Page 374 - Essential Haematology

360 / Chapter 26 Coagulation disorders

thrombophilia, an association with recurrent mis- Thromboelastography: n ear -
carriage (see Chapter 27 ). p atient t esting

Thromboelastography (TEG) is a technique for
Massive t ransfusion s yndrome
a global assessment of haemostatic function of
Many factors may contribute to a bleeding disorder a single blood sample in which the reaction of
following massive transfusion. Blood loss results in platelets with the protein coagulation cascade is
reduced levels of platelets, coagulation factors and observed from the time of the initial platelet fi brin
inhibitors. Further dilution of these factors occurs interaction through platelet aggregation, clot

during replacement with red cells. strengthening and fibrin cross - linkage to eventual
clot lysis. It is suited as a monitor of haemostasis in
Management surgery (e.g. of the liver or heart) associated with
Platelet concentrates are given to maintain a platelet haemostatic defects. Freshly drawn blood is placed
9
9
count > 50 × 10 /L or 80 – 100 × 10 /L in cerebral in a cuvette which is oscillated, the motion being
injury or after trauma. The PT and APTT should transferred to a pin which transmits defl ection as

be kept to less than 1.5 times normal with torsion to a photoelectric detector with computer-

fresh frozen plasma given initially at 15 mL/kg. ized data capture. As fibrin strands form, the fi brin
Cryoprecipitate is given to keep fibrinogen at least clot affects movement of the pin. The normal trace

1 g/L. Recombinant VIIa (RCT) is used in patients shows the rate of initial fibrin formation, the time

with massive blood loss after trauma or surgery to to formation of a clot (coagulation time), strength
reduce haemorrhage but remains off label ’ as RCT of the fibrin clot, clot lysis index or retraction.
‘

in such situations has failed to unambiguously Typical patterns showing results in fi brinolysis,

prove benefit and there is a significant rise of throm- hypercoagulability, haemophilia and thrombocyto-
bosis in such patients. penia are shown in Fig. 26.11 .

Th e results of haemostasis screening tests in The PFA - 100 may also be useful in testing plate-
acquired bleeding disorders are shown in Table 26.6 let function before and during surgery (see p. 343 )
and a summary of the indications for use of fresh but it is not suitable to use as a stand alone screening
frozen plasma in Table 26.7 . test for primary haemostatic disorders.
SUMMARY ■ Coagulation disorders may be inherited or ■ Treatment is with recombinant or

techniques, the gene being carried on the
acquired.

X chromosome.

■ Haemophilia A is the most common

concentrates of factor VIII, or with drugs
inherited defi ciency of a clotting factor. It is

severe if factor VIII activity in plasma is
(e.g. DDAVP (desmopressin)).
< 1% of normal. It presents with excess

■ Factor IX defi ciency has a similar pattern

of inheritance and clinical manifestations.
bruising or prolonged bleeding after

trauma and spontaneous bleeding, usually

frequent inherited bleeding disorder.
into muscles and joints, which can result in ■ Von Willebrand disease (VWD) is the most
joint deformity. Haemorrhage occurs from mucous

■ Many older patients are infected with membranes, skin cuts and post - trauma. It

hepatitis C or HIV as a result of receiving usually has a dominant inheritance. Platelet
contaminated blood products. function is abnormal and VWF levels
■ The APTT is prolonged and PT normal. usually low.

■ Antenatal diagnosis is usually carried out ■ Acquired coagulation disorders include

by polymerase chain reaction (PCR) those caused by vitamin K defi ciency (e.g.