Case 18 - AAA

Question 1

What is AAA?

Answer 1

Dilatation of the aorta >50%

Ectasia=dilatation 50% or less of the diameter

Question 2

How does the location of an aortic aneurysm change the risk of surgery?

Answer 2

Thoracic - highest risk as the cross-clamping will cause ischaemia to more organs

Abdominal - medium risk, as there will still be ischaemia but not to as many organs

Popliteal - Biggest risk due to limbs becoming ischaemic

Question 3

How do you describe an aortic aneurysm?

Answer 3

Location
Size
Shape
Simple/complications

Question 4

RFs for AAA?

Answer 4

HTN
Older than 60
Smoker
FHx
Male

Question 5

How can exam pick up AAA?

Answer 5

Should palpate just superiorly to the umbilicus
When fingers move apart its a pulsatile mass
When fingers move up its an expansile mass

Tend to have other aneurysmal changes
Exam only picks up half of AAA

Question 6

What are signs and symptoms of AAA?

Answer 6

Asymptomatic
Back pain
Tenderness
Limb ischaemia
Triad of collapse, low BP /flank pain

Question 7

Differentials for AAA?

Answer 7

Perforated viscous
Acute pancreatitis
Biliary colic
Aortic dissection
Acute mesenteric occlusion

Question 8

Causes of AAA?

Answer 8

Mycotic - infection of the vessel wall
Connective tissue disorders
Atherosclerosis
Inflammation

Question 9

What investigations can be done for a suspected AAA rupture/dissection?

Answer 9

FAST USS - done when there’s undifferentiated hypotension
Can detect free fluid in the abdomen

CT angiography - Determines if endovascular repair is possible by looking at the position of the aneurysm in the aorta

Question 10

When should you treat a AAA?

Answer 10

Always treat when its symptomatic
When it’s <4.5cm monitor with yearly USS
When it’s >5.5cm consider surgery on a risk-balance basis.3 monthly USS

Question 11

How does endovascular surgery treat AAA?

Answer 11

Need good proximal infrarenal neck and iliac arteries
From the inside, insert a stent
Spinal anaesthesia
There’s a smaller risk than with open due to lack of cross clamping and therefore ischaemia of organs
May need a secondary procedure, and there are leaks

Question 12

How does open surgery treat AAA?

Answer 12

Replace the affected segment with graft/tube/bifurcate
Under general anaesthetic
CV stress from cross clamping
Can cause renal failure
Fairly high mortality

Question 13

What is an aortic dissection?

Answer 13

When there is a cut in the intima, and the blood seeps through between the intima and media
It builds up and clots
Then an exit tear when the blood builds up and forces its way back through the intima

Question 14

What can causes a dissection of the aorta?

Answer 14

HTN
Connective tissue disorder
Aneurysm
Trauma

Question 15

What is the Stanford classification of aneurysm?

Answer 15

A is when its before the junction of the LSCA. Treat with surgery
B is after. Use medical management

Question 16

What are 4 types of shock?

Answer 16

Hypovolaemic
Obstructive
Distributive
Cardiogenic

Question 17

What is hypovolaemic shock?

Answer 17

When there isn’t enough blood e.g. trauma, leads to a reduction in circulating volume
Reduction in circulating volume > ischaemia

Question 18

What is cardiogenic shock?

Answer 18

When there is heart dysfunction, there will be a reduction in circulating volume
Ischaemia

Question 19

What is distributive shock?

Answer 19

When there is vasodilation and reduced perfusion of the blood away from vital organs leading to ischaemia of certain organs
e.g. SIRS and anaphylaxis

Question 20

What is obstructive shock?

Answer 20

Failure of circulatory flow e.g. PE, pneumothorax

Question 21

What are the signs of shock?

Answer 21

Prolonged CRT
Oligouria
Metabolic acidosis
Cool skin
Cognitive changes

Question 22

What types of fluids can be used in shock?

Answer 22

Crystalloids - Are not made of large molecules, but small molecules dissolved in solution
Go to ECF

Colloids - used to bulk up circulating volume and draw water back into the circulating volume
But, risk of allergic reactions and anaphylaxis

Question 23

What is the approach for major haemorrhage?

Answer 23

1) Resuscitation
2) Stop bleeding, reverse coagulation, local management if necessary
3) Team approach -Communication with the lab early on. Group and save. Order packs from the lab - Pack 1 is 4 packs RBC, 4 FFP. Pack 2 is pack 1 + platelets, cryoprecipitate
4) Monitor clotting due to coagulopathies due to dilution of clotting factors
5) Be aware of complications - Renal dysfunction, DIC, acute coagulopathy of shock

Question 24

What is the criteria for having a major haemorrhage?

Answer 24

Needing 4 units over 1 hour or 10 units in 24 hours

>150ml a minute

Question 25

How is DIC caused by fluid?

Answer 25

As clotting inhibitors are used up, thrombin increases and fibrinolysis increases
FDP (fibrin degradation product) and D-dimer increase = DIC

Question 26

How is acute coagulopathy caused by fluids?

Answer 26

Tissue damage leads to tissue factor release
There is clotting and fibinolysis is activated
Extra Protein C leads to bleeding