Autonomic Dysreflexia: The Full Bladder That Can Cause a Stroke
Your client is a 32-year-old with a C6 spinal cord injury from a diving accident two years ago. He’s in for a pressure injury on his sacrum. You walk in and he says, “My head is pounding. Something’s wrong.” His face is flushed and sweaty. You check his blood pressure: 214/118. His heart rate is 48.
His baseline BP runs about 95/60.
That’s autonomic dysreflexia, and it’s one of the few neuro topics where the NCLEX expects you to act in a very specific order. A stroke, seizure, or retinal bleed can happen in minutes if nobody fixes the problem. The good news is that the fix is usually simple, often as simple as an unkinked catheter tube.
Below: who gets it, why, what it looks like, the exact action order, and how it differs from spinal and neurogenic shock.
Who Is at Risk
The magic number is T6. Clients with a spinal cord injury at T6 or above are at risk. The higher and more complete the injury, the higher the risk. Up to 90% of people with cervical or high thoracic injuries are susceptible, and it’s uncommon with injuries below T10.
Timing matters too. Autonomic dysreflexia usually shows up after the acute phase of the injury, once spinal shock has resolved and reflexes below the injury return. Most first episodes happen within the first year, but it’s a lifelong risk. On the exam, the client is often months or years out from the injury and in the hospital for something unrelated.
“Six and up, sit ’em up.” T6 or higher means at risk. Sitting upright is the first move. If a question stem gives you a T10 or L2 injury, autonomic dysreflexia is probably not the answer they’re looking for.
Why It Happens (The Short Version)
You don’t need a neuro fellowship for this. You need three ideas.
- Something irritates the body below the injury. A full bladder, a packed rectum, a pressure injury. The client may not feel it at all.
- The sympathetic nervous system fires below the injury, unchecked. The noxious signal travels up the spinal cord, hits the injury, and can’t reach the brain. Instead, it triggers a huge sympathetic reflex at the cord level. Blood vessels below the injury clamp down hard, and blood pressure skyrockets.
- The brain tries to fix it and can only do half the job. Baroreceptors in the carotids and aortic arch sense the high pressure. The brain fires the vagus nerve, which slows the heart (that’s the bradycardia). It also tries to send a “relax” signal down the cord to dilate the vessels. That signal can’t get past the injury.
So you end up with a body split in two. Above the injury, the parasympathetic response wins: flushing, sweating, nasal stuffiness, slow heart rate. Below the injury, the sympathetic response wins: pale, cool, goosebumps, intense vasoconstriction.
The headache comes from the blood pressure. And the blood pressure won’t come down on its own until you remove the trigger.
Signs and Symptoms Above vs Below the Injury
The NCLEX loves this split. If you can sort findings by “above” and “below,” you can answer almost any assessment question on this topic.
| Location | What You See | Why |
|---|---|---|
| Head | Severe, pounding headache; blurred vision; nasal congestion; anxiety or a sense of doom | Sudden severe hypertension; vasodilation above the injury |
| Above the injury | Flushed, red skin; profuse sweating | Reflex vasodilation above the injury as the brain tries to compensate |
| Heart | Bradycardia (sometimes other dysrhythmias) | Baroreceptor reflex through the vagus nerve |
| Blood pressure | Systolic 20 to 40 mm Hg or more above baseline; can exceed 200 | Massive vasoconstriction below the injury |
| Below the injury | Pale, cool skin; goosebumps (piloerection) | Unopposed sympathetic vasoconstriction |
A couple of notes on the numbers. Many people with high spinal cord injuries have a low baseline BP, often 90 to 110 systolic. So a reading of 140/90 might look “only mildly high” to a new nurse but actually be 40 points above that client’s normal. Commonly taught thresholds: a rise of 20 mm Hg or more above baseline counts as an episode in adults (15 mm Hg in children), and a systolic of 150 or more is where most protocols consider medication. Different guidelines word this slightly differently, so learn the concept: compare to baseline.
