Lecture 4- Anemia

TCP/platelets

• small, round, nonnucleated cells

• critical values: <20,000 or >1million/mm3

• platelets aggregate then initiate coagulation factor cascade

thrombocytosis

• increased platelets

• iron deficiency anemia- causes maximal stimulation of cellular production by the marrow

  • platelets dont need iron to grow, therefore they respond to this stimulation

• malignant disorders

• polycythemia vera- hyperplasia of all cell lines

• postsplenectomy syndrome

• RA

thrombocytopenia

• decreased platelets

• production dysfunction- bone marrow failure, fibrosis, tumor, pernicioius anemia, chemo

• sequestration- hypersplenism

• accelerated destruction- due to antibodies, infections, drugs, prosthetic heat valves, hemolytic anemia

• consumption of platelets due to disseminated intravascular coagulation (DIC)

  • clotting and bleeding at the same time

  • sepsis, blood cancer, snake venom

• hemorrhage

interferring factors: platelets

• platelets can clump, automated counting error

• menstruation- decrease amnt of platelets just before

• meds- estrogens and OCPs can increase amnt of platelets

  • chemo, histamin 2 blockers, thiazide diuretics

• living at high altitudes

• strenuous exercise

intrinsic coagulation study

• assess adequacy of intrinsic and common pathways (clotting time)

• aPTT

  • critical >70 seconds

• PTT

  • critical >100 seconds

• CF I, II, V, VIII, XII, IX, XI

extrinsic coagulation study

• assess adequacy of extrinsic and common pathways (clotting time)

• PT (prothrombin time)

  • critical >20 seconds

• INR (international normalized ratio)

  • critical > 5

• CF I, II, V, VII, X

why order aPTT

• evaluate unexplained bleeding

• DIC

• initiating/monitoring anticoagulation (HEPARIN, LMWH) and DOACs

• liver dz

why order PT/INR

• eval unexplained bleeding

• DIC

• initiating/monitoring anticoagulation (WARFARIN)

• liver synthetic functions

• platelet function testing

• pre-op testing

common pathway

• CF X converts prothrombin→ thrombin which activates fibrinogen → fibrin clot

PT/extrinsic pathway

• shorter pathway

• factor VII to activate factor X

PTT/intrinsic pathway

• longer pathway

• XII, XI, IX, VIII, activate factor X

deficiency in factor 7 will ____

prolong PT but not PTT

deficiencies in factors XII, XI, IX, and VIII will _____

prolong PTT but not PT

common causes of prolonged PT/INR and PTT

• acquired or inherited deficiences in CF

• anticoagulation

• biliary obstruction

• DIC

• liver dz

• vitamin K def (VII, IX, X)

• other meds (ex. allopurinol)