Fluid

Last updated: Mar-12-2003

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Dry Weight

Your dry weight is your weight without excess fluid. You may have this weight if your kidneys could have removed the excess fluid from your body. Your dry weight is determined by your doctor, based on his/her experience and your input. Your dry weight should be the lowest you can reach while still feeling well.
Note that your dry weight is not a sacred number. After the weekend it may be more difficult to remove all the extra fluid you gained, so be it. You should follow changes in your dry weight and inform your doctor. If you have just started dialysis your dry weight may rise, as you feel better.
Weight gain as a result of fluid retention has some distinctive signs. You have to know your body and be able to recognize swelling and puffiness in the ankles, feet, wrists, fingers, face, eyelids, and other places. Note that there are up and down cycles for women as well as for men.

In addition, there is a pattern of blood pressure change that repeats during dialysis. Change in this pattern implies gaining or losing weight, (but also change in blood count).
A good digital scale at home is a big help in controlling your weight. A cheap bathroom scale is not good enough. Note that the scale in the unit may be a little off from yours. This offset may change slightly over time.
Avoid false weight readings due to different clothes and shoes. Shoes may weigh as little as 0.1 kg (slippers) to as much as 2 kg. Pants may weigh from 0.3 to 1 kg. Jackets may add 1 to 2 kg.
Be sure that the scale reads zero before stepping on it.

Dehydration

In some cases you may lose fluid and go below your dry weight. This may occur at the end of dialysis or for the rest of the day after dialysis, and is accompanied by low blood pressure and elevated pulse rate.
You may feel the following symptoms:

• Shortness of breath, nausea.
• Dry throat, raspy voice, losing your voice.
• When you sit at the table, pain in the back of your neck, as if your head weighs a ton.
• When you get up from sitting, instant dizziness, because there is not enough blood supply to the brain. You should immediately sit, then try again slowly.
• In your car, normal daylight may be dazzling.
• In bed, cramps in you legs when you stretch them.
• While doing a light physical job, cold sweat.

In severe cases your access may clot, mostly while sleeping, because of low blood flow.
The solution to this problem is to drink more. A cup of salty broth can give you immediate relief.
Reasons for loosing too much fluid are:

• You gain weight and your dry weight is not raised accordingly.
• You get a false weight because of heavier clothing.
• You eat after dialysis. Eating moves fluid from your blood stream into your stomach.
• You still make urine or sweat a lot.
• In a warm and dry place you may lose up to 1 kg a day by breathing alone.
• You have a severe diarrhea.

Fluid Weight Gain

The one-size-fits-all recommendation of 1-kg gain per day is totally wrong. Anyone can see that the effect of excess fluid differs between a 100-lb. person and a 200-lb. person.

Fluid restriction is not about how much you drink but how much you gain, and that is not gain per day but gain between treatments. If you make urine or sweat you can drink more.
Gain of 2.5% to 3% of your body weight is easy to remove; gain above 4% to 4.5% is hard to remove and may cause cramps, dizziness, and low BP during and after the treatment.

Fluid Control

To begin with, measure the volume of the cups/glasses in your household. Note the volume of cans/bottles that you use to drink.
Remember that beer/wine are like any other fluid.
Ice, ice cream, jelly (gelatin), and anything that is liquid at room temperature, is fluid.
Most foods contain 70% to 90% of water (especially fruits and veggies).
Hint: If for some reason you don't eat you can drink a little more.

