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.