Guidelines on Anesthesia and Analgesia in Rabbits

1. Principal Investigator: Responsible to ensure appropriate anesthesia and/or analgesia is provided for all rabbits undergoing potentially painful procedures, including survival surgery, unless otherwise indicated in the relevant approved protocol.

1. Special considerations when anesthetizing rabbits
   1. Acclimation: Animals should be acclimated to their environment for a minimum of 72 hours, habituated to handling, and evaluated for obvious clinical signs of disease prior to anesthesia. Non-SPF rabbits may be infected with Pasteurella multocida; underlying lung damage from this pathogen may lead to respiratory arrest under anesthesia.
   2. Handling and Restraint: Rabbits are easily stressed by handling and induction.
      1. To avoid excessive anxiety in the pre- and post- anesthetic periods, provide an environment devoid of extraneous noise, including loud talking.
      2. The amount of restraint and its duration should be kept to the minimum required to accomplish the necessary procedure.
      3. To reduce the time of restraint, equipment and reagents should be ready to use prior to handling the animal.
      4. Pre-anesthetic doses of sedative/tranquilizer agents are often used to facilitate immobilization and to reduce anxiety.
   3. Fasting: Rabbits cannot vomit, therefore fasting is not mandatory. They do tend to accumulate food and fluid within the oral cavity and oropharynx. For this reason, a pre-anesthetic fast of 1-4 hours is recommended. Fasting also reduces the overall volume of the gastrointestinal tract thus reducing pressure on the diaphragm while under anesthesia. Fasting for longer periods of time may predispose them to post-operative ileus and may decrease blood glucose levels.
   4. Surgical Position: Tilting the surgical table so that the rabbit’s head is slightly elevated will reduce pressure on the diaphragm. Anesthetizing a rabbit on a level surface is also acceptable, however, caution should be taken to avoid inadvertently elevating the rabbit’s hindquarters.
   5. Apply sterile non-medicated ophthalmic ointment to the eyes to prevent corneal drying during anesthesia or sedation.

1. More detailed information regarding injection techniques and maximum quantities safely administered to rabbits can be found in Guidelines on Administration of Substances to Laboratory Animals.

1. More information on anesthetic/sedation monitoring requirements can found in Anesthesia and Sedation Monitoring Guidelines.
2. The goal of monitoring should be to maintain normal cardiac function, respiratory function, and body temperature. Understanding the basic physiologic effects of the anesthetics used is paramount to correctly interpreting monitoring parameters. More information on anesthetic and sedative effects on physiologic parameters can be found in Anesthesia and Analgesia Drug Descriptions. 
3. Table 1: Physiologic Data of Rabbits
   

   	Temperature	Heart Rate (beats per minute)	Respiratory Rate (breaths per minute)
   Without Anesthesia	100.4 – 104 F (38 – 40 C)	130 – 325	30 – 60 in resting rabbit
   With Anesthesia	T >98 F (>37 C)		20 – 30

1. Hypothermia
   1. An external heat source should be provided during the entire anesthetic and recovery period. For examples of approved external heat supplementation products, please refer to Anesthesia and Sedation Monitoring Guidelines.
2. Fluids
   1. Providing fluid support during anesthesia is important particularly if a procedure lasts 30 minutes or more. More information on appropriate fluid rates can be found in Guidelines on the Performance of Surgery in Non-Rodent Mammals.
3. Vascular Access
   1. The placement of indwelling intravenous catheters is advised. The lateral (marginal) ear veins are easily accessed and the preferred site. The application of lidocaine-prilocaine EMLA® cream to the ear 30 minutes before venipuncture has been recommended to reduce pain. A tranquilizer or sedative can also be given prior to catheter placement to help decrease the rabbit’s stress level. The cephalic and recurrent tarsal veins can also be utilized.
4. Airway Access
   1. Endotracheal Intubation: Several techniques have been devised to simplify the difficult task of endotracheal intubation. The narrow mouth diameter, large tongue, limited range of jaw opening, and prominent incisors make placement of an endotracheal tube challenging.
   2. V-Gel (supraglottic airway device) placement: This device allows easier airway access when compared to endotracheal tubes. However, the V-Gel does not protect the airway from aspiration as effectively as endotracheal intubation, as it is placed over the larynx as opposed to within the trachea . Also, there is a risk of tongue cyanosis.
   3. Please contact the ULAM Training Core to set up a time to learn how to correctly and safely perform endotracheal intubation or V-Gel placement in the rabbit.

1. More information on required monitoring parameters during post-operative recovery can be found in Guidelines on the Performance of Surgery in Non-Rodent Mammals and Anesthesia and Sedation Monitoring Guidelines.
2. If a large number of surgeries are being conducted at one time, post-surgical animals may be housed together following anesthesia and prior to full recovery if they are continually observed. This is to ensure that more alert animals do not injure non-responsive cage-mates.
3. Nutritional support should be withheld until the animal is fully recovered and ambulating normally.

