What is the most likely underlying cause of ABG results showing a pH of 7.25 and HCO3- of 18?

The pH of 7.25 indicates acidosis, as it is below the normal range of 7.35 to 7.45. The bicarbonate level of 18 mEq/L is also below the normal range of approximately 22 to 28 mEq/L, indicating a primary metabolic process, specifically metabolic acidosis.

In this scenario, the most likely underlying cause is an issue related to the kidneys. Acute kidney injury can lead to an accumulation of acids due to impaired renal function, which can cause metabolic acidosis. The kidneys are responsible for excreting hydrogen ions and reabsorbing bicarbonate. When the kidneys are not functioning optimally, as in acute kidney injury, this balance is disrupted, leading to a decrease in bicarbonate concentration and consequently a lower pH.

Understanding the other options helps clarify why they do not apply. Chronic respiratory acidosis would typically show elevated carbon dioxide levels, leading to an increase in bicarbonate as the body attempts to compensate, which is not reflected in the provided levels. Metabolic alkalosis is characterized by an elevated pH and bicarbonate level, contrary to what is presented. Finally, respiratory alkalosis results from a decrease in carbon dioxide and an increase in pH, which