Why not thrice weekly HDF compared to Daily Nocturnal HD?

I recently blogged about why Daily Nocturnal HDF wasn’t recommended to me by some experts in home HD. One of my colleagues at NephroPlus, Rajesh, asked a very pertinent question in the comments: “But why go for long durarion and frequent HD when you can get the benefits of HDF with shorter and less frequent sessions?”

Great question, Rajesh.

The reason is fluid removal. Any type of dialysis primarily performs two functions - toxin removal and fluid removal. Since the kidneys are not performing well for someone on dialysis, the excess toxins and fluid in the body need to be removed. This is done by dialysis. Now, while the toxin removal rate can be improved by various methods like increasing the blood flow rate, dialysate flow rate, using a better dialyzer etc., the fluid removal is constrained by one important factor that cannot be changed - the body’s ability to lose fluid without having side effects.

The average human body can lose only about 400-500 ml/hour during dialysis without experiencing side effects. Removing fluid more rapidly could lead to symptoms like muscle cramps, hypotension etc. Whichever modality of dialysis you choose, however high or low you set the blood and dialysate flow rates and whichever type of dialyzer you use, you cannot change this fundamental characteristic of the human body.

By doing daily, nocturnal HD, you are giving more hours of dialysis which means you are removing the fluid over a longer duration which reduces the rate of fluid removal to well below this 400 ml/hour limit. This enables you to drink significantly more fluid and yet not experience the side effects of rapid fluid removal.