The Elusive Dry Weight: A Dialyzor’s Lessons Learned
The elusive dry weight: that magical number that controls every treatment. Take off too much and you can have the dreaded cramps, blood pressure crashes, and worse. Take off too little and leave with that heavy, bloated feeling, puffy ankles, and wheezing. The bottom line is that the kidneys control water in your body and how your body gets rid of it. If they are not working properly, your body is going to have water buildup somewhere and everyone retains water differently: belly, ankles, fingers, and lungs, to name a few.
It is very distressing to see people starting dialysis who simply accept that it is OK to experience blood pressure crashes, cramping, fainting, and take hours or even days to recover from a treatment due to fluid removal. Treating these episodes with pickles, pickle juice, mustard, broth, tonic water, saline, and water, etc…are stopgap measures, but should never be acceptable, ongoing techniques to regulate what is, essentially, your lifeline. Here is what some other dialyzers have said about water:
“I am new to dialysis, today was only my 8th session. What I'd like to know about is blood pressure dropping. I never had a problem with this until I began dialysis, in fact I have high blood pressure. The past 2 or 3 times I've had dialysis, I've come home and about 30 minutes to an hour later my blood pressure drops drastically. Everything goes dark like I am going to pass out and my hands and face go numb. It lasts for a few minutes and then my bp will go back up.”
“My nurse said they are still trying to find my dry weight. I am new to all of the dialysis terms, so I don't know what profile means or the numbers for it. How do I know when I am at my dry weight? I only gain between 1-2 pounds in between dialysis days (M/W/F) and lose between 2 & 3 pounds after treatment.”
“It really freaked me out with my vision constantly going dark at first.”
“Also new to dialysis. Came home the other day and next thing I know I'm waking up laying on the floor. Very scary. Told I need to drink more after dialysis.”
“…started out on two BP Meds, then down to one...then they told him not to take it on the days he did dialysis. Now, 6 months in, he doesn't take any BP Meds. His BP was good during treatment, he had some issues with it being really low right after they unhooked him. They had him drink broth...or pickle juice, turned out he was dehydrated. It's a delicate balance act....”
“My BP drops too after dialysis…one trick that helps me is a kick of sodium… i like pickles so my dietician approved me to have a Vlasic low sodium pickle spear when my BP drops at home..”
I have always wondered at the insanity of removing excess water to the point where a bolus of saline is required, or you are told to drink salty broth or pickle juice. Removing too much water also causes your body to crave fluids to replace what was removed, which creating an insatiable thirst that, in turn makes you drink more, and increases your blood water volume, creating a never-ending spiral of destruction.
If you only gain 1-2 kilos between treatments, why do they insist on removing 2-4 kilos, especially if there are no obvious signs of fluid overload—only to end up adding saline when the body “crashes”. Kind of defeats the purpose, doesn’t it?
I found it very disturbing to read this Q and A exchange between dialysis nurses that I found by accident on a nursing website:
“I am fairly new to dialysis (9 months now), but at our clinic, as well as in our acutes department, we are never to turn the UF completely off. The minimum we can go is 300 ml/hr. and if that is not sufficient to stop the cramping or hypotension we give fluid back. It would take someone with more experience than me to give you the rationale behind that policy, but at no time do we ever completely turn off the UF, even if we are not to remove any fluid. We simply set the UF rate to 300 and return whatever we remove.”
NOTE: This is one that I find particularly disturbing, in that they just return whatever fluid they remove! An exercise in futility?
“Even though I'm a new nurse let alone new to dialysis, my manager, charge nurse, and fellow staff RNs have all stressed turning off the UF when the patient is in distress, whether it be cramping or low BPs. Why continue stressing the body and heart on pulling more fluid if the BP is too low or the HR is too high?
NOTE: finally, the first voice of reason in over 2 pages of comments!
If the nurses entrusted with our care do not understand the concepts of water balance and how the machines work, how can we possibly feel safe? We need to learn! It is critical, for us, the dialyzors, to learn the nuances of our bodies, and how, when and where water affects us, so our water removal is done at a rate that does not cause problems.
When you start dialysis, balancing water buildup is the most critical and, perhaps, even life-threatening issue you will encounter. According to the U.S. Renal Data System (USRDS), cardiovascular disease and stroke are the most prevalent causes of death in dialysis patients, and have been linked to fluid overload. Too much or too little water removal can lead to heart complications, and even death.
Dr. John Agar describes water removal as a “waterfall” effect. Dialysis removes toxins and water from the blood. Once water is removed from the blood, a chain reaction, or waterfall, starts. Water from inside cells shifts to the “interstitial” fluid around the cells, and this water in turn, shifts into the bloodstream. This waterfall, or water moving from inside cells to between cells to blood, takes time. If you take water out of the blood too fast, as many in-center dialysis treatments do, your body cannot keep up, which starves your organs and tissues of oxygen-carrying blood, causing cramping, blood pressures crashes (“stunning”), vomiting, and even passing out.
Ultimately, if you keep this type of treatment up, you will damage your heart and organs. (Your gut is not immune, either. A side effect of removing too much water is stunning the gut, which releases toxins into the bloodstream that can trigger inflammation and even sepsis.)
