Diet for Patients with Renal Failure on Hemodialysis*
Renal insufficiency is the term used to define the disease in which the kidneys are no longer able to perform their functions satisfactorily. Renal failure may be acute, when it occurs suddenly and lasts less than 3 months, or chronic when loss of renal function is persistent and progressive. For more details, read:
In this text we will address the diet of patients with chronic renal failure on hemodialysis. Later I will write a text for patients with renal insufficiency in conservative treatment, that is, that do not still need dialysis.
The kidneys are vital organs, meaning without them we can not survive. The two kidneys together are usually able to filter 90 to 125 ml of blood per minute, which means somewhere between 130 and 180 liters per day. When this function falls to less than 60 ml/min, we are facing a picture of renal failure. When filtration falls below 10-15 ml/min, the kidneys are no longer able to perform their minimal functions and the patient must undergo hemodialysis under the risk of dying from complications of this malfunction.
The calculation of renal function is usually done by measuring creatinine.
When the kidneys do not work, all the toxins, all the metabolic waste produced by the normal functioning of our cells and all the excess of the substances that we ingest, be they minerals like phosphorus and potassium, or the very amount of liquids consumed throughout the day, can not be eliminated in the urine, accumulating inappropriately in the body.
Five subjects are of great importance in the diet of patients with hemodialysis renal failure: liquids, potassium, salt, phosphorus and proteins.
One of the main signs of end-stage renal failure is fluid accumulation, manifested as increased blood pressure and edema (swelling) throughout the body. The vast majority of patients on hemodialysis still have urine because the ability to excrete water is the last function the kidney loses. However, this excretion is progressively smaller and in terminal stages is no longer sufficient to eliminate all excess water consumed throughout the day.
Let's imagine the following situation: a patient with renal insufficiency in very advanced phase consumes daily 2 liters of water between liquids and food (the more pasty the food, the more water it contains). Like anyone, it naturally loses an average of 500-600 ml/day on the skin (through perspiration) and in the stool. Due to kidney disease, he urinates only 1 liter per day. This may sound like a lot, but it means that daily it will accumulate something close to 500 ml of liquids. In one week it will be 3,500 ml. In a month they are 15000 ml or 15 liters of water.
Because of lack of control over water consumption, it is extremely common for patients to undergo dialysis filled with edema and with more than 15 kg of excess fluid (1 liter of water weighs 1 kg).
As the months pass, the tendency is for the hemodialysis patient to urinate less and less until it reaches the point where no more urine is produced. At this point, virtually all the fluid consumed will remain in the body until it is removed by hemodialysis. Ultrafiltration is the name given to fluid withdrawal during a hemodialysis session.
So how should water be consumed in hemodialysis patients?
If the patient still urinates, the daily consumption calculation should be: Urine volume in 24 hours + 500 ml.
That is, the patient can consume the same amount of fluids as urine, plus 500 ml, equivalent to natural losses throughout the day. We consider liquids: water, tea, soft drinks, alcoholic beverages, juices, ice cream, soup, coffee, milk, yogurts etc...
As all food has water, at the end of the day there will still be a positive balance, but since dialysis is done every 2 days, this is not enough to cause greater problems.
If the patient does not urinate, their ideal consumption should be around 500-600 ml. In practice this is very difficult because the western diet is very rich in salt, which triggers thirst and makes the patient look for water more often.
In the patient who does not urinate or very little urine (less than 200 ml/day), all the liquid that enters, remains in the body. Remember: 1 liter of water = 1 kg. Therefore, if the patient consumes 2 liters of water, he will gain 2 pounds of weight.
In general, it is indicated that the patient does not lose more than 4% of his weight in a session of 4 hours of hemodialysis. This means that a 70 kg patient should not ultrafilter more than 2800 ml. So this is the weight gain limit between one session and another.
We always suggest to patients that they have a scale at home to control weight and consequently fluid intake.
Excess weight and inability to reach dry weight at the end of the dialysis sessions is related to a higher mortality. 90% of cases of hypertension in hemodialysis patients are linked to excess fluid.
The water that enters the body and does not go out has to go somewhere. At first it stays inside the blood vessels causing hypertension. Then it begins to overflow and goes to the legs. Finally, excess fluid begins to affect the lungs leading to pulmonary congestion and, subsequently, acute pulmonary edema.
How then to restrict the consumption of liquids?
The most important step is to limit salt intake, since it causes thirst and causes the patient to seek more water. I'll specifically mention the salt below.
Some tips:
Always use small cups
Avoid soups or other liquid foods that carry salt
Avoid soft drinks or other sugar-rich drinks, as excess sugar also causes thirst
If thirsty, wet your mouth frequently, but do not drink the water
Suck on small ice rocks to relieve thirst
Calculate the allowed liquid in 24 hours and place it in a single bottle. Drink this volume throughout the day
Always weigh yourself after eating and control weight gain by avoiding consumption of liquids outside of meals
Potassium is a mineral salt essential for the functioning of cells. However, when in excess, it can lead to serious complications, especially fatal cardiac arrhythmias. Excess potassium in the blood is called hyperkalemia.
