Biomedical Engineering Reference
In-Depth Information
19.1 OVERVIEW
The current generation of blood substitutes are actually poor RBC substitutes,
which primarily carry out only the oxygen-carrying function of hemoglobin.
Ideally such agents should replicate the functions of platelets, plasma coagulation
factors, and their various activation processes, a true volume expansion, carrying
and activating immune cells (WBC), and so forth, as well as oxygen carrying
functions.
Properly screened placental umbilical cord blood, freshly collected after the
birth of a healthy baby, is an ideal and true blood substitute with enormous clini-
cal potential. This blood has a rich mix of fetal and adult hemoglobin, in addition
to a high platelet count and coagulation factors, and contains WBCs and plasma
fi lled with cytokine and growth factors. The constituents of this precious blood are
developmentally hypo-antigenic and also maintain an altered metabolic profi le.
All these factors make it a real and safe alternative to adult blood, especially in
emergencies caused by any etiology of blood loss. It may also have the potential
to prevent ischemia and eventual hypoxic-triggered organ failure syndromes.
19.2 THE PROBLEM OF SAFE BLOOD TRANSFUSION AND
THE GLOBAL SCENARIO
The need to develop a blood substitute is now urgent, not only because of increas-
ing concern over the worldwide HIV/AIDS epidemic, but also because of sudden
terrorist attacks and other disaster scenarios, which appear to have become
endemic and which compel a requirement for safe blood or blood substitutes to
save lives. The storage of frozen blood to combat such emergencies is often a
complex, cumbersome and costly task.
It is a well-known fact that a large number of war casualties die as a result of
hemorrhagic shock. Bellamy projected in 1984 that the percentage of wounded
soldiers who die in battlefi elds would increase from 20% to 26% unless the
soldiers are evacuated within two hours, and 32% if not evacuated within
24 hours (1). The majority of soldiers and civilians killed in action, crossfi re, or
bombings die due to blood loss from compressible wounds. These deaths could
be prevented if there was a timely transfusion of blood or a blood substitute. The
real problem, however, is the availability of safe, screened blood for immediate
use emergencies.
The imperative of having a steady supply of blood for transfusion is also
highlighted in a report of the World Health Organization (WHO) in 2000. This
revealed that there are about 500,000 pregnancy-related deaths globally, and at
least 25% of the maternal deaths are due to a loss of blood (2).
So far as the safety of blood meant for transfusion is concerned, Sloand et al.
reported in 1995 that an estimated 13 million units of blood worldwide are
not tested against human immunodefi ciency viruses (HIV) or hepatitis viruses.
Moreover, in some developing countries, 80% of the blood supply comes from
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