PBL Topic 2 Case 8 Flashcards
(158 cards)
1
Q
Identify the clinical features of a massive pulmonary embolism
A
- Severe central chest pain (cardiac ischaemia)
- Shock, pale, clammy, syncope
- Tachypnoeic, tachycardic, hypotension
- Gallop rhythm and widely split second heart sound
2
Q
Explain how thrombin is removed from the blood
A
- Adsorbed by fibrin filaments
- Combines with antithrombin III which inactivates thrombin
- Heparin binds to antithrombin III, which removes Factors XII, XI, X and IX
3
Q
Identify two other factors found in the cytoplasm of a platelet
A
- Growth factor
- Fibrin-stabilising factor
4
Q
Why are immobilised patients more at risk of a deep leg vein thrombosis?
A
- Reduced calf muscle contraction
- Reduction in pressure
- Reduced venous return
- Increased risk of stagnation and hence DVT
5
Q
How are platelets formed from megakaryocytes?
A
- Megakaryocytes fragment either in the bone marrow or soon after entering the blood
6
Q
Outline type 2 von Willebrand’s disease
A
- Inherited autosomal dominant condition
- Partial qualitative abnormality of vWF
- Minor clinical features such as bleeding following minor trauma or surgery
7
Q
Why is there vasoconstriction following trauma to a vessel?
A
- To reduces the blood flow through the damaged vessel
- To prevent blood loss
8
Q
What is the diameter of a platelet?
A
- 1 - 4 uM
9
Q
What is the role of the mitochondria in platelets?
A
- Formation of ATP and ADP
10
Q
Why is warfarin not given in the later months of pregnancy?
A
- It can cause inter-cranial haemorrhages in the baby during delivery
11
Q
Explain why aspirin potentiates the effects of warfarin
A
- Inhibition of platelet function
12
Q
What is Prekallikrein also known as?
A
- Fletcher Factor
13
Q
Outline the clinical features of immune thrombocytopenia purpura
A
- Mucosal bleeding
- Purpuric rash
- Skin bruising
- Menorrhagia in females
14
Q
What is international normalised ratio?
A
- Used to determine prothrombin time
- Which measures the effect of warfarin
15
Q
What is an embolism?
A
- Mass of material
- That is able to lodge in a vessel
- And block its lumen
16
Q
What are thrombocytes?
A
- Platelets
17
Q
What is heparin?
A
- Injectable Anticoagulant
18
Q
Why is heparin not typically given subcutaneously?
A
- Delay of up to 60 minutes
19
Q
What does a CXR show with a a massive pulmonary embolism?
A
- Oligaemia
- Dilation of pulmonary artery
20
Q
Explain why cephalosporins potentiate the effects of warfarin
A
- Inhibit the reduction of Vitamin K
21
Q
Outline the pathophysiology of a pulmonary embolism
A
- Va/Q = infinity
- Intrapulmonary dead space
- Reduced surfactant as a result of reduced perfusion
- Alveolar collapse
- Hypoxaemia
22
Q
What is the normal Activated Partial Thromboplastin time?
A
- 26 - 37 seconds
23
Q
Outline the pathophysiology of immune thrombocytopenia purpura
A
- Antibodies coat platelet
- Which binds to Fc receptors of macrophages
24
Q
Where do the majority of venous thrombi lodge?
A
- Pulmonary circulation as a pulmonary embolism
25
Identify the main unwanted effect of warfarin
- Haemorrhage
26
What is the most common cause of embolism?
- Thrombus
27
Identify three treatments of immune thrombocytopenia purpura
- Corticosteroids as immunosuppressive therapy
- IgG infusion to block Fc receptors
- Splenectomy
28
Why are diuretics and vasodilators avoided in the treatment of pulmonary embolism?
- Patients are already hypotensive
| - These will further reduce cardiac output
29
What does a CXR show in multiple recurrent pulmonary emboli
- Oligaemia
| - Enlarged pulmonary arterioles
30
von Willebrand factor as a carrier protein for what molecule?
- Factor VIII
31
How are ventilation and perfusion assessed in Va/Q scanning
- Ventilation is assessed using radioactive xenon
| - Perfusion is assessed by injection of micro-aggregates of 99mTc-albumin
32
What is Factor V also known as?
- Proaccelerin
OR
- AC-globulin
OR
- Labile Factor
33
What is the role of thrombomodulin?
