VETINUITY
Does calcium lower the potassium?
No. Calcium restores the threshold gap across the cardiac cell membrane within minutes and lasts about 30 to 60 minutes; it buys time while insulin, dextrose and unblocking the urethra bring potassium down.
● ANSWER
Sourced & dated
How do you treat hyperkalemia in a blocked cat?
Vetinuity's blocked-cat table: calcium gluconate 10% at 50-100 mg/kg IV over 10-20 min protects the heart, then regular insulin 0.5 U/kg with dextrose moves potassium into cells.
● VETINUITY BLOCKED CAT HYPERKALEMIA CALCULATOR
Vetinuity blocked cat hyperkalemia calculator
Run calcium on ECG. Dilute 50% dextrose to 25% or less before giving it peripherally.
● WHAT'S DOCUMENTED
Vetinuity’s blocked cat hyperkalemia table: give calcium gluconate 10% at 50 to 100 mg/kg (0.5 to 1 mL/kg) IV over 10 to 20 minutes on ECG to protect the myocardium, then regular insulin 0.25 to 0.5 U/kg IV with 1 to 2 g of dextrose per unit of insulin to shift potassium into cells, then relieve the obstruction. The Vetinuity blocked cat hyperkalemia calculator above returns each dose and the volume to draw up. Vetinuity, the clinical assistant from emergency veterinarian Brian Toncray, DVM, keeps this sequence on hand for the cat that arrives with a heart rate of 120.
When to treat the potassium first
Treat before unblocking when serum potassium is above about 7.5 to 8 mEq/L, or at any value when the ECG shows bradycardia, absent P waves, wide QRS complexes or tall tented T waves. A cat with a heart rate under 140 and a large bladder should be presumed hyperkalemic until the result comes back. Place an IV catheter and start a balanced crystalloid; potassium-containing fluids such as LRS do not worsen hyperkalemia and correct acidosis better than 0.9% NaCl.
The three tools and how long they last
| Treatment | Onset | Duration | What it does |
|---|---|---|---|
| Calcium gluconate 10% | 1 to 3 min | 30 to 60 min | Protects conduction, no change in K |
| Insulin plus dextrose | 15 to 30 min | Hours | Moves K into cells |
| Sodium bicarbonate | 15 to 30 min | Hours | Moves K into cells, treats severe acidosis |
Bicarbonate is reserved for severe metabolic acidosis (pH under about 7.1) and is never mixed in the same line as calcium, which precipitates. Terbutaline and salbutamol also shift potassium but add tachycardia and are rarely needed once insulin is on board.
After the obstruction is relieved
Potassium falls quickly once urine flows, and post-obstructive diuresis can swing the cat into hypokalemia within 12 to 24 hours. Recheck electrolytes at 4 to 6 hours, match fluid rate to urine output, and add potassium chloride when the value drops below range.
Related: lorazepam for urethral obstruction, feline idiopathic cystitis and shock fluid boluses.
● SOURCES
- 1. Iimori Y, Johnson PA, Thomovsky EJ, et al. Emergency management of hyperkalemia in dogs and cats - Part 2: Diagnosis and treatment. Can Vet J. 2026;67:563-571. PMID 42095171. Treatment. Checked 2026-10-26.
- 2. Schaer M. Hyperkalemia in cats with urethral obstruction. Electrocardiographic abnormalities and treatment. Vet Clin North Am. 1977;7(2):407-414. PMID 867738. Abstract. Checked 2026-10-26.
- 3. Merck Veterinary Manual: Urolithiasis in Small Animals. Urethral obstruction. Checked 2026-10-26.
● RELATED ANSWERS
- Lorazepam for Urethral Obstruction in Cats
A 2026 JAVMA randomized controlled trial found lorazepam given after hospitalization was associated with zero urethral obstruction recurrences in male cats.
- Shock Fluid Bolus Volumes for Dogs and Cats
Vetinuity's shock bolus table: isotonic crystalloid 10-20 mL/kg over 15-30 minutes in dogs and 5-10 mL/kg in cats, reassessed after each, or 7.5% hypertonic saline at 3-5 mL/kg in dogs.
- Addisonian Crisis in Dogs: Emergency Treatment
Addisonian crisis requires emergency stabilization with IV fluids, close monitoring and replacement of deficient glucocorticoid support, tailored to the dog’s abnormalities.
- RECOVER CPR Guidelines for Dogs
RECOVER CPR guidelines for dogs: compression rate and depth, ventilation, drug therapy, monitoring, post-arrest care, and what the 2024 update changed.
- Canine DKA: Insulin CRI Protocol and Rates
Vetinuity's canine DKA table: add 2.2 U/kg regular insulin to 250 mL 0.9% NaCl, start at 10 mL/h, and step the rate and dextrose down as glucose falls.
● FAQ
How often should glucose be checked after the insulin dose?
Every 1 to 2 hours for at least 6 hours, keeping dextrose in the fluids, because the insulin effect outlasts the dextrose bolus.
Should the cat be sedated before unblocking if potassium is high?
Stabilize the heart first. A cat with bradycardia and a sine-wave ECG gets calcium and insulin before any sedation or catheterization attempt.
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SEE HOW VETINUITY HANDLES THIS.
Vetinuity explains clinical options with journal citations.
The veterinarian diagnoses and prescribes.