Autotransfusion with RBC and Platelet-Rich Plasma：Intraoperative Autotransfusion（2）
3. QUALITY OF CELLS, ADVERSE EFFECTS
3.1. WASHED BLOOD
Cell separators remove Plasma from salvaged shed blood, eliminating potentially Toxic products of injured red cells and procoagulants <|[21]|>. Thus, the RBC concentrate is virtually Devoid of any particulate matter, including plasma proteins, coagulation factors and platelets (except for a small, clinically non-relevant fraction of nonfunctional cells and residual heparine) <|[10, 21]|>. Leucocytes are discharged to a varying degree, depending on the IAT device used <|[22]|>. Most of the Endogenous compounds released at the operative site and substances introduced by the surgeon are Washed out, as well as anticoagulants, antibiotics and other systemically administered drugs <|[23-25]|>. Conversely, some other endogenous Byproducts may be Concentrated (catecholamines, anaphylatoxines, leukotrienes, endotoxines) <|[25, 26]|>. Especially in orthopedic cases, wound blood frequently contains nonemulsified fat from bone marrow or subcutaneous depots which may ultimately cause venous fat embolism <|[11]|>. Devices based on discontinuous centrifugation cannot remove or filter out fat particles. Continuously processing cell separators are more effective in clearing fat and other contaminants such as inflammatory mediators <|[11, 14, 15]|>.
Excessive retransfusion of salvaged RBC and Saline may cause significant hematologic changes : Electrolyte and Acid-base balance may be disturbed by increase of sodium and chloride serum levels, and decrease of magnesium, ionized calcium, pH, pCO2, protein and albumine <|[25]|>. Extended IAT use may also cause a certain degree of hemolysis. While the consecutively augmented potassium release is counteracted by the washing process <|[11]|>, no cell separator can provide a complete clearence of Free hemoglobin, and serum levels may temporarily be elevated <|[8, 14, 15, 27]|>. Furthermore, since washed blood does not contain coagulation factors and platelets, massive RBC autotransfusion results in Dilutional coagulopathy and a Decrease of circulating platelets, requiring administration of the appropriate allogeneic components <|[6, 8, 19, 28]|>. Coagulation may further be disturbed by Prolonged hypothermia and shock, as well as by Reinfusion of residual heparin <|[1, 28]|>. Other adverse effects, such as Air embolism, Microembolism and Changes in 2,3-DPG affecting oxygen-carrying capacity of the red cells <|[8]|>, have become extremely rare if nonexistent after the arrival of electronically controlled, up-to-date cell separation devices.
3.2. UNWASHED BLOOD
Retransfusion of Unwashed autologous whole blood has been demonstrated to be safe and equieffective to Cell separation <|[16-19, 21]|>. However, the Quality of unprocessed blood is Inferior with a Higher return of lysed cellular debris, platelet microaggregates, fibrin split products, d-dimer, activated complement and free hemoglobin, indicating imbalanced coagulation due to pronounced hemostatic activation and increased hemolysis <|[Table I]|> <|[6, 19, 21, 27]|>. Especially in patients systemically anticoagulated for surgical purposes, simple IAT may not be detrimental in smaller amounts <|[6,19]|>, but larger quantities may lead to severe hemostatic disturbances with the potential of triggering Disseminated intravascular coagulation <|[6]|>. Because of this limited tolerance to unwashed wound blood, the total amount of retransfusion should clearly be restricted <|[6, 18, 21, 27]|>.
4. INDICATIONS
Intraoperative cell salvaging should be considered for all acute Emergency procedures. In severely traumatized patients with intense hemorrhage, the use of IAT may literally be life-saving due to a possibly limited supply of allogeneic blood to compensate for extreme blood loss. For practical purposes, the proper handling and processing of allogeneic blood transfusions in severe emergency situations may also pose substantial logistic challenges, thus supplemental autologous RBC supply provided by the comparatively simple IAT procedure may be extremely helpful. For these reasons, it is recommended that at least one IAT device should always be available and prepared in emergency rooms and operating units, and the attending staff must be well-trained in its proper use <|[4]|>.
In elective surgery, the routine application of IAT is controversial because of unpredictable cost-effectiveness <|[29, 30]|>. IAT has been shown to work efficiently in major orthopedic <|[9, 12, 31]|>, cardiac <|[32]|>, urologic <|[33, 34]|>, vascular <|[27]|>, intracranial <|[35]|> and gynecological <|[36]|> surgery and in emergency procedures, such as spinal trauma <|[37]|>. However, due to the wide variety of surgical, patient-related and institutional factors, it is difficult to define specific surgical procedures where IAT should always be used, and the overall blood salvage may not cover more than 25% of all perioperative blood losses <|[5, 12]|>.
<|[Table II]|> lists major surgical specialties where IAT can be successfully used and may be implemented in the perioperative blood saving strategies. As one practicable clinical guideline, the use of IAT is recommended for all major surgical procedures with anticipated blood loss of ≥ 1,000 ml <|[2, 5, 29]|>. At this level, IAT becomes cost-effective, but patients who are estimated to lose less than 1,000 ml are likely to receive little benefit yet incur substantial costs <|[29]|>. On the other hand, cost-effectiveness calculations limited to short-term perspectives do not take into account the enormous additional costs that may arise due to transmission of viral diseases or other adverse effects related to allogeneic transfusions <|[5, 38]|>.
Unfortunately, estimates of allogeneic blood requirement by preoperatively available data are very difficult and unreliable, even for planned, uncomplicated surgery <|[12, 39]|>. The anesthesiologists individual experience and knowledge of institutional circumstances (based on retrospective analyses), the type of procedure, and the patients red cell reserve, body mass and gender are yet the most helpful parameters in predicting intraoperative blood loss <|[12]|>. One rather elegant solution to this dilemma is the use of inexpensive intermediate storage bags whenever blood loss cannot be properly anticipated. Anticoagulated shed blood is put on hold, and when the amount of collected blood is sufficient to justify the use of IAT, it can be transferred to the cardiotomy reservoir and be further processed <|[4]|>. This strategy allows to save costs, while providing maximal patient safety.
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