Page 424 - Essential Haematology

410 / Chapter 29 Blood transfusion

circulatory overload. Iron chelation therapy, to multiple antibodies for whom it is diffi cult to iden-
avoid iron overload, should be considered with tify matching donor blood.
patients on a regular transfusion programme (see
Chapter 4 ).
Granulocyte c oncentrates
Erythropoietin is widely used to reduce transfu-

sion requirements (e.g. in patients with renal failure, These are prepared as buffy coats or on blood cell

on dialysis, cancer patients and myelodysplasia). separators from normal healthy donors or from
Factor VIIa can reduce transfusion need in patients patients with chronic myeloid leukaemia. Th ey have
with major haemorrhage (e.g. at surgery or after been used in patients with severe neutropenia
9
trauma). ( < 0.5 × 10 /L) who are not responding to antibi-
Red cell substitutes are under development but otic therapy but it is not usually possible to give
have not yet proven clinically valuable. Th ese syn- suffi cient amounts. They may transmit CMV infec-

thetic oxygen - carrying substitutes are often fl uori- tion and must be irradiated to eliminate the risk of
nated hydrocarbons and stromal - free pyridoxylated causing GVHD.
and polymerized haemoglobin solutions.

Platelet c oncentrates
Autologous d onation and t ransfusion
These are harvested by cell separators or from indi-

Anxiety over HIV and other infections has vidual donor units of blood (Fig. 29.7 b). Th ey are
increased the demand for autotransfusion. Th ere are stored at room temperature. Platelet transfusion is
three ways of administering an autologous used in patients who are thrombocytopenic or have
transfusion: disordered platelet function and who are actively
bleeding (therapeutic use) or are at serious risk of

1 Predeposit Blood is taken from the potential
bleeding (prophylactic use).
recipient in the weeks immediately prior to elec-
For prophylaxis, the platelet count should be
tive surgery. 9
kept above 5 – 10 × 10 /L unless there are additional
2 Haemodilution Blood is removed immediately
risk factors such as sepsis, drug use or coagulation
prior to surgery once the patient has been anaes-
disorders for which the threshold should be higher.
thetized and then reinfused at the end of the
For invasive procedures (e.g. liver biopsy or lumbar
operation.
puncture) the platelet count should be raised to

3 Salvage Blood lost during the operation is col- 9
above 50 × 10 /L. For brain or eye surgery the
lected during heavy blood loss and then 9
count should be > 100 × 10 /L.
reinfused.

Therapeutic use is indicated in bleeding associ-
Autotransfusion is the safest form of transfu- ated with platelet disorders. In massive haemor-
9
sion with regard to transmission of viral disease rhage the count should be kept above 50 × 10 /L.

though it has a higher risk of bacterial contamina- Platelet transfusions should be avoided in
tion and of clerical errors. For predeposit, the indi- autoimmune thrombocytopenic purpura unless

vidual must be fit enough to donate blood and the there is serious haemorrhage. They are contraindi-

predicted operative replacement transfusion should cated in heparin - induced thrombocytopenia,
be 2 – 4 units. Larger replacement transfusions thrombotic thrombocytopenic purpura and haemo-

would require blood to be collected over a longer lytic uraemic syndrome (see p. 337 ).
period and red cells stored in the frozen state, Refractoriness to platelet transfusions is defi ned
which is even more labour intensive and expensive. by a poor platelet increment post - transfusion
9
9

The high cost and initial restriction of its use to ( < 7.5 × 10 /L at 1 hour or < 4.5 × 10 /L at 24

patients undergoing elective surgery means that it hours). The causes are either immunological (mostly
can benefit only a minor proportion of the total HLA alloimmunization) or non - immunological

number of blood recipients. Preoperative autotrans- (sepsis, hypersplenism, DIC, drugs). Platelets
fusion is largely reserved for those patients with express HLA class I (but not class II) antigens and