The Past and the Present

Haemodialysis was first started in Hong Kong in about 1966 in the Queen Mary Hospital. In 1977, the renal unit in the Princess Margaret Hospital was operational with 16 dialysis stations. There was significant advance over these years.

1. Vascular access

The most difficult part in haemodialysis is how to take blood out of a patient for cleaning. The usual blood flow need is around 250 ml/minute and in many countries, a blood flow rate of 300 to 400 ml/minute is common. The usual peripheral vein cannot support such high flow rate and in practice, an arterio-venous fistula needs to be created.

The arterio-venous fistula is made by connecting the radial artery with the cephalic vein, the blood flow in the radial artery is diverted to cephalic vein. After 4 - 6 weeks, the cephalic vein is open up with the wall thickened and blood can be obtained by inserting a needle. The arterio-venous fistula is the best form of vascular access because it has a long life span and low incidence of infection. There is little hindrance with the patients' daily activities such as bathing or swimming etc.

The main drawback of fistula is the long waiting time, sometimes the patients cannot wait for that long. In the early days, an arterio-venous shunt was created to provide vascular access in this period.

An arterio-venous fistula was inserted by putting a plastic cannula into an artery and another into a neighboring and then joining them together. The two limbs can be disconnected, the arterial limb to provide the blood outflow and the venous side the return pathway. It can be used immediately after operation, but complications like infection and clotting make them unsuitable for long term use. The group in the Princess Margaret Hospital prefered to create the shunt in the feet so as to spare the upper limb vessels for fistula creation.

Over the year, temporary vascular access is provided by cannulating great veins such a femoral vein, subclavian vein and the internal jugular vein. A double lumen can be inserted so that one needle can provide blood inflow and outflow. Subclavian and internal jugular catheters can last a few months and they are useful for temporary dialysis.

One form of double lumen catheter is called Perm-cath. It is made of an inert material and it is inserted into the internal jugular vein and comes out of skin though a subcutaneous tunnel. The chance of infection is reduced and it can provide dialysis for years. Many patients like these catheters because there is no need for needle puncture.

After blood is taken out of the body, it goes to a dialyser (artificial kidney). In early days, dialysers are large and they have to be built by the dialysis nurses using cellophane sheets. It was later replaced with disposable flat plate dialyser. In late 70's, virtually all dialysers are of the hollow fiber design. The dialyser consists of many hollow tubes, blood flows inside the fibers and the dialysate flows on the outside. Since the fiber is made of semi-permeable material, toxins can diffuse from the blood to the dialysate.

Previously the dialysis membrane is made of cellulose derived from plant cell wall. In recent years synthetic membrane is getting popular and many such membranes claim to be more biocompatible. Many patients do feel better while on such biocompaticle dialysers. Recently the price of such dialysers has dropped drastically and they price gap is not large.

In early days, dialysis machines are of the batch tank type. They are simple, reliable but bulky. Modern dialysis machines are of the 'proportionate pump' type. In the early models, the dialysis staff calculateed the negative pressure needs to remove the desired amount of water from the patient and input the data into the machine. Such method was not accurate. These machines are virtually replaced by ones which have volumetric ultrafiltration control, meaning that the machine can control and monitor the volume of fluid removed automatically.

Earlier dialysate contained acetate as a buffer base but the buffer base in our body is bicarbonate. The acetate will diffuse into the patient's blood and will be converted into bicarbonate. Some elderly patient cannot covert the acetate at a fast enough rate and symptoms such as headache, nausea and hypotension can occur. Modern machines can now use both bicarbonate and acetate dialysate.

The dialysate was purchased as dialysate concentrate and had to be diluted with water. The tap water must be purified with a series of process, the most important being reverse osmosis treatment which can remove the dissolved ions and the pyrogens.

In the coming years, the development of dialysis facilities in Hong Kong will depend not so much on technological advance by on health care financing. Dialysis is an expensive treatment which few people can afford. In Hong Kong, the patients in the public sector are heavily subsidized but the Government is unlikely to finance the medical service at its present rate of growth. The private patients need to pay all the expenses themselves but with the aging population and the economic setback, the burden is increasingly difficult to bear. One way to solve this problem is the medical insurance system and the Government has recently released the report from the expert group from the Harvard University. With a rational medical financing system, dialysis treatment will further improve.

Lecture to St Teresa's Hospital, 21^st April, 1999