Final answer:
An aspirin overdose initially causes metabolic acidosis due to the acidified blood from aspirin's active metabolite. The body then compensates by hyperventilating, which leads to respiratory alkalosis as CO2 levels fall.
Step-by-step explanation:
An aspirin overdose can lead to complex changes in acid-base balance within the body. Initially, an overdose of aspirin causes metabolic acidosis due to the acidity of aspirin's active metabolite, sulfasalicylic acid. The body attempts to compensate for this acidosis through hyperventilation, which leads to the exhalation of CO2 and subsequently may cause respiratory alkalosis. This is a compensatory mechanism to counteract the acidity caused by the overdose.
Therefore, the correct answer to the student's question regarding an aspirin overdose causing either metabolic & respiratory acidosis, metabolic & respiratory alkalosis, metabolic alkalosis & respiratory acidosis, or metabolic acidosis & respiratory alkalosis is: 'D. Causes metabolic acidosis & respiratory alkalosis'.