Chapter 21 Blood Therapy
Blood therapy procedures
1. What is the recipient’s blood tested for during the routine typing of blood? What is the risk of transfusing blood to patients without typing the recipient’s blood?
2. How is the crossmatching of blood accomplished?
3. How does the transfusion of O-negative packed red blood cells in an emergency situation affect the patient’s subsequent transfusions?
4. What does type-specific blood refer to? What is the chance of a significant hemolytic reaction with the transfusion of type-specific blood to a patient?
5. What does a type and screen refer to? When is a type and screen typically ordered? What is the chance of a significant hemolytic reaction with the transfusion of typed and screened blood to a patient?
6. What is contained in preservative solutions for the storage of blood? What is the benefit of adding adenine to the preservative solution?
Blood components
11. Name the components that can be derived from whole blood. What is the advantage of using components for blood therapy instead of whole blood?
12. What is the hematocrit and total volume in a unit of packed red blood cells?
13. How much will hemoglobin concentration increase with the transfusion of a single unit of packed red blood cells?
14. What is the indication for the administration of packed red blood cells?
15. What solutions may be used to reconstitute packed red blood cells for administration?
16. What potential complication associated with the administration of whole blood is less likely to occur with the administration of packed red blood cells?
17. What is the advantage of using whole blood for massive blood loss replacement?
18. What is the recommended ratio of packed red blood cells to fresh frozen plasma and platelets when transfusing for massive blood loss replacement?
19. When is the administration of platelets indicated during surgery?
20. How much will the platelet count increase after the administration of 1 unit of platelets?
21. What are some of the risks associated with the administration of platelets?
22. What is fresh frozen plasma? What is contained in fresh frozen plasma?
23. When is the administration of fresh frozen plasma indicated during surgery?
24. What is cryoprecipitate? What is contained in cryoprecipitate?
Complications of blood therapy
26. Name some potential complications of blood therapy.
27. What is the risk of the transmission of infectious diseases with the transfusion of blood?
28. What are the various types of transfusion reactions that may occur with blood therapy?
29. Why are febrile transfusion reactions thought to occur? How do febrile transfusion reactions manifest?
30. How are febrile transfusion reactions treated?
31. Why are allergic transfusion reactions thought to occur? How do allergic transfusion reactions manifest?
32. How are allergic transfusion reactions treated? How are allergic transfusion reactions distinguished from hemolytic transfusion reactions?
33. Why are hemolytic transfusion reactions thought to occur?
34. What are the clinical signs that a hemolytic transfusion reaction has occurred? Which of these are masked by anesthesia?
35. What diagnostic tool provides evidence that a hemolytic transfusion reaction has occurred?
36. What are some consequences that can follow a hemolytic transfusion reaction?
37. What is the treatment for a hemolytic transfusion reaction?
38. What is transfusion-related acute lung injury (TRALI)?
39. Describe the immunosuppression that may accompany blood transfusions.
40. What are some metabolic abnormalities that may accompany blood transfusions?
41. How much does the serum potassium level increase in patients after the transfusion of blood?
42. How do concentrations of 2,3-diphosphoglycerate change with the prolonged storage of blood? How does this affect oxygen delivery to the tissues?
43. How does the administration of citrate in blood products affect the recipient’s serum calcium concentration?
44. What is the potential risk of hypothermia with the administration of blood products?
45. What are some ways in which massive blood transfusions can result in coagulation disorders?
46. What is dilutional thrombocytopenia? What is the treatment of dilutional thrombocytopenia?
47. Which clotting factors may decrease in concentration in the patient’s blood with massive transfusions? What percent of each of these clotting factors is necessary to maintain hemostasis during surgery? How can this clotting factor deficiency be treated?
Autologous blood transfusions
48. What is the advantage of the administration of autologous blood over homologous blood for necessary blood transfusions?
49. What is an acceptable schedule for the collection of predeposited blood for autologous blood transfusion? How can anemia secondary to the donation of autologous blood be minimized?
50. What are some complications that can occur with autologous blood transfusions of predeposited blood?
51. How is the intraoperative salvage of blood for autologous blood transfusions accomplished? What are some relative contraindications to the intraoperative salvage of blood?
52. What are some complications that may accompany the intraoperative salvage of blood for autologous blood transfusions?
