For what clinical indicator should a nurse assess a client who is having a gastric lavage?

The correct answer is: Increased serum levels of bicarbonate.

Gastric lavage causes an excessive loss of gastric fluid, which resultis in excessive loss of hydrochloric acid (HCl). HCl usually neutralize the sodium bicarbonate (NaHCO3) secreted into the duodenum by the pancreas. Since the gastric lavage causes the loss of HCl, the intestinal tract absorbs the excess bicarbonate, and alkalosis (increased levels of bicarbonate) results.