## **Core Concept**
The patient presents with acute renal failure, hyperkalemia (elevated potassium levels), and signs of fluid overload (mild dyspnea, 4 kg weight gain) following a major surgical procedure. The electrocardiogram changes are likely related to the electrolyte imbalances, particularly hyperkalemia. The initial treatment should focus on stabilizing cardiac membranes and managing hyperkalemia.

## **Why the Correct Answer is Right**
The correct answer involves administering **calcium gluconate**. Calcium gluconate is used to stabilize cardiac membranes and counteract the cardiac effects of hyperkalemia, such as peaked T waves, widened QRS complexes, and potentially life-threatening arrhythmias. It does not lower potassium levels but is essential in the acute management of hyperkalemia to prevent cardiac complications.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because, although **sodium bicarbonate** can help manage hyperkalemia by driving potassium into cells in exchange for hydrogen ions, it is not the immediate treatment for stabilizing cardiac membranes.
- **Option B:** This option is incorrect because **insulin and dextrose** can help lower potassium levels by driving potassium into cells, but they do not immediately stabilize cardiac membranes.
- **Option D:** This option is incorrect because **furosemide** can help manage fluid overload and potentially reduce potassium levels but does not immediately address the cardiac effects of hyperkalemia.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that in the setting of hyperkalemia, especially with electrocardiographic changes, the immediate priority is to stabilize cardiac membranes with **calcium gluconate**. This is a critical step before other interventions that aim to lower potassium levels or enhance its cellular uptake.

## **Correct Answer:** . **Calcium gluconate**