TECHNIQUE

Inhalational Anaesthesia Induction in Rabbits (Disease Investigation & Management - Treatment and Care)

Summary Information
Type of technique Health & Management / Disease Investigation & Management / Techniques:
Synonyms and Keywords --
Description Exposure of a conscious rabbit to anaesthetic vapours to induce anaesthesia. Note: this is NOT a preferred way to induce anaesthesia in rabbits, due to their apparent aversion to vapours of volatile anaesthetics and breath-holding response, as well as struggling, when exposed to volatile anaesthetics. (B601.16.w16, J34.23.w1)
  • If this method of induction is used, the rabbit should be premedicated with an appropriate sedative. (B600.5.w5, B601.16.w16, J15.30.w2)
Pre-medication
  • Give an appropriate sedative agent: (B601.16.w16)
Induction
  • Place the rabbit under physical restraint. (B601.16.w16)
  • Place a face mask on the rabbit, giving it 100% oxygen for at least two to three minutes. (B600.5.w5, B601.16.w16, J15.20.w2,  J15.30.w2)
    • This is important to prevent severe hypoxaemia when the rabbit breath-holds in response to the volatile anaesthetic agent. (J83.35.w1)
  • Start giving the gaseous anaesthetic agent.
    • Isoflurane:
      • 3.4 - 4.5% (J15.13.w7)
      • Up to 5%. (J15.30.w2)
      • Gradually increase the concentration over about five minutes, to reach 1.5 - 2.5% (following premedication with fentanyl/fluanisone). (B600.5.w5)
    • Sevoflurane up to 7%. (J15.30.w2)
    • Halothane. (B600.5.w5)
      • 3.0 - 4.0%. (J15.13.w7)
      • 4%. (J34.17.w1)
      • 4% halothane in 100% oxygen, following sedation with acepromazine maleate 2 mg/kg subcutaneously. (J495.43.w5)
      • 5%. (B538.59.w59)
    • As an adjunct to the volatile anaesthetic agent nitrous oxide can be given during induction (50:50 mixture with oxygen); this may smooth induction. (B600.5.w5)
      • Nitrous oxide should not be used during maintenance of anaesthesia. (B600.5.w5)
  • Note: the rabbit will usually show breath holding. (B601.16.w16)
    • If the rabbit shows prolonged apnoea, remove the face mask temporarily and place it back over the rabbit's face once it starts breathing again. (B601.16.w16)
    • Repeat as necessary until the rabbit loses consciousness. (B601.16.w16)
    • Gradually increasing the anaesthetic concentration sometimes reduces breath-holding. (J15.20.w2)
    • Concentrations of anaesthetic sufficient to trigger breath-holding in rabbits may remain for as long as 30 minutes after an anaesthetic vapouriser has been switched off. (B601.16.w16)
  • Note: if switching to endotracheal intubation, this must be carried out rapidly, since anaesthesia lightens very rapidly once the face mask is removed and the rabbit is no longer receiving the anaesthetic agent. (B601.16.w16)
Maintenance of anaesthesia
Recovery
  • If nitrous oxide has been used, pure oxygen should be given for at least 10 minutes before the end of anaesthesia. (B600.5.w5)
  • Cease administration of the volatile anaesthetic agent. (B601.16.w16)
  • Recovery is rapid.
Appropriate Use (?)
  • Without premedication, only in some research settings. (J83.35.w1)
  • When rapid post-anaesthetic recovery is important. (J15.20.w2)
Notes
  • Struggling (indicating aversion) can be minimised and breath-holding delayed with very slow induction with desflurane; however this increases the time for induction to about 20 minutes. (J83.35.w1)
  • Halothane is now being superseded by other agents. (J15.30.w3)
Complications/ Limitations / Risk
  • Rabbits struggle violently when exposed to volatile anaesthetic agents, indicating they find this method of anaesthetic induction aversive. This has been demonstrated for halothane, isoflurane and sevoflurane; less struggling occurs associated with desflurane. (J83.30.w2, J83.33.w1, J83.35.w1, J290.23.w1)
  • Rabbits breath-hold when exposed to volatile anaesthetic agents, with associated significant reduction in heart rate, and development of hypoxaemia, hypercapnoea and acidosis. (J83.30.w2, J83.33.w1, J83.35.w1, J290.23.w1)
    • Gradually increasing the anaesthetic concentration may reduce breath-holding. (B600.5.w5, J15.20.w2)
  • Pre-medication with a sedative reduces physical struggling and thereby the risk of the rabbit injuring itself, but does not prevent breath-holding (thought therefore to be a diving reflex) with associated hypercapnoea and acidosis. (J290.23.w1)
    • The fall in arterial PaO2 (partial pressure of oxygen), and the degree of hypercapnoea, were less severe with desflurane than with isoflurane, probably due to faster loss of consciousness. (J83.35.w1)
  • If nitrous oxide has been used during induction it must then be switched off and 100% oxygen used for carriage of the volatile anaesthetic agent during anaesthetic maintenance. With prolonged use, nitrous oxide may diffuse into spaces such as the caecum and may cause gastric dilatation. (B600.5.w5)
Equipment / Chemicals required and Suppliers
Expertise level / Ease of Use
  • This procedure should only be carried out by an individual with appropriate clinical training and practical experience.
Cost / Availability Variable cost and availability of drugs and appropriate anaesthetic equipment.
Legal and Ethical Considerations In some countries there may be legislation restricting the use of this type of technique to licensed veterinarians. For example in the UK: "The Veterinary Surgeons Act 1966 (Section 19) provides, subject to a number of exceptions, that only registered members of the Royal College of Veterinary Surgeons may practice veterinary surgery." (See: LCofC1 - RCVS Guide to Professional Conduct 2000 - Treatment of Animals by Non-Veterinary Surgeons).

Use of Drugs (Medication):

  • Many drugs are not registered for use in lagomorphs and care should be taken in their use, with proper regard for possible toxic effects. Consideration should be give to relevant legislation regarding the use of drugs.
  • In any country, drugs are unlikely to be specifically licensed for use in non-domestic mammals. 
    • In Europe the prescription cascade must be followed, and the client's informed consent should be obtained, whenever a drug is used which is not licensed for use in a given species. (B284.5.w5)
    • In the UK, guidelines regarding the use of drugs are set out in the Royal College of Veterinary Surgeons Guide to Professional Conduct 2000: (see: LCofC1 - RCVS Guide to Professional Conduct 2000 - Choice of Medicinal Products).
Author Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee Molly Varga BVetMed DZooMed MRCVS (V.w125)
References B600.5.w5, B601.16.w16, J15.13.w7, J15.20.w2, J15.30.w2, J34.23.w1, J83.30.w2, J83.33.w1, J83.35.w1, J290.23.w1, J495.43.w5, W713.Oct08.w1, W713.Oct08.w2, W713.Oct08.w3, W713.Oct08.w4, W713.Oct08.w5

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