Week 7 - Haemostasis and Coagulation

Flashcards on Haemostasis and Coagulation

5 Steps of Haemostasis

Vessel Spasm, Platelet plug formation, Coagulation, Clot retraction, Clot dissolution

Adhesion

Transient tethering during platelet plug formation.

Activation

Secretion during platelet plug formation.

Aggregation

Process of platelets clumping together.

Thrombin

Generated from prothrombin at sites of tissue injury. Catalyses conversion of fibrinogen to fibrin.

Fibrin

The extrinsic pathway and intrinsic pathway lead to its formation.

Realistic coagulation

TF:FVIIa, FIX, FX, Prothrombin, Fibrinogen, Fibrin

Plasminogen activators

t-PA

Fibrinolysis

Plasmin

Arterial thrombosis

Myocardial Infarction, Ischaemic stroke, Peripheral artery disease.

Venous thrombosis

Deep Vein Thrombosis.

Bruise (haematoma)

Micro or macroscopic tearing of the blood vessels.

Bruise Color Changes

Red-blue - haemoglobin, Green - biliverdin, Yellow - bilirubin, Golden - hemosiderin

Haematomas

Purple / red coloring caused by bleeding under the skin, color doesn't blanch upon pressure

Causes of Abnormal Bleeding

Vascular defects, platelet number, platelet function, coagulation

Primary Haemostatic Disorder examples

Thrombocytopenia, VWD

Coagulation Disorder example

Haemophilia

Haemostatic Investigations

Full blood count, Blood film or smear, Bleeding time, PFA-100, Platelet aggregation studies, Flow cytometry, Serum thromboxane, AspirinworksÒ, Coagulation Assays, Prothrombin time (INR), Activated partial thromboplastin time, Thrombin Time, Factor Assays, PCR, D-dimer Assays

Aspirin

Reduces platelet activity by inhibiting the production of thromboxane A2 (TXA2).

Prothrombin Time (PT)

Assesses extrinsic pathway

Activated Partial Thromboplastin Time (aPTT)

Assesses intrinsic pathway

Thrombin Time (TT)

Assesses common pathway

PT (Prothrombin Time)

Warfarin use is monitored with this test.

INR

(patient PT / normal PT)ISI

Warfarin replacements

Oral FXa inhibitors such as Rivaroxaban / Apixaban

Deficiencies or defects of intrinsic pathway

Haemophilia A / B, FXI, FXII, prekallikrein, HMWK.

Factor Assays

Testing for deficiencies.

Inhibitor assays

Testing for inhibitors.

Risk assessment for families with bleeding disorders

Analysis of Pedigree, Phenotype, Genotype.

PCR Role

Amplification of DNA.

Most common uses of PCR

Haemophilia A/B and von Willebrands Disease.

D-dimer assays

Raised with fresh venous thrombosis.