Hematology Flashcards
1st line of defense against bleeding
vasoconstriction; occurs in response to endothelial damage; key mediator: endothelins (blockers are used in pulmonary HTN)
Activated protein factors in the coagulation cascade
activated forms have an “a” added to their Roman numeral ex: 1a, Va, Xa
become *serine proteases
Thrombin
factor IIa; thrombin can make more thrombin via positive feedback ex: activates V, XI and VIII - a way to amplify the coagulation cascade
Factor VIII
produced in endothelial cells (not liver like other factors); circulates bound to vonWillebrand Factor; released in response to injury
VIII-vWF
Extrinsic Xase
TF bearing cells (injury), enzyme: Factor VIIa and Factor X as a substrate
all require phospholipids and calcium
Intrinsic Xase
platelets, enzyme: Factor IXa, co factors VIII and substrate Factor X
all require phospholipids and calcium
Calcium in the coagulation cascade
considered Factor IV and is REQUIRED for clot formation; activated platelets release Ca2+
NOTE: EDTA binds Ca2+ in blood samples and prevents clotting
Factor XII
aka Hageman factor
can activate factor XI
importance is for testing of coagulation system b/c it is activated by contact w negative charges (expose to silica)
basis for partial thromboplastin time (PTT)
Prekallikrein Deficiency
rare condition that results in MARKEDLY prolonged PTT due to an inability to activate XII normally (cannot activate bradykinin), but there are NO BLEEDING problems
usually comes known when pt has an abnormal PTT test
Coagulation Inhibitors
Antithrombin III
Proteins C and S
TF pathway inhibitor
Antithrombin III
a serpin (inhibitor of serine proteases); produced by the liver and activated by endothelium (make heparin sulfate molecules) - basis of the role of: heparin drug therapy
Deficiency = hyper coagulable state
Protein C and Protein S
glycoproteins synthesized in the liver as a zymogen (inactive) and activated into activated Protein C (APC) by thrombomodulin; works to primarily inactivate factors Va and VIIIa
Deficiency = hyper coagulable state
Tissue Factor pathway inhibitor
inactivates Xa via two mechanisms:
directly binds Xa
Binds TF/FVIIIa complex which then prevents X activation
plasma levels are increased when heparin is administered
Plasminogen activators
Tissue plasminogen activator (tPA) and urokinase; activated by streptokinase
used in therapy for acute MI and stroke
Primary Fibrinolysis
rare condition where plasmin is overactive; causes increased FDP with normal D-dimer
“hyperfibrinolysis” - no clot to cross linked fibrin means no products of breakdown = no D-dimers
plasmin can deplete clotting factors (similar to DIC) there will be increased PT/PTT w bleeding
seen in pts w prostate cancer: release of urokinase to cirrhosis: loss of alpha2 antiplasmin
Vitamin K
required for the synthesis of many clotting factors: II, VII, IX, X, C and S
Deficiency = bleeding
Warfarin is a vitamin K antagonist; pts on warfarin who take antibiotics that target gram (-) can develop supra therapeutic INR due to disruption of vitamin k producing intestinal flora
Erythrocyte Sedimentation Rate (ESR)
increased in inflammatory conditions by “acute phase reactant” ex: Fibrinogen, Ferritin and C-reactive protein (CRP)
Platelets
derived from megakaryocytes; do not contain a nucleus, regulated by thrombopoietin (TPO); aid in hemostasis and activated by injury
platelets actions
1st - adhesion: to sub-endothelium
2nd - aggregation: platelet-platelet binding
3rd - secretions: release of granule contents
Net result of sealing an opening in the vascular tree
von Willebrand Factor
a large glycoprotein synthesized by endothelial cells (in Weibel-Palade bodies) and megakaryocytes (alpha granules); released in vascular injury
3 important functions of VWF
1 - carrier protein for Factor VIII
2 - binds platelets to damaged endothelins
3 - binds activated platelets together (aggregation)
Platelet adhesion
vascular damage leads to exposed collagen, vWF binds the collagen and then vWF binds GP1b on platelets
Platelet aggregation
platelets have already underwent adhesion, now there is platelet activation mediated by GPIIb/IIIa receptor and now they can stick together via binding to fibrinogen or vWF linked to other platelets
Basis for IIb/IIIa receptor blocking drugs - blocks aggregation
Platelet secretion
platelets are activated by either binding to collagen or by activating substances
When one platelet is activated it can secrete substances to activate other platelets:
