Final answer:
A nurse should monitor for neuromuscular and electrolyte disturbances in a patient with hypomagnesemia, including visual disturbances, muscle weakness, impaired coordination, numbness, tingling, cramps, tetany, seizures, and possibly arrhythmias.
Step-by-step explanation:
The nurse caring for a patient with hypomagnesemia due to long-term therapy with lansoprazole should monitor the patient for several manifestations associated with this condition. Hypomagnesemia can lead to neuromuscular and electrolyte disturbances. Specifically, the patient may present with visual disturbances, muscle weakness, impaired coordination and balance, numbness, and tingling sensations. Additionally, as hypomagnesemia can influence calcium and potassium levels, symptoms analogous to hypocalcemia like muscle cramps, tetany, and seizures, as well as signs of hypokalemia such as muscle weakness and arrhythmias, might also be observed.