Applied Science
Describe the major components of whole blood available for transfusion.
Components of whole blood that are used in transfusions include packed red blood cells (PRBCs), fresh frozen plasma (FFP), platelets, and cryoprecipitate.
One unit of PRBCs can potentially replace up to 500 mL of blood in a patient. In a 70-kg adult, 1 unit of PRBCs transfused can be expected to increase hemoglobin by 1 g/dL.
FFP is used to replace coagulation factors. Response is monitored with activated partial thromboplastin time and prothrombin time.
Cryoprecipitate is a centrifuged product of plasma that contains concentrated amounts of factor VIII:C, factor XIII, von Willebrand factor, fibronectin and fibrinogen.
Describe the appropriate compatibility tests ordered prior to blood transfusion.
Type-and-screen identifies the patient"s ABO-Rh type and screens for common antibodies in the patient"s serum.
Crossmatch combines the donor blood with the patient"s serum to assess for agglutination and ensures safe transfusion with reduced risk of hemolytic reaction.
Both type-and-screen and crossmatch orders are required in hospital transfusion protocols prior to transfusion of blood products in nonemergent settings.
Demographic/Epidemiologic Considerations
Understand that surgical and critically ill patients, some of whom have anemia (thiếu máu), require more blood transfusions than healthy ones.
In hospital settings, studies have shown that about 5% to 69% of red blood cell (RBC) transfusions occur in surgical patients.
The study of anemia and blood transfusion in the critically ill, or the CRIT study, documented that 44% of all critically ill patients receive at least one blood transfusion during their intensive care unit (ICU) stay.
The pathophysiology-sinh lý bệnh of chronic anemia in critically-nặng ill patients involves several processes.
Inflammation and increased cytokines lead to decreased-giảm erythropoietin and availability of iron.
Hepcidin, produced by the liver in response to interleukin-6, inhibits intestinal iron absorption-hấp thu and release-giải phóng from macrophage storages.
More frequent phlebotomies lead to blood loss. Occult mucosal blood loss may occur.
Indications
Understand the indications for transfusion of blood products.
The Transfusion Requirements in Critical Care (TRICC) trial recommends a restrictive transfusion strategy: to transfuse RBCs for hemoglobin less than 7 g/dL and to maintain-duy trì hemoglobin between 7 and 9 g/dL.
For more information about the transfusion of various blood products, see the following tables (from Surgery: Basic Science and Clinical Evidence, 2nd ed.):
RBCs (Table 9.2)
Plasma (Table 9.3)
Platelets (Table 9.4)
Cryoprecipitate (Table 9.5)
Key Decision Making/Prevention
Be able to identify and manage patients with acute or delayed transfusion reactions.
Patients should be transfused slowly and monitored-theo dõi very closely during the first 4 hours. It may be necessary to stop the transfusion immediately.
Assess and maintain airway, breathing, and circulation.
Initiate-bắt đầu intravenous fluids, and monitor for hypotension and shock.
Depending-tùy thuộc on the severity of the clinical picture, it may be necessary to administer antihistamines for allergic-dị ứng reaction, antipyretics-thuốc hạ sốt for fever, corticosteroids or epinephrine for anaphylaxis-phản vệ, and diuretics-lợi tiểu to maintain urine output.
Send a fresh urine sample, remaining blood units, and two new blood samples from the opposite vein (coagulated and anticoagulated) for investigation. Collect 24-hour urine for evidence of hemolysis.
For more information, see the following tables (from Surgery: Basic Science and Clinical Evidence, 2nd ed.):
Mild and moderate blood transfusion reactions (Table 9.7)
Life-threatening reactions (Table 9.8)
Investigation of acute transfusion reactions (Table 9.9)
Recognize patients with active hemorrhage and be able to manage-kiểm soát this condition with a massive transfusion protocol (MTP).
MTP is used for a patient with ongoing hemorrhage, typically-điển hình from trauma or gastrointestinal bleeding, who requires fluid resuscitation-hồi sức.
It uses an RBC:platelet:plasma ratio of 1:1:1 to more closely represent whole blood.
This method of transfusion has been shown to decrease mortality-tỷ lệ tử vong in the trauma setting when performed within the first 6 hours.
MTP decreases complications seen with the transfusion of RBCs alone such as dilutional-do pha loãng coagulopathy-rối loạn đông máu, and it mitigates the subsequent "lethal triad" of coagulopathy, acidosis, and hypothermia-hạ thân nhiệt.
To prevent coagulation, blood products are stored-bảo quản with citrate. In patients who undergo large-volume blood product resuscitation, citrate binds-liên kết with ionized calcium, resulting in hypocalcemia.
Long-term Considerations/Risks/Complications
Describe the potential-tiềm ẩn risks and complications regarding-liên quan the transfusion of blood products, and be able to counsel-tư vấn patients about these risks.
Febrile-sốt and allergic reactions are the most common negative responses to blood transfusions. They are caused by antibodies against the donor"s-của người hiến tặng white blood cells and serum proteins, respectively. Allergic reactions may present with pruritus-ngứa, pain at the infusing intravenous site, and urticaria-nổi mề đay.
Hemolytic-tán huyết reactions caused by antibodies against the donor"s RBCs, most commonly caused by human/laboratory error, may also occur. These can be severe and can lead to hypotension, hemodynamic-huyết động collapse-suy giảm, coagulopathy, acute renal failure, and death.
Anaphylaxis can occur-xảy ra in patients who have immunoglobulin A deficiency-thiếu and results in angioedema-phù mạch, hives-nổi mề đay, wheezing-thở khò khè, and hypotension.
Infectious-truyền nhiễm diseases (eg, cytomegalovirus, hepatitis B, hepatitis C, HIV) are rare but may still take place after implementation of blood sample screening and testing. For more information, see Figure 9.5 from Surgery: Basic Science of Clinical Evidence, 2nd ed.
Bacterial infections can occur from contamination of blood products.
Transfusion-related acute lung injury can lead to hypoxia-thiếu oxy, need for mechanical ventilation-thở máy, and acute respiratory distress syndrome-ARDS.
Outcome Metrics/Quality Considerations
Discuss restrictive transfusion strategies, according to the TRICC trial, in the setting of critical care or sepsis in hemodynamically stable and normovolemic patients.
Reserving RBC transfusions to maintain a hemoglobin between 7 and 9 g/dL is associated with lower mortality rates when compared with more liberal transfusion strategies.
Restrictive transfusions are superior to liberal transfusions in decreasing mortality in critically ill patients (with the exception of those with myocardial ischemia or unstable angina), and these patients experience fewer complications.
Increased transfusions in chronic critically ill patients lead to increased numbers of hospital stays, ICU admissions, deaths, and other complications.