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2368 Part XIII: Transfusion Medicine Chapter 138: Blood Procurement and Red Cell Transfusion 2369

affect calcium levels) used to anticoagulate the donor’s blood while it is in donor evaluation and testing adds to blood safety in important ways,
the cell separator. This type of reaction is managed by slowing the blood and the medical history is important as illustrated by the 90 percent
flow rate through the instrument, which slows the rate of citrate infusion. reduction in HIV infectivity from the use of donor-selection criteria
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In leukapheresis, donors can be given glucocorticoid and/or G-CSF to identifying HIV risk behavior. Tests for transmissible diseases further
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increase the granulocyte count, and the sedimenting agent hydroxyethyl reduce the proportion of infectious donors. Donor deferral regis-
starch is used in the cell separator to improve the granulocyte yield. When tries detect individuals who previously were deferred as blood donors
G-CSF and glucocorticoids are used, approximately 60 percent of donors but who for various reasons attempt to donate again. Currently, the
experience side effects, usually myalgia, arthralgia, headache, or flu-like risk of acquiring a transfusion-transmitted disease ranges from one
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symptoms. The major side effect of hydroxyethyl starch is blood volume per 150,000/unit for hepatitis B to one per 2,135,000/unit for HIV
expansion manifested by headache and/or hypertension. (Table 138–3). Thus, although the blood supply is safer than ever, trans-
fusion is not risk free and should be undertaken only after careful consider-
LABORATORY TESTING OF DONATED ation of the patient’s clinical situation and specific blood component needs.
BLOOD RED CELL TRANSFUSIONS

Each unit of whole blood or each apheresis component undergoes a
standard battery of tests, including those for blood type, red cell anti- Red blood cell (RBC) transfusions are indicated to increase oxygen car-
bodies (including ABO, Rh, minor antigens), and transmissible diseases rying capacity in anemic patients. While oxygen extraction and deliv-
(Table 138–2). Additional tests, such as those for cytomegalovirus (CMV) ery may be measured using invasive procedures, these methods are not
antibodies, may be done. During the last few years, testing for West Nile available in most clinical settings. As a result, the decision to transfuse
virus and Trypanosoma cruzi have been added. Babesia is another trans- RBCs is often based on Hgb or Hct value(s).
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fusion transmissible disease for which a donor screening test has been Transfusing RBCs to a critically anemic patient will increase the
developed. It is not clear whether routine testing will be introduced. oxygen-carrying capacity; however, the utility of RBC transfusions in
an asymptomatic patient with a Hgb between 6 and 10 g/dL is less clear.
SAFETY OF THE BLOOD SUPPLY Most of the large, prospective, randomized controlled studies looking
at RBC usage and transfusion triggers did not specifically address the
Ironically, the improvements in blood safety have occurred at a time question of increased oxygen-carrying capacity at various Hgb/Hct
of the public’s increased fear of transfusion and the more cautious use levels. Instead they used the more practical markers of mortality, end-
of blood components by physicians. Each step in the overall process of organ dysfunction, or adverse events to determine the efficacy and safety
of restrictive (low Hgb threshold) versus liberal (higher Hgb threshold)
transfusion strategies.
TABLE 138–2. Laboratory Tests for Transmissible Agents
of Donated Blood RED BLOOD CELL TRANSFUSION THRESHOLDS
Agent Disease The Transfusion Requirements in Critical Care (TRICC) trial was the
Treponema Syphilis first adequately powered study to compare a restrictive and liberal strat-
egy for RBC transfusions in critically ill patients. A total of 838 ICU
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Hepatitis B antigen Hepatitis B
s patients were randomized into two groups: a liberal arm, which main-
Hepatitis B antibody Hepatitis B tained Hgb concentrations between 10 and 12 g/dL and gave transfu-
c
Hepatitis B virus nucleic acids Hepatitis B sions when the Hgb concentration fell below 10 g/dL; and a restrictive
arm, which maintained Hgb levels between 7 and 9 g/dL and used a
Hepatitis C antibody Hepatitis C Hgb value of 7 g/dL as the trigger for transfusion. The exclusion crite-
Hepatitis C nucleic acids Hepatitis C ria included age younger than 16 years; active blood loss at the time of
enrollment; admission after a routine cardiac procedure; chronic ane-
HIV-1 and HIV-2 antibody AIDS
mia; imminent death; and others. Thirty-day mortality from all causes
HIV nucleic acids AIDS was the primary outcome measure. Secondary outcomes included
West Nile virus nucleic acids West Nile infection 60-day mortality, death during hospitalization, and multiple-organ dys-
function (MOD). The severity of a patient’s illness was classified using
Bacteria* Sepsis
the Acute Physiology and Chronic Health Evaluation II (APACHE II)
HTLV-I antibody Leukemia scores. This and other patient characteristics were statistically similar
Lymphoma in the two study arms. This study was designed as an equivalency trial,
and overall found similar results in the two groups for 30-day mortality
Tropical paresis
(18.7 vs. 23.3 percent; p = 0.11), as well as for the secondary outcomes.
HTLV-II antibody Disease unknown Thirty-day mortality rates among patients in the restrictive transfusion
Trypanosoma cruzi † Chagas disease arm who were less acutely ill (APACHE II ≤20) (8.7 vs. 16.1 percent; p =
0.03), or were younger than 55 years old (5.7 vs. 13.0 percent; p = 0.02).
West Nile virus Viral infection
The restrictive group also received fewer transfusions (54 percent) than
CMV ‡ CMV disease the liberal group. The authors concluded that “a restrictive strategy is as
least as effective as and possibly superior to a liberal transfusion strategy
CMV, cytomegalovirus; HTLV, human T-cell lymphotropic virus. in critically ill patients.…”
*Only platelet concentrates tested. Studies conducted after the TRICC trial have used various cate-
† Only first time donors are tested. gories of high-risk patients to better define RBC transfusion thresholds
‡ Of use for immunodeficient recipients. in these populations (Table 138–4). Studies have focused on patients

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