Final answer:
To remove excess fluid during dialysis, it is important to gradually remove the fluid over several sessions.
Step-by-step explanation:
In order to remove a large amount of fluid weight gain from a patient during dialysis, it's crucial to gradually remove the excess fluid over several sessions (option B). This allows the body to adjust and prevents complications that could arise from removing the fluid too quickly. Increasing the dialysate sodium concentration (option A) or administering a diuretic medication during dialysis (option C) may not be effective or safe for all patients, as it depends on the individual's specific condition.