Intubation Of Anaesthetised Patient

Front 1

What are the 7 reasons to place a endotracheal tube in an anesthetized animal?

Back 1

1) Prevent obstruction and maintain patent airway throughout anesthesia.
2) Prevent aspiration of GIT contents that may be regurgitated.
3) Facilitate the administration of Oxygen and other medical gases including the inhalational agents.
4) Minimise environmental contamination with anaesthetic agents.
5) Facilitate mechanical ventilation (Intermittent positive pressure ventilation).
6) Reduce the anatomical dead space associated with breathing by bypassing the nasal passages.

Front 2

Describe the murphy’s tube (4)

Back 2

1.Most common type
2.Same diameter throughout the length of the tube.
3.Proximal end has a connector to the anaesthetic circuit.
4.The distal end has a bevel and an opening called Murphy’s eye to prevent obstruction if the tube becomes obstructed.

Front 3

What are the advantages of cuffed versus uncuffed ETT?

Back 3

Inflation of the cuff ensures that the space between the ETT and the wall of the airway is not patent. This prevents aspiration of material from the pharynx into the lungs and prevents gases being delivered to the lungs from leaking out of the patient into the atmosphere.
A cuffed ETT is required if an animal need to be ventilated. During ventilation the inpred air will follow the path of least resistance.

Cuffs can cause some resistance to passage of ETT in animals with airway disease, esp high volume low pressure cuffs which may sit completely flat against the wall of ETT when deflated. In animals with partially obstructed airways, placement of uncuffed ETT can be easier and is recommended in emergencies. The uncuffed tube can be exchanged for a cuffed one once the animal is stable. TO prevent inward compression and patial obstruction of the ETT when the cuff is inflated the wall of the cuffed ETT is thicker and have greater outside diameter than an uncuffed tube. As a result an ETT with a comparatively smaller internal diameter is required when a cuffed ETT is selected for use instead of uncuffed ETT. This will increase resistance to breathing esp when using small ETT (4-5mm ).

Front 4

What are the 2 types of cuffs available?

Back 4

1. Low volume high pressure cuffs : In older style rubber ETT. Increase chance of pressure necrosis.
2. High volume low pressure cuffs: Most common. Larger size, larger distributionof pressure, lower chance of pressure necrosis. Can still occur.

Front 5

What does the size of the cuffs refer to? What sizes are available?

Back 5

Internal diameter of ETT. Uncuffed 2-mm. Cuffed 3-20mm

Front 6

What are the 2 considerations taken for selecting ETT sizes for patients

Back 6

1. Apparatus dead space: No gas exchange. Increased if the ETT tube is past the incisors. For a given tidal volume, increased dead space reduces the proportionsof the tidal anaesthetic gases that can be delivered and carbon dioxide that can be removed. In adition increased dead space will also lead to increased rebreathing of expired alveolar gas that contain CO2.
2. Resistance: Proportional to radius. As a result a small decrease in radius can cause a large increase in the resistance to breathing. Hence choose the safest largest ETT. Resistance is also linearly proportional to the length of the ETT. Thus minimizing the length of the tube beyond animal mouth.

Front 7

Laryngoscopes. What are they for?

Back 7

Aids in intubation for visualization of the larynx.

Front 8

In what animals is the laryngoscopes not useful? And what animals essentially require it?

Back 8

Cattle and horses.
Small ruminants and pigs

Front 9

What are the straight or curved blades for?

Back 9

The straight blade is designed to depress the epiglottis and the tongue. The curved blade is designed to depress the tongue and pull the epiglottis down without directly touching the epiglottis. This is preffered in animals prone to laryngospasm.

Front 10

What are stillettes ?

Back 10

They are malleable plastic coated metal stylet used to alter the curvatureof the entotracheal tube. It prevents the ETT from bending during intubation.
Can be used to guide ETT into the airway. Useful when larynx is not visible due to swelling disease or small ruminats or pigs. ETT fed over the stillettes as its fed into the larynx by direct visualization. Can also be used to exchange old ETT for a new one. Dog urinary catherter is useful instead of a stillettes.

Front 11

What are the 3 steps to be taken prior to induction?

