Does Fluid Intake During Dialysis “Count” as Fluid Weight Gain?
I was recently asked the following [edited] question:
“Do you include rinse-back and an on-dialysis drink in working out the amount of fluid to take off? Let’s say I gained 1 litre and thus have 1 litre to remove to reach target weight. But, I then (1) have a drink during dialysis and (2) include the fluid I use for rinse-back. Do I need to take off 1.5 litres? Or, just the 1 litre?”
This is a very good question, and there is no absolutely right answer to it. There are several variables that are hard to be certain about, but let me try to break it down without confusing the situation even more!
In the example, a 1 litre weight gain is pretty minimal for an adult. The heavier someone is, the less a 1kg (1 litre) weight gain is, relative to body weight. As most adults are somewhere between 55-100kg in weight, 1 litre is at most about 2% of body weight. Assuming that a dialysis session will need to be at least 2 hours long (for solute removal, regardless of fluid status), removal of 0.5 litres/hour (i.e., no more than 1% of body weight/hour) would not challenge the blood volume at all. Nor, for that matter, would removal of 1.5 litre over 2 hours (or more).
But, most likely gain more than 1kg (1 litre), and the more fluid there is to remove, the faster it must be removed in any given dialysis treatment. When fluid to remove is a volume greater than about 7-8 ml per kilogram of body weight per hour of dialysis, trouble starts. This is when the vexed issues of (1) fluid consumed during dialysis and (2) rinse-back fluid start to come into play.
Imagine that the amount to remove is 4 litres, and the treatment is a planned 4 hours. This requires removal of 1 litre per hour. This might still be a safe rate if the patient is heavy—but may already be unsafe if the patient is light. Ideally, fluid removal rates should be less than 7-8 ml for every kg of body weight in each hour of dialysis.
See how BODY WEIGHT influences ultrafiltration (UF) RATE. The first example table* uses the same amount to remove and same dialysis duration, but differing target weights.
*Note that ALL of the examples below are made up purely to illustrate points.
|
Target Weight |
Fluid Gain |
Time (Hours) |
UF Rate |
Outcome |
|
Example 1 |
||||
|
150 Kg |
4 Kg (= 4 liters = 4000 mL) |
4 |
(4000 ÷ 150) ÷ 4 =6.6 ml/Kg/hr |
Safe |
|
Example 2 |
||||
|
100 Kg |
4 Kg |
4 |
(4000 ÷ 100) ÷ 4 = 10 ml/Kg/hr |
Getting Dangerous |
|
Example 3 |
||||
|
50 Kg |
4 Kg |
4 |
(4000 ÷ 50) ÷ 4 = 20 ml/Kg/hr |
Downright Lethal |
See how TIME influences the UF rate. The second example table uses the same amount to remove and target weight, but differing dialysis durations.
|
Target Weight |
Fluid Gain |
Time (Hours) |
UF Rate |
Outcome |
|
Example 1 |
||||
|
100 Kg |
4 Kg |
6 |
(4000 ÷ 100) ÷ 6 = 6.6 ml/Kg/hr |
Safe |
|
Example 2 |
||||
|
100 Kg |
4 Kg |
4 |
(4000 ÷ 100) ÷ 4 = 10 ml/Kg/hr |
Getting Dangerous |
|
Example 3 |
||||
|
100 Kg |
4 Kg |
2 |
(4000 ÷ 100) ÷ 2 = 20 ml/Kg/hr |
Downright Lethal |
See how the AMOUNT TO REMOVE influences the UF rate. The last example table uses the same target weight and treatment time, but a differing fluid gain to remove.
|
Target Weight |
Fluid Gain |
Time (Hours) |
UF Rate |
Outcome |
|
Example 1 |
||||
|
100 Kg |
2 Kg |
4 |
(2000 ÷ 100) ÷ 4 = 5 ml/Kg/hr |
Very Safe |
|
Example 2 |
||||
|
100 Kg |
4 Kg |
4 |
(4000 ÷ 100) ÷ 4 = 10 ml/Kg/hr |
Getting Dangerous |
|
Example 3 |
||||
|
100 Kg |
6 Kg |
4 |
(6000 ÷ 100) ÷ 4 = 15 ml/Kg/hr |
Very Unsafe |
So, should fluids taken in during dialysis and rinse-back fluid given afterward “count” when you calculate how much to remove in a given session? Let’s look at both.
- Fluids you drink during dialysis
To a degree, it depends when you drink this fluid. Early on in a treatment, your gut will likely absorb the fluid, so it should technically count. But, we (and many other dialysis services) suggest that you drink no more than a standard cup or tea (or the like) during a treatment, or about 180-200 ml. This is a reasonably small amount, and in the range of normal weighing error. Thus, we don’t count it as extra fluid to remove. If anything, it will add to the fluid gain for the next treatment. Certainly this is the case if you drink fluid at or near the end of a treatment. Then, it is clearly best to regard this as part of the fluid gained between treatments to remove next time.
- Post dialysis rinse-back
This is clearly post-dialysis fluid, and should strictly be counted as the start of the next fluid gain.
In general, then, you would not want to remove the “extra” volume at a treatment. Doing so runs the risk of removing water that is not yet in your bloodstream. Pulling water that is not in your blood can cause your blood pressure to drop—which is not likely to be a good ploy. You would need to add water or even saline (water + salt) to correct the error, or you may have all of the symptoms and effects of volume depletion:
- Nausea
- Vomiting
- Dizziness
- Clouded mental state
- “Flats”
- Organ stunning
The key variable to get right is your predialysis target weight. If target weight is correct, removing more water beyond that can reduce your blood volume. Of course, the real problem is that we really don’t know how to accurately measure a true and ideal target weight (in real time). For all that has been written about bioimpedance techniques, ultrasound to assess the vena cava or lung fluid status, hormone analysis, etc...none are practical at the clinic chair/bedside. And, they are certainly utterly impractical for home patients. Target weight is, in truth, still a clinical guess, though a wise physician and/or a well-trained home patient can get pretty close to it, most of the time.
