What are the causes for abnormal bleeding?



ThromboelastogramsWhat are the causes for abnormal bleeding?ThrombocytopeniaPlatelet dysfunctionAbnormalities of the clotting cascadeHow can we assess platelet function?ThromboelastographyBleeding timePlatelet function analyser (PFA-100)How do we perform a TEG?0.3 mL of blood is placed in an oscillating cup as it rotates around a piston connected to a recorder at 37°CAs fibrin strands form between the cup and piston, the oscillations are transmitted and recordedDraw a normal TEG.The TEG trace progressively describes activation of the coagulation cascade, fibrin formation, the fibrin-platelet interaction (clot stability), clot retraction, and fibrinolysisWhat is r?r = reaction time (normally <6 minutes)Measured from sample placement until the amplitude reaches 2 mmRepresents activation of the coagulation cascade (intrinsic)Prolonged with heparin, coagulation factor deficiencyIf abnormal, consider FFPInitiation What is k?k = clot formation time (normally <6 minutes)Measured from r until the amplitude reaches 20 mmRepresents fibrin formation Requires normal intrinsic clotting factors, fibrinogen and plateletsAmplification What is the α angle?Measured from the top of r to the k valueNormally 60 degreesRepresents the rate of clot propagationIf abnormal, consider fibrinogen = cryoprecipitateWhat does the maximum amplitude represent?Represents clot strengthNormally 60 mmSignificantly disturbed by platelet abnormalitiesWhat is A60?= Amplitude 60 minutes after maximum amplitude is achievedRepresents clot lysis or retractionWhat happens in haemophilia or antigoagulation?Prolonged r and kDecreased α and maximum amplitudeWhat happens in thrombocytopenia or antiplatelet agents?Decreased maximum amplitudeWhat happens in fibrinolysis?Continuous decrease in maximum amplitudeWhat happens in hypercoagulability?Short r and kIncreased α and maximum amplitudeHow does the platelet function analyser work?Citrated whole blood is drawn through a hole in a collagen-coated membrane which is bound to adrenaline or ADPUnder the shear stress influences, platelets aggregate and seal the holeThis is sensed by a pressure transducerThe time taken for platelets to occlude the hole is referred to as the closure time ................
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