iBSc: Question 9

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iBSc Question 9

• By Alan McLeod

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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!

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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)

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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)

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Question 9

• On day 14, Mrs Kennedy develops sudden onset
  chest pain and shortness of breath.

• Q9.4
• List three likely diagnoses (3)

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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)

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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)

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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)

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The Answers

• View these on note view rather than on full
  screen additional notes are provided for some
  slides

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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

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Fractured Neck of Femur
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Fractured Neck of Femur
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Chest Pain Differentials
I Infectious / inflammatory Pneumonia, pleurisy, Costochonditis
G Genetic / ideopathic
E Endocrine
T Trauma Fractured rib, pulled muscle, pneumothorax
V Vascular Myocardial 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
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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

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Thrombosis

• The three main factors leading to thrombus are
  Virchows 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.

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Thrombus Formation

• Platelet activation
• Fibrinogen ? fibrin
• Fibrin assembles into long fibrils
• Platelets Fibils Clot
• RBCs join later

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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

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Vitamin K and Warfarin
Factors 2,7,9 10
Gamma carboxylated

• Factors 2,7,9 10 must be gamma carboxylated
• Vitamin K is a vital cofactor
• Warfarin inhibits enzyme
• Prevents Vitamin K recycling

Oxidised Vitamin K
ReducedVitamin K
Vitamin K
-
-
Warfarin
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ATIII and LMW Heparin
No substrate binding
LMW Heparin
IIa

No substrate binding needed
Xa
Xa
Xa
Factor Xa

Note the change in ATII conformation
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ATIII and Unfractionated Heparin
Heparin

Factor IIa (Thrombin)
ATIII
Xa
Xa
Xa
Factor Xa

Note the change in ATII conformation
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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

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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.

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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.