Blood flows on one side of membrane while dialysate flows on the other side. To ensure effective dialysis a high blood flow is required for taking blood from the body to the dialysis machine. The blood flow required is about 5ml/kg body weight /min. Usually 250 ml to as much as 500-600 ml if tolerated.
The way to achieve this is through creation of dialysis access. This may be temporary or permanent.
A temporary access is made in those patients who will require dialysis for a few days to few weeks as in acute kidney injury ( also called earlier as ARF or acute renal failure), while awaiting creation of a permanent access.
Temporary access is obtained by inserting a tube in neck veins (Int Jugular Vein) usually on right but sometimes on left side. It is uncommon nowadays to use subclavian (behind collar bone ) or upper thigh veins. The advantage of this is that it is ready to use immediately however it often gets infected and may cause clot formation in the vein in which it is placed. It should be used for less than 2 weeks and never handled by patient. Sudden dislodgement may cause bleeding. In case long term dialysis is required and AV fistula( read further on to know about AVF) is not yet ready a permanent dialysis catheter which is useful for a few months is a far better though costly choice.
The method of choice is creation of arterio-venous fistula (AVF). It is usually made in the wrist but if blood vessels are small or thrombosed it is at times made in arm near elbow. This requires surgery usuaally under local aneasthesia. The failure rates are higher if done by inexperienced surgeons (1 in 2 to 1 in 4 AVFs may fail.)
It takes 2 to 3 months to mature and hence should be made much before the need of dialysis arises. It should be checked to see that it is working. If there is stoppage of flow early treatment may make it work again but if delayed another AVF creation is required.
If injured rapid bleeding may occur. So protect these from injuries. Do not allow these to be used for drugs and samples other than in dialysis room by dialysis personnel.
A good AVF is a life line for patients. Get it made early & keep it functional !!