Haematology Flashcards
What is DIC?
A syndrome characterised by the systemic activation of blood coagulation, which generates intravascular fibrin, leading to thrombosis of small- and medium- sized vessels, and eventually organ dysfunction.
DIC is characterised by evidence of both thrombin and plasmin activation.
What are the risk factors for developing DIC? (12)
- Infections (especially sepsis)
- Malignancy (especially leukaemia’s)
- Major trauma including crush syndrome
- Incompatible blood transfusion
- Transplant rejection
- Severe liver disease
- Pancreatitis
- Heat stroke
- Dissecting aortic aneurysm
- Complications post-surgery
- Recreational drugs
- Anti-phospholipid syndrome
How can DIC present?
Aside from the obvious features of the underlying condition causing the DIC,
- Large bruises
- Spontaneous bleeding at venipuncture sites, on the soft palate, legs and site of trauma
- Bleeding from at least three unrelated sites is typical:
- ENT
- GI
- Respiratory tract
- Site of venepuncture or IV fusion - Confusion or disorientation
- Fever
- Signs of haemorrhage
- Signs of ARDS
- Signs of thrombosis
What investigation results indicate DIC?
- Platelet count is typically low, with a downward trend, especially in acute sepsis associated DIC
- Fibrin degradation products including D-dimer are elevated. D-dimer is useful in diagnosis and monitoring of DIC. Although not specific, a normal D-dimer excludes DIC as it is highly sensitive.
- Prothrombin time (PT) is elevated (prolonged)
- Activated partial thromboplastin time (aPTT) elevated (prolonged)
- Fibrinogen level low, although this may be normal in more than half of cases
What is acute non-haemolytic reactions during transfusion?
Incompatible transfused red cells react with the patient’s own anti-A or anti-B antibodies or other alloantibodies (anti-Rhesus) to red cell antigens. Complement can be activated and may lead to disseminated intravascular coagulation.
What are the chances of ABO incompatibility and mortality when red cells are mistakenly administered?
- 33% risk of ABO incompatibility
2. 10% risk of mortality with the severest reaction seen in a group O individual receiving group A red cells.
In order for a clot to be formed, what is needed?
- Platelets
- Vessel wall
- Clotting factors
What happens with those three elements for a clot to form? (platelets, vessel wall, clotting factors)
Platelets stick together and to the vessel wall lining, to plug the hole. A fibrin clot formation then occurs to make the plug more stable.
What mediates the adhesion of platelets to the vessel lining?
Von willibrand factor
What are the causes of a prolonged PT (prothrombin time)? (7)
- Deficiency or inhibition of one or more of factors II, V, VII, X and fibrinogen
- Liver disease
- Warfarin
- Vitamin K deficiency
- DIC
- Massive blood transfusion
- Gross over-heparinisation
What can cause an isolated prolonged prothrombin time? (4)
- Early liver disease
- Early warfarin administration
- Early vitamin K deficiency
- Factor VII deficiency (rare)
What part of the coagulation pathway is the ‘motor’ and what is the ‘engine’?
The prothrombin is the motor as it starts of the initial thrombin burst, and this then triggers the engine as it activates the ‘intrinsic system’
What are the causes of a prolonged activated partial thromboplastin time? (9)
- Deficiency or inhibiton of one or more of factors II, V, X, VIII, IX, XI, XII, or fibrinogen
- Liver disease
- Warfarin
- Vit K deficiency
- DIC
- Massive transfusion
- Heparin-unfractionated
- Lupus anticoagulant
- Haemophilia
What are the causes of a prolonged PT AND APTT? (5)
- Deficiency of II, V, X, fibrinogen
- DIC
- Vit K deficiency
- Liver failure
- Warfarin
What are the properties of LMW heparin?
LMWH has a higher ratio of of anti-Xa to anti-IIa activity (compared to fractionated heparin) and has a longer half life allowing for once daily administration. Heparin also has a more predictable anticoagulant response; monitoring is not routinely required.
Why would a patient need to monitor heparin levels?
If they have renal diease (4 hours post dose as this is the half life)
What can the complications of heparin be?
- Heparin induced thrombocytopenia (HIT) - drop in platelet count >50% from baseline, usually 5-10 days after starting
- Skin/allergic reactions
- Bleeding
What can attempt to treat bleeding with unfractionated heparin/LMWH?
Protamine sulphate (derived from fish sperm - check patient does not have fish allergy)
How is INR calculated?
