3.3 Autonomic Dysreflexia Recognition & Emergency Protocols

Autonomic Dysreflexia

Autonomic Dysreflexia (AD), also known as autonomic hyperreflexia, is an acute, life-threatening syndrome characterized by massive, uninhibited cardiovascular sympathetic discharge. It is considered a medical emergency. If not promptly recognized and treated, the severe hypertension can lead to status epilepticus, myocardial infarction, intracranial hemorrhage, and death. AD typically occurs after spinal shock has resolved and is a lifelong risk for individuals with spinal cord injuries at or above the T6 level.

Pathophysiology

The mechanism of AD involves a disconnect between the sensory input, the sympathetic nervous system, and the brain's control mechanisms.

1. The Trigger: An unperceived noxious (painful or irritating) stimulus occurs below the level of the spinal cord injury. Because the spinal cord is damaged, these sensory pain signals cannot reach the brain to be consciously perceived.
2. Sympathetic Surge: These blocked sensory signals instead trigger a massive reflex sympathetic surge from the thoracolumbar sympathetic nerves located below the level of injury. This causes profound, widespread vasoconstriction in the splanchnic bed and lower extremities.
3. Hypertension: The massive vasoconstriction leads to a rapid and severe increase in systemic blood pressure.
4. Baroreceptor Response: The carotid and aortic baroreceptors detect the dangerous spike in blood pressure and send signals to the brainstem (vasomotor center).
5. The Disconnect: The brain attempts to lower the blood pressure in two ways. First, it sends inhibitory parasympathetic signals via the vagus nerve, which slows the heart rate (bradycardia). Second, it attempts to send inhibitory signals down the spinal cord to stop the sympathetic surge and cause vasodilation. However, these inhibitory signals cannot pass the spinal cord lesion.
6. The Result: The patient experiences severe hypertension and reflex bradycardia. Vasodilation occurs above the level of injury (causing flushing, sweating, and headache), while profound vasoconstriction persists below the level of injury (causing pale, cool skin).

Recognizing the Symptoms

Nurses must maintain a high index of suspicion for AD in any patient with a T6 or higher injury who suddenly develops a headache. Symptoms can develop rapidly:

• Severe, Pounding Headache: Often the first and most prominent symptom reported by the patient.
• Hypertension: A sudden, significant elevation in blood pressure. Crucial Note: Patients with high-level SCI typically have low baseline resting blood pressures (e.g., 90/60 mmHg). Therefore, a blood pressure of 130/80 mmHg in these patients may represent a hypertensive emergency.
• Bradycardia: The heart rate drops reflexively, often into the 40s or 50s.
• Diaphoresis and Flushing: Profuse sweating and flushed, erythematous skin above the level of injury (face, neck, upper chest).
• Pallor and Piloerection: Pale, cool skin and goosebumps (piloerection) below the level of injury due to severe vasoconstriction.
• Nasal Congestion and Blurred Vision: Other common signs of cranial vasodilation.
• Apprehension and Anxiety: The patient often reports a feeling of impending doom.

Common Triggers

The most common triggers are related to the bladder, bowel, and skin. Finding the trigger is the key to treatment.

Emergency Nursing Protocols

Immediate, aggressive intervention is required. Do not wait for a physician's order to initiate the basic protocol.

1. Sit the Patient Up: Immediately elevate the head of the bed to 90 degrees or sit the patient upright. This takes advantage of orthostatic hypotension to help lower the blood pressure.
2. Assess and Monitor: Monitor blood pressure and heart rate every 2-5 minutes.
3. Loosen Tight Clothing: Remove any constrictive clothing, abdominal binders, or anti-embolism stockings to remove potential skin triggers.
4. Assess the Bladder: This is the most likely culprit.
   • If the patient has an indwelling catheter, check the tubing for kinks. If obstructed, irrigate gently or replace the catheter immediately.
   • If the patient does not have a catheter, perform a straight catheterization immediately, using generous anesthetic jelly (e.g., lidocaine urojet) to prevent further triggering.
5. Assess the Bowel: If the bladder is empty, check for fecal impaction. If an impaction is present, apply a topical anesthetic (e.g., lidocaine jelly) to the rectum before attempting digital disimpaction to avoid exacerbating the AD.
6. Administer Antihypertensives: If the blood pressure remains dangerously high (typically systolic >150 mmHg) despite identifying and removing the trigger, or if the trigger cannot be immediately found, rapid-acting pharmacological intervention is necessary. Common agents include:
   • Nitroglycerin (paste or sublingual)
   • Nifedipine (immediate release)
   • Hydralazine
7. Identify Other Triggers: If bowel and bladder issues are ruled out, conduct a rapid, thorough skin assessment for pressure ulcers, ingrown toenails, or other sources of irritation.
8. Document and Educate: Thoroughly document the episode, the trigger, and the interventions. Because AD is a lifelong risk, extensive patient and family education on recognizing symptoms and self-management is critical prior to discharge.