Therapy for hyperkalaemia in cats

In mild cases of hyperkalaemia (K+ < 6.0 mmol/L), the hyperkalaemia will resolve with the administration of potassium-free fluids.

Moderate elevations of K+ (6.0-8.0 mmol/L) does not usually result in life-threatening cardiac arrhythmias, and can usually be treated with IV fluids (free of potassium), and treating the underlying cause of hyperkalemia.

If K+ exceeds 8.0 mmol/L, or where cardiotoxicity is seen, calcium gluconate is used as a first line treatment. Calcium gluconate at 1ml/kg of 10% solution over 3-4 minutes with ECG monitoring. Rapid onset of action and lasts for approx 1 hr. NB: Calcium gluconate counteracts toxic effects of K+ on the heart, but does not lower serum K+ concentration.

Alternatives (second-line treatment, following calcium gluconate) for moderate to severe hyperkalemia include: dextrose (0.5-1.0 g/kg, if using 50% glucose then diluted 1:4, and give slowly IV). Dextrose drives K+ back into the cells by effects on endogenous insulin secretion. Used alone, dextrose will lower K+ levels within 1 hr.

Calcium gluconate then dextrose can be followed by intravenous regular insulin. Consider concurrent insulin administration for the very severe (K+ > 8.0 or 9.0 mmol/L); as this will provide a more immediate effect than dextrose alone, Adequate IV fluid support is vital since vasodilation and collapse can result from IV insulin administration. Give 0.5 IU/kg of regular insulin as an IV bolus, diluted 1:4, following the dextrose bolus. Support with 2.5% dextrose-supplemented fluids, and monitor for hypoglycaemia. May be repeated if needed. Effect lasts several hours.

In addition, the use of sodium bicarbonate may also be considered as a treatment for moderate to severe hyperkalaemia and acidosis. This reduces serum K+ levels as it causes K+ to shift into the cells, in exchange for hydrogen ions, which move into the extracellular space. Give based on the calculated bicarb deficit (equals measured base deficit x weight in kg x 0.3); and give 1/3 of this amount IV, then reassess base deficit and K+ levels before administering more. Alternatively, give an empirical dose of 0.5-1.0 mEq/kg; over 10-15 minutes, then re-evaluate. The concerns with sodium bicarbonate administration in FLUTD patients is that sodium bicarbonate will reduce the plasma ionised [Ca]. As cats with urethral obstruction may already have a low serum ionised [Ca], other options listed above may be preferable, except in cases of severe metabolic acidosis.