There are many ways to reduce thirst and drinking. Cutting on sodium is the most effective way.
Some unusual ways are:

• Drink very hot or ice cold (and carbonated) beverages.
• With cold beverage, fill and swish it in your mouth, drain it over the sink, then swallow what's left in your mouth.
• Drink beverages that you like less, like diet, non-alcoholic beer, water.
• Drink from small cups.
• If you pour from a bottle, return it to the fridge before you drink.
• Try candies, ice cubes, frozen grapes, frozen lemon wedges, or popsicles.
• Find out which foods/drinks make you thirstier.
• Keep yourself busy.
• Don't talk too much.
• Don't spoil the joy of drinking by swallowing pills. Take all pills that can be taken with food: chew the food until you are ready to swallow, then put the pills in. This is easier than taking pills with water.
• Don't drink while you eat. With a few refills you may drink too much without notice. Enjoy your drink after the meal.
  If you must drink during the meal pour a glass before you eat and don't refill it.
• If allowed, drink during the treatment. You can enjoy it without guilt. However, finish most of it before the last hour so it will be removed by the dialysis. Of course, the UFR setup should include what you intend to drink.

Fluid Removal

The effect of fluid removal is different among various patients, however some common behavior exists.

The fluids that have to be removed are of different types:

• Regular fluid gain
• Fluid consumed during dialysis
• High fluid gain
• Hard to reach (lungs, heart)

Usually, about one half of the excess fluid is in the blood and another half is in the tissues between the cells (extracellular fluid). The fluid in the tissues causes swelling and is harder to remove.
Fluid removal, as well as the whole dialysis process is based on equilibrium (balance) or the lack thereof.
Wastes and minerals move from the blood into the dialysate because there are more of them in the blood and less in the dialysate. This is called diffusion.
Fluid (water) is removed from the blood because inside the dialyzer the blood has higher pressure than the dialysate has. This is called ultra filtration (UF).
Wastes and minerals are also removed with fluid. This is called convection.

While the dialysis cleans the blood, wastes and water move from the tissues into the blood. However, this process has its own timing as follows:

• For a regular gain the flow of water from the blood into the dialysate may be slower than the flow from the tissues into the blood. So the patient blood pressure is maintained over the treatment.
  A special case is when the patient gains too little or none. Many machines require a minimum UFR of 0.3 kg per hour. This is to ensure that there is always a flow from the blood into the dialysate and not back. In this case the patient should drink or saline should be administered. Saline is easy to remove, because it is available in the blood.
• For fluid consumed while on the machine, some amount of time is required to absorb the fluid from the stomach into the blood. This time is faster for beverages with sugar and clear beverages. Drinking while on the machine improves the dialysis because more waste is removed when more fluid flows through the dialyzer membranes (by convection, see below). Based on the weight gain, about 1 liter (1 quart) can be consumed. Every patient should find out for him/herself how much fluid s/he can remove during a treatment. (4 kg is my limit). It is advised to finish the beverage about an hour before the end of treatment, so that it will not stay in the body.
• When the weight gain is too high the flow of water from the blood is faster than the flow from the tissues into the blood and there may be a temporary reduction of the patient's blood pressure.

In any case in which more fluid must be removed, since electrolytes, especially sodium, are removed from the tissues with the water, cramps may occur, usually during the last hour of the dialysis.

To compensate for the sodium loss, sodium modeling is used. Usually a step dose of sodium is given during the first 30 to 60 minutes, or a linear setup begins the sodium on high and gradually reduces it along the dialysis.
The sodium attracts water so it helps to extract the water from the tissues, without removing sodium from the tissues and therefore avoiding cramps. Later the sodium is dialyzed.
The need for sodium is higher when the patient gains more fluid weight.

If cramps occur, the immediate action is to lower the feet (provided that the patient has enough blood pressure.) The second action is to give the patient saline.
If the cramps are severe the technician can administer sodium or dextrose.

To extract even a higher amount of water the UFR can be set so that more fluids will be removed at the beginning and less at the end. This is called UF profiling.
For example, to remove 3 kg in 3 hours, instead of 1 kg/hour use:
1^st hour - 1.5 kg/hour
2^nd hour - 1 kg/hour
3^rd hour - 0.5 kg/hour

In contrast to constant UFR, the rate at which water is removed from the blood is reduced as the amount of water coming from the tissues is reduced, thus avoiding patient's blood pressure drop.
In the conventional way, when blood pressure drops, in most units the technician gives the patient a cup of chicken broth or extra saline, which misses the goal of removing fluids.
In addition, the doctor may unnecessarily raise the dry weight of the patient.
Note that in new machines like the Fresenius 2008H, the variable UFR is a built-in feature.

