blood transfusion

TRANSFUSION

Worldwide, more than 75 million units of whole blood are estimated to be donated ‎
every year.‎
Blood Availability ‎
Blood centers must be able to supply blood in response to acute crises. Sporadic ‎
shortages of blood and blood products (e.g., packed red cells, platelet products, ‎
albumin, intravenous immunoglobulin, and clotting factor concentrates) are ‎
potentially life-threatening. ‎
Blood Replacement:‎
‎ Considerable debate surrounds the hematocrit level or hemoglobin concentration that ‎
mandates blood transfusion. According to the guidelines, red blood cells are not ‎
infused for moderate anemia in stable women.‎
For the woman acutely bleeding, we recommend rapid blood infusion if the ‎
hematocrit is less than 25 volumes percent, and similarly, if hemoglobin is less than 8 ‎
g/dL and there is imminent surgery, acute operative blood loss, acute hypoxia, ‎
vascular collapse, or other factors present.‎
Clearly, the level to which a woman is transfused depends not only on the ‎
present red cell mass, but also on the likelihood of additional blood loss.‎

Whole Blood and Blood Components: ‎
Compatible whole blood is ideal for treatment of hypovolemia from catastrophic ‎
acute hemorrhage. ‎
Whole Blood ‎
A unit of blood is collected as a donation of 450 mL ± 10% into a citrate ‎
anticoagulant that also contains phosphate and dextrose. The red cell and hemoglobin ‎
‎(Hgb) content is variable and dependent on the donor s hematocrit and the precise ‎
volume bled.‎
Whole blood is stored at 4 ± 2° C to diminish red cell utilization of adenosine ‎
triphosphate and to preserve their viability, which should be at least 70% at the end of ‎
a shelf life of 35 days. After 10 days of storage, all predonation 2,3-‎
diphosphoglycerate is lost, but up to 50% is regenerated within 8 hours after ‎
transfusion.‎
In Western countries, however, whole blood is rarely used because within a few ‎
hours or days, some coagulation factors (especially factors V and VIII) and platelets ‎
decrease in quantity or lose viability. At 4° C, platelets undergo a shape change from ‎
discoid to spherical that is irreversible after 8 hours, and their in vivo survival is ‎
reduced to 2 days.‎
It has a shelf life of 40 days, and 70 percent of the transfused red cells function for at ‎
least 24 hours following transfusion. ‎
One unit raises the hematocrit by 3 to 4 volume percent. ‎
Whole blood replaces many coagulation factors, especially fibrinogen, and its plasma ‎
expands hypovolemia from hemorrhage. ‎
Importantly, women with severe hemorrhage are resuscitated with fewer blood donor ‎
exposures than with packed red cells and components.‎
For women who are more stable and do not have massive blood loss, packed red ‎
blood cell transfusions are suitable. According to the National Institutes of Health, ‎
component therapy provides better treatment because only the specific component ‎
needed is given.‎
DILUTIONAL COAGULOPATHY.‎
‎ When blood loss is massive, replacement with crystalloid solutions and packed red ‎
blood cells usually results in a depletion of platelets and soluble clotting factors, ‎
leading to a dilutional coagulopathy that clinically is indistinguishable from ‎
disseminated intravascular coagulopathy. This impairs hemostasis and further ‎
contributes to blood loss. ‎
The most frequent coagulation defect found in women with blood loss and multiple ‎
transfusions is thrombocytopenia.‎
Because stored whole blood is deficient in factors V, VIII, XI, and platelets, and all ‎
soluble clotting factors are absent from packed red blood cells, severe hemorrhage ‎
without factor replacement may also cause hypofibrinogenemia and prolongation of ‎
the prothrombin and partial thromboplastin times. ‎
In some women, frank consumptive coagulopathy may accompany shock and confuse ‎
the distinction between dilutional and consumptive coagulopathy.‎
‎ Fortunately, in most situations encountered in obstetrics, treatment of both types of ‎
coagulopathy is the same.‎
Component replacement is rarely necessary with acute replacement of 5 to 10 ‎
units of packed red blood cells or less. ‎
When blood loss exceeds this amount, consideration should be given to evaluation of ‎
platelet count, clotting studies, and plasma fibrinogen concentration. ‎
Fortunately, in practice, the level of various clotting factors required for adequate ‎
hemostasis is quite minimal.‎
In the bleeding woman, the platelet count should be maintained above 50,000/?L ‎
with the infusion of platelet concentrates. A fibrinogen level of less than 100 mg/dL ‎
or sufficiently prolonged prothrombin or partial thromboplastin times in a woman ‎
with surgical bleeding is an indication for fresh-frozen plasma administration in doses ‎
of 10 to 15 mL/kg.‎