- Prevents clotting in the normal vascular system:
- Binds to thrombin and slows the clotting process
- Activates protein C that inactivates Factor Va and Factor VIIIa
34
How is Prothrombin Time performed?
- Addition of tissue factor and calcium to patient's plasma
35
What will ABGs show in pulmonary embolism?
- Normal or reduced PaO2 and PaCO2
| - That becomes markedly abnormal (metabolic acidosis) in massive pulmonary emboli
36
Explain why co-trimoxazole potentiates the effects of warfarin
- Inhibition of hepatic drug metabolism
37
What occurs if emboli lodge in smaller peripheral vessels?
- Gangrene
38
Platelets are derived from which type of cell?
- Megakaryocyte
39
What is meant by individual empowerment?
- Giving people responsibility for their health
40
How do either of these pathways result in prothrombin activator formation?
- Cascade of clotting factors
41
What is Factor XI also known as?
- Plasma Thromboplastin Antecedent
OR
- Antihaemophilic Factor C
42
What is Factor XII also known as?
- Hageman Factor
43
What is the first-line diagnostic test for pulmonary embolism and why?
- CT pulmonary angiography
- Shows extent of emboli
- Highlights alternative diagnosis
44
What is the difference between theory of reasoned action and planned behaviour?
- Theory of planned behaviour includes behavioural control as an additional determinant of intentions and behaviour
45
Outline the developmental approach to theories of eating behaviour
- Exposure refers to neophobic responses that shapes view of food
- Social learning refers to food choices changes through watching others eat
- Associative learning refers to rewards for eating behaviour or food as a reward for other behaviour
46
Outline two functions of warfarin
- Oral Anticoagulant
| - Vitamin K antagonist
47
Is joint bleeding a feature of a platelet defect (e.g. thrombocytopenia) or a coagulation defect (e.g. haemophilia)
- Coagulation defect (e.g. haemophilia)
48
What does Activated Partial Thromboplastin Time measure?
- Factors XII, XI, IX, VIII, X, V, prothrombin and fibrinogen
49
Outline the mechanism of action of heparin
- Activation of antithrombin III
- To inhibit thrombin, heparin must bind to AT3 and thrombin
- To inhibit factor Xa, heparin must bind to AT3 only
50
What is thrombocytopenia?
- Spontaneous bleeding
| - When blood platelet count falls
51
Outline type 4 von Willebrand's disease
- Autosomal recessive condition
- Complete deficiency of vWF
- Severe bleeding
52
How can females be affected by Haemophilia
- Lionisation towards the abnormal X chromosome
53
What is the normal Prothrombin time?
- 12 -16 seconds
54
Outline the cognitive approach to theories of eating behaviour
- Attitudes towards foods
| - Perceived behavioural control
55
What is Factor VIII also known as?
- Antihaemophilic Factor
OR
- Antihaemophilic Globulin
OR
- Antihaemophilic Factor A
56
When is prothrombin formed?
- Following the rupture of a blood vessel
57
Explain why necrosis in soft tissues may occur in patients taking warfarin
- Thrombosis in venules
| - Inhibition protein c synthesis
58
How is the platelet plug strengthened?
- Fibrin formation
| - Between aggregating platelets
59
Why is warfarin not given in the first months of pregnancy?
- It is able to cross the placenta
| - It is teratogenic
60
Outline the pathogenesis of thrombotic thrombocytopenic purpura
- Reduction in ADAMTS-13,
- A protease that breaks down large vWF into smaller factors that can interact with platelets
- Aggregation of platelets to these large vWF
61
Outline the boundary model of overeating
- Dieters take longer to feel full
- Dieters set a boundary which limits what they can eat
- Dieters cross this boundary until they feel full
62
Why is genotyping necessary when administering warfarin
- VKORC1 gene is polymorphic
| - Warfarin is metabolised by CYP2C9, a substate of P450 isoenzymes, which is also polymorphic
63
What is meant by social engineering?
- Ill health is influenced by poverty, lack of education and poor living conditions
- Objectives should be to improve these standards
64
Why are IV fluids given in pulmonary embolism?
- Patients are hypotensive
| - Fluids increase right heart pumping
65
What is the most common cause of venous thrombosis?
- Stasis
66
How are platelets removed from the body?
- Macrophages in the spleen
67
What is the role of fibrin-stabilising factor?
