Correct Answer: B

Rationale: The correct answer is B: Hypoventilation. A PaCO2 of 48 mm Hg indicates an elevated level of carbon dioxide in the blood, which is typically seen in hypoventilation where the lungs are not effectively removing CO2. Hypoventilation leads to respiratory acidosis. Option A is incorrect because hyperventilation would decrease PaCO2 levels. Option C is incorrect as it does not directly relate to PaCO2 levels. Option D is incorrect as increased excretion of HCO3- would not directly affect PaCO2 levels.

Correct Answer: C

Rationale: Step-by-step rationale for choice C: 1. Advance directives should be made by the patient to reflect their wishes. 2. Developing it before illness ensures clarity and avoids confusion. 3. Patients may not be able to make informed decisions in critical conditions. 4. Family or surrogates may not accurately represent the patient's wishes. Summary: A - Family in critical condition may not know the patient's wishes. B - Hospital admission process may be too late for clear decision-making. D - Healthcare surrogate may not fully understand the patient's preferences.

Correct Answer: D

Rationale: Step 1: Restlessness is an early sign of hypoxemia due to the body's response to low oxygen levels. Step 2: Restlessness occurs as the body tries to increase oxygen intake. Step 3: Other choices are incorrect because clubbing and cyanosis are late signs, while hypotension is not a specific early sign of hypoxemia.

Correct Answer: B

Rationale: The elevated BUN and creatinine levels with a normal BUN/creatinine ratio indicate impaired kidney function. This pattern is commonly seen in acute kidney injury, such as acute tubular necrosis (ATN). In ATN, there is damage to the renal tubules leading to decreased excretion of waste products, resulting in elevated BUN and creatinine levels. The normal BUN/creatinine ratio suggests that the impairment is due to renal tubular dysfunction rather than prerenal causes like hypovolemia or postrenal causes like urinary obstruction. Increased nitrogen intake would not produce this specific pattern of results. Fluid resuscitation would likely result in dilution of BUN and creatinine levels, leading to lower values.

Correct Answer: B

Rationale: The correct answer is B (80 to 125 mL/min) because this range reflects the normal glomerular filtration rate (GFR) in adults. GFR measures the rate at which blood is filtered by the kidneys, typically around 125 mL/min. A GFR below 60 mL/min indicates kidney dysfunction, making option A incorrect. Option C (125 to 180 mL/min) is above the normal range. Option D (more than 189 mL/min) is too high and could indicate hyperfiltration, common in conditions like diabetes. Therefore, choice B is the most appropriate within the normal GFR range.