What physiological imbalance does metabolic alkalosis typically result from?

Metabolic alkalosis typically results from an increase in bicarbonate (HCO3-) or a loss of acid from the body, which can occur through several physiological processes. One of the most common causes of metabolic alkalosis is excessive vomiting. During vomiting, the stomach contents, which are rich in hydrochloric acid (HCl), are expelled. This loss of gastric acid decreases the amount of hydrogen ions (H+) in the body, leading to an increase in blood pH and a relative increase in bicarbonate concentration, which is characteristic of metabolic alkalosis.

In contrast, excessive hydration does not commonly cause metabolic alkalosis; it can lead to dilutional effects, potentially impacting sodium or potassium levels, but not necessarily causing the alkalosis itself. Chronic diarrhea tends to lead to metabolic acidosis, as it results in the loss of bicarbonate along with other electrolytes. Pneumonia, an infection of the lungs, can affect oxygen exchange and carbon dioxide levels, but it is not directly associated with causing metabolic alkalosis.