53. What is the hemodilution technique for autologous blood transfusions? What are some advantages of this technique?
Answers*
Blood therapy procedures
1. Routine typing of the recipient’s blood tests for the presence of A or B or both A and B antigens on the recipient’s red blood cells and for the presence of anti-A or anti-B antibodies in their serum. It also tests for the presence or absence of Rh(D) antigen on the red blood cell. The purpose of typing the recipient’s blood is to avoid the transfusion of incompatible blood to the recipient. This may occur if the patient has antibodies to A or B or to A and B in their serum and they are transfused red blood cells that have the corresponding antigen on the red blood cells. Likewise, if a recipient lacks the Rh(D) antigen, the transfusion of the Rh(D)+ blood would be incompatible. The risk of transfusing patients who have not had this typing done, or who have had it done incorrectly and the blood is incompatible, is a transfusion reaction. In this case, the transfusion would result in disastrous, rapid intravascular hemolysis. (372-373)
2. Crossmatching of blood is done to test for a serious transfusion reaction before the administration of the blood to the recipient. A crossmatch test is accomplished by incubating the recipient’s plasma with the donor’s red blood cells. There are three steps to the process, which in its entirety takes about 45 minutes to perform. The first phase is the immediate phase, in which the blood is tested for ABO compatibility at room temperature. It also tests for incompatibilities in the M, N, P, and Lewis groups. The second phase is the incubation phase, which tests for the presence of antibodies at 37° C. Albumin or a low ionic strength saline solution is added to the products of the first phase to cause the agglutination of weak or incomplete antibodies that are present. The last phase is the antiglobulin phase, in which antiglobulin is added to the products of the second phase. Incomplete antibodies in the Rh, Kell, Duffy, and Kidd systems will be detected by this step. In each phase, incompatible blood will result in agglutination during the crossmatch test. (372-373)
3. In emergency situations in which acute large blood loss requires rapid administration of blood, there may be inadequate time to perform a type-and-cross or even to wait for type-specific blood. In these situations, O-negative packed red blood cells are administered because they lack the A, B, and Rh(D) antigens. O-negative red blood cells cannot be hemolyzed by anti-A or anti-B antibodies that may be present in the patient’s blood and is therefore termed the universal donor. After the administration of 2 units of O-negative packed red blood cells, subsequent blood transfusions may have to be continued with O-negative blood. The concern is that the transfusion of blood that is the patient’s type may result in major intravascular hemolysis of donor red blood cells by increasing titers of transfused anti-A and anti-B antibodies. The risk of continued use of O-negative packed red blood cells under these conditions is minor hemolysis of donor red blood cells and hyperbilirubinemia. In most centers, however, the need for O-negative blood is rare. Subsequent transfusions with the patient’s own blood type is usually possible and preferred. (372-373)
4. Type-specific blood refers to blood that has only been typed for the A, B, and Rh antigens. Type-specific blood testing is merely the first phase, or the immediate phase, of the crossmatch. It requires only about 5 minutes to perform. The chance of a significant hemolytic reaction with the transfusion of type-specific blood to a patient is about 1 in 1000. Type-specific blood is most frequently transfused in emergent situations in which time does not allow for a formal crossmatch. (372-373)
5. A type and screen refers to a recipient’s blood that, in addition to being typed for the A, B, and Rh antigens, has been screened for the most common antibodies. A type and screen is performed by incubating the recipient’s plasma with commercially prepared type O red blood cells that contain all the antigens able to cause a hemolytic reaction. Agglutination would designate a positive antibody screen, and the recipient’s serum is further tested for identification of the antibodies responsible for the agglutination. If, however, no agglutination results, the patient is said to be antibody screen negative. In a type and screen the patient’s blood is not matched to a specific unit of donor blood. This allows for 1 unit of blood to be available for more than one patient. A type and screen is typically ordered for surgical procedures in which the risk of transfusion is remote. If the patient subsequently requires transfusion, the immediate phase of a crossmatch blood test is performed to exclude blood type incompatibilities before its administration to the patient. The chance of a significant hemolytic reaction with the transfusion of typed and screened blood to a patient is 1 in 10,000. (373)
