Blocked Cats: The Five-Minute Hyperkalemia Race

Claire Brooks

Picture this scenario. An owner walks up to the front desk, and, and they say their male cat has been sitting in the litter box all morning, straining hard, maybe crying a little bit, and they think, well, he is just constipated. So he is waiting in the lobby. But behind that lobby door, his urine output has completely stopped, his kidneys are backing up, and his blood potassium is climbing toward a level that could literally stop his heart in the next ten minutes. Dr. Sikina, I, I think every emergency tech remembers the first time they realized just how fast a blocked cat can turn upside down.

Dr. Erika Sikina

Oh, absolutely. Feline urethral obstruction, or FUO, it is one of our most common true emergencies. But here is the remarkable thing, Claire. When we move fast and follow our clinical standards, survival to discharge is well over 90 percent. But that success, it, it hinges entirely on the technician at triage. If that cat sits in the lobby because someone misreads stranguria, that straining, or misreads frequent penile licking as constipation, we lose precious time.

Claire Brooks

Right, because to an owner, straining in the box looks like straining to defecate. They, they often do not know the male urethra is so narrow that a tiny plug of mucus, or crystals, or even just inflammation from feline idiopathic cystitis, FIC, can shut the whole system down. So when a cat like this comes through the front door, what is the exact AVS standard for triage?

Dr. Erika Sikina

The rule is absolute. Any male cat presenting with straining or a history of small frequent urinations, where you feel a large, firm, turgid bladder on gentle palpation, that cat is an automatic Level 1 RED triage. Period. You do not assess them in the lobby. You pick them up and bring them straight to the treatment area. And you alert a DVM immediately.

Claire Brooks

Straight to the treatment area. No waiting for paperwork. And, and I remember early in my career, seeing a cat that was already decompensated. He was completely flat on the table, cold to the touch, just staring off. And his heart rate was... I mean, it felt like a slow crawl. It is terrifying because you expect an ER cat to be tachycardic from stress and pain!

Dr. Erika Sikina

That is a classic pitfall. Technicians see a quiet, slow heart rate and think, oh, he is just calm. No! In a blocked cat, bradycardia and hypothermia are massive red flags for severe hyperkalemia. In fact, we have a very specific metric for this that every tech should memorize. A heart rate below about 120 beats per minute, remember a normal cat runs 160 to 220, paired with a rectal temperature below 96.6 degrees Fahrenheit... that combination is about 98 percent predictive of a serum potassium over 8 mEq per liter which is a critical emergency.

Claire Brooks

Ninety eight percent! That is incredible. So if you feel a cold cat with a slow heart rate and a tight bladder, you do not even need to wait for the lab results to know his heart is in immediate danger from potassium toxicity.

Dr. Erika Sikina

Exactly. Cold and bradycardic equals hyperkalemic emergency until proven otherwise. IV catheter access and an ECG go on before anything else.

Claire Brooks

Okay, so we have rushed this cat back. He is a RED triage. Now we enter what you call the five minute race. And step one is something that separates great emergency technicians from the rest: the, the one stick protocol. Walk us through that, Dr. Sikina.

Dr. Erika Sikina

When a cat is hyperkalemic and potentially hypotensive, their veins are often fragile and hard to find. The last thing you want to do is poke them three or four times. So when you place that peripheral IV catheter, you pull your initial stabilization blood right out of the catheter hub during placement. One stick does it all. You grab your PCV and total solid, and you run your EPOC point of care panel, immediately.

Claire Brooks

And on that EPOC point of care panel, you are getting blood glucose, creatinine, BUN, venous blood gas, and electrolytes, especially potassium. And what is the protocol when those numbers pop up on the screen?

Dr. Erika Sikina

You find the doctor and say them out loud! Do not just type them into the chart or print the paper and wait for the doctor to see it. If that potassium comes back at 8.5 mEq per liter, you call out to the treatment room, potassium is 8.5, blood gas shows metabolic acidosis! The potassium and blood gas drive the next five minutes of clinical management. And while that blood is running, another team member has already hooked up continuous ECG monitoring and then obtained a blood pressure.

Claire Brooks

Right, because hyperkalemia changes the electrical conduction of the heart in a very predictable ladder. Can you talk through those ECG stages? Because seeing them in real time is wild.

Dr. Erika Sikina

It really is. As potassium rises, say between 5.5 to 6.5 mEq per liter, you start seeing mild changes: tall, peaked, or tented T waves, and the QRS complex might start to widen. Then, as it creeps into moderate territory, around 6.5 to 8, the PR interval prolongs, P waves start flattening out or disappearing entirely, and the QRS gets even wider as the heart rate slows down into bradycardia. And then, above 8 mEq per liter, in severe hyperkalemia...

Claire Brooks

You get that terrifying sine wave pattern.