PACKED RED BLOOD CELLS. ‎
Red cells are provided in various formats that differ with respect to the presence of ‎
additive solutions and the extent to which white cells are removed. Solutions that ‎
contain combinations of saline, adenine, phosphate, bicarbonate, glucose, and ‎
mannitol provide better red cell viability during storage and allow up to a 42-day ‎
shelf life. ‎
Red cells should not be taken out of refrigeration until the time of the transfusion ‎
because of a risk for bacterial proliferation within the pack at room temperature. ‎
Red cells that have been out of refrigeration for 30 minutes or longer cannot be ‎
returned to stock and, if still required, should be transfused immediately. ‎
A unit of red cells should be infused over a maximum period of 4 hours.‎
Cells packed from a unit of whole blood have a hematocrit of 60 to 70 volume ‎
percent, depending on the method used for preparation and storage. A unit of packed ‎
red blood cells contains the same volume of erythrocytes as whole blood and also ‎
raises the hematocrit by 3 to 4 volume percent.‎
Indications for Red Blood Cell Transfusion ‎
If a transfusion is appropriate, a benefit should occur. ‎
Guidelines from several professional groups recommend that blood not be transfused ‎
prophylactically in patients without risk factors until the Hgb level is 6.0 to 8.0 g/dL; ‎
an Hgb threshold of 8.0 g/dL seems appropriate in surgical patients with no risk ‎
factors for ischemia, whereas a threshold of 10 to 11 g/dL can be justified for patients ‎
who are considered to be at risk: those with myocardial ischemia or infarction, heart ‎
failure, chronic lung disease, or chronic kidney disease. ‎
Packed red blood cell and crystalloid infusion are the mainstays of transfusion ‎
therapy for most cases of obstetrical hemorrhage.‎
PLATELETS. ‎
For consumptive thrombocytopenias such as disseminated intravascular coagulation ‎
‎(DIC), platelet therapy is supportive but not effective until the underlying cause is ‎
treated. ‎
Platelet Dose ‎
One unit of random donor platelets contains about 5.5 × 1010 platelets.‎
‎ However, no consensus exists for a standardized platelet dose, and clinical trials ‎
have used a broad range of platelet doses.‎
Each unit transfused should raise the platelet count by 5000/?L.‎
Platelet survival is 5 to 7 days in patients with platelet counts in the normal range, but ‎
only 1 to 2 days in patients with platelet counts of 10,000 to 20,000 cells/?L—levels ‎
at which most thrombocytopenic patients are maintained to prevent hemorrhage.‎
If single-donor platelets are not available, random donor platelet packs are used. ‎
These are prepared from individual units of whole blood by centrifugation, and then ‎
resuspended in 50 to 70 ml of plasma.‎
The donor plasma must be compatible with recipient erythrocytes.‎
Further, because some red blood cells are invariably transfused along with the ‎
platelets, only platelets from D-negative donors should be given to D-negative ‎
recipients.‎
Platelet transfusion is considered in a bleeding patient with a platelet count below ‎
‎50,000/?L. In the nonsurgical patient, bleeding is rarely encountered if the platelet ‎
count exceeds 5000 to 10,000/?L.‎

