Alternative Strategies for Management of Blood Loss During Surgery
Patients undergoing elective surgical procedures with a high probability for transfusion can donate their own blood for use during that surgery. Collec-tion is usually started 4–5 weeks prior to the pro-cedure. The patient is allowed to donate a unit as long as the hematocrit is at least 34% or hemoglo-bin at least 11 g/dL. A minimum of 72 h is required between donations to make certain that plasma vol-ume returns to normal. With iron supplementation and erythropoietin therapy, at least 3 or 4 units can usually be collected prior to operation. Some stud-ies suggest that autologous blood transfusions do not adversely affect survival in patients undergoing operations for cancer. Although autologous transfu-sions likely reduce the risk of infection and transfu-sion reactions, they are not risk-free. Risks include those of immunological reactions due to clerical errors in collection, labeling, and administration; bacterial contamination; and improper storage. Allergic reactions can occur due to allergens (eg, ethylene oxide) that dissolve into the blood from collection and storage equipment.
This technique is used widely during cardiac, major vascular, and orthopedic surgery . The shed blood is aspirated intraoperatively into a reservoir and mixed with heparin. After a sufficient amount of blood is collected, the red cells are con-centrated and washed to remove debris and anti-coagulant and then reinfused into the patient. The concentrates obtained usually have hematocrits of 50–60%. To be used effectively, this technique requires blood losses greater than 1000–1500 mL.
Contraindications to blood salvage and reinfusion include septic contamination of the wound and perhaps malignancy. Newer, simpler systems allow reinfusion of shed blood without centrifugation.
Acute normovolemic hemodilution relies on the premise that if the concentration of red cells is decreased, total red cell loss is reduced when large amounts of blood are shed; moreover, cardiac out-put remains normal because intravascular volume is maintained. One or two units of blood are typi-cally removed just prior to surgery from a large-bore intravenous catheter and replaced with crystalloid and colloids so that the patient remains normovole-mic but has a hematocrit of 21–25%. The blood that is removed is stored in a CPD bag at room temper-ature (up to 6 h) to preserve platelet function; the blood is given back to the patient after the blood loss or sooner if necessary.
Patients can request donated blood from family members or friends known to be ABO compat-ible. Most blood banks discourage this practice and generally require donation at least 7 days prior to surgery in order to process the donated blood and confirm compatibility. Studies comparing the safety of donor-directed units to that of random donor units have found either no difference, or that ran-dom units from blood banks are safer than directed units.