6. Solutions used to preserve blood include phosphate, dextrose, and adenine. The addition of adenine to the preservative solution of blood allows red blood cells to resynthesize adenosine triphosphate. This allows red blood cells to continue to fuel their metabolic requirements and increases their survival time in storage. Phosphate acts as a buffer, and dextrose provides energy to the red blood cells. (373)
7. Blood can be stored for 21 to 35 days. The duration of the storage of blood is determined by the requirement that at least 70% of the red blood cells be viable for more than 24 hours after transfusion. (373)
8. Blood is stored at a temperature of 1° C to 6° C. This slows down the rate of glycolysis in red blood cells and increases their survival time in storage. (373)
Decision to transfuse
9. The decision to transfuse should be based on a combination of (1) monitoring for blood loss, (2) monitoring for inadequate perfusion and oxygenation of vital organs, and (3) monitoring for transfusion indicators, especially the hemoglobin concentration. (373)
10. The fundamental indication for the transfusion of blood is to increase the oxygen-carrying capacity of the blood. The key question is when hypovolemia exists, what type of fluid should be given? Measurement of actual blood loss and hemoglobin levels are important. Because there are no direct measures of the oxygen-carrying capacity, the hemoglobin concentration is usually the basis on which the decision to transfuse is made. Blood transfusion is almost always justified when the hemoglobin value is less than 6 g/dL and is rarely justified when the hemoglobin value is greater than 10 g/dL. Oxygen transport is maximized when the hemoglobin level is 10 g/dL, such that the transfusion of blood at hemoglobin levels above 10 g/dL may provide no further benefit to the patient. The threshold for the transfusion of blood between hemoglobin values of 6 g/dL and 10 g/dL is further modified by several factors. These include the patient’s age and medical status, the surgical procedure and the potential for ongoing losses, and the extent to which the patient’s current anemia is chronic or is due to blood loss that is acute. For example, patients with coronary artery disease and who are at risk for myocardial ischemia may benefit from keeping the hemoglobin level no less than 10 g/dL, whereas a young healthy patient may not be transfused until the hemoglobin level is 6 to 7 g/dL. The decision to transfuse blood must therefore be made on an individual basis. (373-375)
Blood components
11. Components that can be derived from whole blood include packed red blood cells, platelet concentrates, fresh frozen plasma, cryoprecipitate, albumin, plasma protein fraction, leukocyte-poor blood, factor VIII, and antibody concentrates. The advantage of using components for blood therapy instead of whole blood is that a patient’s specific deficiency can be directly corrected. It also allows for prolonged storage, the retention of unnecessary components for other patients who may need them, and the avoidance of transfusing unnecessary components that could potentially contain antigens or antibodies. (374-375)
12. In a given unit of packed red blood cells, the total volume is about 250 to 300 mL and the hematocrit is about 70% to 80%. (374)
13. A single unit of packed red blood cells will increase adult hemoglobin levels by about 1 g/dL. (374)
14. The administration of packed red blood cells is indicated for the treatment of anemia (i.e., hemoglobin <10.0 g/dL). The purpose of transfusing packed red blood cells is to augment the oxygen-carrying capacity of the blood by increasing the hemoglobin concentration. If available, whole blood may be preferred to also treat hypovolemia. (374-375)
15. Packed red blood cells can be administered either alone or reconstituted in crystalloid or colloid. Reconstitution with 50 to 100 mL of saline facilitates the administration of packed red blood cells. Crystalloid solutions that are hypotonic should not be used to reconstitute packed red blood cells. Hypotonic solutions can result in red blood cell swelling and lysis. Examples of hypotonic solutions include glucose-containing solutions and Plasmanate. The reconstitution of packed red blood cells in solutions containing calcium (e.g., lactated Ringer solution) may result in clotting. (374)
16. The potential for citrate toxicity that can result from the administration of whole blood is less likely to occur with the administration of packed red blood cells simply because there is less volume of citrate infused with each unit of packed red blood cells. (377)
17. Whole blood transfusion may be advantageous over packed red blood cell transfusion when blood losses are greater than 30% of the blood volume, or when massive, as in the case of trauma. Whole blood transfusion under these circumstances is associated with a decreased incidence of hypofibrinogenemia and possibly coagulopathies. (374-375)
