Filed under: @ 7:07 am

About 2 1/2 years ago now Andrew’s renal function had declined to the point where his nephrologist started talking about dialysis. For those not in the know, dialysis is a process by which the metabolic wastes and other excess gunk is filtered out of the blood stream and discarded. This job, of course, is generally done by the kidneys, but if the kidneys aren’t capable of doing it we’ve fortunately developed a couple of ways to work around that.

Hemodialysis is probably the first thing that comes to mind when someone thinks “dialysis”. Hemodialysis is the process of removing the patient’s blood, running it through what is basically a mechanical kidney, then putting it back in. (No of course the blood isn’t removed all at once! It’s a gradual process.) Hemodialysis requires, depending on the degree of renal dysfunction, multiple trips to a dialysis center per week and a 4-6 hour treatment period where the patient is hooked to the machine at every visit. Hemodialysis also requires the creation of an arteriovenous shunt, a connection between an artery and a vein, in a convenient location so that the patient can be hooked to the machine more easily.

Peritoneal dialysis takes advantage of a weird quirk of humans’ natural physiologic processes and chemistry.

Pardon me while we take a brief side trip into:
It is an extremely simplistic definition, but to understand the idea of osmolality you need to think about a pile of white sugar and a drop of water. If the drop of water is placed at the very edge, just barely touching, the pile of sugar it will eventually get sucked into the sugar. That’s because the sugar is hyperosmolar (it has more stuff in it) and the water is hypo-osmolar. And which law of thermodynamics is it, the second? Or is it the third? Anyway whichever law of thermodynamics it is, a higher energy (or more osmolar) body will gradually loose energy (or osmolality) to a lower energy (or less osmolar) body until the two are at equilibrium.
Like a dry sponge sucking up a puddle of water on a counter top. You get the idea.

Peritoneal dialysis involves the introduction of a fluid of a lower osmolality than that of human blood into the peritoneal cavity (the abdominal cavity.) Because the peritoneal membrane, the “sac” in which one’s abdominal organs are contained, is a. extremely permeable and b. has an incredible blood supply, metabolic waste products and other kidney filtered gunk, gets slurped through the walls of the blood vessels into this fluid then discarded.

The benefit of hemodialysis over peritoneal dialysis is that hemodialysis runs no risk of peritonitis. The down side, of course, is that you only do it a couple of times per week which means that in between times you feel progressively more gross because your blood has a bunch of gunk in it that you don’t need. Oh, and the part about being hooked to a machine for 4-6 hours at every session and not being able to move.
The benefit of peritoneal dialysis over hemodialysis is that it’s done daily, you tend to feel better, and it can be done at home which means less of an impact on your work and travel time. PD, however, means that you have an indwelling catheter placed in your abdomen. Basically a tube that runs from your insides to the outside world. You can’t immerse yourself in water — no bathtub, no swimming, no hot tub, no boating (in case you fall in) — and you have to be painstaking in your handling of the PD catheter, the catheter site itself, your hands, your dialysis supplies, and your surroundings while you’re doing it. One slip up and you’ve got peritonitis, an infection in your abdominal cavity which is not only life threatening it means that you have to switch to hemodialysis.

A friend who has been on dialysis on and off for a long time describes dialysis along as a “mostly full time job”. Neither option is fun, both options are cumbersome, and basically what they do is keep you alive. Which is, of course, better than dead, but there’s a big difference between just existing and actually living.

Andrew had a series of surgeries in early 2017 to create an arteriovenous fistula (it’s on the under side of his left arm, you can feel his whole arm pulsing like crazy if you grab the right spot) and to place a PD catheter. The PD cath was placed but remained buried under the skin until it was needed, but it was still there.
The fistula and the PD cath were ominous and hopeful signs all at once.

4 Responses to “Dialysis”

  1. YakBoy Says:

    I am stealing your explanation of dialysis to use on families when their loved one is going on CRRT in the ICU (CRRT = continuous renal replacement therapy, basically slow 24/7 hemodialysis)

  2. margaret Says:

    <blockquoteI am stealing your explanation of dialysis to use on families when their loved one is going on CRRT in the ICU

    Which one? The one about sugar, kitchen sponges, and osmolality or the one about dialysis being a mostly full time job and there’s a big difference between existing and living?
    Just wondering. I’m honored regardless.

  3. YakBoy Says:

    Sugar, kitchen sponges and osmolality.

    Most of the time the explanation of “the machine is taking over for the kidneys” is enough but every now and then a bit more depth is required. I frequently run into issues explaining things because I tend to assume that if I understand it, it can’t be all that complicated.

    Sometimes that isn’t true.

  4. Scot Cederblom Says:

    Actually, I called it a part time job you don’t get paid for. And don’t forget the two extremely large needles that get rammed into you 3 times a week, and the mess when one comes out during treatment.

Leave a Reply

All comments containing hyperlinks are held for approval, so don't worry if your comment doesn't show up immediately. (I'm not editing for content, just weeding out the more obvious comment spam.)

All portions of this site are © Andrew Lenzer, all rights reserved, unless otherwise noted.