Post on 15-Jan-2016
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iBSc: Question 9
By Alan McLeod
Getting the best marks
Read the whole question – a latter section may give you a
clue about an earlier one.
To see how many points you need look at the marks
allocated – for example a 3 point question is generally looking for 3 salient points
If giving a list answer put the best answers first – examiners will not usually mark answers too
far down a list
Always write something – it may get you part of a mark and is anonymised so
no one will think you are stupid!
If you genuinely have no clue then re-write the question to see if this sparks
some ideas.
If not then move on and come back at the end. And remember – always
write something.
Good luck!
Question 9
Mrs Kennedy (78) has been in
hospital for 2 weeks after
fracturing her left neck of femur.
Q9.1• Describe the blood
supply of the femoral head (3)
Question 9
The fracture is intracapsular and was repaired 10 days ago by a
surgical procedure
Q9.2• Why is the intracapsular
site important in terms of outcome? (2)
Q9.3• What procedure was
most likely used (1)
Question 9
On day 14, Mrs Kennedy develops
sudden onset chest pain and shortness of
breath.
Q9.4• List three likely
diagnoses (3)
Question 9
A pulmonary embolus is
diagnosed by ventilation
perfusion scan.
Q9.5• Describe the main three
vessels that traverse the lung and the function of each (3)
Q9.6• Which of these is
obstructed by PE (1)
Question 9
A DVT (deep vein thrombosis) is
found in her left femoral vein.
Q9.7• List the common
components of a thrombus (3)
Q9.8• List two of her risk
factors for DVT (2)
Question 9
She is started immediately on low molecular weight
heparin and warfarin
Q9.9• How do these two
drugs affect clotting (6)
Q9.10• Why is heparin started
as well as warfarin? (1)
The Answers
View these on ‘note view’ rather than on full screen – additional
notes are provided for some slides
Fractured Neck of Femur
Blood supply to head
- In order of importance• Capsular supply
– From Med + Lat circumflex
– From Deep femoral
• Nutrient artery– From deep femoral
• Ligamentum teres– From Medial epiphyseal
Fractured Neck of Femur
Fractured Neck of Femur
Chest Pain Differentials
I Infectious / inflammatory Pneumonia, pleurisy, Costochonditis
G Genetic / ideopathic
E Endocrine
T Trauma Fractured rib, pulled muscle, pneumothorax
V VascularMyocardial infarction, angina, aortic dissection, PE
I Iatrogenic / ingested Surgical scar
N Neoplastic Bony mets
O Organs / other
Oesophagus (spasm, reflux), heart (pericarditis)Lung, Aorta, bones, muscle, cartilege, anxiety
Vessels in the Lung
• Pulmonary Artery– Deoxygenated blood– From Right Ventricle– Oxygenated in lungs– Affected in PE
• Bronchial Artery– Oxygenated blood– From systemic supply– Supplies tissues of lung
• Pulmonary vein– Oxygenated blood– From lungs– To Left atrium
Thrombosis
The three main factors leading to thrombus are Virchow’s Triad
• Flow changes• Endothelial damage• Composition changes
of blood
Usual components of thrombus
• Platelets• Fibrin• Red blood cells
• Several types of thrombus with varying quantities of these.
Thrombus Formation
• Platelet activation• Fibrinogen fibrin• Fibrin assembles into
long fibrils• Platelets + Fibils =
Clot• RBCs join later
DVT
Major DVT risk factors:• Active cancer• Paresis, paralysis or
recent plaster cast of lower extremity
• Recently bedridden for more than 3 days
• Major surgery within 4 weeks.
Lesser risks include:• Oral contraceptive• Long flights or car
journeys• Smoking• Obesity• Family history• Heart failure• Pacemaker
Vitamin KReductase
Vitamin K and Warfarin
• Factors 2,7,9 & 10 must be gamma carboxylated
• Vitamin K is a vital cofactor
• Warfarin inhibits enzyme– Prevents Vitamin K
recycling
Vitamin KReductase
Oxidised Vitamin K
ReducedVitamin K
Factors 2,7,9 & 10
Gamma carboxylated
Vitamin K
Warfarin
--
ATIII and LMW Heparin
IIaIIaIIaLMW
Heparin
XaFactor
Xa
XaXa
*
*
* Note the change in ATII conformation
No substrate binding
No substrate binding needed
ATIII and Unfractionated Heparin
IIaIIaIIa
ATIII
Heparin
Factor IIa(Thrombin)
XaFactor
Xa
XaXa
*
*
* Note the change in ATII conformation
ATIII and Heparin - Summary
• Antithrombin III deactivates clotting factors IIa (thrombin) & Xa
• It does NOT need heparin to do this
• BUT heparin makes it go FASTER
• LMWH only works on Xa
• Longer molecules in unfractionated heparin work on IIa (thrombin) as well
Heparin and Warfarin
Heparin• Effective within hours• Subcutaneous
(LMWH) or IV infusion (unfractionated)
• Not good for home use
• Started early to give immediate cover
Warfarin• Effective within days• Oral• Good for home use• Regular INR checks
needed• Started early to build
up to therapeutic levels before discharge.
The End
The slides here should allow you to mark your own work – remember 1 mark per
answer up to the maximum for the question. Multiply by 4 to get percentage points. I assume a 60% pass mark. Sorry but I am unable to give further advice on
answers due to time constraints.