Alpha granules (most abundant) and Dense granules
Alpha granules and Dense granules platelet secretion
Alpha granules (most abundant): contain fibrinogen, vWF and platelet factor 4
Dense granules: contain ADP, Ca2+ (required for coagulation cascade) and serotonin
Platelet Factor 4
released by alpha granules and binds to endothelial cells
Clinical relevance: Heparin induced thrombocytopenia (HIT) - rare life-threatening effect of heparin admin when antibodies are formed against PF4-heparin complexes; screening test - serotonin release assay
Adenosine Diphosphate (ADP)
released from dense granules of platelets; binds to P2Y1 (Ca2+ release and change in platelet shape) and P2Y12 (platelet degranulation and increase in aggregation)
there are many PsY12 receptor blocking drugs “ADP receptor blockers” : clopidogrel, prasugrel, ticlopidine, ticagrelor = inhibit platelet activity
Thromboxane A2 (TXA2)
powerful platelet activator; basis for aspirin therapy
Thromboxane A2 (TXA2)
powerful platelet activator; basis for aspirin therapy
Bleeding Time
test of platelet function (does not involve coagulation cascade); when prolonged look for explanation that relies within the platelets
Virchow’s Triad
endothelial damage
stasis of blood
hypercoagulability
Common hypercoaguable states
post-op - involves are three conditions of Virchow’s triad: inflammation after surgery = hypercoaguable, immobile = stasis and surgery = endothelial damage
falls/hip fractures/trauma/long plane flights / malignancy / pregnancy / elevated homocysteine / smoking are hypercoaguable states
nephrotic syndrome with hypercoagulable states
loss of anti-clotting factors in the urine; most anti-thrombin III
4 Inherited Thrombophilia’s
Factor V Leiden Mutation
Prothrombin gene mutation
Antithrombin deficiency
Protein C/S deficiency
Factor V Leiden Mutation
abnormal factor V (point mutation); not INACTIVATED by activated protein C (APC) = factor V remains active longer leading to a hypercoagulable state
Prothrombin gene mutation
prothrombin 20210 gene mutation leading to increases prothrombin levels = hypercoagulable state
Antithrombin deficiency
inherited due to gene mutations or acquired due to nephrotic syndrome; classically presents as heparin resistance = escalating dose of heparin w/ no/little change in PTT (heparin activates ATIII)
= hypercoagulable state
Protein C/S deficiency
associated w warfarin skin necrosis; initial warfarin therapy leads to decreased protein C resulting in thrombus of skin tissue = large dark purple skin lesions
bone marrow aspirate
multiple myeloma; bone marrow aspirate has numerous plasma cells with perinuclear paleness and nuclei w “clock-face” chromatin; limits the generation of targeted immunoglobulins and pt at increased risk for recurrent bacterial infections
EPO signal transduction
EPO receptor is Janus kinase 2/signal transducer and activator of transcription (JAK2/STAT) signaling pathway which promotes erythrocyte precursor survival and differentiation
EPO signal transduction
EPO receptor is Janus kinase 2/signal transducer and activator of transcription (JAK2/STAT) signaling pathway which promotes erythrocyte precursor survival and differentiation
bone marrow aspirate
amyloid light-chain amyloidosis is associated with multiple myeloma and other monoclonal plasma cell dycrasias due to deposition of insoluble immunoglobin light chain fibrils in major organs (kidneys); bone marrow sample with >10% plasma cells is strongly associated with MM
pt with persistent fever, fatigue and sore throat
infectious mononucleosis, EBV preferentially infects B lymphocytes by binding CD21 and EBV-infected B lymphocytes then activate cytotoxic CD8+; these reactive atypical CD8+ are the primarily immune response to EBV and are observed in peripheral blood smears
Dactylitis
painful swelling of the hands and feet is a common presentation of sickle cell disease in young children; sickling episodes results in hemolysis which leads to increased indirect bilirubin and lactate dehydrogenase and decreased levels of haptoglobin
types of bleeding
petechiae and skin bleeding - usually from abnormal platelets
joint and deep tissue bleeding - usually from abnormal coagulation factors
types of bleeding
petechiae and skin bleeding - usually from abnormal platelets
joint and deep tissue bleeding - usually from abnormal coagulation factors
Glanzmann’s Thrombasthenia
