Choice of airway

Question 1

Describe the algorithm for deciding between ETT and LMA

Answer 1

? Indication for ETT? Yes --> Use ETT
If no
? Indication for IPPV? Yes --> ETT
If no
Use LMA

Question 2

With regard to indications for intubation: What are the patient factors?

Answer 2

1. Risk of aspiration (Emergency, GORD, Bowel obstruc., autonomic neuropathy - gastroparesis, obesity)
2. Difficulty placing LMA securely (MOODS)
3. Respiratory compromise - IPPV/PEEP required
   - severe lung disease
   - obesity (reduced chest wall compliance)

Question 3

What are the surgical factors the indicate ETT instead of LMA

Answer 3

Operative position (Inaccessible airway)

• Prone for back surgery
• Seated for neurosurgery
• Steep head down/lithotomy for pelvic surgery

Surgical access (protection from blood and surgical debris
- ENT/Dental/opthalmic

Muscle relaxation required and requires IPPV (e.g. laparotomy)

Thoracic surgery
- open chest necessitates IPPV

Neurosurgery
- CO2 control requires IPPV

Prolonged surgery
- IPPV required to reduce WOB

Question 4

What are the other, non-anaesthetic reasons for ETT?

Answer 4

Emergencies

1. Deteriorating airway obstruction
2. Significant airway burns
3. Respiratory failure
4. Cardiorespiratory arrest

Question 5

Summarize the indications for ETT over LMA in anaesthesia

Answer 5

Patient factors (Aspiration risk/RSP compromise IPPV
Surgical factors (Position/Protection/?IPPV)
Emergencies (Burns/Obstruction/Arrest)

Question 6

Describe the risks associated with IPPV through LMA

Answer 6

1. Gastric insufflation –> reflux/aspiration/diaphragmatic splinting–> inefficient ventilation
2. Prolonged pressure on pharyngeal structures (esp. N2O)
3. Pooling of saliva above mask –> leak –> laryngospasm
4. Aspiration risk
5. Inability to increase airway pressures above 20 cmH2O in the event of increased lung compliance

Question 7

List the main complications that can occur during intubation

Answer 7

TRAUMA

• Sore throat (1 in 2 for ETT versus 1 in 5 for LMA)
• Lip lac. perioral bruising (tight ties)
• corneal abrasions/dental damage
• Laryngeal/pharyngeal/tracheal damage –> mediastinitiis/retropharyngeal abscess/air leak

SNS RESPONSE

• SNS–> Increased HR and HPT (IHD, RICP
• Attenuate response: fentanyl/BB (esmolol), lidocaine

DYSRHYTHMIAS (especially in presence of hypoxia/hypercapnoea)

ASPIRATION

MISPLACED TUBE

DIFFICULT or FAILED INTUBATION

Question 8

List early and late complications of endotracheal intubation

Answer 8

EARLY
Displacement (extubation/endobronchial intubation)
Disconnection
Obstruction (intraluminal/extraluminal)
Complications of extubation (wide ranging)

LATE
Tracheal stenosis
Cord/arytenoid dislocation, ulceration, granuloma
Nerve damage (recurrent laryngeal/superior laryngeal)
–> cord paralysis
Sinusitis after prolonged nasotracheal intubation

Question 9

? NEXUS criteria for c-spine imaging

Answer 9

Normal consciousness
No midline tenderness
No neurology
No intoxication
No distracting injury

Question 10

What are the names of the longitudinal contour lines that reference cervical spine alignment

Answer 10

Anterior vertebral line
Posterior vertebral line
Spinolaminar line (posterior margin of the spinal canal)
Posterior spinous line

Question 11

When are flexion and extension views of the c-spine indicated?

Answer 11

To exclude C-spine instability (i.e. in rheumatoid arthritis)

Question 12

What is the AADI and what is the PADI

What films are required to obtain these entities

Answer 12

Anterior atlantodental interval (AADI): the distance between the posterior aspect of the arch of the atlas and the anterior aspect of the odontoid process.

Posterior atlantodental interval (PADI): the distance between the posterior surface of the odontoid process and the anterior margin of the posterior ring of the atlas

Flexion/extension C-spine views are required

Question 13

How is the AADI and PADI interpreted

Answer 13

AADI > 2.5 mm = atlantoaxial subluxation
PADI < 14 mm suggests spinal cord compression

Where there is a risk of cord compression or structural instability: fibreoptic endoscopy and intubation should be considered. (Surgical stabilization should be considered)

Question 14

What are the features that suggest spinal involvement in rheumatoid arthritis

Answer 14

Early onset
Erosive synovitis
Osteopaenia
Ligamentous subluxation
Vertebral fractures

Question 15

What other feature on lateral x-ray suggests difficult laryngoscopy

Answer 15

Reduced atlanto-occipital gap

In the neutral position, if the posterior tubercle of the atlas is already in contact with the occiput, attempts to extend the head result in anterior bowing of the cervical spine and forward displacement of the larynx. An appropriate indirect or fibreoptic technique to securing the airway should therefore be considered.