Page 2025 - Hematology_ Basic Principles and Practice ( PDFDrive )

1796 Part XI Transfusion Medicine

ranitidine, respectively. Corticosteroids, provided in advance of a
Management and Prevention of Allergic Transfusion Reaction
transfusion, also may be useful in patients with serious recurrent
A 34-year-old man with thrombotic thrombocytopenic purpura has reactions.
been receiving daily 60 mg prednisone and daily plasmapheresis for Most anaphylactic transfusion reactions are idiopathic. Case
8 days without complication. Halfway through the ninth procedure, the reports describe moderate or severe anaphylactic reactions in patients
patient rapidly develops severe angioedema of the face and tongue, who are severely IgA deficient (<0.05 mg/dL) and have anti-IgA
stridor, wheezing, and diffuse flushing and urticaria. Tachycardia antibodies. The generalizability of this mechanism is low. Most cases
develops with stable blood pressure. A code is called and the patient of fatal anaphylaxis are not related to IgA deficiency, and most
is administered oxygen, 0.5 mg epinephrine intramuscularly, albuterol severely IgA-deficient people tolerate transfusions well. Thus, patients
nebulizer, diphenhydramine, ranitidine, and methylprednisolone. with incidental IgA deficiency may receive routine blood components,
Symptoms resolve over the next 12 hours without the need for esca- and IgA/anti-IgA testing should be reserved for patients with anaphy-
lated respiratory support. The patient receives another 3 weeks of
plasma exchanges with two sporadic minor allergic reactions (focal lactic reactions. Quantitative haptoglobin can also be considered as
urticaria and pruritus only). a screening test, as rare cases of haptoglobin deficiency are associated
Among chronically transfused patients, most will have none or only with anaphylactic reactions.
one allergic transfusion reaction. Even among the minority of patients
with recurrent reactions, most transfusions will not result in another
reaction, including anaphylactic reactions. Most cases of anaphylaxis HYPOTENSIVE TRANSFUSION REACTION
are idiosyncratic to a specific unit and do not recur, as in this case.
Nevertheless, when platelet and red blood cell components are sub- A less recognized, but severe acute transfusion reaction is isolated
sequently needed, plasma reduction is prudent because anaphylaxis hypotension during or immediately following a blood product infu-
can recur in a minority of patients. Screening for IgA deficiency can
identify the rare cases of anaphylactic reactions caused by severe defi- sion. For adults, the definition includes a drop in systolic blood
ciency. Severe haptoglobin deficiency can occur in Asian populations. pressure greater than 30 mmHg to below 80 mmHg, and it is most
Nevertheless, even among fatal anaphylactic reactions, IgA deficiency likely when hypotension occurs within minutes of the start of the
is not present in most cases. transfusion and resolves quickly after the transfusion is stopped. This
The medications used in the previous case are effective at treating type of transfusion reaction was initially reported after transfusion of
allergic reactions, but not preventing them, according to randomized platelets administered through some types of bedside leukoreduction
controlled trial and observational evidence. Because most transfusions filters. Later it was also reported in other types of blood products
do not result in an allergic transfusion reaction, clinicians sometimes including plasma and RBCs. The pathogenesis of this syndrome
have the confounded belief that adding premedications after a reaction appears to be related to the activation of the contact pathway (prekal-
prevented subsequent reactions, when no additional reaction was to
occur, anyway. Histamine H1 and H2 receptor blockers are readily likrein converting to kallikrein) induced in plasma by the negatively
accessible in nearly all transfusion settings and can readily be admin- charged surface of some leukoreduction filters. Kallikrein activation
istered if allergic symptoms develop. Patients often do not like the stimulates the conversion of high-molecular-weight kininogen to
wide array of side effects associated with premedication, particularly bradykinin. Notably these reactions have also been reported in cases
diphenhydramine. As in the earlier case, the small subset of patients where leukoreduction filters were used before storage, indicating that
with severe or highly recurrent reactions, premedication is reasonable bradykinin generation may occur via pathways other than via bedside
to consider on subsequent transfusions to mitigate symptoms that are filtration. The syndrome is often more severe in patients already
more likely to occur than with unselected patients. taking angiotensin-converting enzyme (ACE) inhibitors. ACE is
identical to kininase II, which is responsible for degrading bradykinin.
Blockage of the kininase II degradation of bradykinin by ACE inhibi-
activating factor, a potent arachidonic acid derivative that mediates tors results in a prolonged bradykinin half-life and a reaction that can
anaphylactic shock, is produced rapidly, along with a variety of other be very severe. Two surgical settings that may pose increased risk of
eicosanoids, for example, leukotrienes. hypotensive reactions include (1) procedures involving the prostate,
Over 90% of allergic transfusion reactions occur during infusion. because another kallikrein gene family member, hK2, can generate
When allergic symptoms develop, transfusion should be stopped and bradykinin, and (2) cardiac bypass surgery because the pulmonary
the patient given 25–50 mg of diphenhydramine. The transfusion vasculature is an important site for kinin metabolism.
may resume, but only if the symptoms resolve and the patient feels
well. A mild allergic reaction (urticaria and pruritus) during a blood
transfusion usually does not progress to a more severe anaphylactic INFECTIOUS COMPLICATIONS OF TRANSFUSION
reaction after infusion of additional blood from the same unit. The
severity of allergic transfusion reactions is not directly related to Transfusion-transmitted diseases are discussed in detail in Chapter
volume infused or infusion rate. 120. A focus on the clinical presentation of acute reactions is pre-
Most patients never experience an allergic transfusion reaction, sented here.
and for those who have one, it is usually isolated. Even among the Bacterial contamination of stored blood can pose grave risks to
minority of patients with recurrent reactions, most transfusions are the recipient. Bacteria can enter the blood collection bag during
tolerated well. Patients who have had more than one mild allergic venipuncture as a result of inadequate skin preparation, during
reaction may continue to receive routine units. Washed RBCs or component preparation, or through the collection of blood from a
plasma-reduced platelets can be used to prevent severe, recurrent donor with an occult infection or asymptomatic bacteremia. Platelet
reactions; however, washing cellular products compromises compo- concentrates, stored at room temperature, have the highest risk of
nent quality. Washing RBCs leads to accelerated in vitro hemolysis. bacterial contamination. Many reports describe fatal septic transfu-
Washing platelets increases platelet activation and lowers posttransfu- sion reactions caused by platelet components containing a variety of
sion platelet count increments. Platelets collected in platelet additive species, including Pseudomonas, Salmonella, and Staphylococcus. Bac-
solution and pooled, solvent detergent plasma are relatively new teria that grow well at refrigerated blood bank temperatures (1°C to
products that have been shown to reduce the incidence of allergic 6°C), including Pseudomonas, Yersinia, Enterobacter, and Flavobacte-
transfusion reactions. Leukocyte depletion or microaggregate filters rium, are organisms commonly associated with a contaminated unit
are of no value. of RBCs. Units of blood that are contaminated need not be obviously
There is no evidence that antihistamine premedication prevents discolored, malodorous, or clotted; it is extremely difficult to deter-
allergic transfusion reactions, although antihistamines do mitigate mine by simple visual inspection whether a unit is contaminated.
symptoms when they occur. Studies in healthy volunteers support a Patients who receive a unit of contaminated blood may develop
synergistic role for treating histamine-mediated reactions with both fever, rigors, skin flushing, abdominal cramps, myalgias, DIC, renal
H1 and H2 receptor antagonists, for example, diphenhydramine and failure, hypotension, and cardiac arrest. These reactions may be