Cerebrovascular Accident

Question 1

What are the cellular changes that occur in the brain with cerebral ischaemia

Answer 1

1. ATP depletion
2. Calcium overload
3. Ion imbalance
4. Generation of reactive oxygen species
5. Inflammatory signals
6. Cell death

Question 2

Regarding the time period between a CVA and elective surgery, define the following: High risk period and low risk period

Answer 2

High risk period: 0 - 3 months after TIA or stroke

Low risk period: > 9 months after TIA or stroke

Question 3

List 6 factors that may disrupt the blood brain barrier

Answer 3

B B B
3Ts 3Hs 3Is

Trauma
Toxins
Tumours

Hypoxia
Hypercapnoea (severe and prolonged)
Hypertension (severe)

Ischaemia (strokes)
Infection
Intractable seizures

Question 4

What are the preoperative concerns for a patient requiring emergency surgery who has had a stroke within the high risk period

Answer 4

1. Exact nature and extent of neurological deficit
2. Co-existing CVS morbidity
3. Co-existing medications (e.g. warfarin)

Question 5

Describe intraoperative neuroprotective strategies when anaesthetising a patient who has had a CVA

Answer 5

1. Tight monitoring (A-line) and control of blood pressure (vasopressors and beta blockers)
   - -> to compensate for impaired cerebral autoregulation
   - -> Maintain and monitor cerebral perfusion pressure ± 70mmHg
   - -> Consider CVS stable induction agents
2. Maintain normocapnoea
3. Avoid hypoxia
4. Maintain euglycaemia
5. Minimize risk of coagulopathy (avoid excessive fluid etc)
6. Optimize analgaesia while avoiding hypotension to ensure adequate inhibition of SNS

Question 6

What are the indications for tracheostomy

Answer 6

1. Expected prolonged mechanical ventilation (>7 days) usually in the ICU setting
2. Emergency airway intervention in a can’t intubate and can’t oxygenate situation
3. Upper airway obliteration: advanced laryngeal cancer
4. Facilitate weaning off mechanical ventilator

Question 7

What are the advantages and disadvantages of tracheostomy tube

Answer 7

Advantages

1. Ease of replacement (once tract has formed)
2. Enhanced speech, mobility, swallowing
3. Ease of suctioning
4. Patient comfort
5. Patient can be nursed outside ICU

Disadvantages

1. Complications at cuff site
2. Local complications
   - Tracheo-Innominate artery fistula formation
3. Infections
   - Increase pulmonary infections
   - Access to mediastinum by infections agents
4. High mortality: inadvertant decannulation before tract formation

Question 8

What are the physiological advantages of a tracheostomy tube versus an ETT

Answer 8

1. Reduced work of breathing
2. Reduced airway resistance
3. Reduced intrinsic PEEP
4. Enhanced ventilator-patient synchrony
5. OVERALL: FACILITATE WEANING from MECHANICAL VENTILATION

Question 9

List 5 possible intra-operative complications when performing a tracheostomy on a patient that is intubated and ventilated

Answer 9

1. Damage to in situ ETT cuff with significant leak and compromised oxygenation and ventilation.
2. Removal of ETT prior to securing definitive placement of tracheostomy tube
3. Bleeding into the the trachea with airway obstruction
4. Bleeding into the airway with aspiration
5. Stromal complications: pneumomediastinum, surgical emphysema, pneumothorax.