Potassium is present in a wide variety of foods and all excess ingested is quickly eliminated in the urine. Thus, the kidneys maintain blood potassium levels within a restricted range that is between 3.5 and 5 mEq/L. Potassium levels above 6 mEq/L are already considered hazardous. Values above 7.5 - 8 mEq/L, if not treated immediately, are incompatible with life.
In people with functioning kidneys this potassium control is done 24 hours a day, every day. In chronic terminal renal insufficiencies, the only way to withdraw the excess is during the 4 hours of hemodialysis performed 3 times a week. As you can imagine, the risk of hyperkalemia is very high if there is no control in the diet.
In the hemodialysis clinics, analyzes are taken once a month before the beginning of the sessions. It is not uncommon to find potassium levels above 6 mEq/L among patients who have no potassium control in their diet. Sometimes we find potassium above 7 mEq/L. These are patients who can at any time enter cardiac arrest and die suddenly.
The potassium values are the explanation of why it is dangerous to miss the hemodialysis sessions.
The great villain of potassium are usually fruits, however, several other foods contain potassium in large quantities. The main ones are: Pumpkin, almond, plum, hazelnut, banana, potato, beet, cacao, coffee, chestnut, carrot, beer, chocolate, coconut, mushroom, apricot, spinach, peas, soya, bean, fig, figs, nuts, chickpeas, yogurt, kiwi, orange, milk, soft, papaya, mango, molasses, melon, cabbage, light salt, soy, ice cream, date, tomato, raisin, pod, vegetables and wine.
The above list is not complete. There are other foods rich in potassium, such as mate and black tea, for example. Meats, be they birds, mammals or fish, also usually have plenty of potassium. Ideally, talk to an experienced hemodialysis nutritionist (most clinics have this professional) to know the quantity and frequency of each of these foods.
Tips to avoid excessive potassium in the diet:
Avoid eating more than 2 pieces of fruit per day. Give preference to those that have low potassium content, such as apple, grape, peach, pineapple, mandarin and strawberry.
As carbohydrates, prefer rice and pasta, because they are poor in potassium.
Avoid fries, because these are very rich in potassium.
Peel and cut the vegetables into pieces. Soak them for at least 2 hours in warm water. Use plenty of water. Then discard the water and wash it for a few seconds under running water. Now you can cook the vegetables normally. Use plenty of water again. This process helps to remove potassium from food.
Do not fry and do not bake vegetables in pressure cooker, steam, or microwave. These processes increase the potassium concentration in food.
Fruits cooked in water lose about half of their potassium.
Our common cooking salt is composed of chlorine and sodium, forming the sodium chloride. Every time we consume too much salt, we are consuming a lot of sodium.
The western diet is very rich in sodium. We got to consume almost 3 times the amount of salt needed. Our taste is so adapted to salty foods that we often do not even realize how much sodium we eat.
Excess sodium in our normal diet is the main factor for the onset of cardiovascular diseases, especially hypertension.
One of the body's ways to control the concentration of sodium in the blood is through the kidneys, eliminating excess in the urine. Once again the patient with chronic renal failure is at a disadvantage. If salt is harmful to healthy people, imagine it for kidney patients.
A healthy person maintains their blood sodium around 140 mEq/L (136 to 145 mEq/L). The kidney by eliminating salt and water can keep these levels always stable. The patient with chronic renal failure can not eliminate excess salt from the urine, and the only way the body can lower blood sodium is by stimulating thirst. Drinking plenty of water, the body can dilute sodium in the blood, bringing its concentration back to normal levels.
Therefore, in addition to all salt-related diseases (hypertension, heart attacks, heart failure, stroke, etc.), chronic renal failure patients who do not control sodium intake are still extremely difficult to control their dry weight. excess of water and contributing even more to the diseases mentioned above.
The less urine the patient, the lower their salt intake should be. The ideal diet should have 2 g of sodium or 5 g of salt (1 g of salt = 400 mg of sodium) per day.
Virtually all industrialized food is high in salt, as are fast-food foods.
The insufficient renal diet should be prepared without any salt, since most foods already have sodium naturally. If necessary, you can use 1 packet of salt (of those squares) containing 1 gram of salt over the food.
There are several types of spices that can be used to enhance the taste of foods without adding salt, including garlic, chives, mint, oregano, parsley, lemon juice, vinegar, nutmeg, bay leaf, celery and others.
Once again it is important the nutritionist's orientation for a better control of salt consumption.
The importance of phosphorus and PTH in chronic renal failure is discussed separately in this text: Renal insufficiency - phosphorus, PTH and bone disease.**
In patients with chronic renal failure on conservative treatment, ie without dialysis, a high-protein diet appears to be associated with an acceleration in the loss of renal function. Therefore, a restriction in the consumption of proteins by this patient is indicated.
In those patients already on hemodialysis, however, this concern no longer makes sense, since there is no longer any renal function to be lost. In addition, this group of patients is more likely to develop malnutrition, which contraindicates protein restriction in the diet.
The ideal is to give preference to high-value biological proteins, which are those of animal origin. Proteins of plant origin are of low biological value, meaning that they are less effectively used by the body.
The great difficulty in providing the necessary proteins for insufficient chronic kidney is the fact that, in the great majority of cases, foods rich in proteins are also in phosphorus, whose consumption should be restricted in this group.
Once again, the guidance of a nutritionist is indispensable for better control of protein consumption.
