Treating the Sick Blocked Cat: What’s New?

By: Dr. Kari Santoro Beer, DVM, DACVECC

Board-Certified Critical Care Specialist

ksantorobeer@vsecvet.com

Veterinary Specialty & Emergency Center

www.VSECVET.com

Over the last few weeks, the VSEC emergency service has been inundated with blocked cats. I don’t know if it’s the humidity, the full moon, or some other supernatural force, but some of them have been SICK! “Fluffy” (names have been changed to protect innocent felines) presented laterally recumbent and bradycardic with severe azotemia and hyperkalemia. He was so sick, we didn’t even have to sedate him to unblock him. When our routine urethral obstructions (UO) throw us for a loop, what extra tricks do you have up your sleeve? Here are a couple of tips I’ve learned based on some difficult cases and recent studies out there…

• Try a caudal epidural. This is a quick, simple procedure that can be performed using preservative-free lidocaine, bupivacaine, and/or morphine. Injection into the caudal epidural space provides anesthesia to the urethra and penis without affecting motor function to the hind limbs, and can facilitate passage of the urinary catheter. A recent abstract presented at IVECCS revealed that caudal epidurals appear to be safe, might decrease the amount of propofol needing during the unblocking process, and can provide nice adjunctive analgesia while patients are in the hospital.¹ The paper referenced below provides excellent diagrams and instructions if you want to give it a try.² I find that this technique works great in cats with significant urethral spasm or in those who have issues maintaining urinary catheters in the hospital due to discomfort or agitation.

• If you can’t unblock him, put the patient under general anesthesia. Like many of us, I learned to unblock my cats under heavy sedation. My go-to cocktail is methadone and midazolam given as an IM or IV pre-med, and propofol IV to effect. Usually, this works just fine. But if the unblocking is tricky, putting the patient under general anesthesia with endotracheal intubation and gas inhalant can help. In addition to providing more smooth muscle relaxation, it also gives you more time (hopefully with less stress of having to keep bolusing the cat propofol!) to work out the kinks in the unblocking process.

• Don’t forget to take a radiograph after your catheter placement! Not only will it help you to evaluate the urinary system for radiopaque stones, which affect around 20-29% of cats, but it can help you avoid disaster.³ All you need is a single lateral abdominal film. Fluffy’s film (Image One) revealed that his urinary catheter was in a bit too far – you can see it curling back caudally and extending into the proximal urethra.

Image One

• Unfortunately, we didn’t catch this at the time, and 48 hours later, when his azotemia, hyperkalemia and hematuria had resolved and we tried to remove the catheter, it was stuck! The distal end of the urinary catheter had advanced into the urethra, causing the catheter to be caught on itself. With some heavy sedation, gentle flushing and catheter manipulation, we were able to remove it, but this was a good reminder of why we should always take (and evaluate!) a radiograph after placement. An example of correct urinary catheter placement is shown for comparison (Image 2).

Image Two

• Get a UA and a culture. Obtaining a urine sample at the time of unblocking (I like to take mine directly from the catheter when I place it) will give you valuable information about your patient’s urine. Does he have stones? Crystals? Much less likely but still possible, an infection? Knowing this information from the beginning can help you guide owners on recommendations for further treatment and therapy. At the end of hospitalization, when I pull the urinary catheter, I also like to get a urine culture. While we try to be as aseptic as possible during the unblocking process, infection can be introduced, and positive culture results occurred in 13-33% of cats in two recent studies.^4,5 Culture samples can be obtained by either taking a sample through the catheter right before removal, or performing a cystocentesis; culturing the tip of the catheter is not recommended due to risk of contamination during catheter removal. While sending all blocked cats home on antibiotics is not recommended since the chances of a UTI are low, culture can help us provide appropriate antimicrobial therapy to those patients who do need it.

• Don’t be afraid of the post-obstructive diuresis. Post-obstructive diuresis, or a urine production > 2 ml/kg/hr occurs in a fair number (46% of cats in one study) of blocked cats within six hours of unblocking.³ While we don’t know exactly what causes this phenomenon, it is thought to be due to a number of factors including accumulation of osmotically active particles in the blood, medullary washout and tubular dysfunction. And it can be SCARY. Once Fluffy began to develop post-obstructive diuresis, his urine output was between 100-120 ml/hr. And he weighed about 5 kg. That’s 20-24 ml/kg/hr! Given how nervous we get about fluid-overloading cats, this can be a nerve-wracking situation. However, it’s incredibly important to meet these cats’ fluid requirements. When this starts to happen, depending on whether or not their azotemia has resolved, I usually match them or even go a bit higher on my fluid rate. The crucial part here is monitoring: check their UOP every two hours, watch their respiratory rate and effort, and weigh them frequently.

After removing Fluffy’s urinary catheter, we kept him in the hospital until he urinated, and sent him home with pain medication (buprenorphine) and a medication for urethral relaxation (prazosin). So far, he’s doing well and our fingers are crossed that with careful monitoring, environmental modification and a diet change to a prescription urinary diet, he will do well. While complicated blocked cat cases like Fluffy can be difficult, they’re a good reminder of how sick these patients can be!

Dr. Kari Santoro Beer is a Board-Certified Critical Care Specialist at the Veterinary Specialty & Emergency Center. The Veterinary Specialty & Emergency Center operates state-of-the-art emergency and specialty veterinary hospitals that are open 24/7/365 in both Levittown PA and Philadelphia PA. For more information about our world-class emergency and specialty care, please visit VSEC on the web at www.VSECVET.com.

1. Pratt C, Balakrishnan A, McGowan E, Drobatz K, Reineke E. Evaluation of bupivacaine and morphine-bupivicaine caudal epidurals in cats with urethral obstruction (Abstract). J Vet Emerg Crit Care 2015; 25(1): S10.
2. O’Hearn AK, Wright BD. Coccygeal epidural with local anesthetic for catheterization and pain management in the treatment of feline urethral obstruction. J Vet Emerg Crit Care 2011; 21(1): 50-52.
3. Cooper ES. Controversies in the management of feline urethral obstruction. J Vet Emerg Crit Care 2015; 25(1): 130-137.
4. Hugonnard M, Chalvet-Monfray K, Dernis J, et al. Occurrence of bacteriuria in 18 catheterized cats with obstructive lower urinary tract disease: a pilot study. J Fel Med Surg 2013; 15(10): 843-848.
5. Cooper ES, Lasley E, Daniels J, et al. Incidence of urinary tract infection at presentation and after urinary catheterization in feline urethral obstruction. J Vet Emerg Crit Care 2013; 23(S1): S13.