Blood and Haemostasis Flashcards
What is left shift?
Left shift or blood shift is an increase in the number of immature leukocytes in the peripheral blood, particularly neutrophil band cells.
Left shift may also refer to a similar phenomenon in severe erythroanemia, when reticulocytes and immature erythrocyte precursors appear in the peripheral circulation
What is the tissue O2 delivery equation and what is its significance?
Tissue O2 delivery: CO x Hb x O2 Sat x 1.34
Don’t only look at Hb levels, Ability of cardiac system to compensate for loss in Hb can still preserve O2 delivery, HR is a good guide to assess anaemic patients and ability to compensate is dependent on time (i.e. SV can increase if anaemia happens slowly overtime)
What are the classifications of anaemia?
- Regenerative (susceptible to haemolysis, quick drop in Hb or O2 delivery, very dangerous)
- Aregenerative (compensate better, more time)
-Microcytic, normocytic, macrocytic
What are the increased signs of production, destruction and loss of RBC?
Signs of increased production -reticulocytes, polychromasia (blue tinge due to Hb formation) Signs if increased destruction -Jaundice (increased serum bilirubin) -haptoglobins LDH Blood Loss -overt (see it)/covert (ask about it)
What are the 6 things to know about how blood is made?
- How much is enough
- RBC 3-5 x 1012 /L, replace every 120 days
- WBC 2-6 x 109 /L, replace every 3-5 days
- Platelets 150-400 x 109 /L, replace every 10 days
- Where is it made
- Yolk sac - first few weeks
- Liver and spleen - 6wks-7months (can be enlarged by re-recruiting liver and/or spleen in diseases of the blood to make more blood cells)
- Bone marrow - 7 months-whole life (bone marrow sampling from the pelvis) - Pluripotent stem cell
- Capable of self renewal
- Differentiate into all haemopoietic cell lines
- Give rise to lymphocytes and osteoclasts
- Exist in small numbers in marrow - Bone marrow stroma
- Provides specific environment for BM to grow, complex
- Change in adhesion molecules mark progression of cells through the stroma
- Bone marrow in continuity with blood circulation - can find its way back to BM when injected into veins - Haemopoietic Growth factors
- Glycoprotein hormones
- Local and circulating action
- Multiple effects mediated through specific receptors, Conformational change when binding to receptor - Haematinic
- Iron: in Hb carries O2, need adequate levels in diet
- B1: animal products,
- Folate: green leafy vegetables
What is Virchow’s triad?
Abnormalities in:
- Vessel Walls
- Blood flow
- Blood composition
can all lead to thrombosis!
What is the principle of coagulation testing and what does it tell us?
Take patient sample, spin it and separate plasma from cells, only do tests on plasma (no endothelium, platelets or cells) and add activation factors which activate cascade at a certain point and measure time until clot formation
- artificial construct, not a true measure of physiology, can only predict clinical behaviour and integrity of factors within the cascade.
- must maintain sample integrity and undertake duplicate testing!
What are the consequences of abnormal levels of thrombin?
Insufficient Thrombin = bleeding
Excessive thrombin = thrombosis
What is subunit co-operativity and how does it explain sigmoidal O2 binding?
Co‐operativity
1. Haemoglobin needs to have high “ affinity ” to bind O2 in the lungs. (Hb is ~90% saturated)
- Once the Hb‐O2 complex reaches the tissue thatconsumes oxygen, the O2 needs to be transferred to myoglobin. (Hb in venous blood is 64% saturated)
- Sigmoidal curve: represents weak‐binding state at low P02 and strong binding state at high P02
- conformational change at one subunit induces increased O2 binding affinity in adjacent subunit in a co-operative manner (progressive stabilisation of tense state with increased O2 binding and vice versa)
Hb makes up …% of RBC dry content?
97%
How is CO2 transported by Hb?
@ tissues: 15% of CO2 formed is carried on amino terminal of deoxy-Hb as carbamate
@ lungs: O2-Hb binds CO2 less readily than deoxy-Hb, so CO2 is released in lungs
What are the effects of allosteric effectors to achieve variable sigmoid binding of oxygen?
2,3‐BPG: binding decreases Hb affinity for O2 => helps release O2 in the tissues
The Bohr effect: Acid is produced in the tissues
‐ The binding of protons to Hb lowers its affinity
for O2
How does foetal Hb differ from adult and what is the significance?
‐ HbF (containing 2 gamma subunits instead of beta) binds O2 with greater affinity than the mother’s HbA (adult form of Hb) because HbF binds 2,3‐BPG less avidly than HbA.
‐ this gives the foetus access to oxygen carried by the mother’s HbA.
What is mutation causes sickle cell anaemia (HbS) and what are the consequences?
Mutation is a one base change from Glutamate to Valine
HbSS => susceptible to sickle‐cell crisis (e.g vaso‐occlusion)
‐ HbSA => no symptoms = sickle‐cell trait; some protection from malaria
