Discuss the processes involved that lead to a 2 unit transfusion of packed RBC's (this could include: donor selection, blood testing and processing, criteria for transfusion, etc)

(Example 1)

Blood donors are screened by history for high risk behaviors (unprotected sexual intercourse with multiple partners, intravenous drug use), travel history (to areas endemic for malaria), past and present illnesses, and drug usage. Donor confidentiality is maintained, and the donor can elect to anonymously indicate exclusion of the blood. After donor screening, blood is collected and separated into components. The blood is tested for HIV-1 and 2, HTLV-1, HBV, HCV, and syphilis by RPR.

Blood may be washed, glycerolized, and frozen for long term storage of rare types. Gamma irradiation may be done for units transfused to immunocompromised patients. For routine use of packed RBC's, a "type and screen" is ordered if there is <10% probability of usage. Blood is ABO typed, and screened to determine the presence of irregular antibodies. A regular "type and cross" is done if there is a greater likelihood of blood usage, but such crossmatched units are removed from the inventory. Crossmatching consists of testing recipient serum with donor RBC's for incompatibility. However, in an emergency type O Rh negative blood may be used without crossmatching.

RBC's should be transfused only when necessary to improve the symptomatic patient's oxygen carrying capacity. Severe anemias and acute blood loss from trauma or surgery are common indications. In general, transfusion may be considered when the patient's Hgb is 7 to 8 gm/dl and Hct 21 to 24%, though very ill patients may require transfusion at a higher Hct.

Discuss the processes involved that lead to a 2 unit transfusion of packed RBC's (this could include: donor selection, blood testing and processing, criteria for transfusion, etc)

(Example 2)

Blood may be transfused from the recipient--an "autologous" donation. This is the safest form of transfusion, but is not completely without problems (clerical errors, bacterial contamination). A "directed" donation occurs when the recipient wants specific persons to donate blood, but it is not necessarily safer than random blood, because directed donors are under pressure to give blood and may not be totally honest in the screening process. Moreover, the risk of transfusion-associated graft versus host disease is increased with directed donations because relatives are more likely to be closely HLA matched, or donation from husband to wife may increase the risk for subsequent hemolytic disease of the newborn with future pregnancies.

Blood is screened for blood borne pathogens, including HIV, HBV, HCV, HTLV-1, and syphilis. Since 60 to 100% of a donor population is seropositive for CMV, this is not routinely screened, but only tested for units to be used in infants and immunocompromised patients. Blood is "forward" typed to determine the major blood group antigens (A, B, O, or AB) and Rh typed (positive or negative for D); the blood is "back" typed to determine the corresponding antibodies (anti-A, anti-B, anti-A and B, or none). An antibody screen is performed. A type and cross removes the blood for 72 hours from the general inventory for use by other patients. The risk for a hemolytic transfusion reaction using type-specific blood wtihout a crossmatch is only 1/250,000.