The Minicoil Artificial Kidney
David Dukes (M 1958)
Willem Kolff ’s successful development of the artificial kidney in Holland during World War II led to a tremendous demand for haemodialysis throughout the world. In 1960 Denys Blainey (renal physician) and Paul Dawson-Edwards (urologist) set up the first Birmingham Renal Unit in the General Hospital (now the Children’s), using the Travenol twin-coil version of Kolff ’s machine. Although effective, its large blood volume, lack of a blood leak detector and any means of measuring how much fluid was being removed from the patient, apart from by continuous clinical observation, meant that doctors needed to be present throughout treatment (usually Jim Lawson and the author, who were then surgical and medical SHOs respectively).
At this time Belding Scribner, in Seattle, invented the arteriovenous shunt, which enabled repeated dialysis to be done conveniently over prolonged periods. In Birmingham it was apparent that demand for dialysis would soon exceed supply. Could dialysis be simplified, using the patient’s arteriovenous pressure difference to provide blood flow through the coil, and gravity to circulate dialysate around it?
And what was the best dialysate membrane? The first question was addressed with the technical help of Mr N. Rogers, of Messrs Capon Heaton, who were experienced manufacturers of plastic intravenous equipment. The second question was answered by testing various membranes for permeability to electrolyte using equipment devised by David Rowe in John Squire’s department of Experimental Pathology.
The author ran the tests in his room while working at the old Children’s Hospital – sometimes to the distress of other residents because of the noise of the machine! Reconstituted viscose cellulose turned out to be the best membrane and Capon Heaton used this as a lay-flat tubing in their new artificial kidney.
This was the age of the minicar and the miniskirt and so it was inevitable that the new device, less than the size of a football, would be dubbed “Minicoil”. In use it was suspended at the patient’s bedside. Above it, on a trolley, stood a reservoir of dialysate with a thermal jacket; flow of fluid over the coil was controlled by a gateclip. Arterial and venous lines, at the ends of the coil, were connected to appropriate ends of the patient’s shunt. Because transmembrane pressure was negligable, so was ultrafiltration, and so glucose was added to the dialysate to remove water from the patient by osmosis. Amazingly, it worked, and nurses were happy to supervise it.
The author used it at East Birmingham Hospital (now Heartlands) and Keith Harding at R.A.F. Cosford. Its main disadvantage was the small surface area of membrane, and internal resistance to blood flow sometimes prolonged dialysis. These defects were overcome by members of the R.A.F. hospital at Halton who worked with Capon Heaton to produce the “Twin Minicoil” which used a blood pump; this vastly improved its performance and reliability. Twin minicoils were used extensively in this country, and also by the author and his wife, Heather, in Harare, until the advent of hollow fibre dialysers in the 1970s