4.5 Mediastinum Anatomy

Question 1

What is mediastinum? * The

Answer 1

1. • The mediastinum lies between the right and left pleurae
2. • It extends from the sternum in front to the vertebral column behind,

and it contains all the thoracic viscera excepting the lungs

• Superior mediastinum
• Anterior mediastinum
• Middle mediastinum
• Posterior mediastinum

Question 2

Superior mediastinum

Answer 2

1. ° Located above the manubriosternal angle
2. ° Bounded posteriorly by T1-4;
   above it is continuous with the neck;

below it is continuous with both
anterior and posterior mediastina

3. organs:
   Thymus,
   Oesophagus,
   thoracic duct,
   trachea and bronchi
4. Vessels:
   Aorta (arch) and brachiocephalic trunk,
   SVC and both brachiocephalic veins,
   left common carotid artery,
   left subclavian artery
5. Nerves:
   Both phrenic nerves and vagi,
   left recurrent laryngeal nerve

Question 3

• Anterior mediastinum

Answer 3

° Between sternum anteriorly and the pericardial sac posteriorly

° Contains the sternopericardial ligament, fat, and lymph nodes

Question 4

• Middle mediastinum

Answer 4

° Between anterior and posterior mediastinum

° Structures include the
pericardium,
heart,
phrenic nerves,
pericardioacophrenic vessels,
origin of great vessels

Question 5

• Posterior mediastinum

Answer 5

° Between pericardial sac and anterior surface of the vertebral bodies

° Structures include
descending aorta,
oesophagus,
azygous system of veins,
vagus nerve,
thoracic duct,
lymph nodes,
thoracic splanchnic nerves

Question 6

What is the nerve that traverses through the neck/chest and abdomen?

Answer 6

Vagus

Question 7

Where does it lie in the neck, chest?

Answer 7

1. Neck:
   Within carotid sheath along the tracheo oesophageal groove
2. Chest

° Right:
Passes behind the right brachiocephalic vein,
crosses right subclavian artery,
crossed by azygos vein,
travels posterior to the hilum of right lung

Left:
behind left brachiocephalic vein,
crosses aortic arch,
travels posterior to the hilum of left lung

Question 8

Where Does Vagus N. travel in abdomen

Answer 8

• Abdomen

1. ° Right:
   enters abdomen via the oesophageal hiatus of the diaphragm,
   right and posterior to the oesophagus,
   runs along left gastric artery to
   the coeliac plexus
2. ° Left:
   is left and anterior to the oesophagus in the hiatus,
   lesser curvature of the stomach and pylorus

Question 9

Where does the oesophagus start and how long is it?

Answer 9

• At C6 and it is 25 cm long

Question 10

Why is the oesophagus important to anaesthetists?

Answer 10

1. • Mode of feeding—so placement of NG tube
2. • Mode of monitoring—doppler/ TOE/temp
3. • Inadvertent injury—bougie, tracheostomy
4. • Air into stomach especially in children—regurgitation risk
5. • Inadvertent oesophageal intubation

Question 11

How would you anaesthetise for food bolus removal or ingested foreign body?

How many need intervention

What are the implications

Answer 11

Eighty percent of ingested foreign bodies will pass without the need for
intervention.

implications

1. • Risks of impaction,
     with obstruction or
     perforation depending on the type
     of the foreign body
2. • Risk of aspiration
     depending on the location of the foreign body
3. • Usually (not necessarily)
     paediatric population
4. • All issues relating to a shared airway
5. • Underlying oesophageal motility disorder causing impaction

Question 12

How would you anaesthetise for food bolus removal or ingested foreign body?

Timing

Answer 12

Management
* History, examination, and investigations to ascertain
the type and location of the foreign body

Timing of intervention

• Emergency intervention in patients
  with esophageal obstruction or
  ingestion of sharp objects
  leading to perforation or

batteries leading to liquefaction necrosis and perforation

• Nonurgent:
  Coins in the esophagus may be
  observed for 12−24 hours in
  an asymptomatic patient

Question 13

How would you anaesthetise for food bolus removal or ingested foreign body?

Airway

Answer 13

Airway control

• The most acceptable technique to remove a
  gastrointestinal foreign body remains controversial.

Initial management includes assessment of the
patient’s ventilatory status and an airway evaluation

GA with endotracheal intubation

a. Patients unable to manage their secretions (high aspiration risk)

b. Cases of proximal oesophageal foreign body ingestion

c. objects that are difficult to remove

d. When rigid oesophagoscopy is needed

e. Pediatric population

-vs-

Conscious sedation
With midazolam in other patient groups