In elderly patients with heart failure with unstable oral intake or infection, tolvaptan use can cause adverse events, such as dehydration and hypernatremia, and patients who had a lower heart rate, lower BUN levels, lower plasma CRP levels, and higher serum albumin levels, all of which could indicate a good general condition, and early tolvaptan use resulted in a higher number of patients being discharged alive, even among those older than 80 years. Here, CRP is linked to infection.