Certified Pediatric Nurse (CPN)

What laboratory result would you expect for a child experiencing vomiting for 24 hours?

1. Metabolic acidosis

2. Metabolic alkalosis

3. Respiratory acidosis

4. Respiratory alkalosis

The correct answer is: Metabolic alkalosis

In a child experiencing vomiting for 24 hours, metabolic alkalosis is the most expected laboratory result. This condition arises due to the loss of stomach acid, which contains hydrochloric acid (HCl) during vomiting. As acidic gastric contents are expelled, the body has increased bicarbonate relative to hydrogen ions, leading to an elevated arterial blood pH and thus facilitating metabolic alkalosis. The mechanism involves the loss of hydrogen ions, which results in a decrease in the acidity of the body fluids. Furthermore, if the vomiting results in electrolyte imbalances, such as loss of potassium, the body may respond by retaining bicarbonate, further enhancing the alkalotic state. In contrast, the other options do not typically occur in the case of vomiting. Metabolic acidosis is associated with conditions that result in an excess of hydrogen ions or loss of bicarbonate, which isn't the case with simple vomiting. Respiratory acidosis occurs due to an accumulation of carbon dioxide from hypoventilation, which does not directly relate to vomiting. Respiratory alkalosis is typically seen when there is excessive breathing or hyperventilation leading to the loss of carbon dioxide. Thus, metabolic alkalosis aligns best with the physiological changes occurring during prolonged vomiting in a child.