Dr. Erika Sikina

Yes! A sine wave pattern or severe ventricular arrhythmias. That is a cat on the verge of cardiac arrest. So if you see those P waves disappear or those T waves tenting, you shout it out to the doctor immediately.

Claire Brooks

Now, when the doctor calls for emergency treatment for hyperkalemia, tech execution has to be sharp. And I think there is often confusion about what each drug actually does. Like, calcium gluconate... a lot of people think calcium gluconate lowers potassium, right?

Dr. Erika Sikina

That is such a common misconception! Calcium gluconate does not lower serum potassium by a single fraction of a unit. What it does is stabilize the heart's myocardial cell membranes. It antagonizes the toxic effect of hyperkalemia on the heart, essentially protecting the cardiac tissue and buying us time. That is why we keep calcium gluconate right on the crash cart. When the doctor orders it, you give it IV slowly over 10-15 minutes, while watching the ECG closely. You should literally see those abnormal wave forms begin to normalize on the monitor as it goes in. We keep the 23% Calcium Gluconate on hand so it must be diluted with 0.9% sodium chloride before administering.

Claire Brooks

This buys the heart time, but then we actually have to clear or move that potassium. How do we do that?

Dr. Erika Sikina

We commonly administer a combination of dextrose and regular insulin, to drive potassium out of the bloodstream and shift it back into the cells. But as techs, if we give regular insulin, we have to monitor blood glucose like a hawk afterwards because hypoglycemia is a major risk. Simultaneously, we give an opiod pain medication and start an IV fluid bolus to expand vascular volume, improve renal perfusion, and dilute that potassium concentration. Generally, a potassium over 7.5 mEq per liter requires active drug treatment, and anything over 9 is immediately life threatening. In cases of mild to moderate potassium elevation, some doctors will give just dextrose IV and a dose of terbutaline or a puff of albuterol to help shift potassium into the cells. When giving dextrose IV, always dilute per doctor instructions and make sure the catheter is patent before and during administration.

Claire Brooks

So calcium gluconate to protect the heart, insulin and dextrose to shift potassium into cells, plus pain medication and IV fluids to dilute and flush. That whole sequence happens in minutes while the patient is being prepped for deobstruction.

Dr. Erika Sikina

Exactly. And once the patient is stabilized cardiovascularly, we move to relieving the physical obstruction. Now, sometimes a doctor will elect to perform a decompressive cystocentesis first.

Claire Brooks

Wait, let us talk about that, because cystocentesis on a hugely overdistended, fragile bladder sounds nerve wracking. What is the standard there?

Dr. Erika Sikina

It can buy time but definitely has risks! If the bladder is severely distended, removing urine with a butterfly needle attached to an extension set, a 3 way stopcock, and a syringe can relieve that high back pressure on the kidneys, drop intra abdominal pressure, make the cat much more comfortable, and gets us a clean baseline urine sample. But you have to weigh the risk. An overdistended bladder wall is thin, and if the cat moves or if the bladder drops down, there is a risk of rupture or urine leakage. To minimize risk, the cat must be completely sedated so it doesn't move. In the majority of cases, placing an indwelling urinary catheter promptly under proper sedation is preferred over decompressive cysto.

Claire Brooks

And getting that cat properly sedated and comfortable is key. A moving cat during unblocking is a dangerous thing for that delicate urethra.

Dr. Erika Sikina

Crucial. These cats are in immense pain. We titrate sedation very carefully, especially in patients that were recently hyperkalemic. A really elegant tool some doctors use is a sacrococcygeal, or coccygeal, epidural block. As technicians, we prepare the site by clipping and prepping over the lumbosacral or coccygeal space, opening sterile gloves and local anesthetic like bupivacaine or lidocaine. That epidural provides profound local analgesia and relaxes the urethral sphincter, which makes unblocking so much smoother and less traumatic.

Claire Brooks

That makes such a difference. Now, walk us through the tray setup for urinary catheter placement. What catheters and tools need to be ready before the cat is under?

Dr. Erika Sikina

You need your sterile gloves and drape, clippers, chlorhexidine scrub, and sterile saline. For the unblocking itself, ask your doctor their preferences. Some may want to have an open ended tomcat catheter on hand, which is stiffer and used to clear the plug or flushing debris through retropulsion. But for the indwelling catheter that stays in the cat, they'll want a softer, less traumatic catheter, like a 3.5 French slippery sam. You also need sterile lubricant, one 30ml and two 12 mL syringes filled with sterile saline for flushing, a sterile bowl, 3-O nonabsorbable suture, needle drivers, thumb forceps, an E collar, and a closed urinary collection bag with lines.

Claire Brooks

And there is a very specific rule about how far that indwelling catheter goes in, right? You do not just go for the biggest and push it all the way to the hub.

