Autonomic Dysreflexia (Autonomic Hyperreflexia)

Autonomic dysreflexia is a dangerous clinical condition in patients with severe spinal cord injury at or above the level of the sixth thoracic vertebra (T6). It causes sudden uncontrolled and life-threatening hypertension because of inadequate physiological balancing by the two parts of the autonomic nervous system – the sympathetic and parasympathetic pathways.

Autonomic Dysreflexia originates from the following process: pathophysiological.

Presentation

Patients usually present with one of several symptoms –

Clinical examination reflects the split nature of the condition -there is bradycardia, constriction off the pupils and nasal congestion [6].

Above the level of the injury the skin reflects unopposed parasympathetic activity with -

while below the lesion there is sympathetic activity but no inhibition by descending parasympathetic activity–

A range of underlying problems can induce attacks. These include (but are not limited to) – [7]

  • Urinary tract problems - bladder distension, urinary tract infection, calculus;
  • Gastrointestinal tract disturbances - Bowel distension or impaction, gastritis, gastric reflux or ulcers, gallstones, gastrocolic irritation, anal fissures, hemorrhoids or appendicitis;
  • Reproductive tract stimulation – menstruation, pregnancy (especially labour and delivery), vaginitis, sexual intercourse, ejaculation, epididymitis, scrotal compression;
  • Invasive investigations - cystoscopy, colonoscopy, surgery;
  • Vascular conditions - deep vein thrombosis, pulmonary emboli;
  • Skin problems – blisters, burns or sunburn, contact with hard or sharp objects, constrictive clothing, shoes, or appliances, pressure ulcers, ingrowing toenail, insect bites;
  • Temperature fluctuations;
  • Bone disease or damage – fractures, arthritis.

Workup

Clinical examination should identify the distribution of skin signs;

Blood pressure rise above baseline will be significant in both systolic and diastolic – more than 20mm Hg systolic and more than 10 mm Hg diastolic. This will be associated with bradycardia.

Treatment

Treatment depends on early diagnosis of the condition by all those involved with the patient, including the family, to enable ots prompt implementation.

Patients should never be left alone since this is a medical emergency.

Elevate the patient’s head, lower his/her feet to reduce the blood pressure and loosen clothing.

Correction relies upon prompt removal of the underlying cause – ask the patients for their suggestion as to the cause.

Short-acting antihypertensive drugs may be administered but care must be taken onrecent or intercurrent administration of medication for erectile dysfunction e.g. (Viagra), Vardenafil (Levitra) or Tadalafal (Cialis) [8].

Oral mediations may include glyceryl trinitrate or (spray or tablets) or nifedipine (Adalat) tablets.
Parenteral agents may be used in an appropriate hospital setting potentially with adequate analgesia (e.g morphine) or local epidural anaesthesia.

Prognosis

The severity of the underlying spinal lesion makes autonomic dysreflexia a constant threat to such patients. Sustained hypertension can lead to a wide range of secondary hypertensive problems including brain and retinal hemorrhages, myocardial infarction or seizures, and some of these can prove fatal [5].

Etiology

Autonomic dysreflexia is caused by a lesion in the spinal cord at, or above, the level of the thoracic vertebra 6 (T6) that affects neural pathway and the flow of impulses to and from the brain. This means that the sympathetic nervous system is dominant below the level of the spinal and neurological injury while the parasympathetic system is dominant above it. Trauma is the most likely cause of such an injury [2].

Epidemiology

The autonomic nervous system is that part of the peripheral nervous system which carries motor information to the visceral organs and glands of the body. Its sympathetic fibres control the body’s ‘fight-or-flight’ response by increasing bronchodilation and blood flow to skeletal muscles and the lungs while diverting blood flow away from the less important gastrointestinal tract and skin. It also increases the heart rate and the contractility of cardiac muscle. Conversely the parasympathetic fibres (mainly through cranial nerves X - the vagus nerve - and sacral nerves S1, S2 and S3) act in opposition to the sympathetic system through a negative feedback control. The parasympathetic action is the preservation of energy and recovery from ‘fight-or-flight’. Mechanisms include reducing heart rate and blood pressure, encouraging digestion and absorption of food and excreting waste products [3].

The level of T6 is of great significance because the great splanchnic vasculature derives its innervation from T5 – T9. Lesions below T6 usually allow enough descending parasympathetic pathways to exert adequate inhibition of the sympathetic activity.

With autonomic dysreflexia, the body’s physiological response is not balanced correctly. A strong input from sensory nerves originating below the spinal lesion will enter the spinal cord and rise towards the brain. However, passage beyond the site of the spinal injury is limited or non-existent. As a result the influence of the sympathetic reflex is far greater than any counterbalance by the parasympathetic part of the system. Common sources of this sensory input are the bladder or the bowels.

Sex distribution
Age distribution

Pathophysiology

The pathophysiology of autonomic dysreflexia has not been fully identified yet. It has been suggested that peripheral alpha-adrenergic receptors develop increased responsivity below the spinal lesion and that this is linked with a low basal catecholamine levels as a result of the spinal injury. These receptors potentially have a lowered threshold for adrenergic stimulation, as well.

Large sensory input stimulates a massive reflex discharge in the thoracolumbar sympathetic nervous system and the paraspinal sympathetic ganglia. This results in direct vasoconstriction by nerve stimulation of perivascular receptors and indirect vasoconstriction by the epinephrine and norepinephrine released into circulation by the adrenal medulla. This in turn results in widespread vasoconstriction, mainly in the splanchnic (subdiaphragmatic) vasculature. The result is hypertension mainly through peripheral and splanchnic vasoconstriction [4].

