Anesthesia Guidelines: Rabbits

Find guidelines for rabbit anesthesia, including anesthetic drugs and procedures.

Research Animal Resources (RAR) veterinary staff designed these guidelines to be general recommendations, not an inclusive list of all possible drug combinations that can be used in rabbits. Consequently, guidelines do not reference specific research-associated concerns. 

If you have questions about using anesthetics for your particular situation, please work with your area veterinarian to develop the most effective anesthetic plan.


Species-specific considerations

Pasteurella multocida

Non-specific pathogen free (SPF) rabbits may be infected with Pasteurella multocida. Underlying lung damage from this pathogen may lead to respiratory distress or arrest under anesthesia.  Animals with any sign of respiratory disease must be clinically evaluated by the area veterinarian prior to anesthesia.  

Fasting

Rabbits cannot vomit, so fasting is not mandatory. However, a pre-anesthetic fast of one to four hours is recommended, as they accumulate food and fluid within the oral cavity and oropharynx. Additionally, fasting reduces the overall volume of the gastrointestinal tract, reducing pressure on the diaphragm while under anesthesia. Fasting for longer periods of time may predispose them to post-operative ileus and decrease blood glucose levels.

Head elevation

Tilting the surgical table to slightly elevate the head will reduce pressure from the gastrointestinal tract on the diaphragm. 

Atropine esterase

If using parasympatholytic drugs to prevent bradycardia or decrease secretions, remember that rabbits may produce atropine esterase. This degrades atropine into inactive products. Glycopyrolate (0.01-0.02 mg/kg) appears to maintain effectiveness in rabbits with atropine esterase.  


General considerations

Acclimation period

Do not use newly arrived animals for experimental procedures until 72 hours after entry into the facility. A one-week acclimation period is recommended. This stabilization period is not required for animals used acutely (anesthetized and euthanized at the end of the procedure), although it is recommended. This provision allows animal to acclimate to the facility and reduces the chance of stress-induced disease, including anesthetic death.

Habituation

Rabbits are easily stressed. Habituate animals to handling before beginning studies involving anesthesia.  

Heat support

Rabbits are extremely susceptible to hypothermia, which slows recovery and further stresses the animal. This is due to their large surface area and the fact that most anesthetic agents lower body temperature. To prevent hypothermia, provide supplemental heat during anesthetic procedures and recovery. Regardless of heat source, do not place animals directly on the heat.

Catheterization

Following sedation, place an indwelling catheter to administer anesthetic drugs, emergency drugs, and intravenous fluid support. The lateral (marginal) ear veins are easily accessed and are the preferred site. Applying lidocaine-prilocaine (EMLA®) cream to the ear 30 minutes before venipuncture reduces discomfort. A tranquilizer or sedative such as Acepromazine (0.25-1.0 mg/kg IM) can also be used prior to catheter placement to help decrease the rabbit’s stress level.

Monitoring

Regardless of the anesthetic administered, monitor rabbits to avoid excessive depression of cardiac and respiratory functions, or insufficient anesthesia. Parameters to monitor in an anesthetized rabbit include:

  • Anesthetic depth: Toe pinch. 
  • Respiratory rate and pattern: The normal, undisturbed rate is 20-60/minute.
  • Mucous membrane color: Should be pink, not blue or gray. 
  • Heart rate: Between 120-325 beats/minute.
  • Body temperature: Should be maintained above 98℉.

Recovery

During the immediate post-anesthetic period, remove food and water from the cage. Do not replace food, hay, and water until the animal is fully awake and ambulatory. Rabbits should eat as soon as possible after an operation to help prevent ileus. A small amount of treats (e.g., apples, carrots, kale) or syringe-fed Critical Care diet may aid in promoting post-operative eating.


Anesthetic drugs and procedures

Rabbit anesthesia is generally broken up into premedication (sedation), anesthetic induction, and anesthetic maintenance.  

As with other species, anesthesia (maintenance) can be accomplished via inhalation or parenteral methods.

Sedation

Sedation

Administering sedative drugs decreases excitement and causes relaxation to allow for placement of indwelling catheters (for IV drug and fluid administration) or allow for intubation (for inhalation anesthesia). For some procedures, sedation and maintenance are covered by the initial drug administration.

The injectable anesthetics of choice are Ketamine combinations with either Xylazine or Diazepam. If additional anesthesia is needed, re-dose with 1/3 the original calculated dose of ketamine. Do not redose Xylazine due to its hypotensive effects.