FRESH-FROZEN PLASMA. ‎
This component is prepared by separating plasma from whole blood and then ‎
freezing it.‎
Approximately 30 minutes are required for the frozen plasma to thaw. It is a source ‎
of all stable and labile clotting factors, including fibrinogen. It is often used in the ‎
acute treatment of women with consumptive or dilutional coagulopathy. Fresh frozen ‎
plasma is not appropriate for use as a volume expander in the absence of specific ‎
clotting factor deficiency. It should be considered in a bleeding woman with a ‎
fibrinogen level below 100 mg/dL or with abnormal prothrombin and partial ‎
thromboplastin times.‎

CRYOPRECIPITATE. ‎
This component is prepared from fresh-frozen plasma. Cryoprecipitate contains ‎
factor VIII: C, factor VIII: von Willebrand factor, fibrinogen factor XIII (about 200 ‎
mg), and fibronectin in less than 15 mL of the plasma from which it was derived.‎
Cryoprecipitate is an ideal source of fibrinogen if levels are dangerously low and ‎
there is oozing from surgical incisions. ‎
There is no advantage to the use of cryoprecipitate for general clotting factor ‎
replacement in the bleeding woman instead of fresh-frozen plasma. The exception to ‎
this is in states of general factor deficiency where potential volume overload is a ‎
problem, and in a few conditions involving deficiency of specific factors.‎


Typing and Crossmatching: ‎
Blood and blood components for transfusion should, in most cases, be the same blood ‎
type as the patient. Obtaining an accurate ABO/Rh grouping for a patient is the most ‎
significant serologic test performed before transfusion. ‎
When type-specific blood and components are unavailable or emergency ‎
circumstances do not allow their identification or use, type O-negative red cells ‎
should be used unless the recipient is blood group AB, in which case options include ‎
A, B, or O red cells. Group O is the only choice for group O recipients and is the ‎
alternative choice for both group A and group B.‎
Red cell antigens other than ABO and D are not routinely considered when selecting ‎
donor blood products for transfusion unless clinically significant, ‎

Complications of Blood Transfusion: ‎
Each unit of blood or any component is associated with risk of exposure to blood ‎
borne infections. However, during the past several decades, substantial advances have ‎
been achieved in blood transfusion safety. Currently, the most serious known risks ‎
are administrative error leading to ABO-incompatible blood transfusion, transfusion-‎
related acute lung injury (TRALI), and bacterial and viral transmission.‎
TRANSFUSION-ASSOCIATED ADVERSE REACTIONS
‎ ‎
‎ ‎
Risk per Unit Infused
ABO incompatible blood transfusions
‎1 in 30,000 to 60,000‎
‎ ‎
Fatalities
‎1 in 600,000‎
Delayed serologic reactions
‎1 in 1600‎
Delayed hemolytic reactions
‎1 in 6700‎
Transfusion-related acute lung injury
‎1 in 8,000‎
Graft-versus-host disease
Rare
Fluid overload
Underestimated
Febrile, nonhemolytic transfusion reactions
‎ ‎
‎ ‎
Red blood cells (non–leukocyte reduced/leukocyte ‎
reduced)‎
‎1 in 200/1 in 300‎
‎ ‎
Platelets (non–leukocyte reduced/leukocyte reduced)‎
‎1 in 5–20/1 in 25–50‎
Allergic reactions
‎1 in 30–100‎
Anaphylactic reactions
‎1 in 150,000‎
Iron overload
After 80–100 U‎
Post-transfusion purpura
Rare
Immunosuppressive effects
Unknown