Watch for the stem that gives you a BP of 150/94 and a client with a spinal cord injury who “usually runs 90s systolic.” That’s not mild hypertension. That’s autonomic dysreflexia until proven otherwise. Also, some clients have a “silent” episode: dangerously high BP with few or no symptoms. Trust the numbers.
Common Triggers
Anything that would hurt or irritate a person with an intact spinal cord can trigger an episode. In practice, three systems cause most of them.
Bladder (Most Common)
Roughly 85% of episodes trace back to the urinary system. Think:
- Bladder distension from a missed intermittent cath
- Kinked, clamped, or clogged indwelling catheter
- Overfilled drainage bag or a bag positioned above the bladder
- Urinary tract infection or bladder stones
Bowel
- Constipation or fecal impaction (the second most common cause)
- Rectal exams, enemas, or digital stimulation done without anesthetic lubricant
- Hemorrhoids
Skin and Everything Else
- Tight clothing, shoes, abdominal binders, or leg bag straps
- Pressure injuries, burns, sunburn, ingrown toenails
- Lying on a hard object or a wrinkle in the sheets for too long
- Menstrual cramps, labor, sexual activity
- Fractures or other painful injuries below the level of injury
Pressure injuries show up a lot because these clients have limited mobility and sensation. If you need a refresher on staging, our pressure injury stages guide walks through all of them.
The Priority Action Order
This is the part the NCLEX tests hardest. The client is in a hypertensive emergency, and every step in this sequence is designed to bring the BP down as fast as possible while you hunt for the cause.
Notice the medication comes late. The best antihypertensive here is an empty bladder.
Raise the head of the bed to 90 degrees, or sit the client up in the wheelchair. Lower the legs if possible. Gravity pools blood in the lower extremities and drops BP almost immediately. This takes seconds and needs no order.
Never lay this client flat. And definitely don’t put them in Trendelenburg.
Clothing, shoes, abdominal binders, compression stockings, leg bag straps. Some sources list this together with Step 1 because you do them in the same breath. Either way, it comes before the bladder check.
Because the bladder is the most common culprit, look there next.
- Indwelling catheter: Follow the tubing from the client to the bag. Look for kinks, clamps, or a bag that’s full or sitting too high. If nothing’s obvious and urine isn’t flowing, the catheter may be blocked. Follow your protocol to irrigate gently or replace it.
- No catheter: Check for bladder distension (a bladder scanner is helpful) and catheterize using lidocaine gel to reduce stimulation.
Drain the bladder slowly and steadily. Many clients see their BP fall as soon as urine starts flowing.
If the bladder isn’t the cause, suspect a fecal impaction. Use a generous amount of anesthetic lubricant (such as lidocaine 2% gel) before a gentle digital check. Some protocols say to wait a few minutes after applying it. If the BP climbs during the check, stop and let the lidocaine work longer.
Keep rechecking the blood pressure and heart rate throughout the whole episode. Once it resolves, keep monitoring for at least two hours, because symptoms can come back and BP can drop too low once the trigger is gone, especially if medication was given.
If you can’t find or remove the cause quickly, or the systolic stays at 150 mm Hg or higher, notify the provider. Fast-acting antihypertensives are the next step. The ones you’ll see on exams:
- Nitroglycerin 2% ointment applied to skin above the level of injury. Easy to wipe off if BP drops too low.
- Immediate-release nifedipine, given as bite-and-swallow (sublingual use is no longer recommended).
- Captopril is another option in some protocols.
Before any nitrate, ask about PDE-5 inhibitors like sildenafil or tadalafil. Many clients with spinal cord injuries take them. The combination can cause profound hypotension.
When an NCLEX question asks “What should the nurse do first?” for autonomic dysreflexia, the answer is almost always sit the client upright. Checking the catheter is a great answer, but it’s second. Calling the provider is important, but you don’t leave a client with a BP of 220 lying flat while you make a phone call. Position first, then find the cause.
This kind of “everything is correct, but which comes first” question is classic NCLEX prioritization. Our prioritization and delegation guide breaks down how to rank actions like this when every choice looks right. The Recognizing Complications and Emergency Response lesson drills the same pattern across other emergencies.
