Clinical Rotation Questions Flashcards
What three components are necessary for an adequate hemostatic response?
intrinsic factors, extrinsic factors, and platelets
Define hemostasis.
arrest of the escape of blood by either natural means (clot formation or vessel spasm) or artificial means (compression or litigation)
Define coagulation.
cessation of blood flow due to the actions of clotting factors, platelets, blood vessels, and the fibrin/fibrinolysis systems
Define the extrinsic system.
clotting factors not contained in blood: thromboplastin (tissue factor III), VII, X, V, II, I
Define the intrinsic system.
clotting factors contained in blood: XII, XI, IX, VIII, X, V, II, I
Define fibrinolysis.
dissolution of fiber by enzymatic action
Why is there usually a delay between trauma and the onset of bleeding in coagulation disorders?
deficiency of platelets or coagulation factors that adversely affects the normal hemostasis process
Differentiate between hereditary and acquired clotting defects.
hereditary disorders are congenital, meaning that they are due to genetic inheritance and not due to outside factors; acquired clotting defects are the result of other disease states or medication, and genetics play no role
What are the principle and interpretation of bleeding time?
Measures how fast small blood vessels in the skin stop bleeding. A blood pressure cuff is inflated around the patient’s upper arm while two small cuts are made on the lower arm. Cuff is immediately deflated, and blotting paper is touched to the cuts every 30 seconds until the bleeding stops, which should take between 1 and 9 minutes. Abnormal results can indicate blood vessel defects, platelet aggregation disorders, or thrombocytopenia; bleeding time can also be increased due to certain drug therapy.
What are the principle and interpretation of clot retraction?
Measures time it takes a platelet plug to undergo retraction, the last stage of the coagulation cascade. Blood is collected in a red top tube and allowed to clot. It is incubated at 37*C and checked at 1-, 4-, and 24-hour intervals. If half the total clot volume is serum within 24 hours, the results are considered normal. Abnormal clot retraction can indicate acquired or hereditary platelet disorders (specifically Glanzmann thrombasthenia), thrombosis, or other coagulation disorders.
What are the principle and interpretation of ethanol gelation testing?
Designed to detect the presence of fibrin monomers in the plasma, used to aid in the diagnosis of DIC and in distinguishing it from primary fibrinolysis. 0.1 N sodium hydroxide is added to citrated plasma to increase pH to >7.7. Addition of ethyl alcohol will then cause precipitation of any fibrin monomers present (+ result). Negative tests are allowed to sit for an additional 9 minutes; if gel or precipitate forms, 0.1 N NaOH is added. Persistance of gel or precipitate is +.
What are the principle and interpretation of euglobulin clot lysis?
Screening procedure for the measurement of fibrinolytic activity. The euglobulin fraction of plasma (plasminogen, fibrinogen, plasminogen activator) is precipitated with 1% HC2H3O2. Precipitate is removed and dissolved in a buffered borate solution. Thrombin is added to clot the euglobulins, and clot is incubated at 37*C. Time of complete clot lysis is recorded (normally not before 2 hrs.). 2 hrs. indicated circulatory collapse, adrenaline injections, sudden death, pulmonary surgery, pyrogen reactions, obstetric complications, or extreme stress.
What is the euglobulin clot test most useful for?
monitoring urokinase and streptokinase therapy
What are the principle and interpretation of fibrin degradation products (FDP)?
Also called Fibrin Split Products (FSP); plasmin proteolytically cleaves fibrinogen into fragments X and Y (early products), and fragments D and E (late products). Measurement provides an indirect assay of fibrinolysis. The most common test is the Thrombo-Wellcotest (direct latex agglutination slide test). Whole blood is added to thrombin (ensures clotting) and soy bean enzyme inhibitors (prevents fibrin breakdown). After clotting, serum is diluted 1:5 and 1:20 with glycine buffer, then mixed with latex particles coated with anti-FDP. Agglutination at 1:5 is >10 ug/mL; agglutination at both is >40 ug/mL; and no agglutination is
What are the principle and interpretation of the Lee-White (whole blood) clotting time?
Measures the coagulation time of whole blood. 4 mL of blood are collected and dispensed into test tubes in 1 mL aliquots. They are placed into a 37C water bath or heating block for 5 min. The last tube filled is then tilted 45 and replaced. This is repeated every 30 seconds until fully clotted; the procedure is then repeated on the remaining tubes. Clotting time is that of the last tube; normal value is 5-15 minutes. Clotting time is increased in Stage I deficiencies and in heparin therapy/presence of circulating anticoagulants.
What is important to remember about the Lee-White test, in regards to its sensitivity and use?
Test is insensitive, and often used to monitor heparin therapy. It monitors Stage I of the intrinsic system, but will not detect deficiencies in Stage II or III.
What are the principle and interpretation of the partial thromboplastin time (PTT)?
Screening procedure for the intrinsic factors (XII, XI, IX, VIII, X, V, II, I). 0.1 mL phospholipid platelet substitute reagent is mixed with 0.1 mL citrated patient plasma. It is warmed for 5 min., and 0.1 mL of 0.02 M calcium chloride is added to initiate clotting. Time required for fibrin clot is recorded. Tests are performed in duplicate and should agree within one second. Normal values are generally
What are the principle and interpretation of the plasma recalcification time?
