Autonomic Dysreflexia During Catheter Changes After Spinal Cord Injury: How to Reduce the Risk
Changing a urethral or suprapubic catheter is usually straightforward. However, in some people with spinal cord injury, irritation of the bladder, urethra or suprapubic catheter tract can trigger autonomic dysreflexia, often called AD.
AD causes a sudden and potentially dangerous rise in blood pressure. It most often affects people with a spinal cord injury at or above T6.[1,2]
Careful preparation, gentle catheter technique and a written emergency plan can reduce the risk.
Important: Autonomic dysreflexia is a medical emergency. Anyone at risk should have an individual management plan prepared by their spinal injury or medical team.
What is autonomic dysreflexia?
AD is an exaggerated nervous-system response to irritation below the level of a spinal cord injury.
The irritation causes blood vessels below the injury to tighten. The brain may be unable to send normal calming signals back down the spinal cord, causing blood pressure to rise quickly.
In adults, AD is usually defined as a rise in systolic blood pressure—the upper number—of more than 20 mmHg above the person’s normal level.[1]
This is important because many people with high spinal cord injuries normally have low blood pressure. A reading that looks normal for someone else may be dangerously high for them.
Severe AD can cause:
Stroke
Seizures
Abnormal heart rhythms
Heart or breathing problems
Loss of consciousness
Death[6]
Why can a catheter change trigger AD?
The urinary system is one of the most common causes of AD.
Possible triggers during a catheter change include:
A full or overstretched bladder
A blocked catheter
Pulling on the catheter
Irritation while removing or inserting the catheter
Difficulty passing the new catheter
Repeated insertion attempts
Inflating the balloon before the catheter is fully inside the bladder
Bleeding or urethral injury
Putting too much fluid into the bladder
A new catheter that does not drain
Both urethral and suprapubic catheter changes can trigger AD.[1,2]
Who is most at risk?
The risk is greatest in people with an injury at or above T6, especially those with:
A cervical or complete spinal cord injury
Previous AD during catheter changes
Frequent bladder-related AD
Repeated catheter blockage
Bladder stones or heavy catheter encrustation
Severe bladder spasms
Difficult catheter insertion
A urethral stricture or previous false passage
A person can still develop AD even if previous catheter changes were uncomplicated.
What are the symptoms?
Possible symptoms include:
Sudden or pounding headache
Sweating above the injury
Facial or neck flushing
Pale or cool skin below the injury
Goosebumps
Blurred vision
Blocked nose
Anxiety or a feeling that something is wrong
Chest tightness
Slow, fast or irregular heartbeat
Increased muscle spasms
A sudden rise in blood pressure
Some people experience silent AD, where blood pressure rises without a headache or other obvious symptoms. People with a history of silent AD should discuss an individual catheter-change plan with their treating team.[1]
How to reduce the risk
A hospital or clinic may be safer than home for someone with severe AD, silent AD, repeated difficult catheter changes, heavy bleeding or no reliable access to emergency treatment.
Check blood pressure before starting
Before a planned catheter change:
Allow the person to rest.
Measure their blood pressure.
Compare the result with their usual baseline.
Ask about headache, sweating, flushing or other AD symptoms.
Confirm that the catheter is draining.
Do not continue with a routine change if blood pressure is already significantly elevated without first considering the cause.
Routine continuous blood-pressure or pulse monitoring during an uncomplicated catheter change is not usually required. The person should instead be observed for symptoms, with blood pressure checked if AD is suspected.
Prepare everything in advance
Have all equipment ready before removing the old catheter, including:
The correct replacement catheter
A spare catheter
Lubricant
Balloon fluid
Drainage bag and tubing
A blood-pressure monitor
Prescribed local anaesthetic
Prescribed emergency medication
Consider prescribed lidocaine
Guidelines recommend considering 2% lidocaine gel before replacing a urethral or suprapubic catheter in someone at risk of AD.[1]
For selected patients, lidocaine may be placed into the bladder through the old catheter before it is removed.
In one study, AD occurred during:
14.8% of catheter changes after lidocaine pretreatment
47.8% of catheter changes without pretreatment[3]
The blood-pressure rise was also smaller after lidocaine.
Lidocaine does not prevent every episode and should only be used at the dose and concentration prescribed by the treating team.[3–5]
Use gentle catheter technique
The person changing the catheter should:
Fully deflate the balloon before removal
Use adequate lubrication
Never pull or push against resistance
Avoid repeated insertion attempts
Confirm that the catheter is correctly positioned before inflating the balloon
Use the prescribed balloon volume
Stop if there is significant bleeding or unexpected resistance
Do not firmly press or tap over the bladder, as this can worsen AD.[1]
Confirm that the new catheter is draining
After inserting the catheter, confirm that:
Urine is flowing
The tubing is not kinked
The drainage bag is below the bladder
The catheter is not clamped
The bag is not full
Do not repeatedly place fluid into a catheter that is not draining. This may further fill the bladder and worsen AD.
Blood pressure should be checked shortly after the catheter change, particularly in someone who has previously experienced catheter-related AD.
What to do if AD occurs
Stop unnecessary catheter manipulation
Pause repeated or forceful attempts.
If the bladder is full and the catheter has been removed, safe drainage must still be restored urgently by an experienced clinician.