Untreated autonomic dysreflexia can cause hemorrhagic stroke, seizures, retinal hemorrhage, MI, pulmonary edema, and death. A client who becomes confused, has a seizure, or develops a sudden change in vision during an episode needs a rapid response, not a wait-and-see approach.
Autonomic Dysreflexia vs Spinal Shock vs Neurogenic Shock
All three involve spinal cord injuries, and the NCLEX will absolutely put them in the same question. Here’s how to keep them separate.
Spinal shock is a temporary loss of all reflexes below the injury right after it happens. Think flaccid paralysis, no reflexes, and bowel and bladder retention. It’s about reflexes, not blood pressure, and it can last days to weeks.
Neurogenic shock is a type of distributive shock. The injury knocks out sympathetic tone, so blood vessels dilate everywhere and the heart loses its sympathetic push. It also tends to happen with injuries above T6, in the early hours to days after injury.
Autonomic dysreflexia is the opposite of neurogenic shock: too much sympathetic activity below the injury instead of too little. It usually appears later, once reflexes return.
| Feature | Autonomic Dysreflexia | Neurogenic Shock | Spinal Shock |
|---|---|---|---|
| Timing | After acute phase; lifelong risk | Early, hours to days after injury | Immediately after injury; days to weeks |
| Blood pressure | Severely high | Low | Not the defining feature |
| Heart rate | Bradycardia | Bradycardia | Not the defining feature |
| Skin | Flushed and sweaty above; pale and cool below | Warm and flushed (vasodilation) | Varies |
| Reflexes | Present (reflex arcs intact below injury) | Variable | Absent below injury; flaccid paralysis |
| Main problem | Unchecked sympathetic surge | Loss of sympathetic tone | Temporary loss of cord reflex function |
| Key nursing action | Sit up, find and remove trigger | IV fluids, vasopressors, atropine for bradycardia | Supportive care, bladder and bowel management |
Bradycardia shows up in both autonomic dysreflexia and neurogenic shock. Don’t let the heart rate decide for you. Look at the blood pressure. Slow pulse plus high BP and headache means dysreflexia. Slow pulse plus low BP and warm skin means neurogenic shock. Also remember that hypovolemic shock usually comes with a fast heart rate, which helps separate it from neurogenic shock.
For the bigger hemodynamic picture, the Vital Signs: Changes, Trends, and Abnormalities lesson covers how to read trends like these against a client’s own baseline.
Prevention and Client Teaching
Most episodes are preventable. And clients with high injuries often know their own dysreflexia better than new nurses do, so listen to them.
Bladder Program
- Keep a consistent intermittent catheterization schedule (commonly every 4 to 6 hours, per the client’s plan).
- Keep indwelling catheter tubing free of kinks and the bag below the bladder.
- Know the signs of a UTI: cloudy or foul-smelling urine, fever, more frequent episodes.
Bowel Program
- Follow a regular bowel routine at the same time daily.
- Get enough fiber and fluids.
- Use anesthetic lubricant for digital stimulation.
The Elimination lesson covers bladder and bowel programs in more depth.
Skin and Daily Life
- Inspect skin daily, including feet and toenails.
- Reposition on schedule and avoid tight clothing and shoes.
- Protect insensate skin from sunburn and from hot surfaces.
Emergency Plan
- Know personal baseline BP and keep a home BP cuff handy.
- Carry a wallet card or medical alert explaining autonomic dysreflexia, since many ER staff don’t recognize it quickly.
- Teach caregivers the same action order: sit up, loosen clothing, check bladder, check bowel, seek emergency care if BP stays high.
- Tell all providers (including dentists) about the risk before any procedure.
For a quick memory hook on the triggers and actions, check out the Black Belt Recall mnemonic library.
For deeper reading, the StatPearls review on autonomic dysreflexia lays out current thresholds and drug dosing, and the companion review on neurogenic shock is great for the comparison. MedlinePlus also has a clear, client-friendly autonomic dysreflexia overview that’s useful when you’re building teaching plans.
