Additional risks include transfusion-related acute lung injury, a potentially life-threatening condition with symptoms such as dyspnea, fever, and hypotension occurring within hours of transfusion (TRALI), and transfusion-associated immunomodulation (TRIM), which may cause adverse effects such a small increase in the risk of postoperative infection.

Other risks such as variant Creutzfeldt Jakob Disease (vCJD), an invariably fatal disease, remain worrisome. Blood centers worldwide have instituted criteria to reject donors who may have been exposed to vCJD. Screening for transmissible diseases and deferral policies for vCJD designed to improve safety have contributed to shrinking the donor pool. Blood shortages exist in the United States and worldwide. In many industrialized countries 5% or less of the eligible population are blood donors.

As a result, the global medical community has increasingly moved from allogeneic blood (blood collected from another person) towards autologous infusion, in which patients receive their own blood. Another impetus for autologous transfusion is the  position of Jehovah's Witnesses on blood transfusion. For religious reasons Jehovah's Witnesses  will not accept any allogeneic transfusions from a volunteer's blood donation, but may accept the use of autologous blood salvaged during surgery to restore their blood volume and homeostasis during the course of an operation when the blood is kept in a continuous circuit and connected at all times.

Bloodless options
Ways to avoid the adverse events associated with allogeneic transfusion are often grouped under the umbrella term bloodless surgery. There are several so-called bloodless options. These include minimally invasive surgical techniques; erythropoietin (a hormone that stimulates peripheral stem cells in the bone marrow to produce red blood cells);  blood substitutes such as blood volume expanders and oxygen carriers (the latter as yet unlicensed in North America); autologous blood donation, including pre-operative donation (suitable only for scheduled surgery in which transfusion is anticipated) and intraoperative autologous donation or acute normovolemic hemodilution and blood salvage. 

Intraoperative blood salvage has been used for many years, especially in cardiothoracic and vascular surgery, where blood usage has traditionally been high.

Blood salvage procedures
Several processes have been developed to assist in salvaging the patient's own whole blood in the perioperative setting. These can be categorized into three general types of salvage procedures:

1. Cell processors and salvage devices that wash and save red blood cells, i.e., "cell washers" or RBC-savers
2. Direct transfusion
3. Ultrafiltration of whole blood

Regardless of manufacturer, there are many types of cell processors. Cell processors are red cell washing devices that collect anticoagulated shed or recovered blood, wash and separate the red blood cells (RBCs) by centrifugation,  and reinfuse the RBCs. RBC washing devices can help remove byproducts in salvaged blood such as activated cytokines, anaphylatoxins, and other waste substances that may have been collected in the reservoir suctioned from the surgical field. However, they also remove viable platelets, clotting factors and other plasma proteins essential to whole blood and homeostasis. The various RBC-savers also yield RBC concentrates with different characteristics and quality.

Direct transfusion is a blood salvaging method associated with cardiopulmonary bypass (CPB) circuits or other extracorporeal circuits (ECC) that are used in surgery such as coronary artery bypass grafts (CABG), valve replacement, or surgical repair of the great vessels. Following bypass surgery the ECC circuit contains a significant volume of diluted whole blood that can be harvested in transfer bags and re-infused into patients. Residual CPB blood is fairly dilute ([Hb] = 6–9 g/dL; 60–90 g/L) and can also contain potentially harmful contaminants such as activated cytokines, anaphylatoxins, and other waste substances that have been linked to organ edema and organ dysfunction and need a diuretic to reverse.

Hemofiltration or ultrafiltration devices constitute the third major type of blood salvage appearing in operating rooms.  In general, ultrafiltration devices filter the patient's anticoagulated whole blood. The filter process removes unwanted excess non-cellular plasma water, low molecular weight solutes, platelet inhibitors and some particulate matter through hemoconcentration, including activated cytokines, anaphylatoxins, and other waste substances making concentrated whole blood available for reinfusion.

Hemofilter devices return the patient's whole blood with all the blood elements and fractions including platelets, clotting factors, and plasma proteins with a substantial Hb level. These devices do not totally remove potentially harmful contaminants that can be washed away by most RBC-savers. However, the contaminants that are potentially reduced by using RBC-savers, as shown by data from in vitro laboratory tests, are transient and reversible in vivo with hemostatic profiles returning to baselines within hours. The key is that coagulation and homeostasis are immediately improved with the return of concentrated autologous whole blood.

Over the years numerous studies have been done to compare these methods of blood salvage in terms of safety, patient outcomes, and cost effectiveness, often with equivocal or contradictory results. ^1-4

The Hemobag^®

The Hemobag^® is a new type of ultrafiltration reservoir designed to overcome the limitations of RBC-savers and direct retransfusion in cardiac, vascular, and other types of surgery through hemofiltration. The methodology of blood salvaging with the Hemobag^® in the operating room is depicted in this video.

Being a new ultrafiltration method, the Hemobag^® was not included in earlier papers and studies. Studies to date have shown the Hemobag^® to quickly and safely recover substantial proteins, clotting factors, and red cell concentrates. ^5-10