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Autologous Blood Transfusion
Despite reduction of the risk of transmitting viruses such as the human immunodeficiency virus (HIV) or hepatitis B or C (HCV),2,3 autologous blood transfusion remains safer than allogeneic blood transfusion and appropriate for properly selected patients. Exclusive or supplemental use of autologous blood can eliminate or reduce many adverse effects of transfusion. Directed donations -- blood donated by a friend or family member for a designated patient -- are not as safe as the patient's own blood and must not be considered equivalent to autologous donations.
Standards, guidelines, and regulations exist for patient selection as well as processing and transfusion of blood collected using autologous transfusion techniques. These should be used by each hospital's transfusion committee in establishing and monitoring autologous transfusion programs. The following table summarizes the proper use of autologous transfusion techniques for selected surgical procedures.
Autologous techniques are considered inappropriate for many surgical procedures because the expected blood loss is small and it is unlikely the patient will receive a transfusion. The best approach depends, in part, upon the surgical procedure planned. For example, PABD and postoperative blood salvage are appropriate for patients undergoing revisions of total hip replacement, a procedure that frequently necessitates transfusions. However, intraoperative blood loss for total knee replacement is minimal because tourniquets are used. Thus intraoperative blood salvage would not be effective.
Table: Surgical Procedure and Autologous Techniques
For surgical procedures where transfusion is likely, autologous donations can provide some or all of the blood components needed by the patient (see Table I Table: Surgical Procedure and Autologous Techniques ). Nevertheless, PABD does not completely eliminate the possibility that the patient might receive allogeneic blood. If the need for transfusion is greater than anticipated, or insufficient autologous blood has been collected, the patient may need blood from the allogeneic supply. Thus, during the discussion with the patient of the surgical risks and benefits, autologous donations cannot be presented as a guarantee against allogeneic transfusions.
The indications for PABD may be broadened and the number of units to be collected increased under unusual circumstances (e.g., patients with coagulation disorders that increase the risk of bleeding, or patients with alloantibodies for whom locating compatible blood may be difficult).
Selection of Patients
Most patients who are healthy enough to undergo elective surgery will be able to donate blood preoperatively. Determination of suitability for PABD is the responsibility of the physicians caring for the patient and the physician responsible for the blood collections. In deciding to collect autologous blood from a patient, the benefit of decreased exposure to allogeneic blood must be weighed against the risk of making the donation and of delaying surgery for the time needed for adequate regeneration of red blood cells (RBCs). Appropriate patients are those having:
Vasovagal reactions occur in about 2 to 5 percent of all blood donors--either autologous or allogeneic. Most vasovagal reactions consist of lightheadedness due to transient hypotension and bradycardia and are self-limited. Severe reactions with loss of consciousness or seizure activity are uncommon. According to information from the American Red Cross, autologous blood collections result in hospitalization of approximately 1 donor in 16,000 autologous collections per year (written communication, N. Rebecca Haley, M.D., May 1994).
Special consideration should be given to the following situations:
The decision to collect PABD should be based on a discussion between doctor and patient regarding the procedure's risks and benefits, after which the patient can be referred to a blood collection facility. Here, the patient is evaluated for eligibility of autologous donation. Patients distant from the hospital where surgery is planned often can donate at a local blood collection facility and have the blood sent to the hospital.
Many patients can give blood as frequently as every 3 days, although once a week is more common. Patients donating autologous blood may benefit from oral iron supplementation; for example, ferrous sulfate 325 mg P.O. T.I.D. or ferrous gluconate 325 mg five times a day. The optimal donation period begins 4 to 6 weeks before surgery in order for a sufficient number of units to be donated and to enable more complete RBC regeneration. In any case, the last blood donation should not be collected later than 72 hours before surgery to allow for restoration of intravascular volume. A single unit donation a few days before surgery will not be beneficial because minimal RBC regeneration will occur.
