Hyperkalaemia in the blocked cat: first emergency step
4-year-old neutered male cat, blocked for 48 hours, depressed, with a large, firm bladder. Heart rate 110 bpm. The ECG shows absent P waves, wide QRS complexes and tall, peaked T waves.
| Parameter | Result | Reference |
|---|---|---|
| Potassium | 9.1 mmol/L | 3.5–5.5 |
| Creatinine | 8.6 mg/dL | 0.8–2.4 |
| Ionised calcium | 0.95 mmol/L | 1.10–1.40 |
| Venous pH | 7.12 | 7.30–7.40 |
What is the most urgent first step?
chevron_right Show answer and explanation
A. Anaesthetise and catheterise immediately, before stabilising
Relieving the obstruction is essential, but anaesthetising a cat with this ECG without cardioprotection can cause cardiac arrest. Stabilise first.
B. Atropine to correct the bradycardia
The bradycardia is caused by hyperkalaemia, not increased vagal tone, and atropine does not correct the conduction problem. The potassium must be treated.
C. IV furosemide to increase potassium excretion
With the urethra obstructed there is no urine outflow: the diuretic does not remove potassium and may worsen bladder distension.
D. 10% calcium gluconate slowly IV with ECG monitoring
Correct. Calcium restores the myocardial excitability threshold within minutes and protects against fatal arrhythmias, although it does not lower potassium. Potassium is then reduced (dextrose with or without insulin) and the obstruction relieved.
lightbulb Key takeaway
Blocked cat with bradycardia = hyperkalaemia until proven otherwise. Order: IV calcium (protects), dextrose ± insulin (redistributes), fluids and relief of obstruction (removes). The accompanying hypocalcaemia and acidosis worsen cardiac toxicity.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.