Endotracheal Intubation of Rabbits (Disease Investigation & Management - Treatment and Care)

Preparation

• Induce anaesthesia in the rabbit (usually with injectable agents, sometimes with injectable and volatile agents in combination. (J60.13.w1)
• Ensure the rabbit is adequately anaesthetised. (J34.23.w1)
  • Wait until jaw relaxation has developed before intubating. (J15.30.w2)
• Give the rabbit 100% oxygen for at least two minutes before attempting intubation to reduce the risk of hypoxia developing; (B601.16.w16) for a few minutes. (J15.30.w2)
• Consider spraying the larynx with lidocaine spray to reduce the risk of laryngospasm. (J15.20.w2, J15.30.w2, J213.1.w1)
• Note: if intubation fails, try a smaller endotracheal tube. If two or three attempts fail, stop trying to intubate, as continuing risks development of laryngeal trauma (oedema, haemorrhage) and laryngeal spasm, which can lead to respiratory obstruction and may therefore be fatal. (J15.20.w2, J34.23.w1)

Blind intubation

• Pre-measure the tube to the level of the larynx.
• Place the rabbit in sternal recumbency and hyper-extend the neck, bringing the glottis in line with the oropharyx.
  • Lift so the rabbit's front legs are only just on the table. (J15.20.w2)
  • Gently pull the tongue out to one side. (J83.28.w1)
• Insert the endotracheal tube into the mouth to the pre-measured point.
• Listen at the connector end of the tube.
  • Or with a clear endotracheal tube, look for condensation appearing in the tube. (J15.20.w2)
• When breath sounds are loudest (when the tip of the tube is at the glottis during inspiration), gently advance the tube.
  • Often increased breathing sounds and commonly a slight cough are noted when the tube enters the larynx. (J15.20.w2)
  OR when strong fogging occurs in a clear tube, indicating correct positioning at the larynx. (J83.28.w1)
  • Condensation clears as inspiration starts; this is the time to advance the tube. (J213.10.w2)
• If the sounds of breathing are no longer audible (or condensation is no longer appearing and disappearing), the tube has failed to enter the larynx; withdraw and try again. (J15.20.w2, J83.28.w1)
• Hold a bit of fur at the end of the tube and check for movement of the fur in association with inspiration/expiration. 
• Note:
  • It is easy to traumatise the glottis with this method. (J60.13.w1)
  • Repeated attempts at blind intubation are not recommended. (J60.13.w1)

(B545.8.w8, J15.20.w2, J15.30.w2, J60.13.w1, J83.28.w1, J213.1.w1)

Direct visualisation

• Place the rabbit in sternal recumbency and hyper-extend the neck, bringing the larynx in line with the oropharyx.
• Hold the rabbit's mouth wide open. 
  • Either use bandage materials or a dental gag as retractors.
  • Or have an assistant hold the skull in a hyperextended position, while the operator pulls the mandible ventrally.
• Gently pull the tip of the tongue out of the mouth.
  • Take care not to damage this on the lower incisors, which have sharp occlusal surfaces.
• Use a small laryngoscope, otoscope or endoscope to allow visualisation of the glottis.
• With a laryngoscope
  • Use a laryngoscope with a size 0 or size 1 Wisconsin blade.
  • Use the blade to keep the mouth open and (tip of the blade) depress the fleshy torus at the back of the tongue.
  • Note: at this point, often the soft palate is ventral to the glottis.
  • With the tip of the endotracheal tube, elevate the soft palate, revealing the glottis.
  • Observe the glottis.
  • During inspiration, insert the endotracheal tube through the larynx into the trachea.
    • Do not force the tube into the trachea.
  • Alternatively in small rabbits: initially insert a smaller-diameter tube e.g. a 5 or 9 French polypropylene urinary catheter, then remove the laryngoscope and advance the endotracheal tube over the catheter into the larynx. Withdraw the catheter.
• With an otoscope with a closed cone
  • Initially pass a stylet (e.g. 3-5 Fr urinary catheter) through the otoscope and through the larynx into the trachea.
  • Pass the endotracheal tube over the stylet.
  • Remove the connector from the endotracheal tube.
  • Remove the otoscope.
  • Reattach the connector.
  • Or pass the stylet, remove the otoscope, then pass the endotracheal tube over the stylet.
• With an otoscope, rabbit in dorsal recumbency: (B601.16.w16)
  • Grasp the tongue and gently pull it forwards and to one side.
  • Introduce the otoscope into the mouth until the larynx is visible.
  • Pass an introducer (e.g. cat catheter) through the otoscope, through the larynx and into the trachea.
  • If the epiglottis is visible rather than the larynx, use the tip of the otoscope, or the introducer, to gently push this out of the way.
  • Keeping the introducer in position, remove the otoscope.
  • Lubricate the tip of an endotracheal tube with gel such as lidocaine gel.
  • Thread the endotracheal tube (2.5 - 3.0 mm for rabbits 1 - 3 kg) over the introducer and advance this through the larynx into the trachea.
    • If there is some resistance (common) as the endotracheal tube reaches the larynx, gentle rotation while advancing the tube may assist.
  • Once the endotracheal tube is securely into the trachea, withdraw the introducer.
  • Tie the endotracheal tube into position.

