TECHNIQUE

Isoflurane Anaesthesia in Waterfowl (Disease Investigation & Control - Treatment and Care)

Summary Information
Type of technique Health & Management / Disease Investigation & Control / Treatment & Care / Techniques:
Synonyms and Keywords Isoflurane Induction, Isoflurane Maintenance

See also:

Description N.B. Information given in this page is to be used in conjunction with the relevant sections on Anaesthesia and Chemical Restraint within "Treatment and/or Control".

Before using any anaesthetic agent or combination of agents the manufacturer's data sheet on the agent or agents concerned should be consulted, taking particular note of any contra-indications and operator warnings.

Isoflurane is generally considered to be the gaseous anaesthetic of choice for waterfowl. It may be used for minor and major surgical procedures, as well as for restraint e.g. for radiography.

  • Induction using a face mask.
  • Initial 4-5% level may be used for induction, providing rapid induction (J40.56.w1, B11.9.w20, B13.39.w16).
  • Alternative method of low initial level (0.5-1.0%), increasing slowly by increments of 0.5% every 20-30 breaths to effect has also been described, but induction is slower (P7.1.w4, B13.39.w16).
  • Lower level for maintenance e.g. 2.0% to 3.0% .(J13.51.w1, J40.56.w1).
  • May maintain on face mask for short procedures (up to 15 minutes).
  • Intubation recommended for longer procedures.
  • Keep neck extended..
  • Remove endotracheal tube once head and neck control is regained.
  • Hold until fully recovered (usually less than five minutes).
Appropriate Use (?)
  • Isoflurane is generally considered to be the gaseous anaesthetic of choice for waterfowl.
  • May be used for induction.
  • May be used for maintenance.
  • Use with oxygen.
  • Has also been used with oxygen and nitrous oxide - reduces isoflurane concentration required.
  • High safety margin (ratio of anaesthetising dose to lethal dose 1:5.7).
  • Very low solubility (blood/gas coefficient 1.4), gives rapid induction and recovery, therefore reduced pre-operative stress, reduced post-operative hypoglycaemia and hypothermia.
  • Virtually zero metabolism (0.3%) - excretion via the lungs. Not dependent on liver function or kidney function.
  • Provides very good muscle relaxation.
  • Provides good analgesia.
  • Myocardial depression minimal.
Notes
  • Overdose produces apnoea in advance of cardiac arrest: prompt action with artificial ventilation should be effective to produce full recovery.
  • N.B. Preservatives used to maintain the stability of halothane make the vaporiser sticky and may affect the accuracy if an un-cleaned halothane vaporiser is used for isoflurane.
  • Induction may take longer in waterfowl than in most other species.
Complications/ Limitations / Risk
  • A period of voluntary apnoea (breath holding) may be observed after the anaesthetic is first inhaled (J1.36.w1, J40.56.w1).
  • Respiratory depression may be significant; a reduction from baseline 15-23 breaths per minute to 7-11breaths per minute was noted in a study on Pekin ducks (J13.51.w1, P7.1.w4).
  • Low temperatures may affect vapourisation and therefore time to induction (J1.36.w1).
  • Requirement for vapouriser and oxygen (as a carrier gas) may limit the usefulness of isoflurane in the field: propofol may be more suitable for use in some field situations (see: Propofol Anaesthesia in Waterfowl) (J1.36.w1).
  • May be prolonged induction period in swans (P3.1999b.w1).
Equipment / Chemicals required and Suppliers Requires dedicated, accurately calibrated vaporiser, either designed for isoflurane, or cleaned and serviced halothane vaporiser.

Isoflurane: Isoflurane RM (Merial Animal Health Ltd.) clear colourless volatile liquid, purity greater than 99.9% 1-chloro-2,2,2-trifluroethyl difluoromethyl ether; Isoflo (Schering-Plough Animal Health). Clear colourless volatile liquid containing 100% Isoflurane USP (1-chloro-2,2,2-trifluroethyl difluoromethyl ether) (B90).

Expertise level / Ease of Use Procedure should only be undertaken by an individual with appropriate clinical training and practical experience; this would usually be a veterinarian or someone with advanced veterinary technician training.

N.B. Whenever an anaesthetic is undertaken, the anaesthetist must be familiar with emergency protocols. Consideration must be given as to the availability of equipment required to monitor the anaesthetic plane of the animal being anaesthetized and any equipment/drugs required for revival. It is advisable to calculate the doses of any revival agents which may be required in an emergency BEFORE COMMENCING the anaesthetic (V.w6).

Cost/ Availability Relatively expensive.
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 particular bird species 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 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

Before using any anaesthetic agent or combination of agents the manufacturer's data sheet on the agent or agents concerned should be consulted, taking particular note of any contra-indications and operator warnings.

Author Debra Bourne
Referee  
References J1.36.w1, J13.51.w1, J40.56.w1, B11.9.w20, B13.39.w16, B13.46.w1, B14, B37.x.w1, B90, P3.1999b.w1, P7.1.w4, V.w6

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