Measure of overall intrinsic coagulation process. Platelet-poor plasma is mixed with sufficient calcium chloride to neutralize the effect of the anticoagulant, and clotting time is recorded. Normal value is 90-250 seconds. Decreased intrinsic factors will prolong clotting time. Deficiencies in platelets or their activity is not detected.
What are the principle and interpretation of the platelet count?
Impedence method used to obtain a platelet count. Normal range is 150,000-450,000
What are the principle and interpretation of the protamine sulfate test?
Tests for the presence of fibrin monomers and early FDP fragments (X and Y). Protamine sulfate causes the formation of fibrin threads or gel-like clots (paracoagulation). Patient and control plasmas are mixed with 1% protamine sulfate solution and incubated at 37*C for 15 min. Definite fibrin strands are a + result, and indicative of DIC. Fibrin monomers can also be present in pulmonary embolism, cirrhosis, deep vein thrombosis, and acute thromboembolism.
What are the principle and interpretation of the prothrombin consumption time (PCT)?
Performed on serum, testing mainly for Stage I factors of the intrinsic system. Levels of prothrombin should be decreased, resulting in a prolonged PCT. When plasma thromboplastin formation is defective, excess prothrombin remains in the serum. Therefore, when fibrinogen, thromboplastin, and calcium chloride are added, shortened clotting time results. Normal PCT value is >20 seconds; abnormal is
What are the principle and interpretation of the prothrombin time (PT)?
Screening procedure for extrinsic factors (VII, X, V, II, I). 0.2 mL tissue thromboplastin reagent (+ calcium) is mixed with 0.1 mL of citrated patient plasma, and the clotting time is measured. Normal value is generally 10-14 seconds. PT is increased in vitamin K deficiency, liver disease, extrinsic factor deficiencies, DIC, and coumadin therapy.
What are the principle and interpretation of the Saltzman glass bead test?
Also known as the Platelet Adhesiveness Test. Measures the ability of platelets to adhere to glass beads. When anticoagulated blood is passed through a column of glass beads at a constant rate, some platelets will be retained by the beads. Two tubes of blood are drawn - one through the regular vacutainer setup, and the other through a glass bead filter. Platelet counts are then performed on both specimens. The glass bead tube should have 75-95% fewer platelets. The percentage is decreased in Glanzmann’s thrombasthenia, von Willebrand’s disease, uremia, and aspirin ingestion. It is increased in thrombotic disorders, coronary disease, pregnancy, and in patients on oral contraceptives.
What are the principle and interpretation of the Stypven time?
Capable of detecting deficiencies in prothrombin, and factors V and X. Deficiencies in factor VII will not give an abnormal time because the reagent (Russell’s viper venom) has similar activity. Performed as a PT time using Stypven as the source of factor VII and tissue thromboplastin. Normal values are 11-15 seconds.
What are the principle and interpretation of the thrombin time (TT)?
Tests the third stage of coagulation (fibrinogen to fibrin) by measuring the amount of fibrinogen available. A measured amount of thrombin (usually 0.1 mL) is added to 0.2 mL plasma, and the clot time is recorded. Normal values are ~15 seconds. Increased values are seen when fibrinogen level is
What are the principle and interpretation of the thromboplastin generation time (TGT)?
Measures the efficiency with which plasma thromboplastin is formed. Aged serum and absorbed plasma reagents are prepared from the patient sample, which are then mixed with calcium chloride and a substitute platelet factor, and incubated for 6 min. At one-minute intervals, samples are removed and added to normal plasma. Clotting times are recorded, and should be within 12 seconds. Abnormal results lead to normal aged serum (VII, IX, X, XI, XII) and absorbed plasma (V, VIII, XI, XII) substitutes, which determine which reagent corrects the patient sample. Detects deficiencies in factors VIII and IX, and can distinguish between them. Can also detect factor XI and XII deficiencies, but cannot distinguish between them. If patient platelets are used, abnormalities may also be detected.
What are the principle and interpretation of the tourniquet test of Rumpel-Leede (Capillary Fragility Test)?
Measures the ability of small blood vessels to retain blood under stress. Platelet function maintains capillary integrity, so the degree of thrombocytopenia will correlate with test results. Blood pressure reading is taken, and the cuff is inflated to halfway between the systolic and diastolic (but should not exceed 100 mmHg). Cuff is left in place for 5 minutes; after removal, the patient’s arm is inspected for petechiae. If any are present, they are graded from 1+ to 4+. Normal results are “none” to “occasional” (negative test). Positive results are seen in thrombocytopenia, decreased fibrinogen, and vascular purpura.
What are the principle and interpretation of the D-dimer?
Looks for the presence of D-dimers, which indicate that a stable fibrin clot has been lysed. A dilution of the patient’s plasma is mixed with latex particles coated with monoclonal antibodies to D-dimers. Normal levels in adults are 1.0 ug/dL (+ test). Positive results are seen in DIC and thrombotic conditions, though they are negative in primary fibrinolysis.
What is the common name for Factor I, and a condition associated with its deficiency?
fibrinogen; liver disease
What is the common name for Factor II, and a condition associated with its deficiency?
prothrombin; hemorrhagic disease of the newborn (HDN)
What is the common name for Factor IV, and a condition associated with its deficiency?
calcium (Ca2+); deficiency is fatal
What is the common name for Factor V, and a condition associated with its deficiency?
labile factor; parahemophilia
