Correct Answer: C

Rationale: The correct answer is C: Potassium. During treatment of diabetic ketoacidosis, as blood glucose levels decrease, potassium levels can quickly drop due to insulin therapy driving potassium into cells. Monitoring potassium levels closely is crucial to prevent hypokalemia, which can lead to life-threatening cardiac arrhythmias. Choice A: Calcium - Calcium levels are not typically affected by diabetic ketoacidosis treatment and do not require immediate monitoring in this context. Choice B: Chloride - Chloride levels are usually not significantly impacted by diabetic ketoacidosis treatment and do not need close monitoring in this case. Choice D: Sodium - While sodium levels can be affected by dehydration in diabetic ketoacidosis, they are not as critical to monitor as potassium levels during treatment.

Correct Answer: D

Rationale: The correct answer is D: Discontinue the IV infusion and administer the Lantus insulin at bedtime. This is the correct approach because insulin glargine (Lantus) is a long-acting basal insulin that provides a steady level of insulin throughout the day and night. By administering it at bedtime, it mimics the basal insulin secretion in a person without diabetes. This helps maintain stable blood sugar levels overnight. Choice A is incorrect because continuing the IV insulin infusion for 24 hours alongside insulin glargine is unnecessary and may lead to insulin overdose. Choice B is incorrect because discontinuing the IV infusion in several hours without administering the long-acting insulin can lead to inadequate insulin coverage. Choice C is incorrect because insulin aspart is a rapid-acting insulin that should be given with meals, not as a basal insulin replacement at bedtime.

Correct Answer: B

Rationale: The correct answer is B: fluid replacement with 0.45% saline. The patient's symptoms suggest dehydration and hypovolemia, indicated by low blood pressure, elevated heart rate, and lack of urine output. Fluid replacement with isotonic saline would help restore intravascular volume and improve blood pressure. Blood transfusion (A) is not indicated without evidence of significant blood loss. Inotropic agents (C) are used to improve cardiac function, which is not the primary issue in this case. Antiemetics (D) may help with nausea and vomiting but do not address the underlying cause of hypovolemia.

Correct Answer: D

Rationale: The correct answer is D because if a reliable 24-hour urine collection is not possible, a standardized formula can be used to estimate the GFR. This is typically done using the patient's serum creatinine level, age, sex, and race. It is a validated method when direct measurement is not feasible. A: Incorrect. It is still possible to estimate GFR using formulas when 24-hour urine collection is not possible. B: Incorrect. BUN alone is not sufficient to accurately determine renal function. C: Incorrect. BUN/Creatinine ratio is not a direct measure of GFR and may be influenced by other factors.

Correct Answer: C

Rationale: The correct answer is C because the patient was recently discharged after a prolonged course of aminoglycoside therapy, which is a known risk factor for acute kidney injury due to its nephrotoxic effects. Choice A is incorrect because although aminoglycosides can cause kidney injury, the duration of therapy is shorter in this case. Choice B is incorrect because controlled hypertension is not a significant risk factor for acute kidney injury. Choice D is incorrect because fluid overload from heart failure may lead to other complications but is not directly associated with acute kidney injury.