  (B601.16.w16)

• With a rigid endoscope (J83.35.w2, J213.10.w2)
  • Insert a rigid endoscope into the lumen of a (2.5 - 4.5 mm internal diameter) endotracheal tube; only a few mm of the tube should extend beyond the end of the endoscope.
  • Place the rabbit supine with its head extended over the edge of the table and resting on an assistant's hand
  • Insert the endoscope and tube into the rabbit's mouth.
  • Have the assistant pull the rabbit's tongue slightly outwards.
  • Use direct visualisation to advance through the glottis and vocal cords (as they open during inspiration) and into the trachea.
  • Advance the endotracheal tube over the end of the endoscope, further into the trachea.
  • Quickly withdraw the endoscope.
  • Attach the endotracheal tube to the anaesthetic machine. 
• With a semi-rigid endoscope (J513.7.w1, J213.10.w2)
  • Preparation
    • Select an endotracheal tube, 2.0 - 3.5 mm internal diameter, Cole or straight-walled.
    • Trim the tube at the adaptor end if it is longer than 6 inches in length.
    • Insert a semi-flexible endoscope into the tube from its adapter end.
      • Focuscope semi-flexible fibreoptic endoscope with portable handheld light source. (J513.7.w1)
    • Stop with the endoscope still 1-2 mm inside the tube.
      • This maximises the field of view while protecting the patient's tissues from the end of the endoscope and avoiding saliva and mucus collecting in the tip of the tube.
    • Apply a small amount of lidocaine lubricant jelly or lidocaine injectable solution to the larynx or the tip of the endotracheal tube
    • Look directly through the scope using the handheld battery-powered light source.
      • Or visualise via a video monitor if preferred.
    • Anaesthetise the rabbit.
    • Consider giving atropine or glycopyrrolate to decrease salivary secretions.
    • Place the rabbit in lateral recumbency.
  • Intubation
    • Advance the tip of the combined endotracheal tube and endoscope over the base of the tongue until the tip of the epiglottis is visible through the soft palate.
    • Advance the scope gently dorso-caudally, to lift the soft palate and allow the epiglottis to fall forwards.
    • Withdraw the endoscope about 1 cm so the tip rests on the epiglottis and the glottis is visualised.
    • Advance the endoscope and ET tube into the laryngeal opening.
    • On inspiration, advance the endoscope and ET tube into the trachea.
    • Correct positioning is confirmed by the visualisation of the tracheal rings. (J513.7.w1)
    • Withdraw the endoscope. (J513.7.w1)

(J15.20.w2, J15.30.w2, J60.13.w1)

General

• Confirm the position of the endotracheal tube
  • Auscultate both lung fields to check the tube has not passed the bifurcation and entered one of the bronchi. (J513.7.w1)
  • Note: the rabbit will not necessarily cough when the endotracheal tube enters the trachea. (J60.13.w1)
  • Hold hairs at the connector end and observe these for movement as the rabbit breathes. (J60.13.w1)
  • Check that thoracic movement results if positive pressure ventilation is produced using the anaesthetic circuit. (J60.13.w1)
• Secure the endotracheal tube with open-weave bandage tied around the connector and then around the back of the rabbit's head. (J60.13.w1)

Naso-tracheal intubation

• Hyper-extend the neck.
• Lubricate a catheter of suitable size (e.g. in a 2.0 kg rabbit, 2.5 mm catheter) with lidocaine gel. (B601.16.w16)
• Gently insert the catheter into the nares. (B601.16.w16)
• Ensure entrance to the ventral nasal meatus by lifting the muscular nasal fold and directing the tube ventrally and medially as much as possible. (B601.16.w16)
• Pass a small endotracheal tube via the nasal passages on one side and into the pharynx..
  • 1 mm tube for rabbits under 1 kg bodyweight, 2 mm for larger rabbits. (J213.10.w2)
• Listen for breath sounds; when these are loudest, advance the tube into the trachea.
• Note:
  • There is a risk of transferring pathogens from the upper respiratory tract to the lower respiratory tract.
  • Only a small tube can be used; this will not completely protect the airway.
  • This route is useful if oral lesions or oral procedures mean that intubation via the oral route is not possible.

