## Core Concept
Sodium polystyrene sulfonate is a medication used to treat hyperkalemia by exchanging sodium ions for potassium ions in the gastrointestinal tract. It works through the principle of **ion exchange**, specifically targeting potassium ions.

## Why the Correct Answer is Right
The correct answer, **intestinal necrosis**, is a rare but severe complication associated with the use of sodium polystyrene sulfonate, particularly when administered in sorbitol. Sorbitol can cause **ischemia** and **necrosis** of the intestinal mucosa, especially in patients with compromised intestinal circulation or those taking the medication inappropriately. This condition can lead to severe morbidity and mortality.

## Why Each Wrong Option is Incorrect
- **Option A:** While sodium polystyrene sulfonate can cause gastrointestinal side effects like constipation or diarrhea, **gastrointestinal upset** is not typically considered a fatal complication.
- **Option B:** **Electrolyte imbalance** could potentially occur due to the medication's mechanism of action but is not a direct fatal complication specifically attributed to sodium polystyrene sulfonate use.
- **Option C:** Although **cardiac arrhythmias** can result from hyperkalemia, which the drug aims to treat, they are not a direct complication of the medication itself.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the use of sodium polystyrene sulfonate with **sorbitol** significantly increases the risk of intestinal necrosis. Clinicians should be cautious and consider alternative treatments for hyperkalemia, especially in patients with risk factors for intestinal ischemia.

## Correct Answer: D. intestinal necrosis