127 Disseminated Intravascular Coagulation Flashcards
The organs most frequently involved by diffuse microthrombi
Lungs and kidneys
Followed by the brain, heart, liver, spleen, adrenal glands, pancreas, and gut
The most important mediators responsible for the imbalance in DIC
Cytokines
The most important interface in which the interaction between inflammation and coagulation takes place
Endothelium of the capillary bed
Constitutes a sine qua non for most patients with DIC
Endothelial perturbation
Plays a central role in the initiation of inflammation-induced coagulation in DIC
Tissue factor (TF)
TF becomes exposed to blood upon disruption of the vascular integrity, or when cells present in the circulation, such as monocytes, are triggered to express TF.
The in vivo expression of TF is dependent on what cytokine
Interleukin (IL)-6
Other cytokines generated during inflammation, impair the physiologic anticoagulant pathways.
Tumor necrosis factor (TNF)-α and IL-1
Thrombin generated by the TF pathway amplifies both clotting and inflammation through the following activities:
- (a) it activates platelets, giving rise to platelet aggregation and augmenting platelet functions in coagulation;
- (b) it activates factors VIII, V, and XI, yielding further thrombin generation;
- (c) it activates proinflammatory factors via protease-activated receptors (PARs) on inflammatory cells;
- (d) it activates factor XIII to factor XIIIa, which crosslinks fibrin clots;
- (e) it activates thrombin-activatable fibrinolysis inhibitor (TAFI), making clots resistant to fibrinolysis; and
- (f) it increases expression of adhesion molecules, such as L-selectin, thereby promoting the inflammatory effects of leukocytes
Paradoxically, at low concentrations, thrombin exhibits both antiinflammatory and anticoagulant effects because it binds to thrombomodulin and activates protein C to the activated form, which, in turn, downregulates inflammation and serves as an “off switch” for further thrombin generation
The effects of fibrinogen on mononuclear cells seem to be mediated by
Toll-like receptor–4
It is also the receptor of endotoxin.
Procoagulant activity is regulated by three important anticoagulant pathways:
AT, the protein C system, and TFPI
Main inhibitor of thrombin and factor Xa
AT
- Without heparin, AT neutralizes coagulation enzymes in a slow, progressive manner.
- Heparin induces conformational changes in AT that result in at least a 1000-fold enhancement of AT activity.
- Thus, the clinical efficacy of heparin is attributed to its interaction with AT.
Acts with its cofactor protein S and degrades the essential cofactors Va and VIIIa, and hence, is an effective anticoagulant
APC
The main inhibitor of the TF–factor VIIa complex and factor Xa
TFPI
ROLE OF NATURAL ANTICOAGULANT PATHWAYS
(Increased or Decreased)
AT:
Glycosaminoglycans:
Zymogen protein C:
Thrombomodulin:
Plasma levels of C4bBP:
EPCR:
Factor VIII:
AT: decrease
Glycosaminoglycans:decrease
Zymogen protein C: decrease
Thrombomodulin: decrease
Plasma levels of C4bBP: increase
EPCR: decrease
Factor VIII: increase
Inhibits platelet activation and aggregation, blocks neutrophil tethering to blood vessels, and decreases endothelial cell production of various cytokines and chemokines
Prostacyclin
TRUE OR FALSE
LPS-induced DIC so prominently displays tissue infarction leading to multiorgan dysfunction (eg, sepsis) compared with DIC that is predominately induced by TF exposure (eg, head trauma)
TRUE
LPS-induced DIC so prominently displays tissue infarction leading to multiorgan dysfunction (eg, sepsis) compared with DIC that is predominately induced by TF exposure (eg, head trauma)
TRUE OR FALSE
The occurrence of schistocytes in the blood film is uncommon in patients with DIC
FALSE
The occurrence of schistocytes in the blood film is not uncommon in patients with DIC
Patients with DIC may also display signs of thrombotic microangiopathy, causing further consumption of platelets, and nonimmune hemolysis.
A crucial factor in the pathogenesis of this enhanced platelet–vessel wall interaction is
Release of (ultra-large) von Willebrand factor multimers
Account for approximately two-thirds of DIC cases in the major series
Infectious diseases and malignant disorders
TRUE OR FALSE
Patients with chronic DIC usually exhibit major skin and mucosal bleeding.
TRUE
Patients with chronic DIC usually exhibit only minor skin and mucosal bleeding.
The major causes of renal dysfunction in DIC
Renal cortical ischemia induced by microthrombosis of afferent glomerular arterioles and acute tubular necrosis related to hypotension
TRUE OR FALSE
No single laboratory test is sensitive or specific enough to allow a definite diagnosis of DIC
TRUE
No single laboratory test is sensitive or specific enough to allow a definite diagnosis of DIC
One of the best parameters for detection of ongoing DIC
Soluble fibrin in plasma
Conditions associated with elevated FDPs
Trauma, recent surgery, inflammation, or venous thromboembolism
Marker that is elevated in patients with DIC, but this poorly distinguishes patients with DIC from patients with venous thromboembolism, recent surgery, or inflammatory conditions.
D-dimer
International Society on Thrombosis and Haemostasis (ISTH) score indicative of DIC
5 or more
ISTH Score
- Presence of an underlying disorder known to be associated with DIC
- Platelet count (>100 = 0; <100 = 1; <50 = 2)
- Level of fibrin markers (soluble fibrin monomers/ fibrin degradation products) (no increase: 0; moderate increase: 2; strong increase: 3)
- Prolonged prothrombin time (<3 s = 0; >3 s but <6 s = 1; >6 s = 2)
- Fibrinogen level (>1.0 g/L = 0; <1.0 g/L = 1)