Not removing enough water leads to fluid overload, which has another set of complications. One sign of retaining fluid on dialysis, besides edema (swelling) in the hands and feet, is rising blood pressure. The more water you retain, the harder your heart has to work, and the higher your blood pressure soars.
All of this brings me back to dry weight! HD treatments include a prescription for water removal (ultrafiltration, or UF) targeted to “dry weight:” the lowest weight a patient can tolerate without development of symptoms or hypotension (low blood pressure). Dry weight is used to calculate UF volume (amount of water taken off during treatment) and the UF rate, or UFR (how quickly water is removed) for each treatment.
In most cases, dry weight is found by trial and error, often by “challenging” the weight. This is when the nurse adds extra water removal. For example, if you gain 2 kilos between treatments, s/he may suggest taking off 2.5. If you don’t cramp or have blood pressure drops, s/he may assume your dry weight is lower. If you suffer from symptoms, then your dry weight may be on target, or even too high. Clinical assessment of dry weight is crude and often imprecise. The concept of ”challenging” dry weight, or raising the water removed until cramping occurs, seems downright barbaric to me.
A rule of thumb for UFR on a NxStage machine (the machine I am most familiar with. The protocol is similar with other machines) is to keep it less than 10 ml/kg/hr. It is known from more than one study that keeping UF rates at or below 10 ml/kg/hr reduces complications and improves survival. Any higher and your body can’t keep up: your blood pressure will drop, cramping will occur, and you may feel faint, or take hours to recover from your treatment. For those who retain large volumes of water between treatments, it is often impossible to remove it all at a rate of less than 10 ml/kg/hr in the usual 4 hours prescribed—so they raise the rate to remove it faster, which may result in cramping and crashing. If your UFR is less than 10 ml/kg/hr, intracellular water can refill your blood as fast as dialysis removes it. So, your blood volume won’t drop and your blood pressure will be stable. If your UFR is higher than 10 ml/kg/hr, your intracellular water can’t keep up with replacing the water lost from your blood. Your blood volume must fall and your blood pressure will drop, too. (You’ll feel awful.) The more your UFR exceeds 10 ml/kg/hr, the greater the gap between water loss and capillary (blood vessel) refill. The greater the gap, the higher the risk of affecting your blood pressure. The longer your treatment time and the lower your UFR, the lower your relative risk of stunning, cramping and damaging your organs.
One way YOU can take control of your fluid removal is to use the Ultrafiltration Rate Calculator on Home Dialysis Central. If you find that your UFR falls is in the red zone (greater than 10 ml/Kg/hr), then you know you will need to increase your time to safely remove all that water. This is not a problem if you are doing home therapy, but if you are in-center, it is going to require a change in your doctor’s order, and you may meet with resistance from the staff. If faced with the risk of removing too much water, too fast, and stunning your organs, cramping, and crashing, the alternative is to remove less water until you can get your doctor on board with giving you longer treatment times—or reduce your fluid gains.
At the end of the day, YOU are in charge – you own your treatment. It is your right, and your responsibility, to understand all you can about your treatment: the rate of blood flow, the amount of water removed, your UFR, and your labs (all of them, not just the sugar-coated results they give you with smiley faces).
The obvious solution is that the more water you need to remove, the longer your treatment needs to be. Removing fluid slowly, over time, allows your body to balance itself during this process. Have you ever seen the Panama Canal? The ship cannot progress until the lock is completely full, then it passes to the next lock, where it is lifted up, and then to the next lock. Each lock is balanced before the ship can move on. This is how good dialysis should work, and it can best be achieved with home therapies, where you are not limited by the constraints of in-center scheduling and time limits.
Which brings me to my conclusions about dry weight. For dialysis to work for you, you must understand what it does, how it works, and take responsibility for each and every treatment. Don’t just sit in your chair and let someone who may, or may not, understand the complexities of UF, and how it relates to your body leave you cramping, crashing or collapsing post treatment. While pickle juice, mustard, Gatorade and broth are all remedies for that occasional treatment gone wrong, accepting them as an ongoing solution is not OK.
1. Hemodialysis: Diffusion and Ultrafiltration, Journal of Nephrology and Hypertension, http://austinpublishinggroup.com/nephrology/fulltext/ajnh-v1-id1010.php
2. Controlling Volume in Hemodialysis, Renal and Urology News, http://www.renalandurologynews.com/expert-reviews/controlling-volume-in-hemodialysis/article/58097/
3. Home Dialysis Central: http://www.homedialysis.org/life-at-home/articles/your-heart-on-dialysis; http://www.homedialysis.org/life-at-home/articles/fluid-and-solute-removal-part-one; http://www.homedialysis.org/life-at-home/articles/fluid-and-solute-removal-part-two;
5. Danger inherent in high dialysis ultrafiltration rates, http://www.farces.com/danger-inherent-in-high-dialysis-ultrafiltration-rates/
6. Rapid fluid removal during dialysis is associated with cardiovascular morbidity and mortality, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3091945/