TECHNIQUE

General Anaesthesia (Gaseous and Injectable) Techniques of Hedgehogs (Disease Investigation & Management)

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Summary Information
Type of technique Health & Management / Disease Investigation & Management / Techniques:
Synonyms and Keywords --
Description

Before performing any clinical technique, the associated legal and ethical considerations should be consulted, knowledge of the potential complications/ limitations/ risk should be gained, and the level of expertise and qualification required must be ascertained.

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.

Suggested protocols for sedation and general anaesthesia in the hedgehog include:

Light Sedation:

  • Light sedation is not commonly performed in the hedgehog. Progression to full general anaesthesia is the usual course of action.
  • Ketamine has been described as a sedative at a variety of dose rates.
  • Medetomidine 0.1 mg/kg intramuscular alone. Light sedation; reversal using atipamezole. (B267)
  • Diazepam has been suggested for mild sedation.
    • West European hedgehog - Erinaceus europaeus:
      • 1 mg/kg body weight intramuscular or intravenous injection. For sedation. (D93)
      • 1-3 mg/kg body weight intramuscular or intravenous injection. For control of seizures at higher dose range and sedation at lower dose range. (B284.6.w6)
    • Four-toed hedgehog - Atelerix albiventris: 
      • 0.5-2.0 mg/kg intramuscular injection. For mild sedation; may be administered with ketamine for anaesthesia. Also for seizures. (B267)
  • Fentanyl-fluanisone (Hypnorm, Janssen Animal Health) 0.5-1.0 ml/ kg intramuscular route. Sedation for minor procedures. (B284.6.w6)

Gaseous Anaesthesia:

Drug Selection:

Isoflurane is the agent of choice for induction and maintenance of general anaesthesia in the hedgehog. (B22.27.w3, B150.w1, J15.21.w1, J34.24.w1, J60.1.w2)

  • Administration is generally in 100% oxygen. (V.w5, V.w6, V.w26, V.w44)
  • Suggested inspired concentrations of isoflurane for induction of general anaesthesia include:
    • West European hedgehog - Erinaceus europaeus:
      • 5% in oxygen. Routine general anaesthesia.(B284.6.w6, D93)
    • East African hedgehog Atelerix albiventris: 
      • 3-5 % [in oxygen]. Anaesthetic agent of choice; administer using induction chamber or face mask. (B267)
    • "Hedgehog" (species not distinguished between Atelerix albiventris or Erinaceus europaeus):
      • 3-5 % in 100% oxygen. In an induction chamber. (B150.w1)
  • Suggested inspired concentrations of isoflurane for maintenance of general anaesthesia include:
    • West European hedgehog - Erinaceus europaeus:
      • To effect, via face mask. Sedation and narcosis. (B22.27.w3)
      • 1-3% in oxygen. Routine general anaesthesia. (B284.6.w6, D93)
    • "Hedgehog" (species not distinguished between Atelerix albiventris or Erinaceus europaeus):
      • 0.5-3.0 % [in oxygen]. Administer via face mask or endotracheal tube. (B267)
      • 0.5-3.0 % in 100% oxygen. Administer via face mask or endotracheal tube. (B150.w1)

Halothane may also be used for general anaesthesia (J15.21.w1, J34.24.w1, J60.1.w2, B291.12.w12), however the properties of isoflurane are preferable.

  • Administration is generally in 100% oxygen. (V.w5, V.w6, V.w26, V.w44)
  • Suggested inspired concentration of halothane for induction of general anaesthesia include:
  • Suggested inspired concentration of halothane for maintenance of general anaesthesia include:
    • West European hedgehog - Erinaceus europaeus:
      • 1-3 % in oxygen. For maintenance of general anaesthesia.(B284.6.w6)
      • 2-4% in oxygen. For maintenance of general anaesthesia.(D93)
    • "Hedgehog" (species not distinguished between Atelerix albiventris or Erinaceus europaeus):

Methoxyflurane has also been reported for short general anaesthesia.(B156.7.w7, B22.27.w3, B291.12.w12)

Technique:

