Biomedical Engineering Reference
In-Depth Information
from humans. In the end, Haas used heparin, which was first isolated in dog livers
by American researcher Jay McLean in 1916. Heparin caused substantially fewer
complications than hirudin, even when it was insufficiently purified, and it could
be produced in larger amounts. Heparin became and remains the anticoagulant
of choice, with the development of better separation technologies in the 1930s.
In 1923, usage of intact living peritoneum (abdominal lining) was a good dialyz-
ing surface, and German clinical investigator Georg Ganter reported the first use
of peritoneal dialysis in clinical therapy. Subsequently, German physician Hein-
rich Necheles modified his extracorporeal (meaning apparatus carrying the blood
outside the body) device by compressing tubes of peritoneal membrane between
screens of metal mesh, which reduced the enclosed blood volume and increased the
effective surface area. However, due to issues with sterility, peritoneal membranes
suffered from increased incidence of infection. Another development in the 1930s
was commercial production of cellophane (regenerated cellulose acetate) in large
quantities as tubing for sausage casing, which replaced colloidin membranes due to
its better performance and mechanical stability. Later, cuprophan (cuprammonium
cellulose) membranes replaced cellophane due to its better permeability properties.
Dutch physician Willem J. Kolff secured a success in 1945 when he treated a
67-year-old patient with acute kidney failure for a week, which allowed the pa-
tient to be released with normal kidney function. The patient died at the age of 73
from an illness unrelated to the kidney failure. Although Kolff had unsuccessfully
treated 16 previous patients in a series of experiments, this success was the first
major breakthrough in the treatment of patients with kidney disease. The suc-
cess is attributed to the technical improvements in the actual equipment used for
the treatment. Kolff's device consisted of a rotating wooden drum around which
a new membrane made of cellophane was wrapped. Blood was taken from the
artery propelled through the tubing when the drum rotated (using the principle
of Archimedes' screw). The drum containing blood-filled tubes were partially im-
mersed in an electrolyte solution known as dialysate. As the membranous tubes
passed through the bath, the uremic toxins would pass into this rinsing liquid due
to diffusion (described in Chapter 2) and osmosis. Blood was returned to the vein,
largely cleared of urea and unknown toxic substances.
In 1947, Swedish engineer Nils Alwall published a scientific work describing
a modified dialyzer that could better combine the necessary processes of dialysis
and ultrafiltration than the traditional Kolff kidney. The cellophane membranes
used in the dialyzer could withstand higher pressure because of their positioning
between two protective metal grates. All of the membranes were in a tightly closed
cylinder so that the necessary pressure did not need to derive from the blood flow
but could rather be achieved using lower pressure in the dialysate. However, due to
its alleged lack of compatibility with blood (described in Chapter 6), membranes
made from unmodified cellulose lost their market share. They have been replaced
by modified cellulosic and synthetic dialysis membranes, which show a better com-
patibility with blood than unmodified cellulose membranes. As an alternative to
rotating drum dialysers, American biochemists Leonard T. Skeggs, Jr., and Jack R.
Leonards developed parallel plate dialyzers in 1948. In this design, several plates
with ridges and grooves were stacked parallel. A semipermeable membrane rested
between the grooves and the blood flow. Rather than pumping the blood through