18. When transfusing blood components to replace massive blood loss as in trauma, the recommended ratio is 1.5 units packed red blood cells to 1.0 unit of fresh frozen plasma, and 1.0 unit of platelets for every 6 units of packed red blood cells. (375)
19. The administration of platelets during surgery is usually indicated for platelet counts less than 50,000 cells/mm3. Both laboratory analysis and the clinical situation must be taken into consideration. For instance, in cases of surgical trauma or in cases of bleeding in the brain, eye, or airway the transfusion of platelets at a higher number may be warranted. (375)
20. The platelet count will increase by 5000 to 10,000 cells/mm3 after the administration of 1 unit of platelets to a 70-kg adult. (375)
21. Risks associated with the administration of platelets include the transmission of viral diseases and sensitization to the human leukocyte antigens present on the platelet cell membranes. Bacterial contamination is more likely than in any other blood product because they are stored at room temperature. Although the risk is small (1/5000 to 12,000), platelet-related sepsis should be considered in a patient who develops a fever a few hours after receiving platelet therapy. The proper diagnosis can be confused with transfusion-related lung therapy (TRALI). (375-376)
22. Fresh frozen plasma is the plasma portion of 1 unit of donated blood. The plasma is frozen within 6 hours of collection. All plasma proteins are contained in fresh frozen plasma. Included are all the coagulation factors except platelets. This includes factors V and VIII, which decrease in concentration during the storage of packed red blood cells. (375)
23. The administration of fresh frozen plasma is indicated during surgery when the prothrombin time and/or partial thromboplastin times are greater than 1.5 times normal and there is a clinical indication of the need to transfuse. Other indications include the need to reverse warfarin therapy or for the correction of known factor deficiencies. (375)
24. Cryoprecipitate is the plasma fraction that precipitates when fresh frozen plasma is thawed. Cryoprecipitate contains high concentrations of factor VIII, von Willebrand factor, factor XIII, fibrinogen, and fibronectin. (375-376)
25. Cryoprecipitate is useful for the treatment of factor VIII deficiency as in hemophilia A, von Willebrand factor deficiency, and fibrinogen deficiency (e.g., from fresh frozen plasma). The transfusion of cryoprecipitate should be considered when fibrinogen levels are less than 100 mg/dL. (375-376)
Complications of blood therapy
26. Complications of blood therapy include transfusion reactions, metabolic abnormalities, the transmission of infectious diseases, hypothermia, coagulation disorders, acute lung injury, and immunomodulation. (376-378)
27. Because of pre-transfusion interviews for identification of risky donors and the implementation of routine laboratory screening, as well as the use of volunteer instead of paid donors, the risk of transmission of infectious agents to recipients of blood is rare. For example, the risk of infectivity with hepatitis in 1980 was 1 in 10 transfusions, whereas now it is about 1 in 1.5 to 2.0 million transfusions. The risk of infectivity with HIV is now 1 in 1.8 million. Although the risk of transmission of these viruses is small, the potential for transmission still exists and must be discussed with the patient as part of informed consent for transfusion. (374-376, Table 24-2)
28. The types of transfusion reactions that may occur with blood therapy include febrile, allergic, and hemolytic transfusion reactions. (378)
29. Febrile transfusion reactions are thought to occur as a result of antibodies in the recipient’s serum interacting with antigens from the donor’s cells. Febrile transfusion reactions are the most frequently occurring transfusion reaction. A febrile transfusion reaction may manifest as fever, chills, headache, myalgias, nausea, and a nonproductive cough occurring after the initiation of the transfusion of blood. When a fever occurs after a transfusion has been started, a febrile transfusion reaction can be distinguished from a hemolytic transfusion reaction by evaluating the serum and the urine for hemolysis. (378)
30. Febrile transfusion reactions are treated by decreasing the rate of the infusion of blood and administering antipyretics. Persistent cases may require the termination of the blood transfusion. (378)
31. Allergic transfusion reactions are thought to occur as a result of the presence of incompatible plasma proteins in the donor blood. Allergic transfusion reactions manifest as urticaria, pruritus, and occasional facial swelling. (378)
32. The treatment of an allergic transfusion reaction is through the intravenous administration of antihistamines. There are more severe cases of allergic transfusion reactions that are anaphylactic without red blood cell destruction. Those cases are believed to be due to the transfusion of IgA to patients who are IgA deficient. In such situations the blood transfusion should be discontinued. The differentiation between allergic reactions and hemolytic reactions can be made by checking the urine and plasma for free hemoglobin. (378)