HEMOLYTIC TRANSFUSION REACTION: ‎
An acute hemolytic transfusion reaction is most commonly defined as hemolysis of ‎
donor red cells within 25 hours of transfusion by preformed alloantibodies in the ‎
recipient s circulation result from the transfusion of as little as 10 to 15 mL of ABO-‎
incompatible blood. acute hemolysis characterized by disseminated intravascular ‎
coagulation, acute renal failure, and death.‎
Preventable errors, such as mislabeling of a specimen or transfusing an incorrect ‎
patient, are responsible for the majority of these reactions.‎
Signs and symptoms:‎
Signs and symptoms of a transfusion reaction include Fever, which is the most ‎
common initial manifestation, is frequently accompanied by chills, hypotension, ‎
tachycardia, dyspnea, chest or back pain, flushing, severe anxiety, and ‎
hemoglobinuria. ‎
In an unconscious or anesthetized patient, diffuse bleeding at the surgical site may be ‎
the first indication of intravascular hemolysis.‎
Immediate supportive measures include stopping the transfusion, treating ‎
hypotension and hyperkalemia, administration of crystalloid fluids, and sodium ‎
bicarbonate (250 to 500 mg intravenously over a 1- to 4-hour period), to maintain ‎
urine pH at 7.0 and by diuresis with 20% mannitol (100 mL/m2 in 30 to 60 minutes, ‎
followed by 30 mL/m2/hr for 12 hours) or furosemide (40 to 120 mg intravenously).‎
Assays for urine and plasma hemoglobin concentration and an antibody screen help ‎
confirm the diagnosis.‎
Febrile nonhemolytic transfusion reactions: ‎
Febrile nonhemolytic transfusion reactions are common and estimated to occur in ‎
‎0.5% of all red cell transfusions and up to 30% of platelet transfusions. A febrile ‎
transfusion reaction is defined as a rise in temperature of greater than 1° C, which ‎
may be accompanied by chills or rigor, or both.‎
These reactions are thought to be due to a reaction of HLA or leukocyte-specific ‎
antigens (or both) on transfused lymphocytes, granulocytes, or platelets in the donor ‎
unit with antibodies in previously alloimmunized recipients. Multiply transfused ‎
individuals and multiparous women are most likely to experience this type of ‎
transfusion reaction. Febrile nonhemolytic transfusion reactions, especially those ‎
associated with platelet transfusions, may be caused by the infusion of biologic ‎
response modifiers, such as cytokines, that have accumulated in the platelet ‎
concentrate during storage.‎
Symptoms may occur during the transfusion or not be manifested until 1 to 2 hours ‎
after its completion. The diagnosis of a febrile nonhemolytic transfusion reaction is ‎
generally made by excluding other causes of fever (e.g., bacterial contamination of ‎
blood, acute hemolytic transfusion reaction).‎
Febrile nonhemolytic transfusion reactions in susceptible populations can often be ‎
prevented by administering antipyretics before transfusion of blood components. ‎
Prestorage leukocyte reduction is recommended to prevent reactions that occur as a ‎
result of the accumulation of cytokines during storage.‎
Allergic Reactions ‎
Allergic reactions can be mild, moderate, or life-threatening in severity and are ‎
associated with the amount of plasma transfused. From 1 to 5% of all blood ‎
transfusion recipients experience mild allergic reactions.‎
Anaphylactic transfusion reactions
sometimes associated with antibodies to IgA, which are common in the population ‎
and have an incidence of approximately 1 in 700 individuals. However, the incidence ‎
of anaphylactic transfusion reactions is much lower, 1 in 20,000 to 50,000.‎
Urticarial reactions: ‎
Not well understood but are believed to be an interaction between antibodies in the ‎
recipient s plasma and plasma proteins in donor blood. There is not usually a specific ‎
identifiable antigen to which the patient is reacting.‎
Symptoms are generally mild and include localized urticaria, erythema, and itching. ‎
However, anaphylactic or anaphylactoid reactions, which can occur after the ‎
transfusion of only a few milliliters of blood or plasma, include skin flushing, nausea, ‎
abdominal cramps, vomiting, diarrhea, laryngeal edema, hypotension, shock, cardiac ‎
arrhythmia, cardiac arrest, and loss of consciousness. Fever is notably absent. In ‎
some instances there may be symptoms indicative of airway involvement, such as ‎
hoarseness, wheezing, dyspnea, and substernal pain. ‎
Management begins with discontinuation of the transfusion. Treatment is ‎
diphenhydramine (25 to 50 mg intravenously), but more severe episodes may require ‎
aggressive therapy.‎
Patients who experience recurrent allergic or urticarial reactions can be pretreated ‎
with antihistamines before transfusion. Washed red blood cells may be indicated for ‎
patients who experience repeated severe urticarial reactions.‎
Bacterial contamination:‎
‎ may be introduced into a unit of blood through skin contaminants during ‎
venipuncture or from donors with asymptomatic bacteremia. Multiplication of ‎
bacteria may occur in blood and blood components stored at refrigerated ‎
temperatures but is more likely to occur in blood components stored at room ‎
temperature.‎
Bacterial contamination of red cells is most often due to Yersinia enterocolitica, ‎
followed by Serratia liquefaciens, whereas platelets are most often contaminated with ‎
Staphylococcus and Enterobacteriaceae. The incidence of bacterial contamination of ‎
red cells has been estimated to be 1 in 60,000. The incidence of bacterial ‎
contamination of platelets was estimated to be 1 in 5000.‎
Recipients of units with low bacterial counts may have relatively mild symptoms ‎
such as fever and chills, but transfusion of units with high bacterial counts may result ‎
in severe or fatal reactions. ‎
Clinically, the patient may experience high fever, shock, hemoglobinuria, renal ‎
failure, and DIC. The blood transfusion must be stopped immediately, the patient s ‎
and any untransfused blood must be cultured, and broad-spectrum antibiotics should ‎
be started
Circulatory Overload ‎
Acute pulmonary edema, caused by the inability of the circulatory system to handle ‎
an increased fluid volume, can occur in any patient who is transfused too rapidly. ‎
Although the true frequency of this type of transfusion reaction is unknown, it is ‎
believed to be a common occurrence. Susceptible populations are primarily the very ‎
young, the elderly, and patients with a small total blood volume or cardiopulmonary ‎
disease. Treatment is the same as for heart failure ‎
Delayed Reactions ‎
A delayed hemolytic transfusion reaction generally occurs 3 to 7 days after ‎
transfusion of the implicated unit. ‎
Hemolysis is usually extravascular, and red cells are destroyed in the recipient s ‎
circulation by antibody produced as a result of an immune response induced by the ‎
transfusion. These reactions are most commonly due to an anamnestic response ‎
‎(secondary exposure to a red cell antigen). Red cell destruction does occur between 3 ‎
days and 2 weeks after the transfusion. Patients are generally asymptomatic, and ‎
hemolysis may be noted only by a more rapid decline than usual in the patient s Hgb ‎
or absence of the expected rise in Hgb. ‎
Fever, the most common initial symptom, may occasionally be noted, along with ‎
jaundice; renal failure is rare. Prednisone (1 to 2 mg/kg/day) is indicated for more ‎
severe reactions.‎

