Haematology

Question 1

what are the main functions of blood?

Answer 1

O2 transport
clotting
healing/infection
transport system
homeostasis

Question 2

what is the function of haemostasis?

Answer 2

limits blood loss (haemorrhage) following vascular damage without compromising blood fluidity

Question 3

what are the 3 phases of haemostasis?

Answer 3

vasoconstriction
platelet plug
coagulation

Question 4

what compound is used in blood storage to prevent coagulation?

Answer 4

sodium citrate

Question 5

what is the extrinsic pathway initiated by and how can it be tested?

Answer 5

tissue factors released by damaged cells

tested using prothrombin time (PT)

Question 6

what is the intrinsic pathway and how can it be tested?

Answer 6

initiated by active platelets

tested using activated partial thomboplastin time (APTT)

Question 7

what 3 things are required to carry out the intrinsic and extrinsic pathways?

Answer 7

clotting factors
Ca ions
negatively charged lipid surfaces

Question 8

how long should each pathway test take?

Answer 8

extrinsic (PT): 10-14 seconds
extrinsic (APTT): 30-45 seconds

Question 9

explain the final common pathway in coagulation

Answer 9

platelets release prothrombin activator
(turns prothrombin -> thrombin)
thrombin turns soluble fibrinogen into insoluble fibrin
factor 8 cross links fibrin which then strengthens the clot

Question 10

what is fibrinolysis?

Answer 10

process of clot removal

Question 11

where is plasminogen synthesised and where does it circulate?

Answer 11

synthesised - liver

circulated - plasma

Question 12

what is plasminogen activated by?

Answer 12

a serine protease called tissue plasminogen activator (tPA)

Question 13

what does tPA do?

Answer 13

converts plasminogen into plasmin which breaks down fibrin mesh

Question 14

what is thrombosis?

Answer 14

occlusion of a blood vessel (venous or arterial) by an intravascular blood clot or platelet lump

Question 15

what is intravascular blood coagulation inhibited by and how does it inhibit it?

Answer 15

non-thrombogenic surface of endothelium
prostacyclin (PGI2)
NO

inhibits platelet aggregation and adhesion to vascular wall
inhibits natural anticoagulants (antithrombin III)

Question 16

explain the process of platelet adhesion

Answer 16

adhere to sub-endothelial collagen to activate
platelet surface integrin GPIb permits adhesion to collagen in vessel wall through von willebrand factor bridge

Question 17

how do platelets promote vasoconstriction?

Answer 17

release agents (thromboxane, ADP) promoting vasoconstriction and aggregation
thromboxane initiates arachnoid acid metabolism (vasoconstriction)

Question 18

what changes are seen in platelets after activation?

Answer 18

shape change (discoid -> spherical)
pseudopodia development
expose cell surface integrin GPIIb/IIIa cross linking to fibrinogen

Question 19

what does blood coagulation involve?

Answer 19

coagulation factors (plasma proteins)
phospholipids (platelet surface)
Ca ions

Question 20

what activated plasma proteins?

Answer 20

proteolic cleavage to become active proteases

Question 21

name 4 blood clotting disorders and the factor they lack

Answer 21

von willebrand disease (von willebrand)
haemophilia A (8)
haemophilia B (9)
haemophilia C (11)

Question 22

explain the formation of venous thrombosis

Answer 22

formed by intravascular blood clot in deep veins (often legs)
a fragment may break off (embolus) and block the blood vessel, often the pulmonary artery (DVT)

Question 23

explain the causation of arterial thrombosis

Answer 23

caused by platelet aggregate at side of ruptured atherosclerotic plaque which is then encapsulated by a clot
common in coronary arteries causing MI, or cerebral artery causing theombotic stroke

Question 24

what medications are used to treat thrombosis?

Answer 24

anticoagulant - inhibit coagulation cascade
antithrombotics - inhibit platelet activation
thrombolytics - dissolve clots

Question 25

give an example of anticoagulants and explain their mechanism of action

Answer 25

heparin (sulphated GAG) binds to antithrombin III (anticoagulant) complex binds to/inhibits clotting factors (IIa, IXa, Xa, XIa, XIIa) imediate effect low molecular weight heparin inhibits Xa mostly

Question 26

how do the 2 types of heparin differ?

Answer 26

2 forms: UFH (unfractionated) and LMWH LMWH has more consistent chain length

Question 27

explain the administration of heparin

Answer 27

intravenously or subcutaneously cant cross placenta or BBB used for DVT or pre-eclampsia

Question 28

what are the side effects of heparin?

Answer 28

allergic reactions hyperkalaemia haemorrhage heparin-induced thrombocytopaenia (HIT)

Question 29

explain the mechanism of action of oral anticoagulants

Answer 29

warfarin blocks synthesis of coagulation factors in liver reduces vitamin K reductase blocking carboxylation resulting in no Ca binding to factors II, VII, IX and X

Question 30

when is warfarin used?

