Autonomic Dysreflexia

A patient with a T4 spinal cord injury suddenly develops a pounding headache and a blood pressure of 260/130. You have minutes to find and fix the trigger — or risk a stroke.

Autonomic dysreflexia is a life-threatening sympathetic response occurring in clients with spinal cord injuries at T6 or above. A noxious stimulus below the level of injury — most commonly a distended bladder or impacted bowel — triggers massive, unopposed sympathetic vasoconstriction below the lesion. The body detects the resulting hypertension and attempts compensation via parasympathetic pathways above the injury, producing bradycardia, flushing, nasal congestion, and diaphoresis above the injury line. Below the injury, the skin is pale, cool, and piloerected because descending inhibitory signals from the brainstem cannot reach the sympathetic neurons below the lesion, so the vasoconstriction continues unopposed. Systolic BP can spike 40+ mmHg above baseline and exceed 300 mmHg. The priority nursing action is to sit the client upright immediately to drop BP via orthostatic pooling, then identify and remove the trigger. Check the Foley first: is it kinked, clamped, or blocked? If no catheter is in place, straight-catheterize using lidocaine jelly. If the bladder is not the cause, check for fecal impaction — but apply dibucaine ointment before digital exam to avoid worsening the stimulus. Loosen tight clothing, check for skin pressure. If BP remains critically elevated after trigger removal, pharmacologic options per order may include IV nitroprusside or hydralazine, or oral/sublingual nifedipine.

Key Distinctions

Don't confuse autonomic dysreflexia (hypertension with bradycardia, above-T6 injuries) with neurogenic shock (hypotension with bradycardia, acute phase). Students often think any SCI can trigger dysreflexia — only lesions at T6 or above carry this risk because the splanchnic outflow below T6 controls major vascular beds. The flushing and sweating occur above the injury; pallor and goosebumps occur below — mixing up which half presents which way is a common test error.

Clinical Pearl

Sit up, check the plug. Elevate the HOB first to drop BP, then find the noxious stimulus — bladder is the #1 culprit, bowel is #2.