INR = patient PT/ Control PT
Which drugs potentiate the warfarin effect? (11)
- Cimetidine
- Amiodarone
- Sulphinpyrazone
- Cotrimoxazole
- Erythromycin
- Cephalosporins
- Ampicillin
- NSAIDs
- Chlorpromazine
- Sulphonylureas
- Corticosteroids
Which drugs inhibit factor Xa? (3)
- Rivaroxaban
- Apixaban
- Edoxaban
Which drug inhibits thrombin (factor IIa)?
Dabigatran
What are the contraindications for using DOACs? (3)
- Renal impairment
- Women of child bearing age
- Extremes of body weight
What is aspirin and how does it work?
Aspirin is an antiplatelet and works by inactivating platelet cyclooxygenase. There are no reversal agents and its effect last 4-5 days
In addition to aspirin, what are the other antiplatelet drugs?
- Clopidogrel
- Prasugrel
- Ticagrelor
What type of drugs are clopidogrel and ticagrelor?
P2Y(12) antagonists
What can cause vitamin K deficiency?
- Obstructive jaundice
- Prolonged nutritional deficiency
- Broad spectrum antibiotics
- Neonates (classical 1-7 days)
What is the treatment for vitamin K deficiency?
IV/oral vitamin K 10mg for 3-5 days
Why are patients with liver disease more at risk of bleeding?
The liver is essential to the maintenance of normal levels of coagulation factors, components of the fibrinolytic system, and naturally occurring anticoagulants. Hence patients with liver disease invariably have impaired homeostasis.
Summarise the pathogenesis of DIC?
- Excess thrombin generation
- Reduced natural anticoagulant activity
- Decreased fibrinolysis
How does DIC lead to both clotting and bleeding?
The clotting occurs in the form of thrombosis in microvasculature, leading to organ failure due to fibrin deposition, whereas the bleeding occurs due to using up all the use of platelets and coagulation factors –> thrombocytopenia and coagulation factor deficiency
What would the blood film of a patient with a splenectomy features? (4)
- Howell-Jolly bodies
- Pappenheimer bodies
- Target cells
- Irregular contracted erythrocytes
When is Hb defined as low for men and women?
Men <135g/L
Women <115g/L
What are the symptoms of anaemia? (6)
- Fatigue
- Faint
- Breathlessness
- Headaches
- Palpitations
- Tinnitus
What are the signs of anaemia? (4)
- Pallor
- Tachycardia
- Systolic flow murmur
- Heart failure
What are the causes of microcytic anaemia, MCV <80?
- Iron deficiency
- Sideroblastic anaemia
- Thalassaemia
What are the causes of normocytic anaemia? (4)
- Acute haemorrhage
- Anaemia of chronic disease
- Aplastic anaemia
- Haemolytic anaemia
What are the causes of macrocytic anaemia, MCV>100?
Megaloblastic - Vitamin B12 deficiency - Folate deficiency Non-megaloblastic - Pregnancy - Alcohol
Where is iron absorbed?
Duodenum and upper jejunum
What are the causes of iron deficiency anaemia?
- Chronic blood loss e.g. peptic ulcer, menhorrhagia
- Increased requirement e.g. pregnancy
- Malabsorption e.g. Crohn’s, coeliac
- Malnutrition e.g. poor diet
What are the signs of iron deficiency anaemia? (5)
- Koilonychia (spooning of the nail bed)
- Angular stomatitis
- Glossitis
- Pallor
- Tachycardia
What are the investigations for suspected iron deficiency anaemia?
- Bloods - reduced serum iron, reduced serum ferritin, reduced MCV, reduced transferring saturation
- Peripheral blood film - microcytic, hypochromic RBCs
What are the treatments for iron deficiency anaemia?
- Treat underlying cause
- Ferrous sulphate 200mg TDS
- Consider transfusion if symptomatic at rest e.g. dyspnoea, chest pain
What are the side effects of ferous sulphate tablets?
GI upset - constipation, diarrhoea, cramps, vomiting
What are the chronic disease that often contribute to anaemia of chronic disease?
- IBD
- Rheumatoid arthritis
- CKD
- TB
(chronic inflammation, chronic infection and malignancy)
What is the pathophysiology behind anaemia of chronic disease?
Interleukin 6 promotes an increase in liver hepcidin which alters iron metabolism. EPO normally promotes BM to make RBCs but there is a decrease in response to EPO so there is less production of RBCs over time.
What investigations can be carried out when suspecting anaemia of chronic disease? (5)
- FBC
- MCV
- Increased ferritin
- Decreased reticulocyte count
- Treat the underlying cause
What is the cause of aplastic anaemia?
