Anesthetic Management of Rabbits and Ferrets

Chapter 43
Anesthetic Management of Rabbits and Ferrets


Darn those little critters!


Katrina Lafferty


University of Wisconsin-Madison, University of Wisconsin Veterinary Care, USA



  1. Q. What are common reasons to anesthetize a rabbit or ferret?
  2. A. Rabbits commonly present for anesthesia to address dental issues, ocular trauma, urinary calculi, and for castration or ovariohysterectomy. Rabbits are high-stress creatures; with agitated patients it may be safer and less stressful to anesthetize them, rather than physically restrain, for minor procedures like radiographs or large volume venipuncture. Ferrets are rarely sold intact, so anesthesia for spays and neuters is uncommon. Ferrets regularly present for anesthesia to address adrenal or pancreatic tumors. Both species often require anesthesia for bite wounds, orthopedic repair, spinal trauma, and abdominal exploratory.
  3. Q. Are there any concerns when restraining rabbits or ferrets?
  4. A. Rabbits: Rabbits require extra care with restraint for several reasons. Lagomorphs have highly developed lumbar and pelvic-limb muscles which allow for rapid bursts of speed when escaping predators. Relative to their size, these muscles are larger and more powerful than those of a horse. When a rabbit is lifted or restrained without securing the hindlegs, it is possible for them to fracture or dislocate lumbar vertebrae, causing spinal damage and potential paralysis [1,2]. Rabbits are at increased risk of hyperthermia during physical restraint. They have thick, dense fur and are not able to effectively control temperature through panting or perspiration. Rabbits have large, highly vascular ears that account for up to 12% of total body surface area. The ears are involved in thermoregulation and if covered during restraint hyperthermia can develop [1–3].

    Ferrets: Ferrets may be nippy, but are fairly easy to restrain using the “scruff and stretch” method. The patient is held with one hand grasping the loose skin over the shoulders and the other hand circling the hips firmly. A gentle stretch is used to restrain the patient, without pulling on the hindlimbs. Ferrets will yawn frequently whenever they are held by the scruff [4].


  5. Q. What should be included in a pre-anesthetic exam?
  6. A. The pre-anesthetic examination requirements for rabbits and ferrets are the same as for any other mammal. General information should include accurate weight, body condition score, hydration status, abdominal palpation, and auscultation of the heart and lungs. If possible blood should be collected for laboratory work; packed cell volume, total protein, and blood glucose are the bare minimum needed before anesthesia. If necessary, venipuncture can be done using sedation [2–4]. Table 43.1 includes a list of normal physical and hematologic parameters for rabbits and ferrets.

    Table 43.1 Normal values for rabbits and ferrets.











    Parameter Rabbit Ferret
    Temperature (°F)
    Heart rate (beats/min)
    Respiration rate (breaths/min)
    Hematocrit (%)
    Total protein (g/dl)
    Glucose (mg/dl)
    101.3–104
    135–325
    30–60
    33–50
    5.4–8.3
    75–155
    100–104
    200–400
    33–36
    36–48
    4.5–6.2
    80–117

  7. Q. For how long should rabbits or ferrets be fasted before anesthesia?
  8. A. Rabbits: As a general rule, rabbits are fasted for 0–4 h, depending on nutritional status of the patient. Rabbits are often called a “non-vomiting” species. This group has a highly developed cardiac sphincter which prevents vomiting or regurgitation of food material. Rabbits utilize hind-gut fermentation and may suffer gastrointestinal stasis if held off-feed for extended periods. Some sources recommend withholding food to decrease stomach and intestinal volume, which may affect ventilation under anesthesia, but such fasting does not seem to produce any clinically appreciable results. If the patient will tolerate it, carefully rinsing or swabbing the mouth before anesthesia can remove large food particles. Water should be made available until surgery [5].

    Ferrets: Ferrets have a rapid gastrointestinal transit time, only 3–4 h, and are at higher risk for hypoglygemia. Generally ferrets are held off-feed for 4–6 h; fasting time should be less than 2 h if there is a known insulinoma. Water should be made available until surgery [6,7].


