**Core Concept**
Massive blood transfusion is defined as the administration of more than 10 units of blood or plasma within a 24-hour period, typically to a patient with severe blood loss. The transfusion of large volumes of blood can lead to various complications due to the citrate preservative used in blood products, which can cause hypocalcemia, and the dilution of coagulation factors.

**Why the Correct Answer is Right**
Massive blood transfusion can lead to several side effects, including hypocalcemia due to the citrate preservative in blood products, which binds to calcium ions and reduces their availability. Additionally, the dilution of coagulation factors, such as fibrinogen and clotting factors, can lead to coagulopathy and bleeding. Furthermore, the transfusion of large volumes of blood can also cause an increase in venous pressure, leading to pulmonary edema.

**Why Each Wrong Option is Incorrect**
**Option A:** Hyperkalemia is not typically a direct result of massive blood transfusion, although it can occur in patients with pre-existing renal dysfunction or in the context of massive transfusion of blood products from multiparous women.

**Option B:** Dilutional anemia is a common complication of massive blood transfusion, as the transfused blood products can dilute the patient's own red blood cells. This can lead to a decrease in oxygen-carrying capacity and may require additional transfusions to maintain adequate oxygen delivery.

**Option C:** Hypothermia is a potential complication of massive blood transfusion, particularly in pediatric patients or patients with significant blood loss. The transfusion of cold blood products can cause a drop in core body temperature, leading to hypothermia and potentially life-threatening complications.

**Clinical Pearl / High-Yield Fact**
When administering massive blood transfusions, it is essential to monitor the patient's electrolyte levels, coagulation status, and temperature. Additionally, the transfusion of blood products should be guided by laboratory results and clinical assessment to minimize the risk of complications.

**Correct Answer: B. Dilutional anemia is a common complication of massive blood transfusion.**