**Core Concept**
Massive blood transfusion is a clinical scenario where a patient receives a large volume of blood products, typically exceeding 10 units in a 24-hour period. This can lead to various complications due to the dilutional effects, citrate toxicity, and immune system modulation.

**Why the Correct Answer is Right**
Massive blood transfusion can cause several complications, including:
* Dilutional coagulopathy: The dilution of coagulation factors and platelets can lead to bleeding.
* Citrate toxicity: Excessive citrate can cause hypocalcemia, leading to cardiac arrhythmias and cardiac arrest.
* Hypothermia: The transfusion of cold blood products can cause hypothermia.
* Transfusion-related acute lung injury (TRALI): This is a severe complication involving the transfusion of antibodies that can cause lung injury.
* Hyperkalemia: Transfused blood products can contain elevated potassium levels.

**Why Each Wrong Option is Incorrect**
**Option A:** Dilutional anemia - This is a complication of massive blood transfusion, as the transfused blood products can dilute the patient's red blood cell mass.

**Option B:** Hypokalemia - Transfused blood products typically contain elevated potassium levels, which can lead to hyperkalemia, not hypokalemia.

**Option C:** Citrate toxicity - This is a known complication of massive blood transfusion, as excessive citrate can cause hypocalcemia and cardiac arrhythmias.

**Option D:** Hypernatremia - Transfused blood products do not typically contain elevated sodium levels, making this an unlikely complication.

**Clinical Pearl / High-Yield Fact**
When administering massive blood transfusions, it's essential to monitor the patient's coagulation status, electrolyte levels, and temperature to prevent complications.

**Correct Answer: D. Hypernatremia**