Setting the dialysate Sodium value in Hemodialysis

The dialysate sodium during hemodialysis is a very important factor because it can impact many things. During the dialysis session itself, if the sodium is too high, the patient can get high blood pressure and then, after the session, experience a high interdialytic weight gain due to increased fluid consumption. This high sodium can then cause all kinds of problems during dialysis. If the sodium is set too low, the patient can get cramps or low blood pressure etc. Even in the long run, there are studies currently being done that suggest higher sodium values can result in cardiac complications as well.

So, it is crucial to ensure that the dialysate sodium is set appropriately during our dialysis sessions. The challenge lies in figuring out how to achieve this.

Some dialysis machines allow you to simply set the prescribed sodium, and the machine ensures that the sodium delivered to the patient matches that value. However, there are other machines where you have two settings: one is the base sodium, and the other is the prescribed sodium. Both of these need to be set correctly to ensure that you are receiving the correct sodium during the dialysis session.

The base sodium in the second type of machines I mentioned earlier is essentially the total amount of sodium present in both the part A and part B constituents of the dialysate. You need to add the sodium from part A to the sodium from part B and set this as the base sodium. You then set the prescribed sodium, which determines what is actually delivered to the patient.

In an ideal world, the Part A and Part B would contain the exact sodium levels indicated on their labels. However, this is not always the case. Many manufacturers do not strictly adhere to the proper SOPs to ensure that the labeled amount of sodium is actually present in these solutions.

So, how do we ensure or confirm that we are getting the right sodium if we can't rely on the manufacturer's label?

The key is to monitor the conductivity value displayed on the machine. Most dialysis machines show this conductivity on their display or as an indicator, allowing you to check what the machine is delivering during the dialysis session through the dialysate. This conductivity measurement is the most reliable method because it reflects the actual value of the dialysate after all the mixing has occurred.

If everything is fine—the base sodium is correct, the manufacturer has done a good job with the mixing of Part A and Part B, and the machine is functioning properly—the conductivity should be close to one-tenth of the prescribed sodium value. For instance, if your prescribed sodium is 138, the conductivity on the machine should be around 13.8. It might vary by 0.1 up or down but should not deviate much beyond that.

We don't live in an ideal world, and many things can go awry. The best way to ensure that you are getting the right sodium is to adjust the prescribed sodium so that you achieve the desired conductivity.

So, if you aim for a sodium level of, say, 139 for your session, you must ensure that the conductivity reads around 13.9. For instance, if the conductivity shows 14.1, you should reduce the prescribed sodium by 2 units. Suppose the prescribed sodium is set at 140; reducing it by 2 units to 138 should lower the conductivity by 0.2. Conversely, if you desire a conductivity of 13.9 but the machine displays 13.6, you would increase the prescribed sodium by 3 units. Ideally, this adjustment will bring the conductivity close to 13.9.

You should discuss with your nephrologist what your dialysate sodium should be.

You will also need to collaborate with your dialysis technicians or nurses to make these adjustments, but always keep an eye on that conductivity. It has significant implications for both short-term and long-term outcomes.