Page 356 - Textbook of Pathology, 6th Edition

340 Extravascular haemolysis is more often due to immune even if a small volume (10-40 ml) makes its way into the
antibodies of the Rh system. The clinical manifestations are circulation, whereas a healthy individual is at lesser risk.
relatively less severe and usually consist of malaise and fever 5. Thrombophlebitis. The complication of thrombophlebitis
but shock and renal failure may rarely occur. Some patients is more commonly associated with venesection for blood
develop delayed reactions in which the patient develops transfusion, especially if it is done in the saphenous vein of
anaemia due to destruction of red cells in the RE system about the ankle rather than the veins of the arm. The risk of
a week after transfusion. Such delayed reactions are generally developing thrombophlebitis is further enhanced if the
the result of previous transfusion or pregnancy (anamnestic transfusion is continued longer than 12 hours at a single site.
reaction).
6. Transfusion haemosiderosis. Post-transfusion iron
2. Transfusion-related acute lung injury (TRALI). This is overload with deposition of iron in the tissues of the body
an uncommon reaction resulting from transfusion of donor occurs after repeated transfusions in the absence of any blood
plasma containing high levels of anti-HLA antibodies which loss e.g. in thalassaemia major and in severe chronic
bind to leucocytes of recipient. These leucocytes then refractory anaemias. The body has no other means of getting
aggregate in pulmonary micromutation and release rid of extra iron except iron excretion at the rate of 1 mg per
mediators of increased vascular permeability resulting in day. A unit of whole blood (400 ml) contains about 250 mg
acute pulmonary oedema and signs and symptoms of of iron. After approximately 100 units, the liver, myocardium
respiratory failure. and endocrine glands are all damaged.
3. Other allergic reactions. Besides haemolytic transfusion
reaction, others reactions are as follows: BLOOD COMPONENTS
SECTION II
i) Febrile reaction which is usually attributed to immunologic Blood from donors is collected as whole blood in a suitable
reaction against white blood cells, platelets, or IgA class anticoagulant. Nowadays it is a common practice to divide
immunoglobulins. whole blood into components which include: packed RBCs,
ii) Patients with antibodies against IgA molecule sometimes platelets, fresh-frozen plasma (FFP) and cryoprecipitate.
develop anaphylactic shock on transfusion of blood from other The procedure consists of initial centrifugation at low
human subjects. speed to separate whole blood into two parts: packed RBCs
iii) Allergic reactions such as urticaria may occur. and platelet-rich plasma (PRP). Subsequently, PRP is
iv) Transfusion-related graft-versus-host disease mediated by centrifuged at high speed to yield two parts: random donor
donor T lymphocytes may occur. platelets and FFP. Cryoprecipitates are obtained by thawing of
FFP followed by centrifugation. Apheresis is the technique of
II. NONIMMUNE TRANSFUSION REACTIONS. This direct collection of large excess of platelets from a single
category includes the following adverse effects: donor.
1. Circulatory overload. Circulatory overload resulting in Applications of these blood components in clinical use
pulmonary congestion and acute heart failure is the most are as under:
important and most common complication that may result 1. Packed RBCs. These are used to raise the oxygen-carrying
in death following transfusion. The risk of circulatory capacity of blood and are used in normovolaemic patients
overload is particularly high in patients with chronic of anaemia without cardiac disease. One unit of packed RBCs
anaemia, and in infants and the elderly. The onset may be may raise haemoglobin by 1 g/dl.
immediate, or may be delayed up to 24 hours.
2. Platelets. Transfusion of platelets is done in patients of
2. Massive transfusion. When the volume of stored blood thrombocytopenia who have haemorrhage. Optimally,
transfused to bleeding patients exceeds their normal blood platelet transfusions can be given to a patient with platelet
Haematology and Lymphoreticular Tissues
volume, it results in dilutional thrombocytopenia and count below 10,000/μl. Each unit of platelets can raise platelet
dilution of coagulation factors.
count by 5,000 to 10,000/μl.
3. Transmission of infection. Many diseases can be
transmitted by transfusion of an infected blood. These 3. Fresh frozen plasma. FFP contains plasma proteins and
include: hepatitis (HBV, HCV), CMV infection, syphilis, coagulation factors that include albumin, protein C and S
malaria, toxoplasmosis, infectious mononucleosis, brucellosis and antithrombin. FFP transfusion in indicated in patients
and AIDS (HIV infection). The incidence increases in patients of coagulation failure and TTP. Each unit of FFP raises
who receive multiple transfusions such as cases of coagulation factors by about 2%.
haemophilia, thalassaemia major, acute leukaemias, acute 4. Cryoprecipitate. Cryoprecipitate is a source of insoluble
severe haemorrhage etc. It has, therefore, been mandatory plasma proteins, fibrinogen, factor VIII and vWF. Indications
that prior to any human transfusion, every unit of blood must for transfusion of cryoprecipitate are for patients requiring
be screened for the serologic testing of HIV, HBV, HCV and fibrinogen, factor VIII and vWF. Transfusion of single unit
syphilis and for the presence of malarial parasite. of cryoprecipitate yields about 80 IU of factor VIII.
4. Air embolism. Air embolism is unlikely to occur if the
blood transfusion is carried out with plastic bags with HAEMOLYTIC DISEASE OF NEWBORN
negative pressure as is the usual practice nowadays. A Haemolytic disease of the newborn (HDN) results from the
debilitated person may develop symptomatic air embolism passage of IgG antibodies from the maternal circulation