  (B600.5.w5, B601.16.w16, J213.10.w2)

• Enables provision of supplemental oxygen.
• Protects the lower respiratory tract from foreign material, including fluids (if the tube is tight-fitting or shouldered) during anaesthesia.
• Allows well-controlled anaesthetic gas provision together with minimal atmospheric contamination.
• Enables use of intermittent positive-pressure ventilation (IPPV) if required to assist lung perfusion and if needed during a respiratory crisis.

(J60.13.w1)

• Nasotracheal intubation is useful during oral surgery to deliver oxygen without obstructing access to the oral cavity. (B601.16.w16)

• Rabbits have a small tidal volume, about 4-6 mL/kg; small increases in dead space within the anaesthetic system can significantly affect respiratory efficiency. (J60.13.w1)

• Not appropriate for short anaesthetics where carrying out intubation could unduly prolong the anaesthetic. (J60.13.w1)
• Usually not used for routine dentals, as the tube will reduce oral access. (J60.13.w1)
• Repeated attempts at endotracheal intubation may cause traumatic damage to the larynx (with resultant laryngeal oedema, haemorrhage, laryngospasm or even laryngeal perforation), which can lead to respiratory obstruction and may therefore be fatal. Additionally, repeated attempts at intubation may prolong the required anaesthetic time. (J15.20.w2, J34.23.w1, J513.7.w1) 
  • Attempt intubation only for a limited time (a few minutes). (J513.7.w1)
  • Stop trying to intubate if there is any evidence of injury to the larynx. (J513.7.w1)
• With blind intubation, there is a risk that food or caecotrophs held unseen in the rabbit's mouth may be pushed into the trachea with the endotracheal tube. (V.w125)
• Accidental extubation may occur. (J513.7.w1)
• If the tube is advanced too far it may pass from the trachea into one of the two main bronchi, resulting in aeration of one lung only. (J513.7.w1)
• If the rabbit breaths air, rather than 100% oxygen, prior to intubation, hypoxia may develop rapidly during the intubation procedure. (B601.16.w16)
  • This can be prevented by giving 100% oxygen for two minutes prior to the start of intubation. (B601.16.w16)

• Endotracheal tubes, small, uncuffed, in a variety of sizes. (J60.13.w1)

  • e.g. for a 2.5 kg rabbit, a 2.5 - 3.0 mm tube would be used. (J60.13.w1)

  • Use uncuffed tubes in most rabbits to allow as large an internal tube diameter as possible. (B601.16.w16)
  • In large rabbits (rabbits over 5 kg), a cuffed tube can be used (internal diameter at least 4 mm). (B601.16.w16)

• Note: usually, new tubes need to be shortened so that when the connector is at the lips the end of the tube is in the trachea. Keeping the tube short reduces dead space in the anaesthetic system. (J60.13.w1)

• Local anaesthetic to reduce laryngospasm.

  • e.g. lidocaine spray - Intubeaze, Dechra Veterinary Products) (not licensed for use in rabbits in the UK). (J60.13.w1)

• Stylet to stiffen the endotracheal tube during initial placement, if preferred. (J60.13.w1)

For direct visualisation

• Laryngoscope (Wisconsin size 0 or size 1 blade, rigid endoscope. or otoscope)

  • For visualising the larynx. (J60.13.w1)

  • Wisconsin size 1 for rabbits 3 - 7 kg. (B545.8.w8)

  • Wisconsin size 0 for rabbits 1 - 3 kg. (B545.8.w8)

Over-the-top endotracheal intubation

• Focuscope semi-flexible fibreoptic endoscope with portable handheld light source. (J513.7.w1)

  • The semi-flexible endoscope is rigid enough to act as a guide and push over the soft palate, but soft enough to avoid damaging the animal's tissues. (J513.7.w1)

• Endotracheal tubes, 2.0 - 3.5 mm internal diameter, either Cole stepped wall or straight-walled. (J513.7.w1)

• This procedure should only be carried out by an individual with appropriate clinical training and practical experience.
• Intubation of rabbits needs practice. (J513.7.w1)

• Inexpensive except when expensive endoscopes are used for visualisation.