## **Core Concept**
The patient's symptoms of numbness around the mouth, carpopedal spasm, and a prolonged QT interval on the electrocardiogram are indicative of **hypocalcemia**. This condition often arises in the setting of massive blood transfusions due to the citrate preservative in the transfused blood, which chelates calcium ions.

## **Why the Correct Answer is Right**
The correct answer, **Calcium gluconate**, is the appropriate treatment for hypocalcemia. Calcium gluconate is a form of calcium that can be administered intravenously to rapidly correct low calcium levels. It works by directly replenishing the body's calcium stores, thus alleviating the symptoms of hypocalcemia, including muscle cramps, spasms, and cardiac arrhythmias associated with a prolonged QT interval.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not specify a treatment for hypocalcemia.
- **Option B:** This option is incorrect as it does not address the immediate need to correct hypocalcemia.
- **Option C:** While magnesium and calcium imbalances can be related, administering magnesium would not directly address the symptoms of hypocalcemia presented.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **massive blood transfusions** can lead to hypocalcemia due to citrate in the blood products. Clinicians should monitor for signs of hypocalcemia, such as muscle cramps and a prolonged QT interval, in patients receiving large volumes of blood products.

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