How to Perform Urethral Catheterization in a Blocked Cat

Mar 28, 2022

In this video, we demonstrate step-by-step how to perform urethral catheterization to alleviate urethral obstruction in a blocked cat.

PLEASE NOTE: the patient must first be stabilized before attempting urethral catheterization. Blocked cats can have lethal hyperkalemia, and so this must be identified and addressed before starting urethral catheterization. Urethral catheterization can sometimes be very tedious, and if you don't address the hyperkalemia first, the patient could die while you are trying to alleviate the obstruction. Stabilize the patient first so you can relax and take as much time as you need for urethral catheterization.

Diagnosis of Urethral Obstruction: Feline urethral obstruction should be considered in any cat that has been straining to urinate but is unable to produce a stream of urine. I have also seen several outdoor cats arrive in the later stages of collapse and moribundity that had no history of straining to urinate because they were going outside where nobody could see them. Palpation of a large, distended bladder is reason enough to proceed. There are many different ways perform urethral catheterization. I have a standard approach I take to cases of feline urethral obstruction, to ensure the safety and comfort of the patient. I will walk you through this protocol below:

BEFORE YOU START:

Prepare the Owner: It is always good to discuss the risks and complications of urethral de-obstruction with owners. Complications include urinary bladder rupture, urethral rupture, recurrence of obstruction (down the road; sometimes patients need perineal urethrostomy to prevent recurrence). Stabilizing the patient and alleviating the obstruction are often just the first step. These cats may need to be hospitalized for several days until their kidney values have normalized, the urine is clear (when inflammation and sediment have resolve), and they have demonstrated that they are able to voluntarily void urine once the catheter has been removed. After the obstruction cats can require long-term management, including a special prescription diet and other medications. Future recurrence is not uncommon, and the owners need to know this. Prepare the Patient: Don't get tunnel vision and go straight to unblocking the patient. You must properly assess and stabilize the patient before alleviating the obstruction. Urethral catheterization can be a tedious and lengthy process, and if your patient's potassium levels are too high, your patient could die while you are trying to unblock him. Take-home point: before you start unblocking, you must check the potassium level (administer calcium gluconate if needed) and attend to other steps to ensure that the patient is adequately stabilized to proceed with catheterization.

For stabilizing and preparing the patient: this is the protocol I follow:

Provide supplemental oxygen:
1. If the patient looks sick at all, provide supplemental oxygen in an unobtrusive way. We usually have someone hold the tip of the oxygen tubing up like a microphone, and ask the cat if he knows any good jokes;)
Place an IV catheter and collect blood.
1. It helps to break this up into pieces if the patient is anxious.
2. Start by clipping a spot over right cephalic.
3. Apply EMLA ointment
4. Get your IVC and blood collection set up ready while Emla is kicking in.
  1. Scrub
  2. Tape
  3. Blood tubes, PCV/TP, lactate
  4. prepare your iSTAT cassette or machine for rapidly measuring potassium
  5. You can quickly draw up your buprenorphine and alfaxan; label the syringes.
5. Place IVC (this is your life line) and secure in place.
6. Collect blood sample from the catheter.
Initiate monitoring:
1. Apply monitoring equipment (EKG, blood pressure, SPO2)
  1. If the patient is bradycardic, or if you notice very severe arrhythmias associated with hyperkalemia, get your calcium gluconate 10% drawn up and ready.
  2. EKG abnormalities:
    1. mild hyperkalemia (6 to 7 mmol/L): the tented or high-peaked T waves.
    2. moderate to severe hyperkalemia (7 to 9 mmol/L): prolonged PR intervals and flattened P waves.
    3. severe hyperkalemia (9 to 10 mmol/L): atrial standstill (absence of P waves) and widening of the QRS complex occur with severe hyperkalemia
    4. imminently fatal hyperkalemia (10-12 mmol/L): ventricular arrhythmias, fibrillation, and asystole
Initiate cautious/judicious IV fluid therapy
1. Balanced crystalloid solution (I use isolyte-S) or 0.9% NaCl at peri-anesthetic fluid rate (5-10 ml/kg/h
2. Administer 5ml/kg bolus over 10 min as needed to correct hypotension/shock.
3. Cats can be sensitive to fluid over-zealous IV fluid therapy so keep track of total volume of IV fluids administered, and use caution when approaching/exceeding 30 ml/kg.
EMERGENCY STAT LAB TESTS: at minimum:
1. MEASURE POTASSIUM LEVEL on the quickest machine you have for this. This is the most important parameter to measure and fix right away.
2. PCV/TP , blood glucose, lactate if possible
3. Emergency panel (to provide baseline BUN/UREA and creatinine)
IN SEVERE HYPERKALEMIA + EKG ABNORMALITIES: ADMINISTER CALCIUM GLUCONATE TO PROTECT THE HEART
1. If the potassium level is greater than 8 mEq/L (8 mmol/L) administer calcium gluconate 10% to protect the heart.
  1. Dosing: Calcium gluconate 10%: 0.5-1 mL administered slowly over 5-10 minutes while continuously monitoring EKG. If bradycardia worsens, stop innfusion.
2. Note: calcium gluconate protects the heart from the effects of hyperkalemia, but does not actually reduce potassium levels. Its effects last 20-30 minutes, so you may need to re-dose as you work to reduce potassium levels.
Administer pain relief.
1. I use buprenorphine: 20 mcg/kg IV(0.02 mg/kg IV) for the first dose, and then usually de-escalate the dose to 10 mcg/kg every 4-6 hours depending on how painful the patient is.
2. Sacrococcygeal epidural
Draw up sedation and label syringes appropriately
1. Note: if your patient is not stable (i.e. arrhythmic, bradycardic, hypotensive, etc.), you have more stabilizing work to do before you can safely administer sedation.
2. You can start by drawing up a gentle, short-acting benzodiazepine like midazolam (0.1-0.2 mg/kg)
3. I also like to draw up 3 syringes of alfaxalone (each containing 1 mg/kg), so that you can easily titrate in 0.25-0.5 mg/kg increments, and it is easy to keep track of the total amount that has been given. Drawing the syringes up in 1 mg/kg aliquots also reduces the risk of accidental overdose if too much sedative is drawn up in one syringe.
Image the urinary bladder with ultrasound:
1. Turn on the ultrasound machine
2. Titrate a gentle low-dose sedation as needed to enable positioning in dorsal recumbency.
3. Image urinary bladder, measure and check for free abdominal fluid.

