Final answer:
After an initial dose of valsartan (Diovan), a nurse should monitor for hypotension in an older adult patient with heart failure, volume depletion, and low sodium.
Step-by-step explanation:
When an older adult patient with heart failure, who is volume-depleted and has a low sodium level, is prescribed valsartan (Diovan), an angiotensin-receptor blocker (ARB), the nurse should closely monitor for hypotension after the initial dose. ARBs like valsartan block the effects of angiotensin II, which is a potent vasoconstrictor that directly increases blood pressure and stimulates the release of aldosterone, leading to sodium and water reabsorption. When angiotensin II's effects are inhibited, there can be a sudden drop in blood pressure, especially in a volume-depleted patient. Therefore, it is paramount to monitor for signs of hypotension such as dizziness, fainting, or an unusually low blood pressure reading.