TRANSFUSION-RELATED ACUTE LUNG INJ URY. ‎
TRALI is a life-threatening complication characterized by an acute respiratory ‎
distress syndrome that occurs within 4 hours after transfusion which is characterized ‎
by dyspnea and hypoxia secondary to non cardiogenic pulmonary edema. Although ‎
the actual incidence is almost certainly underreported, the estimated frequency is ‎
approximately 1 in 8000 transfusions Although the pathogenesis of TRALI is ‎
incompletely understood, the mechanisms of injury to (the pulmonary capillaries ‎
endothelium of the recipient, particularly in patients who receive massive ‎
transfusions) appear to involve lipid products from stored components as well as ‎
leukocyte reactions. therapy is supportive, and 90% of patients recover ‎
VIRAL TRANSMISSION.‎
‎ Fortunately, the most feared infection — human immunodeficiency virus (HIV) — is ‎
the least common. With current screening methods using nucleic acid amplification ‎
testing, the time period between infection and the first appearance of viral RNA is 11 ‎
days for HIV and 8 to 10 days for hepatitis C. ‎
As a result, the risk of HIV infection in screened blood is currently estimated to be 1 ‎
in 1.5 to 2 million units transfused.‎
Similarly, the risk of hepatitis C infection is about 1 in 2 million units transfused.‎
The risk of hepatitis B transmission is higher, although it is estimated currently to be ‎
less than 1 per 100,000 units transfused. ‎
The risk of transmitting other infectious diseases with transfusion, such as malaria ‎
and cytomegalovirus, is estimated to be less than 1 in 1 million.‎