What is hemodialysis?
An artificial dialyzer (commonly called 'bone') is needed to clean the patient's excess fluid and toxic substances of metabolism. Patient's blood is drawn from the arterial side, then go through the dialyzer where diffusion (of toxic substances) and convection (filtration) (of excess water) takes place, and then out from the other end of it.
Flow of blood in hemodialysis:
- blood drained out from arterial side
- blood passes through dialyzer
- blood drained back to the patient via the venous side (the flow of blood is driven by blood pump of the hemodialysis machine
An vascular access will be created to allow for blood diversion. It can take the form of arterio-venous fistula when a large vein is connected to a large artery through an operative procedure usually in the forearm (Fig. 12 a) or a double lumen catheter inserted into large veins commonly internal jugular vein in the neck when 1 lumen serves as arterial side and another lumen serves as vein side (Fig. 12 b).
(Fig. 12.a) arterio-venous fistula (a large vein is dissected and connected to the artery)
(Fig. 12.b) double lumen catheter (permcath) in large vein of neck or chest
(Fig. 12.c) a child on hemodialysis
Usually, 3 dialysis sessions will be carried out weekly; and each session will last about 3.5-4 hours. To have better clearance, more sessions will be needed. In between dialysis sessions, the patient has to stick to a more restricted diet (protein and fluid intake) as any excess fluid or solutes will accumulate in the body until next dialysis session.
Each time, the child accompanied by the caretaker has to go back to hospital to undergo hemodialysis. This will lead to a great demand on time and disturbance of social/school life; and also cost in transportation. In this respect, chronic peritoneal dialysis is much better as it is a home-based treatment and it provides a daily continuous clearance. Because of these, nocturnal home hemodialysis has been tried in adults and some children with some success. This way of delivering hemodialysis not only lead to better daytime activities but also results in better clearance (both solutes and fluid) as hemodialysis will be carried out 5-6 times per week and at home. Infection due to bacteremia and exit site infection and access blockade remain the major problems. Sometimes, when peritoneal dialysis has to be suspended due to severe peritonitis (peritoneal membrane infection) resulting in catheter removal, the patient has to be put on hemodialysis temporarily.
