Do you adjust the hemodialysis bicarbonate bath to match the elevated serum bicarbonate level in ESKD patients with hypercarbia due to COPD?

I do not typically for COPD itself, but I do consider it in circumstances where there is severe resp acidemia with no other options for stabilizing their pH. In a subset of patients on home ventilation/AVAPS, they have little reserve to handle even a little more CO2 retention. I will modulate the dialysate bicarb and consider additional oral bicarbonate to try to keep their serum bicarb closer to 28-30. But I also work with their pulmonologist to ensure timing of AVAPS/BiBAP during HD because it is such a high bicarb load over a short time. While data is lacking, the high influx of bicarb in a patient with severe hypoventilation is likely not negligible in its effects. While the question is for COPD, I do this far more in the post-lung tran...

• Generally speaking, hypercarbia in dialysis patients is rarely related to COPD since this will require a reasonable residual kidney function to be able to generate the bicarbonate. GI losses is the primary cause usually. Increasing dialysis bicarbonate level would not help.

Lisawat P, Gennari FJ. Approach to the hemodialysis patient with an abnormal serum bicarbonate concentration. Am J Kidney Dis. 2014 Jul;64(1):151-5. doi: 10.1053/j.ajkd.2013.12.017. Epub 2014 Apr 13. PMID: 24731739.

Good question. Not much data. My answer would be yes, with some exceptions. The body's natural response to hypercarbia is to retain bicarbonate and maintain the pH (people with normal renal function). I would guess it would be beneficial to do the same thing with dialysis when the kidneys are unable to do it. The question is what bicarb level do we shoot for, as obtaining arterial blood gas frequently is unrealistic.

Generally not. The concentration of dialysate bicarbonate in most hemodialysis centers in the US is about 35 mmol/l. Therefore, for most COPD hyperbaric patients with a serum bicarbonate 33-37 mmol/ there will be no net flux of bicarbonate into or out dialysate and no adjustment of dialysate bicarbonate would be needed. In cases of severe CO₂ retention with compensatory serum bicarbonate levels greater than 40 mmol/l, raising a bit the dialysate bicarbonate may be important, to prevent moderate degrees of acidemia, but this would be highly unusual.