The goal of transfusion is to improve oxygen delivery to tissues, provide intravascular volume expansion, and to replace missing or depleted clotting factors in patients with clinically significant hemorrhage, anemia, thrombocytopenia or coagulopathy. Great care must be taken to ensure that the correct blood product is delivered to the correct patient.
There are few indications for the use of whole blood transfusion. Although whole blood can provide volume expansion and oxygen-carrying capacity, the same can usually be accomplished more efficiently by using individual blood components.
Packed red blood cells (PRBC) are prepared from whole blood by removing most platelets and/or white cells. A typical unit of PRBC has 250 mL of RBCs and raises an adult's hemoglobin by 1 gram/dL (hematocrit by 3%). PRBCs increase oxygen-carrying capacity in anemic patients.
The decision to transfuse PRBC is based on individual clinical judgment, taking into account patient's hemodynamic status, underlying medical condition, tolerance for anemia, and risk of end-organ ischemic injury. Adequate oxygen delivery in healthy normovolemic patients can be maintained with hemoglobin levels as low as 7 grams/dL, although patients with comorbid conditions may require transfusion at higher levels of hemoglobin. The usual indications for PRBC transfusion include: (a) acute hemorrhage, defined as blood loss >25% of blood volume, (b) hemorrhagic shock, (c) surgical blood loss greater than 2 L; and (d) symptomatic anemia or being at-risk for ischemic events, ie, patients with hemoglobin <6 grams/dL who have symptoms of end-organ ischemia, ≥55 years of age, have cardiac disease, sepsis, severe infection, or APACHE II score >20.
Type and crossmatch assesses ABO/Rh blood type, the presence of antibodies, and patient and donor blood compatibility. It takes 15 to 30 min to perform and is ordered if the likelihood of transfusion is high. Type and screen assesses the ABO/Rh blood typing and the presence of antibodies. It takes 15 to 30 min to perform and is ordered if the likelihood of transfusion is low.
In critical situations, where there is no time to perform a complete ABO/Rh-typing, group O/Rh-negative blood ("universal donor") can be given to patients without waiting for a complete type and crossmatch. Type O/Rh-positive blood may be used if Rh-negative blood is unavailable but is generally avoided in girls and women of childbearing age. Before transfusion, blood for baseline laboratory tests, type, and crossmatching should be obtained.
PRBC may be further treated to minimize complications in special patient populations, such as neonates, transplant and patients on transplant list, patients who have received prior transfusions, pregnant patients, immunocompromised patients, and patients with hypersensitivity to plasma. Options include leukocyte reduced, irradiated, frozen deglycerolized, washed, and CMV negative PRBC.
A unit of PRBC is usually transfused over 2 hours but can be given much faster using a pressure infusing device or over 4 hours, if needed. Micropore filters are used to filter out microaggregates of platelets, fibrin, and ...