The trouble with using Body Composition Monitors to assess Over-Hydration in Dialysis Patients

Accurately assessing the amount of excess fluid in a dialysis patient has always been challenging. Most dialysis centers currently rely on subjective methods, such as checking for symptoms like shortness of breath, cramps, or hypotension from the previous session. Based on these observations, the dry weight is adjusted. However, this approach often involves guesswork due to various influencing factors. For instance, changes in the patient's dry weight or muscle mass can occur depending on their nutritional intake. Therefore, this assessment is not always precise.

There is a technology known as bio-impedance, utilised by several devices called Body Composition Monitors. These devices claim to offer an objective and reliable method to assess excess fluid in the body, guiding its removal.

I have tried several of these machines, but I have not found any of them to work consistently and reliably over an extended period. Some function well for a few months, others are inconsistent, and some provide significantly inaccurate results.

I do not wish to question the accuracy of all these devices and the technology itself. I believe there are several complexities involved for this technology to function reliably. One key factor is that the technology operates effectively only if there is a certain level of equilibrium in the body. For instance, if someone has just eaten or exercised, these machines may not provide reliable results.

I recall reading a research paper that mentioned this technology works reliably only if the patient has fasted for 10 to 12 hours. However, it is unreasonable to expect patients at a dialysis center to have not eaten or drunk anything for such a long period. Unfortunately, most machines do not specify this fasting requirement as necessary for accurate results.

Furthermore, these machines are priced extremely high, making them inaccessible for many dialysis patients. Some even incur recurring costs for each measurement. This makes the system impractical for widespread use in dialysis centers. If the results were consistently accurate, there might be a case for using them occasionally, perhaps once a month or once every few sessions for patients who can afford it. However, this does not appear to be the current situation.

It is quite unfortunate because this technology could have provided a wonderful solution to this vexing problem in dialysis patients. However, since it will not work, we are left with the current situation and will have to continue to rely on subjective methods to assess the amount of fluid to be removed during dialysis sessions.


Nitin said…
Hi Kamal,
Thanks for sharing your insights! It would be helpful if you could share the paper reference that suggests 'this technology works reliably only if the patient has fasted for 10 to 12 hours.' Additionally, any supporting material on unreliable results after eating or exercising would be helpful. Thank you.
Kamal D Shah said…
Can't find the reference now. It was a while back. But here's a link that has the same information:

1. Impact of Eating:
• Consuming food, especially heavy meals, before a body composition analysis can lead to temporary changes in body weight and hydration status, which in turn can affect impedance measurements and skew results. It is recommended to perform the analysis on an empty stomach for more consistent readings 

2. Impact of Exercising:
• Exercise can cause immediate changes in hydration and muscle glycogen levels. Performing a body composition analysis right after exercising may result in lower impedance due to increased blood flow and sweat, which can make the readings appear leaner than usual. It is advisable to wait for a few hours post-exercise before conducting the analysis to allow the body to return to its baseline state 

3. General Recommendations:
• For the most accurate and consistent results, it is advised to perform body composition measurements at the same time of day, under similar conditions (e.g., similar clothing, fasting state), and before engaging in any physical activity .
Anonymous said…
As you have mentioned its a machine /technology. Any results from such devices need human intepretation that too someone whos knows that particular technology well.
Bioimpedance can be a great tool to assess fluid balance but not on its own.Several other factors will need to be considered like fat mass,muscle mass,nutritional status of patients
People with right expertise have used it successfully .Agree its expensive and may not be applicable for all.