Removal of Edema Fluid by Ultrafiltration with the Disposable Twin-Coil Artificial Kidney
THE artificial kidney is useful not only for the treatment of the uremic state but also in the removal of edema. The states of overhydration1–3 in which hemodialysis can be effective are those in which the kidneys either cannot excrete water, as in advanced renal failure, or will not excrete water, as in intractable cardiac failure. The frequency of overhydration in azotemia is emphasized by the fact that of the last 100 patients who underwent dialysis at the Cleveland Clinic Hospital, 35 required ultrafiltration to remove excess fluid.
During hemodialysis, fluid can be removed either by raising the pressure in the dialyzing unit, which results in ultrafiltration, or by raising the solute concentration of the rinsing fluid which, by osmosis, causes a movement of water from the less concentrated plasma inside the cellophane tubing of the artificial kidney to the more concentrated fluid of the bath. To effect ultrafiltration, the pressure in the disposable twin-coil artificial kidney4 can be increased by constricting the outflow tract with a screw clamp. The pressure in the outflow tract of the artificial kidney, proximal to the clamp, is measured by a Tycos manometer connected to the bubble-catcher system, as shown in Figure 1. The pressure in the bubble catchers can be safely increased to 300 mm. of Hg without rupturing the cellophane tube. The pressure at the point where the blood leaves the coil is approximately 40 mm. of Hg above that in the bubble catchers, with about 50 cm. of difference in . . .