Acidosis is characterized by a decreased blood pH below 7.35, indicating increased acidity in the body fluids. This condition results from either an accumulation of hydrogen ions or a loss of bicarbonate, disrupting normal cellular functions. Maintaining blood pH within a narrow range is crucial for enzyme activity and metabolic processes. In contrast, alkalosis involves elevated pH, and the other options relate to electrolyte imbalances rather than pH changes. Identifying acidosis promptly is essential for surgical patients, as severe pH imbalances can impair organ function and complicate anesthesia management.

Reference: Harrison's Principles of Internal Medicine, Jameson et al., 20th Edition.