One of the main functions of the kidneys is to balance fluid in the body. In renal failure a common problem is not getting rid of excess fluid. This in turn causes fluid overload which can cause high blood pressure, long-term damage to blood vessels, and even damage to the heart. Your fluid restriction depends on your urine output which may decrease as time goes on. Your care team will tell you how much you can drink.
To help keep thirst under control, spread your fluid intake evenly through the day by using small cups. You can also gargle with iced water, suck ice cubes (which still contain 10-15mls of fluid per cube), or chew gum. Avoid salt and salty foods, e.g. crisps, bacon, and soup, as these will increase your thirst. Remember to be careful of hidden fluids, e.g. water for tablets, gravies, custards, and milk on cereal.
The fluid allowance for each patient is calculated on the basis of urine output, plus 500 ml in a 24-hour period. The 500 ml approximately covers the loss of the fluid through the skin and the lungs. The weight gains between dialysis sessions should be no more than 1-1.5 kg for a one day gap and 1.5-2.5 kg over 2-3 days. Generally speaking, the smaller you are, the less weight you should gain.
If you drink too much between dialysis treatments this could lead to excessive fluid in your body, called fluid overload. However, during dialysis because of the need to remove the extra fluid you may experience a drop in your blood pressure. This is called hypotension. Hypotension can make you feel unwell and light headed and can even harm you. Therefore, it is important to adhere to the recommended fluid allowance in order to keep the interdialytic weight gain low. This can help to protect you during your dialysis treatment.