Biomedical Engineering Reference
In-Depth Information
Liposome-encapsulated hemoglobin (LEH) has also been found to be
an effective oxygen carrier, without the adverse effects of vasoconstriction
[Kawaguchi et al. (19)]. Liposome encapsulation appears to increase plasma
retention time; however, adverse immune interactions occur with liposome. This
product has an advantage because it can be freeze-dried and stored at room tem-
perature.
In actuality, the most commonly-used volume replacement solution is the
Ringer-Lactate solution. If modifi ed hemoglobin or fl uorochemicals are added to
Ringers solution so that it can act as an oxygen carrier, and to also increase the
colloid osmotic pressure, even then the functions of clotting and antioxidants will
not be performed.
It has been observed by many sources that treatment with so-called blood
substitutes is not too effective in combating a potential injury in life-threatening
conditions, which have latent possibilities for ischemia-reperfusion injuries, for
instance, sustained ischemia in stroke, severe hemorrhagic shock with intestinal
ischemia, prolonged cerebral ischemia, and so on.
Since these substitutes do not contain any red blood cell antioxidant enzymes
such as catalase and superoxide dismutase, the hemoglobin in the blood substi-
tutes can break down more easily to release heme and iron in the presence of
oxidants in ischemia-reperfusion and thus intensify injuries.
Therefore, newer generation blood substitutes are being tried which may
contain antioxidants as in the case of polyhemogloin-catalase-superoxide dis-
mutase. In fact, artifi cial oxygen carriers are not real blood substitutes. They serve
to carry oxygen to tissues and are either hemoglobin-based or perfl uorocarbon-
based. No artifi cial oxygen carriers are currently approved for clinical use in the
United States.
19.4 WASTAGE OF THE PLACENTA AND ITS CONTENT
In the animal kingdom, swallowing the afterbirth by the mother is a general norm.
Even herbivorous animals, such as the cow, swallow the placenta after the birth
of their babies. Humans, so far, had not seemed to realize the potential of the
afterbirth.
However, recent research suggests that the placenta may prove to be a non-
controversial source of hematopoietic and mesenchymal stem cells as well as
endothelial progenitor cells. There is now widespread successful utilization of
cord blood collected from the placenta after the birth of healthy babies as a stem
cell source in the treatment of pediatric hematological malignancies after mye-
loablative conditioning. Since matching requirements for this type of transplant
are not as strict as for hematopoietic stem cell sources, cord blood began gaining
acceptance in adult patients lacking bone marrow donors [Cornetta et al. (20)].
Apart from oncology, the effi cacy of the clinical use of cord blood has been noted
in Hurler's syndrome, diffi cult spinal injuries, Burger's disease, refractory anemia
and many more intractable and congenital diseases, apart from stroke [Newcomb
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