I don’t think over-drying (i.e. removal of extra volume) is wise. It is better to try to get as close as possible to the assessed target weight and count any post-dialysis fluid return as the first gain for the next treatment. At the end of the day, do we know? Well, no! But, this is the best I can do to explain the inexplicable and advise the unadvisable.
Comments
Jack
Oct 29, 2024 3:32 AM
My dad is getting around 1 kg per day after dialysis. So he is having 3 times dialysis in a week. So in between dialysis, he gain just 1-1.5 kg per day. And sometimes just 0.5kg. he drinks 1l water and urine output is 250ml. Before he was 65kg and now he is 50kg. They were taking 3l everytime.
1.What's the safest UF removal? Is it possible just to clean blood than removing fluid gain?
2.how much liquid he can drink?
He has no swelling. But after dialysis, during night time he can't sleep, he got shortness of breath, his legs are getting cramp, hemoglobin way down, feels like vomiting, cant walk properly because he feels too weak, he bacame skinny and has cough as well as whenever he talks he start to cough.
He has Heparin free dialysis.
Please give me your guidance.
Jennifer Ravert
Oct 29, 2024 6:04 PM
We (Medical Education Institute-- the non-profit behind Home Dialysis Central) have an easy to use tool to figure out if a safe-UFR is being used.
It asks three simple questions:
How much is the fluid removal goal?
How much does the patient weigh?
How long is the treatment?
You can check the tool out here (it is free to use!): https://homedialysis.org/home-dialysis-basics/ufr-calculator
I plugged in your dad's general information that you provided.
A 3L fluid removal goal on a 65 kg patient during a 4 hour treatment gives you a UFR (Ultrafiltration Rate) of 11.5. This is above the point where damage is being done, but not in the red yet.
At 3.5 hours, the UFR is 13.2, which is in the dangerous zone.
At 3 hours, the UFR would be 15.4. This is absolutely within the dangerous zone.
His weight has now been reduced to 50kg. Running those numbers, with a 3L goal and it is:
3 hour treatment: UFR of 20, very dangerous.
3.5 hour treatment: UFR of 17.1, very dangerous.
4 hour treatment: UFR of 15, very dangerous.
A UFR greater than 10 is hard on the body. The safest way to remove fluid is slowly and gently, especially when the patient is smaller and less likely to tolerate aggressive treatment.
If 3L had to be removed on a 50kg patient and the treatment was 8 hours long (nocturnal), the UFR would be 7.5, which is safe.
Plus, he still has residual kidney function and makes some urine on his own. He has symptoms and feels poorly. Is his blood pressure low? It sounds to me like he needs to have his dry-weight re-evaluated and his treatments to pull less water without leaving him volume overloaded-- this can be accomplished by adding treatments, adding time, using diuretics, restricting fluid/sodium-- or a combination of all of the above.
A fluid goal of 2L on a 50kg patient with a 4 hour treatment will give a UFR of 10.
Hope this helps.
Loylyn Jones Walton
Jul 21, 2023 4:11 PM
My dry weight never changed for 6 months at 60.0 kg . That Thursday of my dialysis "incident" was 2.4. Kg/l for 4 hrs. It was the worst! ; Saturday treatment (upon explaining my incident) , the technician lowered the amount of fluid to be taken to 1.6 Kg/L where results were not so severe , but mitigated. I never weighed in 3 lbs or over my dry weight. I began jotting down dry weights in and out on recent treatment dates. Finally! At last adjustments this Tuesday upon my sharing the incident with the Clinical team! My dry weight was changed from 60.0 to 63.0 , fluid weight taken off changed from 1.6 kg/l to 1.2 Kg/L for 4 hrs. . What a huge difference from the adjustment to weight.
I will also share the dry weights in and out . Tues weigh in 64.2, out 63.1 (difference 1.1 L); Thurs. weigh in 64.4, out 63.5 (difference 0.9!). I still experienced nausea and temporal headaches , however, the mitigation was to add fluids!
I am not seeking reassessment of my kidney functions as positive changes are also occurring.
Thank you so much for your dialysis resources! At best, it all may mean less time on dialysis and a higher percentage change in kidney function.
I hope this helps others advocate for themselves.
Beulah Thompson
Aug 17, 2023 7:10 PM
Beth Witten
Jul 21, 2023 4:39 PM
Loylyn Jones Walton
Jul 15, 2023 12:19 PM
My treatment was set at 3 kg/4hrs (the highest ever set!) to remove and my body crashed! I broke into sweats, my heart was beating fast, there was vomiting , nausea, dizziness, my legs were unsteady, the stomach cramping left me with no appetite for hours!
Now I know the reasons why going above 2.5 was harmful. My target weight is 60 kg (I've been told) and I usually gain no more than 2.5 liters of fluid.
Debra Howard
Mar 29, 2023 1:43 AM
Loylyn
Jul 21, 2023 4:20 PM
Wish you the best!
Michael C Harber
Nov 22, 2022 7:31 AM
Jennifer Ravert
Nov 22, 2022 5:24 PM
Sara Slagle
Nov 10, 2021 9:26 PM
Sandy Lawrence
May 13, 2020 8:12 PM
David Leong
Apr 17, 2020 6:50 AM