A more serious condition is when excess fluid accumulates in a hard-to-reach places, for example: around the heart, in the lungs, in the abdomen, or in the ankles.
To remove that fluid, all of the above methods should be used.
In addition, the patients should avoid salt and try to gain as little as possible.
Since this fluid stays in the body, the real dry weight of the patient should be lowered.
If the excess fluid is in the ankles and feet, the patient should lie with elevated feet for the first hour or two of the treatment.

To remove that extra fluid more time is required than the treatment time, so the patient may leave with a lower blood pressure and may have to either stay in the unit or be driven home by somebody else. (The blood pressure may rise after a while).
It may take a few treatments to get rid of these kinds of fluids.
In such a case it is even more important that the UFR for the last hour be mild, thus giving the patient some time to rest.
To be able to remove even more fluid without cramps the dialysate pump can be turned off for the last (or extra) 30 to 60 minutes. It is called UF only or Strictly UF. This will remove fluid with waste and minerals (by convection) without changing the concentration in the body and hence without cramps.

Advantage of convection

Convection in hemodialysis is removing waste and electrolytes with the water that is removed from the blood (UF).
The UF occurs because there is a pressure difference between the blood and the dialysate inside the dialyzer.
This is exactly the way the water and waste are removed by healthy kidneys.
In both cases, the UF takes with it all toxins that can pass thru the semi-permeable fibers in the dialyzer or thru the nephrons in the kidneys.

The kidneys remove water and waste with the same concentration as they are in the blood. We drink pure water to fill the volume and by that dilute the waste in the blood. That way the concentration of waste and electrolytes stay within an optimal range.

Why does the UF remove toxins with it? Some people think that UF-only removes pure water from the blood.
Well, everything that can pass thru the dialyzer membranes goes with the water. If you drink lemonade with a straw the lemon goes with water but the ice cubes don't.

Convection in the dialysis just adds to the diffusion. The convection in the kidneys is continuous and 3-4 hours on the machine are too little for that. But contrary to diffusion, convection is independent of the blood flow rate and it is more potent.
Everything that can be removed by diffusion can be removed more effectively by convection.
How do I know that? To see it for yourself put a tea bag in hot water and wait a few seconds. The water is getting the tea out of the bag by diffusion, slowly. Now squeeze the bag with a teaspoon and see what convection does.

Now how can we increase the UF?
In a few centers, dialysate is added to the blood before it enters the dialyzer, so more fluid can be removed, but this technique is not common yet.
Of course you can drink more at home, but that may overload your vascular system. The other way is to drink on the machine. We have more fluid to remove without accumulating it in our body.
Remember, the better cleansing is not from drinking but because of more UF. The drinking is required to keep your fluid in balance, that is, the UF is increased by the amount you drink.

How much do I drink? 600 to 1000 cc (20 floz to 1 quart).

What do I drink? Clear liquid, tea, water, carbonated diet drinks, no juices and no milk.

How long does it take the fluid to move from the guts into the blood stream?
A few anecdotes:
If you have ever received chicken-broth to increase your blood pressure at the end of a treatment, you know it takes just a few minutes to work and if you feel low because of dehydration, anything you drink helps in a few minutes.
Another example that most people have certainly experienced, after being out on a hot day, you drink a glass of water and in no time you start sweating.
These examples demonstrate that it is a question of minutes, not hours.

And in addition, isn't the pleasure of drinking what you like 3 times a week, guilt free, not a good reason?
Note, don't even dream about doing this if you gain 5 kg between treatments. I gain 2-3 kg.