If a unit of autologous blood is confirmed to be anti-HIV or HBsAg-positive, the Food and Drug Administration (FDA) recommends that it be discarded. However, the donor may be transfused with these autologous components if permitted by the hospital and collecting facility and if appropriate documentation is provided by the patient's physician. The patient's physician should be informed if tests on a unit are positive for anti-HCV, anti-HBc, or syphilis.
Number of Units Donated between one-third and one-half of collected autologous blood components are not used by their donors.23-25 Collections in excess of transfusions are considered inevitable in order to provide sufficient blood to meet the needs of most patients,10 although this complicates the logistics and adds to the costs of an autologous blood program. However, those unused units of autologous blood have given rise to the controversy regarding the appropriate transfusion of autologous collections.
Unused autologous blood is usually destroyed rather than being added to the allogeneic blood inventory. Only a relatively small number of autologous units are suitable for transfusion to other patients because autologous donors often do not meet the health criteria required for allogeneic blood donors. Furthermore, the suitable unit, when no longer needed by the donor, often has a very short shelf life. Thus, the adding of unused autologous blood to the inventory would have little impact on the overall blood supply and should not be considered a justification for requesting autologous donations from patients who are not likely to require transfusion.
Fibrin glue: Fibrin glue mixed with thrombin is a biologic adhesive used during surgery. It is prepared from plasma or cryoprecipitate. If the use of fibrin glue is anticipated and if preoperative donation is feasible, it should be prepared from autologous rather than allogeneic blood.
Autologous platelet-rich plasma: Autologous platelet-rich plasma can be collected from patients in the operating room using apheresis equipment. For cardiac surgery patients, this plasma is removed before cardiopulmonary bypass and returned after heparin reversal. Although the procedure has been advocated as a technique to improve hemostasis and limit blood loss,other data do not support its routine use.
In general, intraoperative blood salvage is appropriate for the following surgical procedures:
Cardiac and vascular surgery: Intraoperative blood salvage is valuable in most major vascular operations and during cardiac surgery. In addition to salvaging blood lost during cardiac surgery, blood remaining in the cardiopulmonary bypass circuit should be recovered.
Orthopedic Surgery: Intraoperative blood salvage has been shown to substantially reduce the need for allogeneic transfusions in such procedures as spinal surgery39 and hip replacement.
Other surgical procedures: Intraoperative blood salvage can be used for other surgical procedures involving major blood loss, such as trauma, liver transplantation, splenectomy, and ruptured ectopic pregnancy. Concerns remain about the safety of cause disseminated intravascular coagulation (DIC); washing the salvaged bl blood salvaged during cesarean deliveries because the infusion of amniotic fluid may ood may not eliminate this risk.
Selection of Patients
Many surgical patients who undergo procedures in which transfusions are likely can benefit from intraoperative blood salvage, especially in cases where preoperative donation is impossible or inadequate.42 If the shed blood is collected by sterile methods and properly reinfused, the procedure has few risks.
Relative contraindications to the use of intraoperative blood salvage include:
Infection: No existing system of blood filtering or washing can completely eliminate bacteria. As a result, intraoperative blood salvage is not routinely used if the field is contaminated with bacteria. Contamination of salvaged blood can occur in procedures with spilled intestinal contents, bacterial peritonitis, abscesses, or osteomyelitis. Nevertheless, for patients with massive life-threatening blood loss, immediate reinfusion of blood recovered from a contaminated field may be appropriate when adequate amounts of allogeneic blood are not available. The safety of using potentially contaminated recovered blood has been evaluated in only a small number of patients. Recovered blood should not be stored since the bacteria may grow and multiply.
Cancer: Malignant cells are not completely removed from salvaged blood by washing or filtration, and there is a theoretical risk that transfusion of blood salvaged during surgery for malignancy may result in metastases. The safety of intraoperative salvage in cancer patients has not been established, although the technique has been performed in some cancer patients. The reinfusion of blood that is grossly contaminated with malignant cells should be avoided.