Sit the person upright
When safe:
Sit the person upright
Lower the legs
Loosen tight clothing, straps or abdominal binders
This may help lower blood pressure.[1]
Check blood pressure
If symptoms of AD occur, measure the person’s blood pressure and compare it with their usual baseline.
Continue to follow the person’s individual AD emergency plan. Recheck the blood pressure as directed until the trigger has been corrected and the person is stable.
Check the catheter system
Look for:
Kinked tubing
A full drainage bag
A catheter that has moved
Blockage
Failure of the new catheter to drain
A blocked catheter should be replaced promptly by someone trained to do so.
Follow the prescribed AD plan
Use only emergency blood-pressure medication that has been prescribed for that person.
Never use another person’s medication or take extra medication without clear instructions.
Important nitrate warning
Nitrate medicines can interact dangerously with erectile-dysfunction medicines such as sildenafil, tadalafil and vardenafil. The AD plan should clearly state when nitrate treatment is unsafe.[1]
When to call for urgent help
Call emergency services or seek urgent hospital care if:
Blood pressure remains high
The catheter cannot be replaced
The new catheter does not drain
There is heavy bleeding or blood clot blockage
Severe headache continues
The person develops chest pain or breathing difficulty
There is weakness, facial drooping or difficulty speaking
The person has a seizure
The person becomes confused, drowsy or unconscious
The trigger cannot be found
Persistent AD should not be managed by continuing repeated catheter attempts at home.
What should happen afterwards?
Check the person’s blood pressure shortly after the catheter change and continue observing them until:
The catheter drains freely
There are no symptoms of AD
Blood pressure is close to baseline
There is no major bleeding
The person is not dizzy or faint
Blood pressure may fall too low after the bladder drains, especially if emergency medication was used.
Record:
Blood pressure before and after the change
Any symptoms
Any catheter difficulty
Whether the catheter was blocked
Local anaesthetic or medication used
How long any AD episode lasted
This information can help improve the next catheter-change plan.
Repeated episodes need investigation
Repeated AD during catheter changes may indicate:
Catheter blockage or encrustation
Bladder or kidney stones
Severe bladder spasms
High bladder pressure
An unsuitable catheter type or size
A urethral stricture
A false passage
Urinary infection
Severe constipation
These issues should prompt a urology review [2]
Catheter-change safety checklist
Before the change
Know the person’s normal blood pressure.
Have the AD plan available.
Check blood pressure.
Check for symptoms of AD.
Prepare all equipment.
Have prescribed lidocaine and emergency medication available.
Ensure the person performing the change is trained.
During the change
Observe for headache, sweating, flushing, discomfort or other AD symptoms.
Use lubrication and gentle technique.
Never force the catheter.
Stop if there is resistance or significant bleeding.
Confirm urine flow.
After the change
Check that urine drains freely.
Recheck blood pressure.
Observe until the person is stable.
Record any AD episode.
Arrange specialist review if episodes recur.
Take home messages
AD is a sudden rise in blood pressure caused by irritation below a spinal cord injury.
People with injuries at or above T6 are at greatest risk.
Catheter blockage, removal and insertion can trigger AD.
AD can occur without obvious symptoms.
Blood pressure should be checked before and shortly after a catheter change.
Routine continuous monitoring during an uncomplicated change is not usually required.
Check blood pressure promptly if symptoms of AD develop.
A written emergency plan is essential.
Prescribed lidocaine may reduce the risk in selected patients.
Never force a catheter or repeatedly flush one that is not draining.
Persistent AD or inability to replace the catheter requires urgent medical help.
NOTE: This article provides general patient information. Catheter changes and treatment of autonomic dysreflexia should follow an individual plan developed by the person’s spinal injury, rehabilitation and urology teams.
Medication doses and blood-pressure thresholds should not be used as instructions for unsupervised treatment.
References
Krassioukov A, Linsenmeyer TA, Beck LA, Elliott S, Gorman P, Kirshblum S, et al. Evaluation and management of autonomic dysreflexia and other autonomic dysfunctions: preventing the highs and lows. Top Spinal Cord Inj Rehabil. 2021;27(2):225-290. doi:10.46292/sci2702-225.
European Association of Urology. EAU Guidelines on Neuro-urology. Arnhem: EAU Guidelines Office; 2026.
Solinsky R, Linsenmeyer TA. Intravesical lidocaine decreases autonomic dysreflexia when administered prior to catheter change. J Spinal Cord Med. 2019;42(5):557-561. doi:10.1080/10790268.2018.1518764.
Solinsky R, Tam K, Linsenmeyer TA. Onset of the action of intravesical lidocaine after spinal cord injury. Neurourol Urodyn. 2020;39(1):376-381. doi:10.1002/nau.24216.
Gray K, Sheehan W, McCracken L, Krogh K, Sachdeva R, Krassioukov AV. Are local analgesics effective in reducing autonomic dysreflexia in individuals with spinal cord injury? A systematic review. Spinal Cord. 2023;61(1):1-7. doi:10.1038/s41393-022-00840-8.
Wan D, Krassioukov AV. Life-threatening outcomes associated with autonomic dysreflexia: a clinical review. J Spinal Cord Med. 2014;37(1):2-10. doi:10.1179/2045772313Y.0000000098.