- Causes covalent bonds between the fibrin monomers
| - Cross-linking of adjacent fibrin fibres
68
Outline five causes of the vascular constriction that occurs following vessel damage
- Myogenic Spasm
- Autacoid factors
- Nervous reflexes
- Myogenic contraction
- Thromboxane A2 from platelets
69
What is streptokinase?
- Purified fraction of haemolytic streptococci
- Forms complex with plasminogen to form plasmin
- Lysis of clots and free fibrinogen
70
What is the significance of Vitamin K in the formation of blood clots?
- Necessary for liver formation of prothrombin, Factor VIII, IX and X, Protein C and S
- In the absence of Vitamin K the tendency to bleed is enhanced
71
What is the action of thrombin on fibrinogen?
- Removal of four low-molecular weight peptides
- Forming one molecule of the fibrin monomer
- Which has the capability to polymerise with other fibrin monomers.
72
When can the diagnosis of pulmonary embolism be excluded?
- If D-dimer is not present
73
What is Factor VII also known as?
- Serum Prothrombin Conversion Accelerator
OR
- Proconvertin
74
What is the function of phospholipids in the cell membrane of platelets?
- Activate multiple stages in the blood clotting process
75
How can atrial fibrillation increase the risk of a thromboembolism?
- Ineffectual movement of the atria causes stagnation
76
What is Factor XIII also known as?
- Fibrin Stabilising Factor
77
Identify the clinical features of multiple recurrent pulmonary emboli
- Breathless, weakness, syncope and angina
- Signs of right ventricular overload with right ventricular heave
- Loud pulmonary second sound
78
Explain the haemolytic anaemia as seen in thrombotic thrombocytopenic purpura
- Red cell fragmentation
79
What is Factor X also known as?
- Stuart-Prower Factor
80
What is the role of glycocalyx?
- Prevents clotting in the normal vascular system
| - By repelling clotting factors and platelets
81
What is Factor I also known as?
- Fibrinogen
82
Outline the mechanism of action of warfarin on Vitamin K antagonism
- Competitive inhibtion of Vitamin K epoxide reductase component 1 (VKORC1)
- Thus inhibiting vitamin K epoxide to its active hydroquinone form
-
83
Outline the two ways in which prothrombin activator is formed
- Extrinsic pathway that begins with trauma to the vascular wall
- Intrinsic trauma that begins in the blood itself
84
How can a myocardial infarction increase the risk of a thromboembolism?
- Endothelial lining is lost
- Underlying collagen is exposed
- Binding of platelets to von Willebrand factor
85
Identify three causes of thrombocytopenia
- Failure of platelet production e.g. megaloblastic anaemia
- Increased platelet destruction e.g. autoimmune thrombocytopenic purpura
- Platelet sequestration e.g. splenomegaly
86
Explain why LMWHs do not increase the action of antithrombin III on factor Xa but not on thrombin
- It is too small to bind to both AT3 and thrombin
87
Identify signs and symptoms of deep vein thrombosis
- Painful, red swelling in calf associated with engorged veins
- Homan's sign (calf pain on dorsiflexion)
- Cyanotic discolouration
- Gangrene
88
How can you use prothrombin time to distinguish between Haemophilia A, von Willebrand's disease and Vitamin K deficiency?
- Prothrombin time is increased in Vitamin K deficiency
| - It is normal in both haemophilia A and von Willebrand's disease
89
What does a CXR show with a small/medium pulmonary embolism?
- Atelectasis
- Pleural effusion
- Raised hemidiaphragm
90
How does serum differ from plasma?
- Serum does not include fibrinogen and clotting factors
91
Identify two cells that produce heparin and where they are located
- Basophils in the blood
| - Mast cells in the connective tissue throughout the body
92
Identify the clinical features of a small/medium pulmonary embolism
- Pleuritic chest pain and dyspnoea
- Tachypnoeic
- Pleural rub and coarse crackles
93
Identify the treatment of a deep vein thrombosis
- Heparin
- Warfarin
- Bed Rest
94
Haemophilia A is a deficiency of which clotting factor?
- Factor VIII
95
Outline the treatment for thrombotic thrombocytopenic purpura
- Plasma exchange, providing a source of ADAMTS-13
| - Rituximab, a monoclonal antibody
96
Outline the function of plasmin
- Proteolytic enzyme
- Lysis of blood clots
- Digests fibrin fibres and Factors V, VIII, XIII and prothrombin
97
What occurs if emboli lodge in in the intestine?