33. Hemolytic transfusion reactions are usually a result of the administration of an erroneous unit of blood to a patient. Transfused donor cells are attacked by the recipient’s antibody and complement, resulting in intravascular hemolysis. As little as 10 mL of donor blood can result in a hemolytic transfusion reaction, which can be fatal. The severity of a transfusion reaction can be proportional to the volume of transfused blood. (378)
34. Clinical signs of a hemolytic transfusion reaction include fever, chills, chest pain, hypotension, nausea, flushing, dyspnea, and hemoglobinuria. All of these are masked by anesthesia except for hemoglobinuria and hypotension. (378)
35. The diagnosis of a hemolytic transfusion reaction can be made by a direct antiglobulin test and rechecking the labeling of the blood with the blood bank. Other laboratory analysis should be performed, including plasma and urine hemoglobin and bilirubin analysis. The plasma bilirubin concentration will peak at 3 to 6 hours after starting the blood transfusion. Hemoglobinuria or hemolysis in the presence of a transfusion and suspected hemolytic transfusion reaction should be treated as one until proven otherwise. (378)
36. Hemolytic transfusion reactions can result in renal failure and disseminated intravascular coagulation. (378)
37. The first step in the treatment of a hemolytic transfusion reaction is to stop the transfusion and notify the blood bank. Subsequent treatment interventions are geared toward preventing renal failure by maintaining urine output. It is believed that renal failure occurs as a result of precipitates in the renal tubules. The urine output is recommended to be maintained at about 100 mL/hr through the administration of lactated Ringer solution and mannitol and/or furosemide as necessary. The urine may also be alkalinized with bicarbonate. Laboratory analysis should be performed, including diagnostic tests of urine and plasma hemoglobin concentrations as well as baseline coagulation studies. Finally, unused blood should be sent to the blood bank along with a sample from the patient for a repeat type and crossmatch analysis. (378)
38. Transfusion-related acute lung injury (TRALI) is acute, noncardiogenic pulmonary edema associated with dyspnea and arterial hypoxemia that occurs within 6 hours of a transfusion. TRALI is the leading cause of transfusion-related deaths in the United States. If TRALI is suspected, the transfusion should be immediately stopped, the blood bank notified, and the exudative fluid from the patient’s endotracheal tube can be evaluated for protein concentration. If platelets have been given, platelet-induced sepsis is part of the differential diagnosis. Standard supportive therapy is required. (376, Table 24-3)
39. A nonspecific immunosuppressive effect of homologous blood transfusions has been established. It appears that this effect is related to the volume of plasma transfused, because whole blood appears to have a greater immunosuppressive effect than packed red blood cells. Blood transfusions have a suggested correlation to an increased risk of the recurrence of tumor or decreased survival in cancer patients. Overall prognosis may be poorer and postoperative infections increased in patients who have received blood transfusions. Removing the white blood cells from blood and platelets, or leukoreduction, is helpful. (376)
40. Metabolic abnormalities that may accompany blood transfusions include increased levels of serum hydrogen and potassium, decreased 2,3-diphosphoglycerate levels, metabolic alkalosis, and hypocalcemia. (376-377)
41. Potassium concentrations in blood stored for 21 days may be as high as 20 to 30 mEq/L. Even after the transfusion of large volumes of blood, serum potassium levels rarely increase with the transfusion of blood. This is in part because the high concentration of potassium exists in a small volume and the total potassium content is small. Nevertheless, hyperkalemia resulting from blood transfusions is occasionally reported. In most cases it was associated with large volumes of blood rapidly infused, typically given at rates greater than 120 mL/min. (377)
42. Concentrations of 2,3-diphosphoglycerate in erythrocytes decrease with the prolonged storage of blood. Decreased concentrations of 2,3-diphosphoglycerate are associated with a shift of the oxyhemoglobin dissociation curve to the left and an increase in the affinity of hemoglobin for oxygen. This could result in a decrease in the delivery of oxygen to the tissues. This effect of a decrease in 2,3-diphosphoglycerate could be further compounded by the presence of acidosis and hypothermia. Although of concern for the effect on oxygen delivery to the tissues, there appears to be little clinical consequence of the decreased level of 2,3-diphosphoglycerate. (377)
