Journal Club "Pharmacological therapy for hyperkalaemia in feline urethral obstruction has no additional benefit over intravenous fluid and calcium gluconate therapy and prompt unobstruction" by Maciorowski et al.

Quick Clinical Takeaways

• For male cats with urinary obstruction presenting with severe hyperkalaemia (serum potassium >= 7.5 mEq/L), prompt unblocking of the cat, intravenous fluid therapy and calcium gluconate administration should be prioritised, particularly for cost-constrained clients
• Cats with urinary obstruction and hyperkalaemia have a good prognosis as long as they receive timely treatment

I've been privileged enough to be able to work in an emergency department in a referral hospital during my rotating internship, during which I've seen a fair share of blocked cats. Many clients express cost constraints, thus adding a layer of complexity to treating these cats. I believe this paper will have a positive impact as it is helpful in showing which treatments should be prioritised to give these patients the best chance of survival given resource constraints.

Aims of the study

The first aim of this study was to compare the relative reduction of serum potassium in male cats with urinary obstruction (UO) that received IV fluid therapy and calcium gluconate alone or with additional pharmacologic interventions (insulin and dextrose, terbutaline or sodium bicarbonate)

Since serum potassium levels have been previously shown to correlate with creatine and BUN levels[1], the secondary aim of this study was to examine the relative reduction of serum creatinine between these groups.

Study Design

This study adopts a prospective, randomised, unblinded design. Male cats from a single teaching hospital were recruited using the following inclusion and exclusion criteria:

Inclusion criteria

• Male cats presenting for UO
  • Inability to urinate
  • Firm, painful, nonexpressible urinary bladder
• UO male cats had to have a serum potassium of >= 7.5 mEq/L
• 1-12 years of age and weigh between 2.5 – 12 kg

 Exclusion criteria

• History of ureteroliths or nephroliths or historic or concurrent congestive heart failure
• Initial therapeutic intervention did not follow the defined initial stabilisation protocol

34 cats met inclusion criteria. The initial stabilisation involved administering 20 ml/kg lactated Ringer solution bolus intravenously and 300 mg of calcium gluconate diluted 1:1 with saline (0.9% NaCl) and given IV slowly over approximately 5 to 10 min­utes as per the primary clinician's discretion. The cats were then randomly assigned to the 4 intervention groups. The researchers were not blinded.

Results

• Median age was 5 years (range 1 to 12 years)
• Median weight 6.1 kg (range 4.5 to 10.6 kg)
• 91.2% of cats were neutered
• All cats survived to discharge

Median baseline serum potassium was 9.0 mEq/L (range 7.5 to 11.8 mEq/L) and the median baseline starting creatinine was 20.1 mg/dL (range 12 to 20.1 mg/dL) with no significant differences between groups.

There were no significant differences in the relative change in serum potassium or creatinine between groups. There were no statistically significant differences in the number of cats that achieved a serum potassium of equal to or less than 6.0 mEq/L by 4 hours between the intervention groups.

Evaluation

This is a really well structured and thought out study with a simple yet impactful takeaway message that can benefit both emergency and general practice veterinarians. Although the sample size is small and this may have masked any statistically significant results, I still believe that it can aid in clinical decision making (prioritising unblocking, IVFT and calcium gluconate administration. Prognosis for blocked cats is generally good if they are promptly treated).

Most of the limitations in this study have been highlighted by the researchers themselves.

1. Small sample size -> with only 8-9 cats per intervention group, there is a higher likelihood of random chance masking any statistically significant differences between the intervention groups. Future studies should perhaps include more cats and even better, be a multicenter study.
2. Some cats had serum potassium and creatinine levels that were too high to be read on analysers -> this could affect quantitative measurement of the reduction in these parameters following intervention
3. The researchers were not blinded in this study, leading to the possibility of measurement bias during the study period. This has been reduced by standardising the analysers used in this study.
4. Cats were excluded if they have a known history of ureteroliths or nephroliths but this was not ruled out via imaging during the study period
5. The laboratory values were rechecked at the 4 hour time point, potentially missing out on interventions that may have resulted in a quicker decrease in serum potassium or creatinine
6. Time from diagnosis to treatment was not standardised -> this may have been influenced by triaging, during which serum potassium may have continued to rise

How I would use this knowledge in clinical practice

Once I have done my physical exam, run the appropriate diagnostics and have diagnosed urinary obstruction and severe hyperkalaemia (>7.5 mEq/hr) in a male cat, I would prioritise providing pain relief, IVFT, calcium gluconate and prompt unblocking if clients face cost constraints. The money that could have been used on additional pharmacologic interventions to treat hyperkalaemia could perhaps be allocated more towards subsequent hospitalisation and supportive care instead.

Note: The information provided is for educational and informational purposes only and does not constitute professional medical advice, diagnosis, or treatment. Please seek a veterinarian if your pet is unwell.

References

1. Lee, Justine A., and Kenneth J. Drobatz. ‘Characterization of the Clinical Characteristics, Electrolytes, Acid–Base, and Renal Parameters in Male Cats with Urethral Obstruction’. Journal of Veterinary Emergency and Critical Care, vol. 13, no. 4, Dec. 2003, pp. 227–33. DOI.org (Crossref), https://doi.org/10.1111/j.1534-6935.2003.00100.x.
2. Maciorowski, Stephanie, et al. ‘Pharmacological Therapy for Hyperkalemia in Feline Urethral Obstruction Has No Additional Benefit over Intravenous Fluid and Calcium Gluconate Therapy and Prompt Unobstruction’. Journal of the American Veterinary Medical Association, vol. 263, no. 10, Oct. 2025, pp. 1268–72. DOI.org (Crossref), https://doi.org/10.2460/javma.25.04.0258.