  • Gaseous general anaesthesia may be induced using an anaesthetic chamber.(B284.6.w6, J15.21.w1, J60.1.w2, B205.17.w17)
    • This technique has the advantage in that handling of the hedgehog is minimised.(V.w26)
  • Alternatively a face mask can be used for induction of gaseous general anaesthesia. 
    • The mask can often be introduced over the nose of a hedgehog (even one which is tightly rolled up).
    • If not, the mask can be placed over the small gap on the underside of the tightly curled hedgehog.
    • As the hedgehog becomes anaesthetised and the muscles relax, the mask can be repositioned over the nose and mouth.
    • Commercial masks can be purchased or improvised with translucent plastic, 90-degree connector from a circuit, sphygmomanometer bulbs (instrument for measuring blood pressure), etc.
    • (J15.21.w1, J60.1.w2, V.w26)
    (B284.6.w6, J15.21.w1, J60.1.w2, V.w26
  • A small face mask may be used for maintenance of gaseous general anaesthesia after induction.
    • It is difficult to avoid environmental contamination with anaesthetic gases (fitting of mask over spines) although some leakage may be useful to reduce resistance in the circuit. Some form of active scavenging should be used to reduce atmospheric pollution.
  • An endotracheal tube may be used in larger individuals once the animal is anaesthetised.
    • A stylet may be used to facilitate insertion of an endotracheal tube.
    • The hedgehog should be positioned lying on its belly (ventral recumbency) with its neck raised up in extension.
    • Care should be taken to avoid trauma to the pharynx caused by repeated unsuccessful attempts at intubation.
    (B150.w1, B284.6.w6, J15.21.w1, V.w26)

Injectable combinations:

  • Gaseous anaesthesia is generally preferred to the use of injectable anaesthesia in the hedgehog, unless specific indications exist.
  • Various drug combinations and doses for injectable anaesthesia in the hedgehog are reported in the literature. Reported effect and duration of stated drug protocols vary, sometimes considerably. The following information should be used as a guide, taking into account the clinical condition of the patient and the experience and preference of the anaesthetist.
  • Injectable combinations may be specifically indicated for procedures involving the jaw, head and teeth.(J60.1.w2)
  • Reversal agents should be used wherever possible to facilitate rapid recovery.
  • For further information on routes of administration see:

Ketamine alone and in combination:

Use of ketamine in the hedgehog at a variety of dose rates has been suggested by a number of authors:

  • Ketamine 80 mg/kg bodyweight, intramuscular injection. Suitable for restraint for examination and minor procedures and may also be used for induction.(J15.21.w1)
  • Ketamine 20 mg/kg intramuscular injection. Sedation and narcosis; inject into the gluteal muscles, not the neck (where there is brown fat). (B22.27.w3)
  • Ketamine 20 mg/kg intramuscular injection.(B117.w7)
  • Ketamine 5-20 mg/kg intramuscular. (J34.24.w1)
  • Some authors have suggested combination of ketamine and isoflurane general anaesthesia for surgical procedures. Post anaesthetic recovery periods in the order of 45 minutes were reported. (B22.27.w3)
    • Surgical levels of general anaesthesia can be achieved with gaseous agents alone and have the advantage of rapid recovery times. (V.w26, V.w44)
  • For Atelerix albiventris - Ketamine 5-20 mg/kg intramuscular injection. Sedation, anaesthesia. Avoid injection into the neck area (where there is brown fat); may be used in combination with diazepam or xylazine; recovery may be rough and/or prolonged. (B267)

A combination of ketamine with a sedative (e.g. benzodiazepine, alpha-2 agonist) is generally preferable to the use of ketamine alone. (V.w5, V.w6, V.w26)

Medetomidine:

A combination of medetomidine and ketamine has been suggested by a number of authors, with reversal of the medetomidine using atipamezole. Suggested dose protocols include:

Xylazine:
  • Atelerix albiventris 0.5-1.0 mg/kg xylazine intramuscular injection. For anaesthesia; may be administered with ketamine. (B267)
  • "Hedgehogs" (species not stated) 0.5-1.0 mg/kg xylazine intramuscular in combination with ketamine (suggested dose 5-20 mg/kg), for general anaesthesia. (J34.24.w1)

Diazepam:

