Definition
- Autonomic dysreflexia is a potentially life-threatening hypertensive crisis in patients with spinal cord injury (SCI) at T6 or above. It results from a noxious stimulus below the lesion, producing unopposed sympathetic outflow, severe vasoconstriction, and sudden marked hypertension
- The compensatory vagal response causes reflex bradycardia, but cannot overcome the sympathetic surge
- Rarely occurs in SCI below T6
Important: If untreated, AD can lead to intracranial haemorrhage, seizures, arrhythmias, or death.
Common Urological Triggers
- Overdistended bladder (retention, blocked/kinked catheter)
- UTI, bladder spasm, bladder stones
- Recent instrumentation (catheterisation, cystoscopy)
Symptoms
- Severe hypertension (often SBP >150 mmHg or >40 mmHg above baseline)
- Pounding headache
- Bradycardia
- Flushing/sweating above, goosebumps below the lesion
- Nasal congestion, chills, blurred vision, anxiety
- Bronchospasm or seizures (late)
Red Flags – Call Emergency Team (2222)
- ⇒Chest pain
- ⇒Breathlessness
- ⇒Confusion or reduced consciousness
- ⇒Seizures
- ⇒Persistent severe hypertension despite interventions
Management
- Sit upright (at least 45 degrees), legs dependent; loosen tight clothing
- Remove noxious stimulus
- Bladder:
- Examine catheter; correct kinks/obstruction
- Flush or change catheter using lignocaine gel
- If no catheter → bladder scan; catheterise if distended
- If no bladder cause:
- Check bowel (DRE with lignocaine), wounds, pressure areas
- Check BP + re-check after every step
- If SBP is >150 mmHg or remains markedly elevated
- Give short-acting antihypertensive
Medication Options
Use rapid-onset, short-duration agents while investigating the stimulus.
- Nifedipine 5–10 mg
- Instruct patient to bite/squeeze capsule contents under the tongue, then swallow capsule
- Prolonged effect even after the trigger resolved
- Glyceryl trinitrate (GTN) spray – 400 micrograms
- Glyceryl trinitrate (GTN) patch – 0.2 mg/hr
- Apply to non-hairy skin above the lesion
- Can be removed once BP improves → reduces risk of prolonged hypotension
- Contraindicated if recent PDE-5 inhibitor use (e.g., sildenafil, tadalafil)