Neurological · Topic 10 of 23
Autonomic Dysreflexia
A patient with a T4 spinal cord injury suddenly develops a pounding headache and a blood pressure of 260/130.
Start here
Autonomic Dysreflexia
A BP spike from a trigger below a T6-or-higher cord injury. Sit up, then find the trigger.
A spinal cord injured at T6, with a dashed line splitting the picture into above and below the injury. A full bladder below the injury sends a signal up the cord; it is blocked at the injury. Below the injury the vessels clamp down: the systolic blood pressure climbs from a baseline of about 104 to 190, and the skin below turns pale and cool with piloerection (goosebumps). The brain senses the high pressure and answers above the injury: it slows the heart from 78 to 50 a minute, and the vessels above widen, so the skin above is flushed and diaphoretic with a pounding headache. Its calming signal down the cord cannot get past the injury.
- A full bladder signals: blocked at the injuryNurse seesa full bladder or a kinked catheter
- Below it, vessels clamp: BP climbsNurse seessystolic 20+ above baseline; pale, cool, piloerectionNurse doessit upright, lower the legs, loosen clothing
- Above it: the heart slows, the skin flushesNurse seespounding headache, flushed and diaphoretic, slow pulseNurse doescheck the bladder first; BP every 2–5 min
Loosen tight clothing · then find and remove the trigger
mmHg, over the patient's own baseline · often only 90–110 — a “normal” reading can be high
Check the bladder and catheter first · the bowel is #2
What sets it off
TriggersSpinal cord injury at T6 or above + a noxious trigger below the injury
Rare cases are reported below T6.
What you'll see
Above and below the injurySigns split at the injury: flushed above, pale below
Red flags
Act nowTreatment: position, then the trigger
In this orderSit up and lower the legs first — blood pools in the legs and the BP drops fast
Catheter in place: check for kinks or blockage; irrigate or replace it. No catheter: straight-catheterize with lidocaine jelly.
Numb first: lidocaine lubricant before a digital rectal check for impaction.
The exam itself is a trigger — it can drive the BP higherFast-acting, per order, once sitting up and removing the trigger have not worked. Nifedipine is bite-and-swallow, not sublingual.
Ask about sildenafil-type (PDE5) drugs before any nitrateMore detail
Nursing priorities
In orderDysreflexia or neurogenic shock?
Don't confuse| Blood pressure | High |
|---|---|
| Heart rate | Usually slow |
| When | Chronic phase, injury at T6 or above |
Teach your patient
LifelongSit up first, then look below the injury — bladder, bowel, skin.
Sources · PVA Consortium for Spinal Cord Medicine CPG: autonomic dysreflexia · Autonomic Dysreflexia (StatPearls) · Autonomic dysreflexia (review) · Autonomic dysreflexia with relative tachycardia · Spinal cord injury and autonomic dysreflexia (case report) · Films: the NurseSavvy learning-flow visuals. Follow your facility's protocol.
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 patients 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 patient 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.
Knowledge Check
3 quick questions on the must-knows for this topic.
What is the priority first action in autonomic dysreflexia?
Loading questions…
Go further
- Commonly confusedIschemic Stroke vs Hemorrhagic StrokeClot vs bleed — the treatment is literally opposite, and getting it wrong is fatal.
- GuideHow to Study for Med-Surg: Stop Memorizing, Start ConnectingMed-surg is the first course where memorizing stops working. Start every topic at the mechanism, climb from know-it to spot-it to act-on-it, and practice questions early at the right difficulty — with a real NGN bowtie to try in-page.
- QuizNursing study gamesSort look-alike conditions and drugs against the clock — the fast way to stop mixing them up.
Ready to practice this topic?
Get a personalized study plan built around this topic — free to try, no card needed.