43. The infusion of citrate preservative during the transfusion of blood can result in a metabolic alkalosis and hypocalcemia. The theory is that the metabolic alkalosis results from the metabolism of citrate in the liver to bicarbonate. Hypocalcemia can result from the binding of citrate to calcium in the intravascular space but is usually attenuated by the mobilization of calcium stores in bone. Hypocalcemia can be augmented by hypothermia, liver disease, or hyperventilation because these will all decrease the rate of metabolism of citrate to bicarbonate. Under these circumstances, the infusion of large volumes of citrate combined with the decreased metabolism of citrate can result in hypocalcemia. Indeed, serum ionized calcium has been found to begin to decrease with a rate of infusion of 1 unit of blood every 10 minutes. This syndrome rarely occurs except where the rate of blood transfusion is more rapid than 50 mL/min, with patients with hypothermia or liver disease, or neonates with immature liver function. Supplemental calcium may be needed in these cases. (377)
44. Intraoperative hypothermia can lead to intraoperative cardiac irritability, especially in the presence of arterial pH abnormalities. Postoperative hypothermia can lead to shivering and increased myocardial oxygen demand. Because blood being stored for transfusion is stored at a temperature below 6° C, the administration of stored blood to a patient can result in decreases in the patient’s body temperature. This risk can be minimized by administering the blood through warmers. It is prudent to confirm that the blood is being warmed to an appropriate temperature of 37° C to 38° C because red blood cells will hemolyze if overheated. Blood warmers are designed to make this concern not likely. (377)
45. Massive blood transfusions can result in two different coagulation disorders: a dilutional thrombocytopenia and a dilution of some of the coagulation factors necessary to clot blood. Either case may manifest clinically as continued frank bleeding without clotting in the surgical site. It may also manifest as hematuria, gingival bleeding, and spontaneous oozing from various puncture areas in both surgical and nonsurgical sites, such as sites of intravenous access. If this clinical situation is noted, disseminated intravascular coagulation and a hemolytic transfusion reaction should also be considered as a potential source for the bleeding abnormalities. (377-378)
46. Dilutional thrombocytopenia refers to the dilution of platelets from their baseline concentration to a decreased concentration by virtue of the loss of platelets during bleeding without subsequent replacement, as with the administration of crystalloid, colloid, or non–platelet-containing blood products. This occurs even with the transfusion of blood because platelet activity has decreased to about 5% of normal after just 2 days of blood storage. The risk of a dilutional thrombocytopenia is the loss of the ability of blood to clot. When platelet counts decrease to less than 75,000/mm3, a bleeding disorder is likely to occur. This level of platelets has been seen to occur after the transfusion of 10 to 15 units of non–platelet-containing blood products to previously healthy patients with previously normal platelet counts. Of note is that patients with chronically decreased platelet counts appear to tolerate thrombocytopenia better than patients with an acute decrease in platelets. The treatment of a dilutional thrombocytopenia by transfusing platelets should be instituted when a combination of clinical status and laboratory analysis confirms suspicions of a bleeding disorder secondary to insufficient platelets. (377)
47. Factors V and VIII are necessary for normal blood clotting. For normal blood clotting to occur there must be 5% to 20% of the normal amount of factor V and 30% of the normal amount of factor VIII. When these factors decrease to below these levels, abnormal blood clotting may result. This is manifest on laboratory analysis as a prolongation of the prothrombin time and/or partial thromboplastin time. The importance of factors V and VIII during the transfusion of blood arises from the decrease in concentration of these factors in stored blood. After 21 days of blood storage, the concentration of factors V and VIII is 15% and 50% of their normal values, respectively. During times of massive transfusions, a decrease in these factors may contribute to bleeding disorders. This is particularly true if the blood being transfused has little plasma volume or has been stored for long periods of time. The treatment of bleeding disorders secondary to a dilution of factors V and VIII is the administration of fresh frozen plasma, which contains all clotting factors. The decision to administer fresh frozen plasma is determined by laboratory analysis and the clinical status of the patient. The administration of fresh frozen plasma is also indicated when laboratory analysis reveals a prolongation of the prothrombin time and/or partial thromboplastin time greater than 1.5 times normal, when normal platelet counts exclude thrombocytopenia as a cause of the bleeding disorder, and when there is uncontrolled bleeding in the surgical field. (377)