Perform decompressive cystocentesis if needed:

If the urinary bladder is maximally distended and hard, it will be difficult to flush saline into the urinary bladder because you will not be able to exceed that pressure. You may need to decompress the urinary bladder [decompressive cystocentesis ] prior so that as you begin to flush the crystals or stone back into the bladder, you will have less pressure from the bladder against you.
Many people are afraid to perform a decompressive cystocentesis on obstructed cats due to the risk of urinary bladder rupture. A recent paper in JVECC showed that there is no increased risk of urinary bladder rupture with decompressive cystocentesis, and sometimes you just need to do it.

For decompressive cystocentesis, I usually use a 22 Ga needle attached to an extension set and 60 ml syringe (or alternatively, a 21 or 23 Ga butterfly catheter attached to a 60 ml syringe), and ultrasound guidance. Handle the urinary bladder very gently, and make sure to hold your needle very still to reduce the risk of rupturing or tearing the urinary bladder wall.

Before you start: Prepare the patient
Step	Helpful Tips
Administer supplemental oxygen	Consider spending $5 on pediatric nasal cannulae. They can be easily secured, are generally well-tolerated, and free up your staff from holding flow-by or a mask up to the patient’s face.
Place an IV catheter and collect baseline blood samples	lavender top tube [EDTA] -serum separator tube -green top tube [sodium heparin]-if required by your in-house analyzers -necessary samples (usually a blue top [sodium citrate]) for assessing coagulation times.
Apply monitoring equipment (EKG, minimally; blood pressure, SPO2 ideally) Collect baseline blood samples if you have a couple minutes to spare.
Initiate intravenous fluid therapy (balanced electrolyte solution such as Isolyte-S, Norm-R, etc.) or 0.9% Nacl	To correct hypotension, deliver cautious bolus at 5-10 ml/kg over 15-20 minutes, repeat if needed Initiate peri-anesthetic maintenance rate of 5-10ml/kg/h depending on hydration status, length of obstruction and underlying cardiac disease.
Administer analgesia	Buprenorphine: 20 mcg/kg (0.02 mg/kg) IV
Check point of care tests and STAT emergency panel	PCV/TP, BG, Lactate Electrolytes (potassium!!), BUN/CRE
Administer Potassium Gluconate 10% if severe hyperkalemia (>8.0 mEq/L or mmol/L) and bradyarrhythmia present.	0.5-1 ml/kg over 5 min while watching EKG; you may need to repeat in 20-30 minutes.
Draw up and label syringes for sedation	Midazolam (0.05-0.2 mg/kg IV) Alfaxan or propofol: draw up several syringes each containing 1 mg/kg (0.1 ml/kg) to enable easy IV titration in 0.25-0.5 mg/kg increments.
Position patient into dorsal recumbency and image urinary bladder using ultrasound	You may need to titrate a little bit of sedation so that the patient can rest comfortably.
Perform decompressive cystocentesis if patient has been chronically obstructed and urinary bladder is maximally distended.	Save urine samples for urinalysis and culture.