Baroreceptors in the neck detect the pressure changes and transmit information to the brain through the glossopharyngeal and vagal nerves (cranial nerves IX and X). In response, the brain carries out two activities:

  • it sends descending inhibitory impulses to shut down the sympathetic surge;
  • it attempts to reduce peripheral blood pressure by slowing the heart rate via the vagus nerve.

In autonomic dysreflexia, the spinal lesion prevents all, or most, brain impulses from reaching the sympathetic outflow levels. In this situation the compensatory bradycardia alone is inadequate  to reduce the hypertension.

The absence of spinal cord integrity means that hypertension remains uncontrolled.

Prevention

All those involved with the patient, including the patient and family, should be trained in the importance of effective management to prevent development of underlying causes, especially constipation or bladder distension [9].

Care of the patient is critical to preventing episodes of this condition. Correct bladder and bowel care is most important to prevent faecal impaction or distension of the bladder. In general, strict hygiene must be maintained during regular bladder routines whether using intermittent catheterisation or in-dwelling Foley catheters. Routines should include regular urological follow-up to monitor the status of the bladder.

Similarly, a routine to maintain appropriate and adequate bowel activity should be developed to prevent constipation.

The prophylactic use of local anaesthetic creams and gels, e.g. dibucaine or lidocaine, for any catheterisation or ano-rectal procedures will reduce the likelihood of autonomic dysreflexia episodes [10].

Summary

Autonomic dysreflexia is a medical emergency that affects a large percentage of patients with a spinal cord injury at the level of the sixth thoracic vertebra (T6) or above. The more extensive the injury the more likely the patient is to suffer from episodes of this condition [1].
Episodes occur because of the inability of the two components of the autonomic nervous system - the sympathetic and parasympathetic – to act together as they should. The sympathetic dominates and creates chronic hypertension that leads to potentially severe results such as myocardial infarcts and brain hemorrhages.

Patient Information

Definition: Acute hypertension in patients suffering from aspinal cord lesion at the level of thoracic vertebra 6 or above, due to the inability of the body’s autonomic nervous system to work effectively because of the spinal lesion itself.

Cause: Normally the sympathetic and parasympathetic parts of the autonomic nervous system work in tandem in a balanced system. A lesion in the spinal cord at T6 or above creates a massive spinal reflex activity by the sympathetic pathways but prevents instruction from the brain through the parasympathetic system from counteracting them. The net result is major vasoconstriction of the splanchnic vessels and massive hypertension.

Symptoms: The symptoms in a patient already experiencing the problems of a damaged spinal cord are commonly headaches, blurred vision or spots before the eyes with constricted pupils, nasal congestion, a feeling of impending doom or apprehension, bradycardia and associated skin changes. Above the level of the spinal lesion the skin is sweating and blotchy, while below it the skin is cool and pale with piloerection and goosebumps. There is an inevitable clinical problem causing an overload of sensory input from the lower half of the body, most commonly from bladder distension or bowel overload.

The blood pressure is significantly raised above baseline levels in both systolic and diastolic phases.

Diagnosis: Diagnosis is primarily based on the patients having a spinal cord lesion and showing the relevant changes in blood pressure and other signs of sympathetic and parasympathetic imbalance, with sweating and blotchy skin above the lesion and pale, cold skin with piloerection and goosebumps below it.

Treatment: Effective treatment requires removal of the underlying cause, e.g distension of the bladder or bowel. Medication may be needed to lower the hypertension but care must be taken to prevent any adverse effects with concomitant medications.

Prevention: Autonomic dysreflexia is prevented by having a well-practised routines for control of potential causes such as impairment of urine or fecal flow and the prevention of pain or discomfort such as ulcers, insect bites, sunburn or infections. All investigations and procedures should be carried out with strict asepsis and adequate analgesia. Labour and childbirth are highly likely to induce episodes of the condition and so adequate preventative measures should be implemented.

Self-assessment

References

  1. Cormier CM, Mukhida K, Walker G, Marsh DR. Development of autonomic dysreflexia after spinal cord injury is associated with a lack of serotonergic axons in the intermediolateral cell column. J Neurotrauma. Oct 2010;27(10):1805-18.
  2. Teasell RW, Arnold JM, Krassioukov A, Delaney GA. Cardiovascular consequences of loss of supraspinal control of the sympathetic nervous system after spinal cord injury. Arch Phys Med Rehabil. Apr 2000;81(4):506-16.
  3. Cardenas DD, Hoffman JM, Kirshblum S, McKinley W. Etiology and incidence of rehospitalization after traumatic spinal cord injury: a multicenter analysis. Arch Phys Med Rehabil 2004; 85:1757.
  4. Roatta S, Farina D. Sympathetic actions on the skeletal muscle. Exerc Sport Sci Rev. Jan 2010;38(1):31-5.
  5. Kirshblum SC, Priebe MM, Ho CH, et al. Spinal cord injury medicine. 3. Rehabilitation phase after acute spinal cord injury. Arch Phys Med Rehabil 2007; 88:S62.
  6. Lindan R, Joiner F, Freechafer A, Hazel C. Incidence and clinical features of autonomic dysreflexia in patients with spinal cord injury. Paraplegia. 1980;18:285-292.
  7. Wan D, Krassioukov AV. Life-threatening outcomes associated with autonomic dysreflexia: a clinical review.J Spinal Cord Med. Jan 2014;37(1):2-10
  8. McMahon D, Tutt M, Cook AM. Pharmacological management of hemodynamic complications following spinal cord injury. Orthopedics. May 2009;32(5):331.
  9. Glickman S, Kamm MA. Bowel dysfunction in spinal-cord-injury patients. Lancet 1996; 347:1651.
  10. Chiodo AE, Scelza WM, Kirshblum SC, et al. Spinal cord injury medicine. 5. Long-term medical issues and health maintenance. Arch Phys Med Rehabil 2007; 88:S76.

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Self-assessment