Radiology

Question 1

Why would you expect CVS collapse in a patient with a pneumothorax?

Answer 1

If the pneumothorax increases in size, it causes meadiastinal shift.

This reduces venous return, CO would fall and result would be profound hypotension with compensatory tachycardia.

Question 2

What are the causes of pneumothorax?

Answer 2

Primary spontaneous - no underlying lung disease

Secondary spontaneous - known lung disease (TB, COPD, malignancy)

Trauma - penetrating chest wall injury, rib #s, blunt trauma

Iatrogenic - IPPV, CVC insertion, nerve blocks, barotrauma

Question 3

How do you judge whether a CXR is adequately exposed or not?

Answer 3

Check if you can see 1st 7 thoracic vertebrae and hilar vessels clearly

Question 4

How recently do you need a pacemaker check prior to surgery?

Answer 4

3 months for an elective case

Question 5

Can you use bipolar diathermy in patients with pacemakers?

Answer 5

Yes. Unipolar should be avoided.

Question 6

What should you have available when anaesthetising a patient with a pacemaker?

Answer 6

• Other pacing facilities
• access to isoprenaline, atropine, glycopyrrolate

Question 7

Why should you avoid the use of nitrous in a patient with a perforation?

Answer 7

Nitrous diffuses into air filled cavities including the bowel.

It exacerbates bowel distension, making surgery more difficult.

Postop it can contribute to intestinal oedema, abdominal distension and nausea.

Question 8

What does this CT head show?

Answer 8

Extensive SAH with hydrocephalus

Question 9

How may a SAH present?

Answer 9

Sudden severe headache

Photophobia

Neck stiffness

Vomiting

Decreased GCS/seizures

Question 10

What are risk factors for SAH?

Answer 10

• presence of cerebral aneurysms
• smoking
• alcohol
• drug abuse
• HTN
• family Hx

Question 11

What is the sensitivity of CT scan for SAH?

Answer 11

95%

If CT is negative, an LP can be done to look for xanthochromia. This will detect 2-5% of SAH who’ve had a -ve CT head.

Question 12

What CVS complications are associated with SAH?

Answer 12

Arrhythmias to ischaemic changes.

MI is a complication of SAH.

Attributed due to increased sympathetic activity following neurological insult.

Question 13

Why is ketamine not a good choice for induction in SAH?

Answer 13

• increases HR/BP/cerebral blood flow and metabolic rate of oxygen (CMRO2)
• therefore raises ICP
• this is against what we’re trying to do - preserve cerebral perfusion pressure
• HTN/hypotension are detrimental

Question 14

What is the problem with maintaining anaesthesia with a MAC>1 in SAH patients?

Answer 14

Volatiles reduce cerebral metabolic rate, but at >1 MAC they abolish cerebral autoregulation.

Question 15

What resp complications are associated with SAH?

Answer 15

• neurogenic pulmonary oedema
• aspiration pneumonia

Question 16

What are the principles of anaesthetic management of SAH?

Answer 16

Prevent secondary brain injury by optimising O2 delivery + reducing demand.

• maintain adequate CPP (>65 mmHg)
• avoid periods of hypoxia + treat anaemia
• aggressive treatment of factors that increase cerebral O2 demand, such as pyrexia/seizures/hyperglycaemia
• steps to minimise ICP
  
  • ventilate to normocapnia
  • adequate anaesthesia and analgesia to reduce cerebral metabolic rate
  • avoid increased venous pressure
    
    • head up tild, no tube ties, adequate paralysis to prevent coughing
  • careful fluid balance to prevent cerebral oedema
  • avoid drugs that increase ICP (ketamine)

Question 17

Is this film adequate?

Answer 17

Yes.

It must include C1-C7 with associated anterior structures, the vertebral column in the centre of the film and it must extend from base of skull to T1.

Question 18

What lines on a C-spine Xray are used to assess vertebral alignment?

Answer 18

• anterior vertebral line
• posterior vertebral line
• spinolaminar line

Any deviation from the line suggests an abnormality.

Question 19

What major abnormality does this show?

Answer 19

Gross instability of the atlantoaxial junction with subluxation of C1 and C2 on C3

Question 20

Why is atlantoaxial instability life threatening?

Answer 20

It is susceptible to even the smallest of traumatic insults.

Injury at this level can denervate the phrenic nerve (C3- 5) leading to respiratory compromise and arrest.

Question 21

What happens to the transverse ligament in atlantoaxial subluxation?

Answer 21

It is damaged or completely ruptured.

It normally holds the odontoid peg in place posterior to the anterior arch of the atlas. It plays a key role in resisting anteroposterior movement of the atlas with the axis and lower C spine.

Question 22

What conditions are associated with atlantoaxial subluxation?

Answer 22

• rheumatoid (70% will have an upper C spine abnormality and 20-25% have frank atlantoaxial subluxation)
• Down’s syndrome
• Osteogenesis imperfecta
• Klippel-Feil syndrome

Question 23

Label this angiogram.

What ECG changes would you see if there was occlusion at the arrow?

Answer 23

A. Left main coronary artery

B. Left anterior descending coronary

C. Circumflex

You’d see ST elevation/depression, T wave inversion and later Q wave formation, in leads V1-4.

Question 24

What does the circumflex artery supply?

Answer 24

Left atrium and posterolateral wall of the left ventricle.

It anastomoses with interventricular branch of the RCA on posterior aspect of heart.

Question 25

What are the sinuses of Valsalva?

Answer 25

Also known as the aortic sinuses.

They are outpouchings of the ascending aorta that occur just superior to the aortic valve.

There are typically three sinuses: right anterior, left anterior and posterior.

They give rise to the right coronary artery, left coronary artery, and the posterior usually contains no vessel origin and is therefore known as the non-coronary sinus

Question 26

Which vessels supply the SA and AV nodes?

Answer 26

Right coronary artery in 90% of people

Question 27

Normal coronary blood flow?

Answer 27

250 ml/min (5% CO)

Question 28

Give 4 factors affecting coronary blood flow

Answer 28

• vessel diameter/patency (presence of atherosclerosis, factors producing coronary vessel dilatation/constriction)
• HR (determines duration of diastole when coronary blood flow is greatest)
• blood viscosity
• pressure gradient between aortic end-diastolic pressure and left ventricular end-diastolic pressure (SVR is main determinant of diastolic pressure therefore must be maintained in those with myocardial disease)

Question 29

What are risk factors for IHD?

Answer 29

• male
• smoking
• obesity
• HTN
• diabetes
• age
• positive family history