**Core Concept**
The patient is likely experiencing acute kidney injury (AKI) secondary to rhabdomyolysis, which is a common complication in patients with prolonged immobilization due to a hip fracture. This condition can lead to hyperkalemia, acidosis, and electrolyte imbalances.

**Why the Correct Answer is Right**
Rhabdomyolysis is caused by the breakdown of skeletal muscle, releasing myoglobin into the bloodstream. Myoglobin can precipitate in the kidneys and cause damage, leading to AKI. The patient's elevated creatinine and urea levels are indicative of this condition. In addition, the patient's hypercalcemia (elevated calcium levels) can also contribute to the development of AKI.

**Why Each Wrong Option is Incorrect**
* **Option A:** Administering intravenous fluids is a crucial step in the management of rhabdomyolysis and AKI. It helps to maintain renal perfusion and prevent further muscle breakdown.
* **Option B:** Monitoring the patient's potassium levels is essential in the management of rhabdomyolysis, as hyperkalemia can occur due to the release of potassium from damaged muscle cells. However, it is not the correct answer in this context.
* **Option C:** Administering diuretics may not be the most effective option in this scenario, as the patient is likely experiencing AKI due to rhabdomyolysis. Diuretics may actually worsen the situation by increasing the amount of myoglobin in the kidneys.
* **Option D:** Administering calcium-channel blockers may not be the most appropriate option in this scenario, as the patient is experiencing hypercalcemia. Calcium-channel blockers can worsen hypercalcemia by increasing the absorption of calcium from the gut.

**Clinical Pearl / High-Yield Fact**
In patients with rhabdomyolysis, it is essential to administer intravenous fluids promptly to prevent further muscle breakdown and AKI. A common mnemonic to remember the management of rhabdomyolysis is "TIPS": **T**ransfusion (of intravenous fluids), **I**ntravenous **P**otassium (to prevent hyperkalemia), and **S**upportive care (to manage electrolyte imbalances and acidosis).

**Correct Answer: D. Administering calcium-channel blockers may not be the most appropriate option in this scenario, as the patient is experiencing hypercalcemia.**