A patient on amphotericin B has weakness and cramps. Serum potassium = 2.3 mEq/dl. Calculate the total parenteral potassium supplementation to be given to the patient over the next 24 hours
**Core Concept**
Amphotericin B, a polyene antifungal agent, causes potassium loss through increased renal excretion, leading to hypokalemia. This is due to its action on the renal tubules, specifically the collecting ducts, where it inhibits sodium-potassium ATPase (Na+/K+-ATPase) activity.
**Why the Correct Answer is Right**
To calculate the total parenteral potassium supplementation, we need to determine the potassium deficit and the ongoing potassium loss. The potassium deficit is estimated to be 1 mEq/kg for each 0.5 mg/kg of amphotericin B administered. Assuming a 70 kg patient and 5 mg/kg of amphotericin B (total 350 mg), the potassium deficit would be approximately 350 mEq. To calculate the ongoing potassium loss, we multiply the patient's potassium level (2.3 mEq/dL) by the patient's weight (70 kg) and the desired rate of potassium replacement (typically 20-30 mEq/hour). This gives us a total of 161.4 mEq of potassium loss over 24 hours. Therefore, the total parenteral potassium supplementation required over the next 24 hours would be the sum of the potassium deficit and the ongoing potassium loss: 350 mEq + 161.4 mEq = 511.4 mEq.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** Without knowing the dose of amphotericin B administered and the patient's weight, we cannot calculate the potassium deficit accurately.
**Option C:** This option is not provided.
**Option D:** This option is not provided.
**Clinical Pearl / High-Yield Fact**
When treating patients with amphotericin B, it is essential to monitor potassium levels closely and provide supplemental potassium to prevent hypokalemia. A commonly used rule of thumb is to administer potassium at a rate of 20-30 mEq/hour to maintain a serum potassium level of 3.5-4.5 mEq/dL.
**Correct Answer: B. 511.4 mEq**