Blood salvaged intraoperatively may be transfused directly after collection or processed (washed) prior to infusion. Controversy exists regarding the relative merits of washed versus unwashed salvaged blood. Washed blood has the theoretical advantage of reducing infusion of free hemoglobin, tissue procoagulants, and debris. Although data regarding the safety of unwashed salvaged blood are limited, this form of autologous blood is usually infused in relatively small amounts (less than 2 L) without significant adverse effects. When collecting blood for infusion without processing, care should be taken to avoid hemolysis (due to high aspiration pressure and surface suctioning) and contamination with tissue debris. Because of the presence of debris and the high incidence of hemolysis, washing salvaged blood during orthopedic procedures is indicated.
Commercially available equipment with disposable software exist for each option:
Semiautomated systems wash the collected blood before reinfusion. The washed RBCs do not contain significant amounts of clotting factors or platelets. A trained, dedicated operator is essential to operate the equipment, even with the newer automated models.
Suction systems that collect blood for reinfusion without washing are modifications of disposable suction systems. These machines are relatively inexpensive and technically easy to set up and use.
To ensure a quality blood product for reinfusion, a well designed program and appropriately trained staff are necessary. The American Association of Blood Banks has developed guidelines and standards that are valuable in designing an effective intraoperative recovery program and maintaining quality assurance.53
Postoperative blood salvage is used most frequently for cardiac and orthopedic surgical patients.
Cardiac surgery: The reinfusion without washing of salvaged blood obtained from mediastinal drainage after cardiac surgery is widespread and appears to be safe and effective. However, reinfusion of unwashed blood may affect laboratory tests. For example, the blood may contain cardiac enzymes, such as creatine kinase, so its reinfusion may complicate the diagnosis of perioperative myocardial infarction.
Orthopedic surgery: Blood salvaged and reinfused after orthopedic surgery (e.g., hip arthroplasty and spinal fusion with instrumentation) may be safe and reduce the amount of allogeneic blood given. Others, however, have not demonstrated the same efficacy. Small amounts have been reinfused with no apparent side effects, but fever, hypotension, and upper airway edema have been reported.
Technique Blood salvaged postoperatively generally is collected from mediastinal, chest, and joint drains and transfused without washing. Because it is defibrinogenated, it does not require anticoagulation prior to transfusion. Although diluted, the blood is sterile and has viable RBCs.
Traumatic Hemothorax: Blood that collects in the thoracic cavity following blunt or penetrating trauma is analogous to blood shed following cardiac or orthopedic surgery. It is defibrinogenated and may be collected and transfused. Typically, this process is accomplished using chest drainage devices that have been adapted for blood salvage.
Reinfusion of anticoagulant: When heparin is used as the anticoagulant, infusion of unwashed blood may cause systemic anticoagulation. In some cases, this anticoagulant effect may be undesirable. However, proper cell washing virtually eliminates the heparin.
Renal insufficiency: Infusion of large quantities of unwashed blood that contain hemolyzed RBCs may contribute to renal failure, particularly in patients with already compromised renal function. Hemolysis can be reduced by decreasing aspiration pressures and avoiding surface suctioning.
Air embolism: As with all intravenous infusions, improper technique, such as applying pressure to air-containing systems, may lead to air embolism.
Mathematical analysis predicts that the efficacy of ANH increases with greater surgical blood loss, higher initial patient hematocrit, and lower post-ANH hematocrit. In addition, mathematical analysis predicts that extreme hemodilution (for example, reduction to hematocrit 0.20), may result in substantial reduction of allogeneic blood transfusions if surgical blood loss is > 50 percent of blood volume. Removal of several units of blood in patients with blood loss of < 50 percent of blood volume may have little or no effect on the requirement for allo-geneic transfusion. Randomized studies show conflicting results regarding the efficacy of ANH, perhaps due to the varying conditions of each study. Further clinical studies are needed to test the models and determine the extent of efficacy.