Dr. Erika Sikina

Correct! An indwelling catheter should be pre-measured and inserted only to the level of the trigone, the neck of the bladder. If you push it too deep, it can coil, cause severe bladder wall irritation, or kink. Once it is positioned, the doctor secures it to the prepuce with nonabsorbable suture and connects it to the closed collection tubing running toward the tail. Once the catheter is secure, you can gently tape the line to the tail and immediately put an E collar on that cat!

Claire Brooks

Because if that cat wakes up for two seconds without an E collar, he will pull that catheter right out! Now, before any systemic antibiotics are given, we also pull a sterile urine sample directly from the catheter and put it in white top tubes for urinalysis and culture. This is usually done as soon as the catheter is in before flushing. But what about post procedure X rays?

Dr. Erika Sikina

Confirmatory radiographs are mandatory. A single lateral view is commonly performed to check catheter placement and verify the bladder appears intact. However, this is also a great time to look for stones in the bladder or urethra. To visualize the entire length of the male cat's urethra and measure stones, you'll need to take three views: a ventrodorsal view, plus two lateral views. One lateral with the hind legs pulled back, and one lateral with the hind legs pulled forward. That gives you an unobstructed view of the pelvic urethral passage to rule out radiopaque stones.

Claire Brooks

And if the doctor suspects a urethral tear or radiolucent stones that do not show up on regular x-ray film?

Dr. Erika Sikina

Then we assist with a positive contrast urethrogram. We instill a urinary friendly contrast agent through a partially inserted catheter while taking exposure radiographs. It lights up the urethral lumen so you can spot any dye extravasation from a tear immediately.

Claire Brooks

So the cat is unblocked, the catheter is secured in place with verified location at the trigone, radiographs look great, and he is resting in ICU. But the danger is far from over. In fact, now we enter what I call the recovery minefield, starting with post obstructive diuresis, or POD.

Dr. Erika Sikina

POD is where sharp technician nursing literally keeps these cats alive. About 88 percent of cats undergoing relief of urethral obstruction experience post obstructive diuresis within the first 48 hours, and it can last for up to 3 days! Their kidneys have been holding back massive amounts of toxins and fluid, and once unblocked, the kidneys just dump huge volumes of urine. We are talking hundreds of milliliters a day in some cats.

Claire Brooks

So if a technician is not meticulously tracking ins and outs, matching fluid intake to urine output, things can go downhill fast in either direction.

Dr. Erika Sikina

Precisely. If you under replace their fluid losses during POD, the cat dehydrates rapidly, goes back into hypovolemic shock, and azotemia worsens. If you over replace fluids without measuring urine output, you can cause more damage to the kidneys or fluid overload that risks putting the cat into heart failure. As technicians, we measure the closed collection bag every 2 to 4 hours, record exact urine output in milliliters per kilogram per hour, weigh the patient twice daily, and adjust IV fluid rate orders with the DVM to match those losses exactly.

Claire Brooks

And keeping that closed collection system sterile is critical. We do not want ascending bacterial urinary tract infections while that catheter is in place.

Dr. Erika Sikina

Strict aseptic technique always. Wipe ports with isopropyl alcohol, keep the collection bag off the floor, make sure the line has no kinks, and keep that E collar secured at all times. Also, monitor pain continuously. We use the Feline Grimace Scale to assess subtle signs of abdominal discomfort or urethral spasms so pain medications can be titrated effectively. We'll often keep them on buprenorphine with a touch of ace for urethral relaxation during their first 24 to 48 hours in hospital, then transition them to gabapentin.

Claire Brooks

And then comes the big moment: pulling the catheter. But the vigilance does not stop there, does it?

Dr. Erika Sikina

Not at all. Reobstruction is remarkably common, reported in about 15 to 40 percent of cats, with the highest risk occurring in the very first week after catheter removal. Once that catheter comes out, you have to monitor the litter box constantly. You need to physically confirm urine production. Is he voiding normal streams? Or is he squatting, straining, vocalizing, or is his bladder re filling? If you suspect re obstruction, you re palpate gently and flag the DVM right away.

Claire Brooks

And when it comes time for discharge, technicians play a massive role in owner education. Helping them understand that diet change, increasing water intake, managing litter box setups, and increasing environmental enrichment while reducing household stress are key to keeping that cat from ending up back in the ER.

Dr. Erika Sikina

Client communication is where we empower owners to succeed at home. Catching early signs of recurrence before the cat becomes hyperkalemic makes all the difference.

Claire Brooks

Dr. Sikina, this has been such a clear, empowering breakdown. From recognizing that cold, bradycardic cat at triage, to running the one stick protocol, reading hyperkalemic ECGs, assisting with precision catheter placement, and mastering post obstructive diuresis nursing in the ICU. It really shows how technician mastery drives survival rates in these life threatening emergencies.

Dr. Erika Sikina

It really does. When technicians own these clinical standards and execute them with speed and precision, we turn high stakes emergencies into great success stories. Thank you, Claire, great chatting as always.