Transfusion of blood and blood products exposes patients to risks
despite all precautions taken. Clinical judgment is required to
determine that the expected benefits of the transfusion outweigh
these risks . Adverse effects , generally referred to as transfusion
reactions , occur with approximately 3% of units of blood transfused
and vary greatly in severity . Most transfusion reactions are mild .
Death due to transfusion is rare . Estimates of the frequency of
blood transfusion-related deaths range from one in 30,000 to one in
500,000 transfusions. The majority of deaths are due to severe
intravascular hemolysis following the administration of ABO-mismatched
blood.
Careful
pre-transfusion testing will prevent some , but not all ,
transfusion reactions . Each blood donation is tested for several
transmissible diseases and red cell antibodies after collection .
Cross match or other pre-transfusion serological testing is
performed to detect antibodies in the recipient's serum that may
shorten the survival of donor red cells.
Such
tests however will not detect antibodies to white cells, platelets
or other blood constituents.
Components of blood can cause transfusion reactions by immunological
or non-immunogical mechanisms . Reactions that occur during or
within 24 hours of the infusion of blood products are called
immediate transfusion reactions. Those that occur some time after
the transfusion are called delayed transfusion reactions.
(see Table 4)
1.
IMMUNE-MEDIATED TRANSFUSION REACTIONS
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a) |
Acute
Hemolytic Transfusion Reactions:
An acute hemolytic transfusion reaction is rare ; it is usually
due to the transfusion of ABO-incompatible blood following the
improper identification of the recipient , either when the cross
match specimen is taken or when the donor blood is transfused .
Signs of acute intravascular hemolysis include fever ,
hypotension, hemoglobinuria and bleeding . A patient under
anesthesia receiving incompatible blood may have unexplained
bleeding with out other signs of a transfusion reaction. |
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An acute , immune-mediated transfusion reaction involves
activation of the complement cascade and may cause:
·
intravascular hemolysis with hemoglobinemia and hemoglobinuria
·
release of vasoactive complement
components resulting in hypotension and shock
·
thrombin and platelet activation resulting in disseminated
intravascular coagulation (DIC)
The renal failure that occurs in some patients
with an acute hemolytic transfusion reaction is caused by
glomerular deposition of immune complexes , DIC , and reduced
renal blood flow due to hypotension rather than by free
hemoglobin .The rapid intravascular destruction of transfused
red cells is a medical emergency due to the risk of renal
failure and/or acute disseminated intravascular coagulation.
THE INFUSION OF THE BLOOD COMPONENT
MUST BE DISCONTINUED AND THE INTRAVENOUS LINE MUST BE KEPT OPEN
WITH SALINE TO FACILITATE APPROPRIATE MANAGEMENT.
Treatment of intravascular hemolysis is
determined by the specific signs and symptoms.Hypotension should
be treated with fluid replacement . Vasoactive drugs are usually
not necessary. Urinary flow should be induced and maintained by
fluid replacement and diuretics . If renal failure is severe ,
dialysis may be required . If renal failure is severe , dialysis
may be required . If the patient has signs and symptoms of a
hemostatic disorder , laboratory tests can determine whether
platelets and/or appropriate coagulation factors should be
administered.
Heparin is usually not indicated because there is no further
activation of the coagulation cascade once the transfusion of
the incompatible red cells is stopped .
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