Autologous blood transfusions
48. Autologous blood donation should be considered for procedures in which significant blood loss is likely to occur. An obvious advantage of the administration of autologous blood rather than homologous blood to patients requiring blood transfusions is the decreased risk of complications associated with homologous blood transfusions, including transfusion reactions and the transmission of blood-borne diseases. In addition, autologous blood donation reserves blood bank stores for other patients, thus decreasing the strain on blood bank resources. (378-379)
49. The collection of predeposited blood for autologous blood transfusion must be done in a manner that will not decrease the patient’s hemoglobin level to unacceptable levels preoperatively. Because of the risk of preoperative anemia, patients selected for autologous blood donation probably should not have significant cardiac or neurologic disease. A collection schedule that can be employed is the donation of 1 unit of blood every 4 days. This can be done for up to 3 units. The final unit of blood must be donated 72 hours or more before the surgical procedure to ensure that the patient’s plasma volume has been restored. Anemia secondary to the donation of autologous blood remains a concern. Patients scheduled to predeposit autologous blood for blood transfusions are typically prescribed ferrous sulfate. Studies have shown that the administration of erythropoietin to these patients may be beneficial as well but requires parenteral or subcutaneous administration and is expensive. (378-379)
50. A significant complication that can occur with autologous blood transfusions is the risk of clerical error leading to the erroneous blood being transfused to the patient. Blood should be checked just as meticulously whether autologous or homologous blood is being transfused. Other complications include sepsis from bacterial contamination or hypersensitivity to stabilizers. (379)
51. The intraoperative salvage of blood should be considered for surgical procedures that result in blood loss from a clean wound and will likely lead to the need to transfuse blood to the patient. Intraoperative blood salvaging is accomplished by semiautomated systems that collect, wash, and store red blood cells in a reservoir for their future administration. The hematocrit of blood prepared in this manner is 50% to 60%, and the pH is alkaline. Relative contraindications to the intraoperative salvage of blood include malignancy and the presence of blood-borne disease. Blood that has been contaminated with bowel contents should probably not be transfused. (379)
52. Complications of intraoperative blood salvaging include a dilutional coagulopathy, the reinfusion of blood treated with anticoagulants, hemolysis, air embolism, fat embolism, sepsis, and disseminated intravascular coagulation. (379)
53. Hemodilution for autologous blood transfusion should be considered for patients who are expected to lose more than 2 units of blood intraoperatively and who have an adequate preoperative hematocrit. It is probably not appropriate for patients with anemia or severe cardiac or neurologic disease. The hemodilution technique involves the removal of venous or arterial blood from the patient just before or after the induction of anesthesia and restoration of the plasma volume with crystalloid or colloid. The volume of blood that can be removed from the patient is dependent on the patient’s preoperative hematocrit, estimated blood volume, and the lowest hematocrit acceptable for that patient. The blood is stored in the operating room at room temperature in a sterile container that contains anticoagulants, and it can be transfused to the patient when it is indicated or after major blood loss has ceased. The blood does not undergo any other biochemical transformations. There are several advantages to the hemodilution method of autologous blood transfusions. This method is less expensive than autologous blood donations and does not require the patient’s cooperation or time that is required for the predepositing of autologous blood. In addition, the decreased viscosity and hematocrit of the blood result in a decrease in the concentration and number of red blood cells lost during the procedure. Finally, the blood that is transfused to the patient has platelet and coagulation factor activity that would have been lost in autologous blood that had been stored. (379)
Conclusions and future directions
54. Transfusions have become increasingly safer primarily due to the decrease in the transmission of infectious diseases. There is an increased emphasis on defining ratios of blood products that should be given (e.g., 1:1 packed red blood cells with fresh frozen plasma or platelets). Consistent with the practice of medicine overall, well-designed protocols will increasingly be the basis upon which transfusion practice is based. (379)