Answer 30

venous thrombosis pulmonary embolism prevention (especially in AF patients) thrombosis prophylaxis after prosthetic insersion (valves)

Question 31

what are the side effects and disadvantages of warfarin?

Answer 31

active in vivo, not in vitro effects delayed can cause haemorrhage crosses placenta/BBB

Question 32

explain the INR

Answer 32

measurement of clotting time or ratio of prothrombin to control target: 2-3 high INR: haemorrhage risk low INR: thrombosis risk

Question 33

what are the advantages of new anticoagulants? (+ example)

Answer 33

rivaroxaban (Xa inhibitor) active imediately dont involve antithrombin III

Question 34

what is the function of andexanet?

Answer 34

reverses factor X inhibitors

Question 35

how does low dose aspirin act as an anti-thrombotic?

Answer 35

irreversibly inhibits cyclooxygenase which causes acetylation of terminal serine which inhibits synthesis of thrombxane A2 and prostacyclin

Question 36

what are thrombolytic agents used for?

Answer 36

venous thrombosis, MI or thrombotic stroke never haemorrhagic stroke (side effect is haemorrhage)

Question 37

what is shock?

Answer 37

life threatening, generalised form of acute circulatory failure with inadequate O2 delivery and utilisation by cells

Question 38

name 4 markers indicating shock

Answer 38

CV status (BP/HR) respiratory rate lactate levels urine output

Question 39

what are the 4 types of shock?

Answer 39

distributive hypervolaemic cardiogenic obstructive

Question 40

what are the causes of distributive shock?

Answer 40

vasoregulation failure (vasodilation) sepsis (toxic inflammatory response) anaphylaxis (biochemical mediator release) neurogenic (spinal injury)

Question 41

what are the causes of hypervolaemic shock?

Answer 41

loss of intravascular volume haemorrhage (trauma, GI bleeding) non haemorrhage (burns)

Question 42

what are the causes of cardiogenic shock?

Answer 42

pump failure MI arrythmias (toxins, medications, valve problems) mechanical

Question 43

what are the causes of obstructive shock?

Answer 43

barriers to cardiac flow/filling pulmonary embolism cardiac tamponade pneumothorax

Question 44

how is distributive shock treated?

Answer 44

fluids vasosuppressors (targets peripheral vasodilation) antibiotics

Question 45

how is hypervolaemic shock treated?

Answer 45

fluid blood stop blood loss

Question 46

how is cardiogenic shock treated?

Answer 46

vasosuppressors inotropes fluids

Question 47

how is obstructive shock treated?

Answer 47

improve obstruction (needle/thrombolysis)

Question 48

what are the main components of blood?

Answer 48

RBC WBC platelets plasma (water, proteins, coagulation factors etc.)

Question 49

name the 5 steps of blood loss in order

Answer 49

intravascular volume loss decreased CO impaired tissue oxygenation end organ dysfunction death

Question 50

explain the vivious cycle of blood loss

Answer 50

hypothermia = decreased coagulation (clotting problem) clotting problem = increased lactic acid in blood (blood more acidic) acidic blood = heart performance decrease resulting in hypothermia

Question 51

what levels of blood loss are seen with each stage of shock?

Answer 51

S1: 750ml (15%) S2: 750-1500ml (15-30%) S3: 1500-2000ml (30-40%) S4: >2000ml (>40%)

Question 52

what pulse and BP observations are seen in each stage of shock?

Answer 52

S1: pulse below 100, BP normal S2: pulse 100-120, BP normal S3: pulse 120-140, BP lower S4: pulse 140+, BP low

Question 53

what respiratory rates and urine outputs are seen in each level of shock?

Answer 53

S1: RR 14-20, UO >30ml/h S2: RR 20-30, UO 20-30ml/h S3: RR 30-40, UO 5-15ml/h S4: RR >40, UO negligible

Question 54

what is the emergency treatment for a catastrophic haemorrhage?

Answer 54

A - airway (c-spine control) B - breathing (oxygenation) C - circulation (haemorrhage control) D - disability E - exposure

Question 55

what is an abrasion wound and how would you treat it?

Answer 55

superficial/deep, dragged against irregular surface remove debris and dress wound

Question 56

what is a laceration wound and how would you treat it?

Answer 56

blunt force trauma causing skin to tear/split at tissue bridging ireegular edges and depth levels irrigate and clean, close wound with glue, staple/suture wound

Question 57

what is an incision wound and how would you treat it?

Answer 57

sharp/penetrating trauma (slash/stab), clean edges, uniform shape investigate for underlying damage

Question 58

what is a degloving wound?

Answer 58

skin/blood supply torn off by major trauma and severe injuries could be limbs/digits entirely

Question 59

what is a bite wound and how would you treat it?

Answer 59

small entry wound prone to infection possibly deep penetration with foreign body test for human blood borne viruses (tetanus), antibiotics, ensure vaccinations up to date, delay closure, irrigate