vasoconstriction, explained by the Poiseuille formula, where pressure in a tube is affected to the fourth power by change in radius (vasoconstriction) and only linearly by change in flow rate (bradycardia). Parasympathetic nerves prevail above the level of injury, which may be characterized by profuse sweating and vasodilation with skin flushing.
Frequency:
In the US: Incidence reported in the literature varies; however, generally reported figures suggest incidence in 48-90% of all individuals who are injured at T6 and above. Some incidence has been reported in SCI as low as T10. AD occurs during labor in approximately two thirds of pregnant women with SCI above the level of T6. The occurrence of AD increases as the patient evolves out of spinal shock. With the return of sacral reflexes, the possibility of AD increases.
Mortality/Morbidity: Morbidity is associated with the hypertension, which can cause retinal/cerebral hemorrhage, myocardial infarction, or seizures. Mortality is rare.
Sex: The male-to-female ratio for sustaining SCI is 4:1; therefore, AD is primarily a male phenomenon.
Age: No specific relationship has been documented between AD and age.
History: The patient generally gives a history of blurry vision, headaches, and a sense of anxiety. Feelings of apprehension or anxiety over an impending physical problem commonly are exhibited.
Physical: A patient may have one or more of the following findings on physical examination:
Causes: Episodes of AD can be triggered by many potential causes. Essentially any painful, irritating, or even strong stimulus below the level of the injury can cause an episode of AD. Although the list is not comprehensive, the following events or conditions all can cause episodes of AD:
Other Problems to be Considered:
Essential hypertension
Pheochromocytoma
Physical Therapy: Physical therapists who treat SCI patients need to have a good understanding of AD and be familiar with the signs and symptoms of this potentially life-threatening condition. When completing physical therapy sessions, the therapist needs to monitor the urinary catheter for any blockage or twisting. If the patient becomes hypertensive during therapy, he/she should be placed in an upright position immediately, rather than remain in a supine or reclining position. The therapist needs to complete careful inspection to identify the source of painful stimuli (eg, catheter, restrictive clothing, leg bag straps, abdominal supports, orthoses).
A less common cause of AD during physical therapy sessions may originate with muscle stretching, either from range of motion (ROM) or passive stretching. If the patient develops AD, the physical therapist needs to treat it as a medical emergency and be familiar with established protocols for medical management within his/her particular setting. The individual therapy session then must be discontinued to allow the patient to stabilize and recover.
Occupational Therapy: Occupational therapy is another discipline involved extensively in the rehabilitation of individuals with SCI. The occupational therapist also must be familiar with the signs and symptoms of AD and be able to respond quickly if the condition develops during a therapy session. The occupational therapist performs extensive training in the performance of activities of daily living (ADL) with patients who have sustained SCI. ADL includes proper bowel and bladder management, which can help prevent the occurrence of AD. The occupational therapist may be involved in establishing a regular bowel program and also may complete patient and family/caregiver education on this aspect of care. Both the occupational and physical therapists should educate the patient and family members about AD and ensure that they are familiar with prevention strategies, signs and symptoms, and proper management of the condition.
Speech Therapy: Generally, the treatment provided by the speech therapist is not associated with any painful stimuli below the lesion that may precipitate an AD response; however, as health care providers involved in the care of individuals with SCI, the speech therapist must be familiar with the manifestations of this potential life-threatening complication.
Recreational Therapy: Recreational therapists also are important members of the rehabilitation team, as they help patients with SCI to become involved in recreational and social activities. As members of the SCI team, they also must be knowledgeable about AD and know how to respond appropriately if the patient develops symptoms during a recreational therapy session.
Medical Issues/Complications:
Complications result directly from sustained severe peripheral hypertension and include retinal/cerebral hemorrhage, myocardial infarction, and seizures.
Consultations:
If the cause of the AD episode is not found and blood pressure remains elevated, recommend that the patient go to the nearest Emergency Department for close monitoring and further investigation of the possible cause. Consult an intensive care specialist for ICU monitoring and treatment of the hypertension.
Check the patient's blood pressure. If blood pressure is elevated and the person is supine, have the person sit up immediately and loosen any clothing or constrictive devices. Sitting leads to pooling of blood in the lower extremities and may reduce blood pressure. Monitor blood pressure and pulse every 2-5 minutes until they have stabilized; blood pressures can fluctuate quickly during an AD episode from impaired autonomic regulation. Survey the person for instigating causes, beginning with the urinary system, the most common cause of AD.
If an indwelling urinary catheter is not in place, catheterize the patient.
If the individual has an indwelling urinary catheter, check the system along its entire length for kinks, folds, constrictions, or obstructions and for correct placement of the indwelling catheter.
If the catheter appears to be blocked, gently irrigate the bladder with a small amount of fluid, such as normal saline at body temperature. Avoid manually compressing or tapping on the bladder.
If the catheter is draining and blood pressure remains elevated, suspect fecal impaction, the second most common cause of AD, and check the rectum for stool using lidocaine jelly as lubricant.
Use an antihypertensive agent with rapid onset and short duration while the causes of AD are being investigated.
The most commonly used agents are nifedipine and nitrates (eg, nitroglycerine paste). Nifedipine should be in the immediate release form; bite-and-swallow is the preferred method of administration, NOT sublingual. Other agents used are mecamylamine, diazoxide, and phenoxybenzamine.
Use antihypertensives with extreme caution in older persons or people with coronary artery disease.
Monitor the individual's symptoms and blood pressure for at least 2 hours after resolution of the AD episode to ensure that elevation of blood pressure does not recur. AD may resolve because of medication, not because of resolution of the underlying cause.
If there is poor response to treatment and/or if the cause of the AD has not been identified, send the patient to ER for monitoring, maintenance of pharmacologic control of blood pressure, and investigation of other possible causes of the AD.
Document the episode.
Deterrence/Prevention:
Good bladder and bowel care (ie, preventing fecal impaction, bladder distention) are mainstays in preventing episodes of AD.
Patient Education:
All medical professionals should educate the patient and family members or caregivers about this potentially life-threatening complication of SCI.
Medical/Legal Pitfalls:
Failure to have a high index of suspicion and recognize the problem quickly could present medical and legal problems for the physician. For example, a physician who assumes that headache and anxiety in a person with complete C6 tetraplegia is a manifestation of depression, without checking vital signs, is at medical/legal risk.
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