Back 11

1. Select the appropriate sized ETT. 2 additional tubes (one smaller and one larger selected).
2. Inflate the cuffs. Leave cuffs inflated while preparing the rest of your equipment as this will help detect leaks.
3. Immediately prior to induction, deflate cuff and lubricate.

Front 12

What are the 8 steps after induction?

Back 12

1. Position the animal so that the larynx can be visualized. Sternal recumbency with head and neck extended
2. Pull tongue to side. Avoid canines.
3. Spray lidocaine in species prone to laryngospasm. Wait 30s.
4. After the larynx is visualized with the laryngoscope, the ETT is passed between the arytenoids. Gentle twisting may facilitate the process.
5. Correct positioning is confirmed by direct visualization as the detecting escape of air from ETT may also indicate gas from stomach or lung. Avoid chest compression. Palpation of the neck is useful for animals without direct visualization like in the horse. Palpation of solid cylinder object (ETT in the oesophagus is consistant with incorrect placement. The gold standard fro confirming the correct position is the detection of expired CO2 capnography.
6. Tie ETT in place secures the tube from dragging off the cuff on the tracheal mucosa and associated trauma.
7. Connect patient to oxygen and inflate cuff. Ideally the cuff should be inflated while listening for leaks during manual inflation for the patients chest by an assistant. The cuff is inflated until no leak is audible during delivery of normal tidal volume. Ideally a manometer should be used to measure the pressure generated during manual inflation of the chest.
8. Once the cuff is inflated the anaesthetic agent is turned on. Check the cuff because the anesthetic will cause muscle relaxation which increases the size of the airway.

Front 13

What are the steps of extubation? (7)

Back 13

Removal of the ETT is performed as soon as the animal is able to swallow and sufficient reflexes have returned to allow the animal to protect the airway from aspiration and obstruction.

1. Prior to termination of anaesthesia, the pharynx is inspected for foreign material/mucus. Remove it.
2. Animal should either be left in theather or moved to quiet place be termination. The animal should not recover in transit as the anaesthetist is less able to deal with any complication that arise.
3. As animal lightens, the tube tie is untied. The cuff is left inflated until the patient starts to swallow.
4. Once swallowing is observed, the cuff is deflated and the tube gently removed. For most animals repeated swallowing should be present before the removal of ETT.
5. After removal, check airway. If good, air movement can be detected at the nostrils or mouth and chest movements should b smooth and normal. If there is no movement of air, chest wall movements exaggerated and or the animal is cyanotic, there is an obstruction so Intubate again. Require readministration of IV agents like propofol.
6. Monitor animal until animal can hold its head up unsupported. Animal should be able to clear stuff from mouth.
7. NO ANIMAL should be stimulated to wake up. These animal will return to the previous level of anaesthesia once they are left undisturbed and if extubation has been performed, the airway may not be protected.

Front 14

What are the 6 common complications with intubation.

Back 14

1. Laryngospasm: Obcerved in cats, pigs, dome small ruminants. Prevented with Lignocaine. Can be sprayed or injected.
2. Endobronchial entubation : If ETT is excessively long, will cause only the entubated lung to be ventilated. Can be prevented by checking the ETT length and shortening the ETT if necessary.
3. Pressure necrosis of tracheal mucosa : overinflation of the cuff, particularly low volume high pressure cuffs. Can lead to scarring and stenosis.
4. Tracheal rupture: can occur in cats due to over inflation of the cuff. Use small syringes to inflate cuff.
5. traumatic intubation can cause swelling of the airway and lead to partioal or complete airway obstruction after extubation.
6. Endotracheal tubes can be obstructed with mucous or due to kinking. The smaller tubes are more at risk of kinking due to relatively thin wall.

Front 15

What are the 3 indications for using a face mask?

Back 15

1. Induction of anaesthesia with inhalation agent.
2. Pre- oxygenation.
3. Delivery of inhalation anaesthetics for maintenance of anaesthesia in animals tat are too small to be intubated (rats and guinea pigs)

Front 16

What are the disadvantages of using a mask?

Back 16

1. Increased risk of rebreathing. High o2 rate required.
2. Environmental contamination. Ensure mask is tight and make sure the room is well ventilated.
3. Remember the airway is not protected. Obstruciton from regurgitation can occur.