AR disorder w deficiency of GPIIb/IIIa receptors; pt present w bleeding often epistaxis; blood smear will show isolated platelets (no clumping); there will be absent platelet aggregation
Bernard-Soulier Syndrome
AR disorder w deficiency of GPIb platelet receptors; results in *large platelets; prolonged bleeding time and thrombocytopenia; epistaxis or menorrhagia (defect in platelet-to-vWF adhesion)
Wiskott-Aldrich syndrome
immunodeficiency in infants; X linked WAS gene mut needed for T cell *cytoskeleton; triad:
immune dysfunction, decreased platelets and eczema
Idiopathic thrombocytopenia purpura (ITP)
decreased platelet survival due to anti-GPIIb/IIIa antibodies; there will be consumption by splenic macrophages
think about what can be causing low platelets: is it bone marrow suppression (not enough being produced) or splenic consumption (dying too early)
Thrombotic thrombocytopenic purpura (TTP)
disorder (def of ADAM13 - acquired antibody) of small vessel thrombus formation; consumes platelets which leads to thrombocytopenia; vWF multimers that are normally broken down by ADAM13 are released and obstruct flow (impaired cleavage of vWF); blood smear will show shistocytes due to shearing of RBCs
PT/PTT normal (unlike DIC)
Symptoms: fever, neurological (HA, confusion, seizures), renal failure and petechiae and bleeding
Hemolytic Uremic Syndrome
commonly seen in children followed by GI infection w E. coli 0157:H7 (shiga-like toxin causes microthrombi) - leads to platelet rich thrombi that deposits in small vessels, typically the kidney (think of TTP that only focuses on the kidney)
Disseminated Intravascular Coagulation (DIC)
widespread activation of clotting cascade; there is diffuse thrombi (platelets/fibrin) leading to obstructive blood flow and ischemia; consumption of clotting factors and platelets; occurs secondary to another process (emergencies and sepsis - endotoxin, malignancies, rattlesnake bites - contain thrombin-like glycoproteins)
presents as bleeding; elevated PT/PTT/thrombin time, low platelets, low fibrinogen, elevated D-dimer
ITP, TTP, HUS, DIC
Uremia
renal dysfunction leading to bleeding; uremia toxins floating around in the plasma prevents the platelets from working properly resulting in prolonged bleeding time; there is a normal platelet count and normal coagulation testing
Platelet level that bleeding occurs
Normal platelet count: 150,000 to 400,000
bleeding occurs when <10,000
von Willebrand Disease
most common bleeding disorder: AD def in vWF; synthesized by endothelial cells and megakaryocytes; carrier for factor VIII and bonds platelets to endothelium (exposed collagen)
*menorrhagia
labs: normal platelet count, normal PT, increased PTT (factor VIII) and increased bleeding time
test: ristocetin cofactor assay - binds vWF
tx: vWF, desmopressin (increases vWF and factor VIII) and aminocapoic acid (inhibits plasminogen activation - less breakdown of formed clots)
Heyde’s Syndrome
GI bleeding associated w aortic stenosis; def of vWF due to his shearing forces of aortic stenosis leading to uncoiling of vWF multimers and now cleavage site for ADAMS13 is exposed (now overactivation of ADAMS13) breaking down vWF and now less sufficient
increased risk of angiodysplasia
Desmopressin therapy in von Willebrand Disease
vWF enhances clotting through both augmentation of platelet binding and stabilization of factor VIII; pts w vWD are deficient of VWF and present w increased bruisability and prolonged mucosal bleeding; desmopressin can alleviate bleeding through endothelial release vWF
Antiplatelets
blocks the formation of activated platelets
Aspirin
IIb/IIIa inhibitors (activated platelets)
phosphodiesterase inhibitors
Anticoagulants
blocks the formation of fibrin
Heparin
Warfarin
Direct Thrombin inhibitors
Factor Xa inhibitors
Thrombolytics
breakup thrombus clots that have already been formed
tPA
Urokinase
Streptokinase
Aspirin
Antiplatelet agent that inhibits the formation of thromboxane A2 via COX inhibition resulting in decreased platelet activation
indicated in coronary disease and stroke
adverse effects: bleeding, ulcers, tinnitus (alters cochlear nerve function); Reye’s syndrome (liver failure and encephalopathy) not given to children except Kawasaki
Thienopyridines
anti platelet drugs: ticlopidine, clopidogrel, prasugrel
irreversible P2Y12 receptor blockers; used in aspirin allergy; major adverse effect of bleeding and rare and dangerous effect of TTP (antibodies to ADAMS13)
Ticagrelor
