Vascular access for patients on haemodialysis
For patients with acute renal failure
As there were no permanent access lines that could be left in site between dialyses, arterial and venous lines had to be inserted and removed for each dialysis. This could be difficult if the patients were in shock. The maximum number of dialyses carried out on any one patient in the first year was six.
|“Mr Sinclair (surgeon) or one of his junior colleagues would cut and put a cannula in into an artery and a vein. After dialysis the vessels would be tied off.” (Dr A Lambie)|
In 1960, the Scribner Shunt became available in Seattle, made by Quinton, Dillard and Scribner. A cannula was inserted into a suitable peripheral artery and one into a suitable vein. The cannulae were connected with a rigid piece of Teflon over a stainless steel arm plate. It was a semi-permanent exteriorised arterio-venous shunt that made repeated access to patients’ circulation possible, allowing long-term intermittent haemodialysis. It was cumbersome and difficult to use, and prone to come apart- particularly between dialyses.
In 1964, a modified version of the Scribner shunt was made. The indwelling cannulae in the artery and the vein were connected with a simple loop of Teflon. This was generally known as the “simplified shunt” or the “poor man’s shunt”, gaining the latter name because the shunt was inserted by the renal Senior House Officers (SHOs) and was not as “beautifully” done as a surgical operation.
|“The shunt could be very hard to insert in patients with bad vessels. It was a nightmare! The procedure also increased the workload of the renal SHOs, as it could take a few hours of an SHO’s time to perform.”” I was gowned up in a room like performing an operation. I would open up radial artery by dissection and put 1 tip in and stitch it up, then put other tip into a vein and stitch it up. The loop can be split open and connect to the dialysis machine. It was joined up at the end of dialysis. It may take up to an hour to create a shunt. I did so many that I could do it within 35 minutes. Eventually it was realised that this procedure should have been performed by the surgeons, and they began to take over the job. Soon after that, in the early 80s, the femoral cannulae and central venous cannulae were introduced, and the simplified shunts were no longer used.”(Dr A Cumming, a Senior House Officer at the Renal Unit at the time)|
Advantages of the “simplified shunt” included a good flow of blood and the possibility for dialyising several times each week. Disadvantages were that the shunts tended to clot. The shunts also got infected, and did not really provide a “permanent” access. Some shunts fell out although they were stitched in, and some were pulled out by patients.
For patients with chronic renal failure
In Edinburgh, a modified version of the Scribner shunt was constructed by Mr I Sinclair, Mr M Henderson, Dr D Simpson (Sinclair I, 1961). The Edinburgh pattern of connector assembly involved connecting the female end-piece to a metal collar, then to a sleeve of size-9 fluon (Teflon), then to the male end-piece. 2 of these were connected to a U-shaped “connecting segment” between the arterial and venous cannulae. A metal sleeve protects the U-shaped segment.
|“Someone used to always drop the metal collar onto the floor, and it had to be boiled to sterilise it. These shunts were really fiddly, especially with your gloves on.” (Dr A Lambie)|
These teflon arterio-venous shunts were used in CRF patients for a few years before the simple Teflon loop shunts (the “simplified shunts”) became available in the late 1960s.
Cimino and Brescia described the creation of a subcutaneous arterio-venous fistula between the radial artery and an adjacent vein in 1966. The Cimino shunt should be created some time before it is envisaged that the patient will start chronic dialysis. The vein becomes dilated and after some weeks can be used for access into the circulation through cannulation with needles. The Cimino fistulas are still being used nowadays.