Table I lists examples of surgical procedures in which expected blood loss may be substantial and ANH may be appropriate, as well as examples of surgical procedures in which expected blood loss usually is not sufficient to warrant ANH.
Selection of Patients
ANH may be employed alone or in conjunction with other forms of autologous transfusion. Although PABD may be inadvisable for some patients with serious cardiac disease, withdrawing blood in the operating room under carefully controlled and monitored conditions offers an alternative for many of these patients. When PABD is undesirable or impossible (e.g., there is a potential for bacteremia or too little time for donation), ANH may be an appropriate solution. ANH can also be considered when malignancy or infection at the operative site precludes the use of intraoperative blood salvage.
Since ANH probably is efficacious only when the hematocrit is reduced to <0.30, additional caution is necessary in patients with hepatic dysfunction or cardiovascular, cerebrovascular, or pulmonary disease.
The amount of blood removed depends on the patient's blood volume and the initial and post-ANH hematocrits. The blood must be collected into properly labeled blood bags containing an anticoagulant. It may be stored at room temperature (to preserve platelet function) for up to 8 hours and up to 24 hours if appropriately refrigerated. The hematocrits of the units will vary between the initial hematocrit and the post-ANH hematocrit.
Hemodilution decreases hemoglobin concentration and oxygen-carrying capacity and content, thereby increasing the potential for critical organ ischemia to the same extent as does surgical blood loss and replacement with non-oxygen-carrying fluid. The lowest safe hemoglobin concentration in humans, with or without disease of critical organs, is not known.
ANH dilutes circulating coagulation factors, as well as RBCs; platelet count decreases to a lesser extent. If abnormal bleeding is observed, laboratory tests of coagulation should be monitored.
Blood components should be transfused only when they are needed. However, objective indications for the transfusion of blood components are difficult to establish. The decision to transfuse RBC's is ideally based on the prevention of tissue hypoxia due to an oxygen transport deficit. No specific method to measure or anticipate a clinically significant deficit exists. In awake patients, symptoms of oxygen deficiency such as headache, lightheadedness, tinnitus, and faintness are nonspecific and do not lend themselves to the avoidance of symptomatic hypoxia. If available, base excess, the oxygen extraction ratio, serum lactate, and cardiac index can be used as surrogate markers. The hemoglobin and hematocrit are easily obtained laboratory values, but are far less likely to reflect the degree of oxygen deficiency in a patient because many other factors affect oxygen transport, such as underlying cardiac or pulmonary disease, cardiac output, and hemoglobin's affinity for oxygen.
Practice guidelines have been based on hemoglobin levels, although the inadequacy of this approach is widely recognized. In general, transfusions at or below hemoglobin levels of 70 g/L (hematocrit 0.21) are appropriate, whereas transfusions at hemoglobin levels above 100 g/L (hematocrit 0.30) rarely are indicated. Between these two levels, clinical circumstances such as the potential for further blood loss and the patient's underlying condition will determine the decision to transfuse.
Should the indications for autologous blood transfusion differ from those for allogeneic blood transfusion?
The comparative indications for the use of autologous or allogeneic blood are controversial. If precise indications for a blood transfusion could be defined, autologous blood could be used only in situations where allogeneic blood would be given. On the other hand, the benefits of allogeneic and autologous RBC transfusions are similar, but the risks of autologous blood are less. Hence, the risk-benefit ratio supports the more liberal use of autologous blood.
Although some physicians may choose to use autologous blood components more liberally than allogeneic components for a given indication, autologous blood should not be transfused merely because it has been collected. For example, the transfusion of autologous RBCs to the slightly or non-anemic patient or the use of autologous fresh frozen plasma in the absence of coagulopathy is inappropriate.
In what order should autologous RBC's be transfused when a variety of autologous components are available?
When multiple autologous RBC components are available, the decision to transfuse should be based on a variety of factors, such as the component's quality, safety, efficacy, and shelf life. Table II lists the shelf life of autologous RBCs.
Table: Shelf life of autologous RBCs
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