Once the Chronic Kidney Disease advances to an eGFR of less than 10 mL/min, initiation of dialysis is indicated. At this stage, there are two options. One is starting Hemodialysis and the second one is Peritoneal Dialysis.
Before we compare Hemodialysis and Peritoneal dialysis, let us first understand more about peritoneal dialysis.
Anatomy of Peritoneum.
Peritoneal cavity is the potential space in the abdomen overlying the intestines and other organs. This space is lined by the peritoneal membrane (mesothelium). This mem
brane contains millions of small capillaries with circulating blood inside them.
This capillary wall acts as the semi-permeable membrane when it is exposed to dialysis solution. Exchange of waste products and the physiological substances occurs across this membrane.
Requirements for Peritoneal Dialysis
- Acatheter that is placed surgically inside the abdomen
- Dialysis fluid ( usually packed as 2 litres or 2.5 litres)
- Connection port between the fluid containing bags and the catheter.
Peritoneal Dialysis Fluid
This is a fluid that contains electrolytes and buffers at physiological concentration. This is let inside the abdomen through the catheter.
Apart from the electrolytes, the fluid contains glucose which draws water from across the capillary through osmotic action. Higher the strength of glucose, more is the amount of fluid drawn. Typically, PD fluids are available as 1.5%, 2.5% and 4.25% glucose solutions.
One problem with glucose as the osmotic agent, is that it crosses the capillary wall and enters the blood circulation, not only causing a loss of the osmotic force, but increasing glucose levels in the patients blood. In diabetics, this means increasing the doses of Insulin.
Icodextrin is a polymer of glucose that does not cross the capillary membrane and has osmotic force equivalent to a 2.5% glucose solution. It is more commonly being used now, although the use is currently limited to the night cycle.
Catheter Placement Surgery
This is a minor surgery done usually under local anesthesia. There are
non-surgical bed-side methods as well, but the surgical method is the most accurate.
- A clean room
- A few antiseptic solutions (easily available everywhere)
- A stand for the solution bag
- Sterile towels ( can be easily sterilized by steam, at home.)
The CAPD Procedure
As shown in the adjoining picture, the PD bag is connected to the catheter.
Note that, the two bags come as pre-connected to a small common stem ( i.e. the bags do not have to be connected to the tubings, they are packed connected to each other).
One bag contains fresh PD solution and the other bag is empty.
If the abdomen has fluid from the previous exchange, this fluid is drained out first, into the empty bag. During this time the bag containing fresh fluid is clamped shut.
Now, the fresh fluid is emptied into the abdomen, simply by opening the clamp. At this time, the clamp of the other bag is kept closed. This fluid now stays in the abdomen for 4 hrs or longer.
So, the only time when an infection can enter the abdomen is, when the common stem (the connector or the extension tube) is connected to the catheter or removed from the catheter with contaminated hands. These are the times, when the hands must be clean.
Please note that this is just an overview of the procedure. The exact procedure including technique of hand washing , sterilizing the equipment and towels and the connection methods will be taught in details at the time one adopts the therapy.