ECG of a patient showed tall T waves with a normal rhythm. Laboratory examination showed serum potassium levels to be 7.5 mEq/ L. Which of the following therapies will lead to the fastest reduction in the serum potassium levels?
Insulin glucose IV
Calcium gluconate
Cation exchange resin
NaHCO3
Severe hyperkalemia requires emergent treatment directed at minimizing membrane depolarization, shifting K+ into cells, and promoting K+ loss.

Administration of calcium gluconate decreases membrane excitability. The effect begins within minutes but is short-lived (30-60 min), and the dose can be repeated if no change in the electrocardiogram is seen after 5-10 min.
Insulin causes IC to shift into cells and will temporarily lower the plasma IC concentration. Although glucose alone will stimulate insulin release from normal pancreatic beta cells, a more rapid response generally occurs when exogenous insulin is administered (with glucose to prevent hypoglycemia). The plasma K+ concentration will fall by 0.5-1.5 mmol/L in 15-30 min, and the effect will last for several hours.
Alkali therapy with intravenous NaHCO3 can also shift K+ into cells. This should be reserved for severe hyperkalemia associated with metabolic acidosis. Patients with end-stage renal disease seldom respond to this intervention and may not tolerate the Na+ load and resultant volume expansion.
When administered parenterally or in nebulized form, beta 2-adrenergic agonists promote cellular uptake of K+ The onset of action is 30 min and the effect lasts 2-4 h.
Therefore, from the above discussion, the fastest acting drug in hyperkalemia is calcium gluconate but it does not reduce potassium level and only counteracts the ECG changes induced by K+ For reducing the potassium level quickly, the drug is glucose insulin.