- Ischaemia bowel
| - Resulting in perforation and peritonitis
98
Outline the general mechanism of blood coagulation
- Clotting cascade activates prothrombin activator
- Which converts prothrombin into thrombin
- Which acts as an enzyme to convert fibrinogen into fibrin that enmeshes platelets
99
Is mucosal bleeding a feature of a platelet defect (e.g. thrombocytopenia) or a coagulation defect (e.g. haemophilia)
- Platelet defect e.g. thrombocytopenia
100
Explain how plasminogen is converted into plasmin
- Injured tissues release tissue plasminogen activator (t-PA)
101
What is the normal concentration of platelets in the blood
- 150,000 - 300,000
| - Per uL
102
Identify three contractile proteins found in the platelet cytoplasm
- Actin
- Myosin
- Thrombosthenin
103
Why are males more likely to be by Haemophilia?
- It is inherited as an X-linked recessive condition
104
What does an ECG show with multiple recurrent pulmonary emboli?
- Signs of pulmonary hypertension
105
How is Haemophilia treated?
- Intravenous infusion of either factor VIII or factor IX
106
Outline the causal model of overeating
- Dieting precedes overeating and contributes to it causally
107
What is high-molecular-weight kininogen also known as?
- Fitzgerald Factor
108
What is the Revised Geneva Score?
- Assess probability of pulmonary embolism
- Takes into account signs, symptoms and risk factors
- Risk factors include malignancy, DVT, surgery or fracture and age
109
What does an ECG show with a small/medium pulmonary embolism?
- Sinus tachycardia
| - Atrial fibrillation
110
Explain the raised lactic dehydrogenase as seen in thrombotic thrombocytopenic purpura
- Haemolysis
111
How is Thrombin Time performed?
- Addition of thrombin to a patient's plasma
112
Outline the vicious circle of clot formation
- The clot initiates positive feedback forming clots in the surrounding blood
- Thrombin acts on many other blood-clotting factors
- Thrombin has a proteolytic effect on prothrombin to release more thrombin
113
Why is heparin not typically given via intramuscular injections?
- This would cause haematomas
114
Outline the intrinsic pathway
- Trauma activates Factor XII
- Release of phospholipids from damaged platelets
- Factor XIIa activates Factor XI in the presence of kininogen and prekallikrein
- Factor XIa activated Factor IX
- Factor IX activates Factor X in concert with Factor VIIIA
- Phospholipids combine with Factor V to form prothrombin activator
- Prothrombin activator splits prothrombin to from thrombin in the presence of calcium ions
115
Identify two factors that determine when blood will coagulate and when they are expressed
- Anticoagulants, blood does not coagulate in a normal vessel
- Procoagulants, blood does coagulate in ruptured vessels
116
How does bleeding after surgery differ between a platelet defect (e.g. thrombocytopenia) or a coagulation defect (e.g. haemophilia)
- Immediate in a platelet defect e.g. thrombocytopenia
| - Delayed in a coagulation defect e.g. haemophilia
117
Identify two causes of Vitamin K deficiency
- Gastrointestinal disease due to poor absorption of fat
- Liver disease (e.g. hepatitis, cirrhosis and acute yellow atrophy) due to bile deficiency, as bile also facilitates fat digestion
118
How can you use Activated Partial Thromboplastin Time to distinguish between Haemophilia A, von Willebrand's disease and Vitamin K deficiency?
- APTT is greatly increased in Haemophilia A
- APTT is increased or decreased in von Willebrand's disease
- APTT is increased in Vitamin K deficiency
119
Identify the investigations carried out to detect a deep vein thrombosis
- D-dimer
- Iliofemoral Thrombosis = B mode venous compression
- Below knee-thrombosis = Venography with ultrasound
120
Is purpura a feature of a platelet defect (e.g. thrombocytopenia) or a coagulation defect (e.g. haemophilia)
- Platelet defect e.g. thrombocytopenia
121
How is BMI calculated?
- Dividing an individuals body weight by their square height
122
Identify five factors that contribute to overeating
- Denial
- High-risk situations
- Loss of control
- Lowered mood
- Cognitive shift
123
What is Factor IV also known as?
- Calcium
124
What is Factor IX also known as?
- Plasma Thromboplastin Component
OR
- Christmas Factor
OR
- Antihaemophilic Factor B
125
What is meant by individual prevention?
- Health is influenced by the behaviours and conditions of the individuals
- Objectives to change health behaviours by education, advertising and specific interventions
126
What is the function of glycoproteins in the cell membrane of platelets?