Urethral Catheterization (Step by Step):

Prepare your supplies:

Prepare your supplies

Start by getting all of your supplies out and ready to go

-Clippers and surgical scrub
-Sterile drape	usually 1-2 mL depending on patient size; I prefer a 25 ga needle to minimize discomfort
Sterile xylocaine lubricating gel or sterile lubricant mixed with 2 mg/kg lidocaine	(2 mg/kg appropriately dosed
-A marker or sharpie
-Sterile gloves (for you) and regular/nitrile gloves (for your assistant)
-A sterile urinary catheter	I prefer to start with a soft and gentle open-ended catheter that can also remain indwelling once it has been passed. My catheter of choice is the 3.5 Fr open-ended Mila catheters. I prefer to not use the stylet, as I worry that this can cause damage to the urethra.
-Several labeled syringes of sterile saline to use for flushing the urethra.	Different sizes (3 cc, 6 cc, 12 cc, 35 cc) enable different pressures while flushing.
-A urine collection set	An empty IV fluid bag that has been kept sterile attached to a fresh IV extension set works great. I prefer to tape/remove any clamps along the iv set so that an assistant does not accidentally clamp/occlude the line, and to label the line as URINARY CATHETER so it does not get confused with the patient's IV line.
-Sample tubes labeled “urine” for urinalysis and culture.
-Suture
-An Elizabethean collar

Position the patient in dorsal recumbency:
1. TItrate sedation to enable the patient to comfortably positioned in dorsal recumbency.
2. As a standard protocol, all patients receiving intravenous sedation receive supplemental oxygen and continuous monitoring of EKG, BP and SPO2.
3. We like to use the small ultrasound/x-ray positioning trough. Scoot the patient's bum toward the end of the trough, and tape the legs up so they are out of the way. You may also need to tape the tail so it is out of the way.
Clip and aseptically prepare the patient.
Drape the area
1. Remember, this is a sterile procedure. If you have cat fur everywhere, it is much more difficult to maintain aseptic technique.
Extrude the penis, and examine the distal urethra.
1. If you notice material occluding the distal urethra (mucus plug, granular material, uroliths, etc.), gently dislodge it.
Introduce the catheter
1. While maintaining the penis extruded, lubricate the catheter with the sterile lubricant mixed with lidocaine and gently introduce it into the distal urethra.
2. Extruding the penis and applying gentle traction so that it is extended in a slightly dorso-caudal direction will make it as straight as possible and can facilitate catheterization.
3. If the catheter passes with minimal resistance into the urinary bladder- great. Skip step 7.
Begin flushing to retropulse the lodged material back into the bladder:
1. While you apply gentle pressure to the penis to occlude the distal urethra around the catheter, have your assistant attach the syringe labeled flush and begin pulsing the syringe in an attempt to flush the crystals or uroliths back into the bladder. If you don't occlude the distal urethra, the flush will splash back at you!
2. Sometimes alleviating obstructions can be tedious and time-consuming. Make sure that you don't get frustrated or start to apply excessive force to these delicate tissues. Just take a deep breath and try a different catheter or different approach if needed. You may wish to use a different size syringe for flushing (a 12cc or a 6cc might provide additional pressure and flow).
Drain the urine from the bladder and save samples for urinalysis and culture.
1. It is very common for this urine to be bloody, especially towards the end, so don't be alarmed. In more chronic cases, the urine may look very dark like red wine or even darker.
Further flush the urinary bladder and urethra using sterile saline:
1. Attach a 35 cc syringe of saline into the bladder. You may begin flush while retracting the catheter so that it is almost out to ensure that any remaining crystals in the urethra have been flushed back into the bladder. Gently agitate the bladder, and then withdraw the saline you infused into the bladder.
2. Repeat 3 times.
Confirm placement of the urinary catheter using ultrasound
1. Use ultrasound to confirm placement of the urinary catheter. You want the catheter positioned a couple centimeters beyond the neck of the urinary bladder. Make sure there is not so much catheter that it can loop back on itself.
Connect to the sterile collection set and urinary collection bag
1. Put tape over (or remove) any clamps along the line of the extension tubing between the catheter and bag, so that the line cannot be inadvertently clamped by an assistant.
2. Put a piece of tape on the collection bag indicating the time and the date, so that you can keep track of urine production. Ensure that the bag is positioned a few feet below the patient so that gravity pulls the urine from the bladder into the bag. Empty the bag and measure the urine volume every 4-6 hours.
Suture the catheter into place and secure
1. Threading suture through a 22Ga needle is a quick and easy way to secure urinary catheters and other tubes used in the ER.
2. Route catheter caudally so that it does not kink and reinforce with additional sutures as needed.
3. Secure with tape to the patient's tail or leg, ensuring that it will not become contaminated.
Infuse local anesthetic via the catheter into the urinary bladder for added relief.
1. Lidocaine: 2 mg/kg
Put an E-collar on the cat.
1. Cats are ninjas. After all that hard work, you don't want your patient to swiftly remove the catheter when you turn your back.

