Page 370 - Essential Haematology

356 / Chapter 26 Coagulation disorders

and platelets occurs as a consequence of many dis- Pathogenesis (Fig. 26.9 )
orders that release procoagulant material into the

The key event underlying DIC is increased activity
circulation or cause widespread endothelial damage
of thrombin in the circulation that overwhelms its
or platelet aggregation (Table 26.5 ). It may be asso-
normal rate of removal by natural anticoagulants.
ciated with a fulminant haemorrhagic or throm-
This can come from tissue factor (TF) release into

botic syndrome with organ dysfunction or run a less
the circulation from damaged tissues present on
severe and more chronic course. The main clinical

tumour cells or from up - regulation of TF on circu-
presentation is with bleeding but 5 – 10% of patients
lating monocytes or endothelial cells in response to
manifest thrombotic lesions (e.g. with gangrene of
pro - inflammatory cytokines (e.g. interleukin - 1,

limbs).
tumour necrosis factor, endotoxin).
Table 26.5 Causes of disseminated 1 DIC may be triggered by the entry of procoagu-

intravascular coagulation.
lant material into the circulation in the following
situations: severe trauma, amniotic fl uid embo-
Infections
lism, premature separation of the placenta, wide-
Gram - negative and meningococcal septicaemia
spread mucin - secreting adenocarcinomas, acute
Clostridium welchii septicaemia
promyelocytic leukaemia (t(15; 17)), liver disease,
Severe falciparum malaria
Viral infection – varicella, HIV, hepatitis, severe falciparum malaria, haemolytic transfu-
cytomegalovirus sion reaction and some snake bites.
2 DIC may also be initiated by widespread
Malignancy
endothelial damage and collagen exposure (e.g.
Widespread mucin - secreting adenocarcinoma
endotoxaemia, Gram - negative and meningococ-
Acute promyelocytic leukaemia
cal septicaemia, septic abortion), certain virus
Obstetric complications infections and severe burns or hypothermia.
Amniotic fl uid embolism
Premature separation of placenta In addition to its role in the deposition of fi brin
Eclampsia; retained placenta in the microcirculation, intravascular thrombin
Septic abortion formation produces large amounts of circulating
fibrin monomers which form complexes with

Hypersensitivity reactions
fibrinogen and interfere with fi brin polymerization,

Anaphylaxis
thus contributing to the coagulation defect. Intense
Incompatible blood transfusion

fibrinolysis is stimulated by thrombi on vascular
Widespread tissue damage walls and the release of split products interferes
Following surgery or trauma with fibrin polymerization, thus contributing to

After severe burns the coagulation defect. The combined action of

Vascular abnormalities thrombin and plasmin causes depletion of fi brino-
Kasabach – Merritt syndrome gen and all coagulation factors. Intravascular
Leaking prosthetic valves thrombin also causes widespread platelet aggrega-
Cardiac bypass surgery tion in the vessels. The bleeding problems which

Vascular aneurysms may be a feature of DIC are compounded by
thrombocytopenia caused by consumption of
Miscellaneous
platelets.
Liver failure
Pancreatitis
Snake and invertebrate venoms
Hypothermia Clinical f eatures
Heat stroke

These are usually dominated by bleeding, particu-
Acute hypoxia
larly from venepuncture sites or wounds (Fig.
Massive blood loss
26.10 a). There may be generalized bleeding in the