  9. Q. Should I include anesthetic premedication for rabbit or ferret patients?
  10. A. Most patients (regardless of species) should receive premedication before general anesthesia. Premedication will reduce fear, stress, and anxiety. This is of crucial importance in these small mammalian species due to their normally high stress levels, which only increase during hospitalization.
  11. Q. What anesthetic premedications can be used for rabbits and ferrets?
  12. A. When creating an anesthetic plan for any patient, consider the procedure and choose an appropriate combination of sedative and analgesic. For non-painful procedures (radiographs, venipuncture, etc.) it is acceptable to use sedatives alone. For situations where pain is anticipated, a balanced anesthetic approach involving sedatives and analgesics should be provided. There is much research demonstrating pain to be detrimental to the healing process. Many veterinary professionals are concerned about side effects associated with premedication in exotic species, primarily sedation, respiratory depression, and ileus. However, the benefits of providing appropriate analgesia (faster wound healing, reduction of pain-induced ileus, humane patient care) greatly outweigh the risks. With careful and conscientious monitoring many of these concerns can be assuaged [8]. Table 43.2 includes dosages and routes for sedative and analgesic drugs.

    Table 43.2 Sedative and analgesic drug doses.










































































    Drug Rabbit
    Dose in mg/kg
    Ferret
    Dose in mg/kg
    Comments
    Sedatives:

    Acepromazine 0.25–1 (IM,SC) 0.1–0.25 (IM,SC) May cause hypotension
    Dexmedetomidine 0.05–0.1 (IM)
    0.0005–0.001 (IV)
    0.04–0.1 (IM)
    0.0005–0.001 (IV)
    May cause bradycardia
    *Atipamezole Equal VOLUME to dexmedetomidine
    (IM,SC,IV)
    Equal VOLUME to dexmedetomidine
    (IM,SC,IV)
    Reverses dexmedetomidine
    Midazolam
    *Flumazenil
    0.25–2 (IM,SC,IV)
    0.05–0.1 (IM,SC,IV)
    0.25–0.5 (IM,SC,IV)
    0.05–0.1 (IM,SC,IV)
    Reverses midazolam
    Ketamine 5–50 (IM,SC) 5–50 (IM,SC) Should not be used as a single agent
    Analgesics:

    Buprenorphine 0.01–0.05(IM,SC,IV) 0.01–0.03(IM,SC,IV) Q6–12 h
    Butorphanol 0.2–2.0(IM,SC,IV) 0.05–0.4(IM,SC,IV) Q2–4 h
    Oxymorphone 0.05–0.2(IM,SC,IV) 0.05–0.2(IM,SC,IV) Q6–8 h
    Hydromorphone 0.05–0.2(IM,SC,IV) 0.1–0.2(IM,SC,IV) Q6–8 h
    *Naloxone 0.01–0.1(IM,SC,IV) 0.01–0.1(IM,SC,IV) Opioids reversal
    (reverses ALL analgesia)
    Morphine 0.1 (epidurally) 0.1 (epidurally) Use preservative-free formulation
    Bupivacaine 1.0 (epidurally) 1.0 (epidurally) Use preservative-free formulation

    IM=intramuscular; IV=intravenous; SC=subcutaneous


  13. Q. What are the preferred sites for intramuscular or subcutaneous injections?
  14. A. Injection sites in rabbits and ferrets are very similar to those in cats and dogs. For subcutaneous injections, the loose skin over the shoulders and back can be used. For intramuscular injections, the lumbar muscles are preferred. Injections in the caudal aspect of the pelvic limbs may irritate the sciatic nerve and cause self-mutilation, particularly in rabbits [2].
  15. Q. Where are the preferred sites for intravenous catheters?
  16. A. Rabbits: IV catheters can be placed in the cephalic, lateral saphenous, marginal ear, and jugular veins. Female rabbits often have a large fold of skin under the chin called a dewlap that may make jugular catheter placement challenging [8,9]. Size 22–26 g intravenous catheters are typically used. Figure 43.1 shows catheter placement in the marginal ear vein of a rabbit. This is the preferred site for long-term catheters.
    c43f001

    Figure 43.1 Catheter placement in the marginal ear vein of a rabbit.


    Ferrets

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Sep 3, 2017 | Posted by in SMALL ANIMAL | Comments Off on Anesthetic Management of Rabbits and Ferrets
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