Biomedical Engineering Reference
In-Depth Information
The placental vessel at term contains approximately 150 ml of blood. Cord blood
contains three types of hemoglobin, HbF, HbA, HbA2, of which HbF constitutes
the major fraction (50-85 percent). HbA accounts for 15% to 40% of hemoglo-
bin, and HbA2 is present only in trace amounts at birth. HbF has a greater oxygen
affi nity than HbA. The oxygen tension at which the hemoglobin of the cord blood
is 50% saturated is 19 to 20 millimeters of Hg, six to eight millimeters Hg lower
than that of normal adult blood. This shift to the left of the hemoglobin oxygen
dissolution curve results from poor binding of the two to three diphosphoglycer-
ate of the HbF.
Cord blood is the richest source of fetal hemoglobin. Fetal hemoglobin
is a natural stress response to hemoglobin synthesis. An attempt is made to
preserve and augment this in case of thalassemia by providing hydoxyurea or
other similar drug support. Other conditions such as pregnancy, diabetes, thyroid
disease, or anti-epileptic drug therapy, can also increase the fetal hemoglobin
concentration. Fetal hemoglobin has an abundant source, that is, the placenta.
In India alone, there are more than 20 million placentas produced as afterbirth
every year.
Cord blood has some other advantages. It is common knowledge that blood
viscosity is a major determinant of blood fl ow. Whole blood is a non-Newtonian
fl uid, that is, its viscosity increases with decreasing shear rate (fl ow rate). Blood
viscosity is determined by hematocrit, plasma viscosity, red cell aggregation
and red cell deformability. The overall viscosity of the cord blood is less than that
of adult blood and has the potential to improve tissue perfusion and oxygen
transfer.
19.6 CORD BLOOD STABILITY IN ROOM TEMPERATURE AND TIME
Moreover, the stability of cord blood at room temperature has also been proven.
Osmotic fragility studies of the cord blood were conducted with .45% NaCl
(N = 40) at 4 °C, 35 °C and 40 °C, with a time gap of 24 hours, 48 hours, 7 days and
14 days, along with oxyhemoglobin (mmole/ml) and plasma hemoglobin (mg/ml)
assessment in identical schedule. The studies proved that the cord blood was rea-
sonably stable at room temperature, as shown in Table 19.1.
This blood has been successfully transfused, after meeting the ethical and
scientifi c formalities for safe transfusion, by a medical research team in Calcutta,
India, as an alternative emergency source of blood transfusion in the background
of anemia and emaciation of any etiology from surgery to medicine, that is, from
HIV or thalassemia to leprosy, or from advanced cancer to patients with a crip-
pling polyarthritis condition, and so on.
Before transfusion, aseptically collected umbilical cord blood was routinely
screened for HIV 1 and 2, Hepatitis B and C, Malaria, Syphilis, blood grouping,
and so on. Red cell serology and other biosafety precautions and quality assur-
ances were strictly adhered to. The potential complications of the blood transfu-
sion therapy can be grossly divided under two categories, that is, immunological
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