Which condition is associated with respiratory acidosis?

Respiratory acidosis occurs when the lungs cannot remove all of the carbon dioxide the body produces, leading to an increase in carbon dioxide levels in the blood. This condition is often associated with various forms of respiratory failure. An overdose of central nervous system (CNS) depressants, such as opioids or sedatives, can suppress respiratory drive, resulting in hypoventilation. This inadequate breathing leads to an accumulation of carbon dioxide, shifting the body's pH towards acidity, which characterizes respiratory acidosis.

In contrast, hyperventilation, dehydration, and severe allergic reactions typically do not cause respiratory acidosis. Hyperventilation generally causes respiratory alkalosis, as it involves excessive exhalation of carbon dioxide. Dehydration can lead to other metabolic imbalances but isn't directly linked to respiratory acidosis. Lastly, a severe allergic reaction may lead to bronchoconstriction and respiratory distress, but it primarily causes conditions like asthmatic attacks rather than directly resulting in respiratory acidosis without significant hypoventilation. Therefore, the association of respiratory acidosis with an overdose of CNS depressants stands out as the most accurate correlation.