anti platelet drug similar to the Thienopyridines but REVERSIBLE antagonist of P2Y12 receptor; unique side effect of dyspnea; not associated with TTP
phosphodiesterase inhibitors (PDE inhibitors)
anti platelet drugs that inhibit phosphodiesterase III in platelets PDE functions to break down cAMP; so there will be increased cAMP leading to decreased platelet activation (ADP is activator of platelets)
two drugs: dipyridamole and cilostazol
Side effects: HA, flushing and hypotension (all due to vasodilation effects)
Dipyridamole
phosphodiesterase inhibitor (PDE inhibitor) that inhibit phosphodiesterase III in platelets; also a blocker of adenosine uptake which raises the adenosine levels leading to vasodilation; used in stroke prevention and cardiac stress testing
Side effects: HA, flushing and hypotension (all due to vasodilation effects)
cilostazol
phosphodiesterase inhibitor (PDE inhibitor) that inhibit phosphodiesterase III in platelets; also raises cAMP in vascular smooth muscle; used in peripheral arterial disease
Side effects: HA, flushing and hypotension (all due to vasodilation effects)
IIb/IIIa inhibitors
anti platelet drugs: Abciximab, eptifibatide and tirofiban
bind and block IIb/IIIa on platelets
unique side effect: thrombocytopenia (monitor platelet count)
IIb/IIIa inhibitors
anti platelet drugs: Abciximab, eptifibatide and tirofiban
bind and block IIb/IIIa on platelets
unique side effect: thrombocytopenia (monitor platelet count)
Heparin
anticoagulant that is naturally found in *mast cells; used in two forms:
unfractionated (varying polymers) and low molecular weight (smaller polymers only)
unfractionated heparin
anticoagulant that activated anti-thrombin III (inactivates multiple clotting factors); increased PTT (intrinsic pathway)
HeparIN = INtrinsic (PTT)
highly variable dose from pt to pt so *dose must be adjusted; long term use can lead to osteoporosis
reversible agent for OD: protamine
protamine
reversible agent for unfractionated heparin overdose; less effective w LMWH; used in cardiac surgery (high dose heparin admin for heart-lung bypass and a quick reversal is needed at completion of case)
for fasted reversal use fresh frozen plasma
Heparin and Thrombocytopenia
many pts see a mild (10-20%) drop in platelets = “non-immune” thrombocytopenia BUT there can be an immune-mediated reaction called Heparin-induced thrombocytopenia (HIT) occurs 5-10 days after; immune complexes bind platelet factor 4-hepain (type II hypersensitivity) IgG and PF4 complexes - arterial/vein thrombosis
Low molecular weight heparin (LMWH)
only the small polymers of heparin; more effective for activating anti-thrombin III to inhibit factor Xa; have very predictable effect w/o having to titrate and monitor PTT and adjust dose
Low molecular weight heparin (LMWH)
only the small polymers of heparin; more effective for activating anti-thrombin III to inhibit factor Xa; have very predictable effect w/o having to titrate and monitor PTT and adjust dose
if monitoring is required: check anti Xa levels EXCEPT in obesity and renal failure pts
Factor Xa inhibitors
Rivaroxaban and Apixaban
used in a-fib as alternative to warfarin; do not require PT/INR; can increase PT and PTT
reversal agent: andexanet alfa = inactive “decoy” of Xa that binds drug
Direct Thrombin Inhibitors
Hirudin, lepirudin, bivalirusin, desirudin, argatroban, and dabigatran
prolong PT, PTT and thrombin time *only UF heparin and DTI’s prolong thrombin time;
Dabigatran
a direct thrombin inhibitor; an oral alternative to warfarin; commonly used in a-fib; do not require PT/INR monitoring unlike warfarin
reversal agent: idarucizumab = anti-dabigatran monoclonal antibody
Warfarin
vitamin K antagonist; inhibits epoxide reductase (keeps vit k in oxidized form); takes days to achieve its effects; must monitor PT/INR (start heparin if you need acute onset)
*crosses placenta; avoided in pregnancy
Fresh frozen plasma (immediate) reversal of warfarin; protamine - reversal drug
Warfarin Skin Necrosis
occurs in pt w protein C deficiency; initial exposure of warfarin will decrease protein C and result in thrombosis of skin tissue; large, dark purple skin lesions
Parvovirus B19
Unenveloped DNA virus that replicates in RBC progenitor cells; decreases erythropoiesis; in chronic hemolysis pts (Sickle cell, hereditary spherocytosis and beta thalassemia major) watch for “aplastic crisis”
classic scenario: worsening anemia with LOW (corrected) reticulocyte count
Glycoprotein IIb-IIIa disorder
no problem in aggregation for vWD