Ongoing care/management:

Analyze your samples
1. In-house analysis
  1. A lot of times, you can see gross granular sediment (like fine sand) precipitating out of the urine after it has sat for 5-10 minutes. I like to show this to the owners so they can understand why their cat has blocked.
  2. If you see bacteria on in-house sediment evaluation, you may start antimicrobial therapy (ampicillin: 20 mg/kg IV q 8h followed by amoxicillin-clavulanate: 14 mg/kg PO once the cat is eating).
2. Urinalysis and urine culture
  1. Be sure to submit a culture so that you can find out if you are dealing with resistant bugs. It is not wrong to submit the urine for UA to an outside reference lab to confirm your in-house findings.
Hospitalization for continued intravenous fluid therapy, monitoring, analgesia and support.
1. A note on hospitalization:
  1. Post-deobstruction hospitalization can last 24-h to a week or longer depending on the situation.
    1. In general the criteria for hospital discharge include:
      1. Kidney and electrolyte values have normalized
      2. The catheter has been removed
        
        In acute cases with minimal inflammation, this can be as early as the next day. In more chronic cases, it may take several days.
        
        Before the catheter is removed, the urine should clear (with resolved inflammation and gross sediment), and any significant inflammation of the penis (or spasm) should have resolved.
      3. The patient has have demonstrated that he is able to voluntarily void urine once the catheter has been removed.
      4. Normal vital signs and able to eat and drink, so that he can maintain hydration and take oral medications at home.
  2. It is ideal for patients these patients to be hospitalized in a facility that offers 24 hour care for several reasons.
    1. If the patient removes its catheter overnight but re-obstructs, you can be back at square one by morning.
    2. Cats are more vulnerable to fluid overload, especially if there is underlying cardiomyopathy. Monitoring for fluid overload is an important part of caring for these guys.
    3. That said, not all owners can afford 24 hour care, and so we always try to find the best plan for both the patient and the owners.
2. Intravenous fluid therapy:
  1. There is no magic recipe for IV fluid therapy rates. Fluid therapy should be adjusted based on the patient's hydration status and ongoing losses. Post-obstructive diuresis is common, so for the first 24 hours, some of these patients can require surprising large volumes of IV fluid. Here are factors to consider:
    1. Maintenance fluid requirement:
      1. Maintenance fluid rate calculation:
        
        Rate in ml/h: = (1.2 x (kg ^ 0.75)) x 70) / 24
        
        Maintenance rate for a 4 kg cat:10 ml/h
    2. Replacement of hydration deficit and ongoing losses:
      1. A 4 kg cat 8% dehyrated has a deficit of 320 ml. If that is replaced over 24 hours, that adds 13 ml/h
  2. In general, I will continue the rate at 5-10 ml/kg for 4-6 hours after the obstruction has been alleviated, and then gradually taper back to 2-3 times maintenance, before weaning back further over the next 24 hours. I try to estimate how dehydrated the patient is, and replace this deficit over 24-48 hours.
3. Ongoing pain management
4. Reducing urethral spasm:
  1. When the patient is able to tolerate oral medications, you can begin to administer medications to reduce urethral spasm. I prefer either Prazosin or Phenoxybenzamine.
    1. Prazosin (0.25-0.5 mg/cat PO every 12-24 hours). Note: this medication can cause low-blood pressure, or worsen existing hypotension. Your patient should be stable before giving this.
    2. Phenoxybenzamine (1.2-2.5 mg/cat PO every 12 hours). Note: this medication can also cause low-blood pressure, or worsen existing hypotension. Your patient should be stable with normal blood pressure before giving this.
    3. Diazepam: not my preferred choice of medications for reducing urethral spasm. I find that I receive a lot of late-night calls from pet owners concerned about urinary incontinence (constant dribbling of urine) when their cats have been placed on diazepam by their vets following an episode of urethral obstruction.
5. Urinary catheter care and monitoring urine output:
  1. At regular intervals, it is important to check the catheter to ensure that it is patent, to provide basic hygiene, and to measure urine output.
  2. At least every 8 hours, the prepuce and urinary catheter should be cleansed with chlorhexidine 4%. I usually draw up a 3 ml syringe of chlorhexidine and lightly flush the area, and follow this with 3 ml of saline.

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