  • "Hedgehogs" 0.5-1.0 mg/kg intramuscular diazepam in combination with ketamine (suggested dose 5-20 mg/kg), for general anaesthesia. (J34.24.w1)
Other Injectable Anaesthetic Agents:
  • Fentanyl-fluanisone (Hypnorm, Janssen Animal Health) 0.2 ml/kg plus diazepam 2.5 mg/kg, both given by intraperitoneal injection, has been described for induction of general anaesthesia. (B205.17.w17)
    • Fentanyl-fluanisone (Hypnorm, Janssen Animal Health) 1-2 ml/ kg intramuscular route has been reported for prolonged anaesthesia.(B156.7.w7)
  • Use of combinations of ketamine and xylazine, phencyclidine HCl and promazine HCl, chloral hydrate, Pentobarbitone sodium are reported historically in the literature for use in Insectivora - Insectivores (Order) (B16.13.w13, B156.7.w7) but are no longer recommended.(V.w26)
  • Experimental trials were performed on free-ranging hedgehogs (Erinaceus europaeus - West European Hedgehog) using a number of reversible injectable anaesthetic combinations. Several were found to be ineffective for chemical immobilisation or associated with unacceptable side effects at the dose rates selected. The paper concluded that a combination of ketamine, medetomidine and fentanyl with atipamezole and naloxone reversal can be recommended for immobilisation. (J2.26.w1)
  • Although no reports of the use of alphaxalone/ alphadolone (Saffan, Schering-Plough Animal Health) for hedgehog anaesthesia had been seen in the literature, its use via the intramuscular route has been suggested to be worthy of trial in the past. (B156.7.w7)
  • Toletamine HCl/ zolazepam at 1.0-5.0 mg/kg combined drug dose, intramuscular, has been suggested for hedgehogs. (J34.24.w1)
Preparation:
  • Stabilisation and treatment of shock should be performed before progression to general anaesthesia wherever possible, unless emergency medical conditions or circumstance dictates otherwise.

    The length of starvation prior to induction of general anaesthesia should be appropriate for the species in question and the likelihood of regurgitation. Clinical judgement should be used as to the pros and cons of starvation in an emergency situation.

    • Starvation is not generally practised prior to general anaesthesia for the hedgehog.(V.w26, V.w44)
    • Care should be taken and consideration given as to security of an airway if the hedgehog is regurgitating or bleeding from the mouth.
    • (V.w26, V.w44)

Anaesthetic Monitoring:

  • The use of anaesthetic monitoring sheets provides a permanent record of the anaesthesia. They may be of particular use for long procedures or where new drug protocols are in use. 
  • Respiratory and heart rates should be monitored during the general anaesthesia.
  • Monitor jaw tone, limb tone, corneal and pedal withdrawal reflexes as a guide to the depth of the anaesthesia.(J2.26.w1)
  • Pulse oximetry can be used where available.
    • Pulse oximetry has been used to monitor stable general anaesthesia using both isoflurane and halothane.(J60.1.w2)

Heat Conservation, Fluid Therapy and Analgesia:

  • Attention should be paid to heat conservation during general anaesthesia, as for all patients with small body weight and a high surface area: volume ratio.
  • Heat mats, reflective metal 'space blankets' or 'bubble wrap' plastic can be used for heat provision and insulation.
  • Warm ambient temperature should be maintained during recovery from general anaesthesia.
  • Consideration should be given as to the need for fluid therapy to replace insensible losses during general anaesthesia. Fluid supplementation is particularly important for long procedures where subcutaneous fluids can be given as a routine.(V.w26)
  • Post-operative recovery may be improved by the administration of analgesics.
Appropriate Use (?)
  • Indicated for all painful procedures.
  • Used for physical examination of casualty hedgehogs which cannot be unrolled or where prolonged examination is required.
  • Used for brief procedures e.g. wound cleaning, radiography.
  • General anaesthesia is recommended prior to euthanasia in order to facilitate access to the hedgehog for injection of barbiturates in a humane fashion. (B156.7.w7, J60.1.w2, V.w26)
Notes
  • --
Complications/ Limitations / Risk
  • Variable drug-specific side effects can occur.
    • For further information consult the manufacturer's data sheet and the specific Chemical Pages in the Drug Formulary. 
Equipment / Chemicals required and Suppliers
  • Anaesthetic machines and calibrate vaporisers, circuits, masks, chambers and monitoring equipment.
  • Anaesthetic drugs.
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.

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
  • Some drugs used for chemical restraint are expensive.
  • Variable cost and availability of these anaesthetic agents between countries.
  • Drugs used for chemical restraint may only be available to veterinary surgeons or other licensed persons.
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 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 - Choice of Medicinal Products).

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.

Authors Becki Lawson (V.w26)
Referee Debra Bourne (V.w5), Suzanne I. Boardman (V.w6), Tiffany Blackett (V.w44)
References B22.27.w3, B150.w1, B205.17.w17, B267, B284.6.w6, J2.26.w1, J15.21.w1, J60.1.w2, D93, W5.Jan01, V.w5, V.w6, V.w26, V.w44

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