Final answer:
The nurse will determine that Mylanta was effective when the symptom of heartburn has been resolved in the patient with GERD.
Step-by-step explanation:
The patient with a diagnosis of diverticulitis, irritable bowel disease, and gastroesophageal reflux disease (GERD) has received a dose of Mylanta 30 mL PO. Mylanta is an antacid used to treat symptoms of indigestion such as heartburn and upper abdominal fullness or pain, which are commonly associated with GERD. As Mylanta acts by neutralizing stomach acid, providing symptomatic relief from acid-related indigestion and heartburn, the nurse will determine the medication was effective when the symptom of heartburn has been resolved.