Which of the following is the first-line treatment for hyperkalemia?

The first-line treatment for hyperkalemia is calcium gluconate. In cases of elevated potassium levels, particularly when they are significantly high or when there are ECG changes indicating the risk of cardiac complications, calcium gluconate functions as a protective agent for the heart. It stabilizes the myocardial cell membranes, effectively reducing the risk of life-threatening arrhythmias that can occur due to elevated potassium levels.

The administration of calcium gluconate is crucial because while it does not lower the serum potassium levels, it counteracts some of the physiological effects that hyperkalemia can have on cardiac function. This is particularly important in acute settings where immediate stabilization of the patient is necessary.

In contrast, sodium bicarbonate, potassium chloride, and diuretics serve other roles in the management of hyperkalemia. Sodium bicarbonate can help in cases where acidosis is present, potassium chloride is actually contraindicated in hyperkalemia as it increases potassium levels, and diuretics can assist in the excretion of potassium but are not always effective in acute settings. Therefore, calcium gluconate is recognized as the appropriate choice to provide immediate cardiac protection in the emergency management of hyperkalemia.