Bone marrow failure
What are the causes of aplastic anaemia/bone marrow failure?
- Idiopathic
- Fanconi’s anaemia (inherited)
- Post viral e.g. hepatitis
- Drugs (NSAIDs, penicillamine)
What investigations may be carried out in suspected aplastic anaemia? (2)
- Blood count - pancytopenia and reduced reticulocytes
2. Bone marrow biopsy - hypo cellular marrow and no abnormal cell population
What is the treatment for aplastic anaemia? (3)
- Treat underlying cause
- Supportive
- Bone marrow transplantation
Where is a bone marrow transplant taken from?
Iliac crest
Why does haemolytic anaemia occur?
When RBCs are broken down faster than they are produced
What are the hereditary causes of haemolytic anaemia?
- Enzyme defects - glucose 6 phosphate dehydrogenase deficiency (favism)
- Membrane defects e.g. hereditary spherocytosis
- Abnormal haemoglobin production e.g. sickle cell anaemia or thalassaemia
What are the acquired causes of haemolytic anaemia? (crap card)
- Immune mediate
2. Non-immediate mediated
What happens to certain LFTs when there is an increased breakdown of RBCs?
- Increased bilirubin
- Increased urobilinogen
- Increased LDH
What would a blood film possibly show (depending on cause) for haemolytic anaemia?
- Sickle cells
- Spherocytes
- Ellipocytes
- Heinz bodies (G6PDD)
- Hypochromic - thalassaemia
What are the clinical features of sickle cell anaemia?
- Symptoms of anaemia/haemolysis - pallor, fatigue, tachycardia, ‘lemon tinge’ skin (pale + jaundice)
- Vaso occlusion - PAIN, chronic renal failure, dactylitis
- Crisis - acute chest syndrome, acute abdomen (mesenteric ischaemia), bone infarction
- Growth failure
- Increased susceptibility to infection (hyposplenism)
Why does sickle cell disease cause the clinical features of sickle cell anaemia?
Due to the shape of the RBC, it disrupts blood flow and breaks down - haemolysis, leading to anaemia. They also obstruct small blood capillaries. Also sequester in the spleen and block it, so you get splenomegaly and it doesn’t work as well.
What are the treatments for sickle cell anaemia? (5)
- Blood exchange/transfusion
- Folic acid
- Hydroxycarbamide (if frequent and painful crisis)
- Antibiotic prophylaxis
- Avoid precipitants and stay hydrated
What is an important side effect of hydroxycarbamide to be aware of?
WBC suppression
What is acute chest syndrome associated with sickle cell crisis?
Pneumonia like syndrome due to sickling in pulmonary vasculature - chest pain, fever, dyspnoea, tachypnoea
What is the treatment for a vaso-occlusive crisis? (ribs, spine, pelvis) (6)
- Cross match blood
- Analgesia - paracetamol, ibuprofen, codeine, morphine IV
- Supportive care - O2 + treat cause
- IV fluids
- Antibiotics
- Give blood if Hb or reticulocytes fall quickly
What is the management for acute chest syndrome? (6)
- CXR, ABG
- Oxygen + spirometry
- Analgesia
- Broad spectrum ABX
- Blood transfusion
- Fluids
What is megaloblastic anaemia?
Unusually large, structurally abnormal RBCs due to defective DNA synthesis
What are the causes of megaloblastic anaemia?
- B12/folate deficiency
2. Drugs
How can B12 deficiency present?
It is macrocytic anaemia with peripheral neuropathy and neuropsych complaints (depression, irritability)
What are the causes of B12 deficiency? (4)
- Poor diet (not enough meat, fish, dairy)
- Malabsorption (pernicious anaemia, Crohn’s, coeliac)
- Reduced gastric breakdown of B12 (previous gastric surgery, atrophic gastritis)
- Drugs (metformin - decreased B12 absorption, PPI)
What is atrophy gastritis?
An autoimmune gastritis with atrophy of parietal cells leading to no intrinsic factor and then B12 isn’t absorbed
Why is B12 not absorbed if there is no intrinsic factor?
B12 combines to IF to form a complex, and this travels to the terminal ileum where it binds with transcobalamin and gets absorbed into the blood stream.
Why is B12 so vital for the body - what is its role?
B12 helps make functioning RBCs and is involved in DNA synthesis of all cells + myelin sheath
Why is B12 deficiency important to correct - what can it lead to?
Subacute degeneration of the spinal cord