A client with a T3 spinal cord injury sustained 18 months ago is lying in bed and reports a sudden pounding headache. The nurse notes flushed, sweaty skin on the face and neck. Blood pressure is 196/112 mm Hg (baseline 102/64) and heart rate is 52/min. Which action should the nurse take first?
- Inspect the indwelling urinary catheter tubing for kinks
- Raise the head of the bed to 90 degrees and lower the legs
- Notify the health care provider of the blood pressure reading
- Apply the prescribed nitroglycerin ointment above the injury
This client has classic autonomic dysreflexia: an injury above T6, severe hypertension far above baseline, bradycardia, headache, and flushing and sweating above the injury. The first action is to sit the client upright and lower the legs. This uses gravity to pool blood in the lower extremities and begins lowering the BP within seconds, before any other intervention is ready.
Why the other answers are wrong:
- A: Checking the catheter is the right next move, since the bladder is the most common trigger. But positioning comes first because it lowers BP immediately while you search.
- C: The provider needs to know, but leaving the client flat while making a call delays the fastest available treatment.
- D: Antihypertensives are used if the BP stays high after positioning and trigger removal. Medication is not the first-line action.
Final Takeaway
Autonomic dysreflexia happens in clients with spinal cord injuries at T6 or above. A trigger below the injury (usually a full bladder) sets off a sympathetic surge the brain can’t shut down. The result is severe hypertension, bradycardia, a pounding headache, flushing and sweating above the injury, and pale, cool skin below it.
Your order of actions: sit the client up and lower the legs, loosen anything tight, check the bladder, check the bowel with anesthetic lubricant, recheck BP every few minutes, and call the provider for antihypertensives if the cause isn’t found or BP stays high. Keep it separate from neurogenic shock by looking at the blood pressure: high means dysreflexia, low means shock.
Train like a black belt. Think like a nurse. 🥋
Ready to Lock In Autonomic Dysreflexia?
Test your neuro and prioritization skills in the Proving Grounds practice exams, grab our printable NCLEX cheat sheets, or warm up with the NCLEX Question of the Day.
FAQ: Autonomic Dysreflexia
What is the first action for a client with autonomic dysreflexia?
Sit the client upright (head of bed to 90 degrees if possible) and lower the legs. This pools blood in the lower extremities and starts bringing the blood pressure down right away. Then loosen tight clothing and look for the trigger, starting with the bladder.
What is the most common cause of autonomic dysreflexia?
Bladder distension is the most common cause. A full bladder, a kinked or blocked urinary catheter, or a urinary tract infection accounts for the large majority of episodes. Bowel problems such as constipation or fecal impaction are second, followed by skin triggers like pressure injuries, tight clothing, and ingrown toenails.
Which spinal cord injury levels are at risk for autonomic dysreflexia?
Clients with a spinal cord injury at T6 or above are at risk. The higher and more complete the injury, the greater the risk. It is uncommon with injuries below T10.
Why is the heart rate slow in autonomic dysreflexia?
The blood pressure spikes because of a massive sympathetic response below the injury. Baroreceptors in the carotid arteries and aortic arch sense the high pressure and trigger the vagus nerve, which slows the heart. The brain cannot send signals down past the injury to relax the blood vessels, so the bradycardia does not fix the hypertension.
How is autonomic dysreflexia different from neurogenic shock?
Both happen with high spinal cord injuries, but they are opposites. Autonomic dysreflexia causes severe hypertension with bradycardia, and it usually appears after the acute injury phase in response to a trigger like a full bladder. Neurogenic shock causes hypotension with bradycardia and warm, flushed skin, and it happens early after the injury because sympathetic tone is lost.
Why use anesthetic lubricant when checking for a fecal impaction in autonomic dysreflexia?
Inserting a gloved finger into the rectum is itself a strong stimulus that can make the episode worse. An anesthetic lubricant such as lidocaine gel numbs the area and reduces that stimulation. Many protocols also say to stop the bowel check if the blood pressure keeps rising.