- Repulse adherence to normal endothelium
| - Promote adherence to injured areas of the vessel wall (especially to collagen)
127
Why is protamine sulphate given with heparin therapy
- Haemorrhage is an unwanted side effect
| - Protamine sulphate is a heparin antagonist
128
What is the treatment of von Willebrand's disease
- Analogue of ADH (vasopressin) known as desmopressin
| - To stimulate release of vWF from endothelial cells
129
What BMI score is considered as obesity?
- BMI score greater than 30
130
Define and outline Virchow's triad
- Three predisposing situations that result in a thrombus
- Changes in the intimal surface of the vessel
- Changes in the pattern of blood flow
- Changes in the blood constituents
131
Where is fibrinogen formed?
- Liver
132
Explain why colestyramine lessens the effects of warfarin
- Reduce absorption of warfarin
133
Identify five risk factors for deep vein thrombosis
- Surgery
- Fracture
- Cardiorespiratory Disease
- Malignant Disease
- Increasing age
134
How is Activated Partial Thromboplastin Time performed?
- Addition of a surface activator, phospholipid and calcium to the patient's plasma
135
How is Va/Q reported and interpreted?
- Reported as a probability
| - Interpreted in context of history and other examinations
136
How can you use bleeding time to distinguish between Haemophilia A, von Willebrand's disease and Vitamin K deficiency?
- Bleeding time is increased in von Willebrand's disease
| - It is normal in both haemophilia A and vitamin K deficiency
137
What is Factor II also known as?
- Prothrombin
138
How do platelets activate nearby platelets?
- Release of ADP, thromboxane A2 and serotonin
139
Haemophilia B is a deficiency of which clotting factor?
- Factor IX
| it is also known as Christmas disease
140
How is heparin typically given?
- Intravenously
141
Outline type 1 von Willebrand's disease
- Inherited autosomal dominant condition
- Partial quantitative deficiency of vWF
- Minor clinical features such as bleeding following minor trauma or surgery
142
What is the normal Thrombin Time?
- 12 - 14 seconds
143
Are muscle haematomas a feature of a platelet defect (e.g. thrombocytopenia) or a coagulation defect (e.g. haemophilia)
- Coagulation defect (e.g. haemophilia)
144
Why does the effect of warfarin take several days to develop?
- The degradation of carboxylated clotting factors takes several days
145
What does an ECG show with a massive pulmonary embolism?
- Right atrial dilation with tall P wave in lead II
| - Right axis deviation, right bundle branch block and T wave inversion
146
Why is heparin not typically given orally?
- It is not absorbed from the git due to its charge and high molecular weight
147
What is Factor III also known as?
- Tissue Factor
OR
- Tissue Thromboplastin
148
Identify four mechanisms that are responsible for prevention of blood loss
- Vascular constriction
- Platelet plug
- Blood clot
- Fibrous tissue in the blood clot
149
What is the role of the Golgi apparatus and endoplasmic reticulum in platelets?
- Synthesis of enzymes
| - Storage of calcium ions
150
What is the most common cause of arterial thrombosis?
- Atheroma
151
Outline the extrinsic pathway
- Release of Factor III which contains lipoproteins and phospholipids
- Lipoprotein complex of Factor III complexes with Factor VII
- Which activates Factor X in the presence of calcium ions
- Phospholipids combine with Factor Xa and Factor V to form prothrombin activator
- Prothrombin activator splits prothrombin to from thrombin in the presence of calcium ions
152
Explain why rifampicin lessens the effects of warfarin
- Induces hepatic metabolism of P450 enzyme
| - Which increases the rate of degradation of warfarin
153
When is phenidione prescribed
- In patients who suffer adverse reactions to warfarin
154
Identify an advantage of LMWH over heparin fragments
- Longer half life
- Effects are more predictable
- Dosing is less frequent
- Therefore monitoring is less routinely required
155
Explain how platelets adhere to the damaged area
- Secrete pseudopodia
- Secrete receptors such as Glycoprotein IB-IX-V complex and GIIB-IIA
- Platelets adhere to underlying collagen via von Willebrand factor
156
What does Prothrombin Time measure?
- Factors VII, X, V, prothrombin and fibrinogen
157
What is the significance of a saddle emboli?
- Located in the bifurcation of the aorta
| - Cutting off blood supply to the lower limbs
158
What is the half life of a platelet?
- 8-12 days