Ketamine+ Xylazine (Rompun®) – recommended

Dose: Ketamine: 10-40 mg/kg + Xylazine: 3-5 mg/kg
Route: IM
Comments: Thermal support is crucial. To prolong anesthesia, supplement with 1/3 dose of ketamine only. Xylazine can be reversed with 0.2-1.0 mg/kg yohimbine IV or IM.


Ketamine + Xylazine + Acepromazine – recommended

Dose: Ketamine: 35 mg/kg + Xylazine: 5 mg/kg + Acepromazine: 0.25-0.75 mg/kg 
Route: IM
Comments: Thermal support is crucial. To prolong anesthesia, supplement with 1/3 dose of ketamine only. Xylazine can be reversed with 0.2-1.0 mg/kg yohimbine IV or IM.


Ketamine + Xylazine + Butorphanol – recommended

Dose: Ketamine: 35mg/kg + Xylazine: 5 mg/kg + Butorphanol: 0.1 mg/kg
Route: IM
Comments: Thermal support is crucial. To prolong anesthesia, supplement with 1/3 dose of ketamine only. Xylazine can be reversed with 0.2-1.0 mg/kg yohimbine IV or IM.


Ketamine + Diazepam (Valium®) – recommended

Dose: Ketamine: 20-40 mg/kg + Diazepam: 1-5 mg/kg 
Route: IP, IM


Ketamine + Dexmedetomidine

Dose: Ketamine: 15-25 mg/kg + Dexmedetomidine: 0.25 mg/kg
Route: IM, SQ

Induction

Induction

Induction refers to an anesthetic administered to place an animal in an unconscious state and allow for tracheal intubation.


Pentobarbital (Nembutal®)

Dose: 30-45 mg/kg
Route: IV
Comments: This agent should only be used IV and never be given IM or SQ. Use with caution, as anesthetic dose is very close to the dose which causes apnea.


Propofol bolus

Dose: 3-10 mg/kg
Route: IV
Comments: Propofol should be used with caution in rabbits as extended use may lead to propofol infusion syndrome*. Propofol causes respiratory depression. Any animal receiving propofol should be intubated following administration.

*Propofol infusion syndrome is characterized by acute bradycardia progressing to asystole. Other features include lipemic plasma, fatty liver, metabolic acidosis, rhabdomyolysis, and/or myoglobinuria.


Isoflurane

Dose: 3-5%
Route: Inhalation
Comments: Pre-sedation is recommended if using an induction chamber to prevent distress to the rabbit. Induction via a facemask on a non-sedated animal can lead to distress and injury, and is strongly discouraged.

Maintenance

Maintenance

Maintenance refers to drugs administered to keep animals unconscious and allow for surgical (or other) procedures to be performed.

Endotracheal intubation: Inhalation anesthesia may be delivered by a facemask, laryngeal mask, or endotracheal tube.

  • The narrow mouth diameter, large tongue, limited range of jaw opening, and prominent incisors make placement of an endotracheal tube challenging.
  • If using an endotracheal tube, a size 2.0-3.5 uncuffed tube is generally appropriate, depending on the rabbit’s size.
  • The endotracheal tube should extend approximately from outside of the mouth to the thoracic inlet. This can be a guide for how far the tube should be inserted upon intubation. 
  • Verify proper placement of the endotracheal tube by ausculting all lung fields for strong breath sounds. If no breath sounds are heard, back the tube out until sounds are heard in all lung fields. 

Gas anesthesia machines: Facemasks and intubation require gas anesthesia machines with an oxygen source and a precision vaporizer. Due to the small respiratory capacity, use a non-rebreathing system.

Ventilation respiratory rates and volumes: If ventilation is required, keep in mind that rabbits have a small tidal volume (4-6 ml/kg) compared to other species. Please consult with your area veterinarian for appropriate respiratory rates and volumes if ventilation is required.

Gas scavenging system: When using inhalant anesthesia, use a fume hood or an anesthetic system equipped with a gas scavenging system to minimize occupational exposure to exiting gases.

Ophthalmic ointments: For anesthetic events lasting more than five minutes and whenever facemasks are used, use an ophthalmic ointment (e.g., Paralube® or Lacrilube®) to prevent corneal drying and trauma.


Isoflurane – recommended

Dose: 1-4% maintenance
Comments: Using isoflurane as the sole agent of anesthesia induction may be associated with breath-holding and distress.

References for these guidelines are available by request.