1. Detailed information on all approved anesthetics and sedatives can be found in Anesthesia and Analgesia Drug Descriptions.
2. All premedicants and sedatives should be administered 15-20 minutes prior to restraint or induction. Duration of action for sedative-analgesic combinations for use in minor procedures is generally 15-60 minutes depending upon combination used.
3. The following drug combinations are for use with minor procedures or as premedicants prior to anesthetic induction.
   1. For dose ranges listed as IV, IM, and SC, use the lower end of the range for IV administration. All dosages are given in mg/kg unless otherwise indicated.
4. Table 2: Sedation Protocols in Rabbits
   

   Drug or Combination	Dose (mg/kg)	Route	Comments
   Diazepam	0.5 – 3	IV, IM	Light to moderate sedation without analgesia. Slow IV administration preferred as painful upon IM injection. Sedation can be reversed with flumazenil (0.01 – 0.1 mg/kg, IM, IV)
   Midazolam	0.25 – 2	SC, IM, IV, IP	Light to moderate sedation without analgesia. Sedation can be reversed with flumazenil (0.01 – 0.1 mg/kg, IM, IV)
   Dexmedetomidine PREFERRED ALPHA-2 AGONIST	0.035 – 0.05	SC, IM	Light to deep sedation with mild to moderate analgesia. Reverse with atipamezole at the same volume as dexmedetomidine (SC, IM, IV).
   Xylazine*	1 – 5	SC, IM	Light to moderate sedation with mild analgesia. Reverse with yohimbine (0.2 – 1 mg/kg, IM or IV) or atipamezole (0.1-1 mg/kg SC, IM, IV).
   Buprenorphine	0.01 – 0.05	SC, IM, IV	Mild sedation with analgesia. Most effective when administered ~60 minutes prior to anesthesia. May cause respiratory depression.
   Butorphanol	0.1 – 0.8	SC, IM, IV	Mild sedation with analgesia.
   Alfaxalone	2.5-6	IM	Moderate sedation up to 40 minutes.
   Midazolam + Butorphanol	0.5 – 1 + 0.2 – 0.5	IM	Mild to moderate sedation with analgesia.
   Alfaxalone + Midazolam	6 +1	IM	Moderate sedation up to 60 minutes (ref 3).
   Alfaxalone + Dexmedetomidine	6 + 0.2	IM	Deep sedation for up to 2 hours (ref 3).
   Alfaxalone + Dexmedetomidine + Butorphanol	6 + 0.2 + 0.3	IM	Deep sedation for up to 2 hours, analgesia for 40 minutes (ref 3).

* Xylazine should be used with caution in rabbits due to anecdotal reports of lesions at the injection site when administered intramuscularly, which has been reported in other species, including humans, rats, and hamsters (see references 2, 9, and 20). Dexmedetomidine is a preferred alternative alpha-2 agonist. If using xylazine, it is recommended to dilute the product to a lesser concentration and to reverse sedation/anesthesia with atipamezole.

1. For dose ranges listed as IV, IM, and SC, use the lower end of the range for IV administration.
2. Anticholinergics: Approximately 1/3 of all domesticated rabbits have a naturally occurring enzyme in their blood (atropinesterase), which causes them to metabolize atropine faster. Repeated dosing of atropine every 10-15 minutes may be required if the heart rate falls below 65 beats/minute. Alternatively, glycopyrrolate may be used. Glycopyrrolate has a slightly longer duration of action compared to atropine and is less affected by circulating serum atropinesterase.
   1. Atropine 0.1-1 mg/kg, SC or IM.
   2. Glycopyrrolate 0.01-0.1 mg/kg, SC, IM, or IV.
3. Injectable Anesthetic Induction Agents Used in Rabbits
   1. Supplemental oxygen should be provided for all injectable anesthetic protocols. These combinations may not provide a surgical plane of anesthesia and should be used in combination with isoflurane. If, for minor procedures, isoflurane is not utilized, in combinations involving ketamine, anesthesia can be prolonged by supplementing with 1/3 dose of ketamine only. All dosages given in mg/kg unless otherwise indicated.
   2. Table 3: Injectable Anesthetic Agents Used in Rabbits 
      

      Drug or Combination	Dose (mg/kg)	Route	Notes
      Ketamine + Midazolam	10 – 25 + 0.2 – 3	IV, IM, SC
      Ketamine + Diazepam	10 – 40 + 0.3 – 5	IV, IM	Diazepam is not water soluble. Do not mix drugs in the same syringe. Provides approximately 20 – 30 minutes of anesthesia.
      Ketamine + Dexmedetomidine	15 – 35 + 0.125 – 0.25	IM, SC	Provides approximately 30 – 45 minutes of anesthesia.
      Propofol	3 – 10	IV	For anesthesia induction only. Utilize slow bolus dosing to effect.
      Ketamine + Xylazine *	10 – 40 + 3 – 5	IM	Provides approximately 30 – 45 minutes of anesthesia.
      Ketamine + Xylazine * + Butorphanol	10 – 40 + 3 – 5 + 0.1	IM	Prolongs duration of anesthesia to 50 – 70 minutes.

4. Anesthetic Maintenance Protocols
   1. Table 4: Inhalation Anesthetic Agents Used in Rabbits
      

      Drug	Dose (mg/kg)	Notes
      Isoflurane (induction)	To effect. Typically 3 – 5%	Calibrated vaporizer and active scavenging use required. Sedation should be used in conjunction with mask or chamber induction to avoid injury and minimize breathholding.
      Isoflurane (maintenance) RECOMMENDED	To effect. Typically 1 – 3%	Calibrated vaporizer and active scavenging use required.
      Sevoflurane (induction)	To effect. Typically 6 – 8%	Calibrated vaporizer and active scavenging use required Calibrated vaporizer and active scavenging use required. Sedation should be used in conjunction with mask or chamber induction to avoid injury and minimize breathholding.
      Sevoflurane (maintenance) RECOMMENDED	To effect. Typically 1 – 3%	Calibrated vaporizer and active scavenging use required.

1. Extreme care must be taken to ensure that a proper level of anesthesia and analgesia is achieved prior to administering a neuromuscular blocking agent.
2. Neuromuscular blocking agents require special monitoring procedures which are detailed in Anesthesia and Sedation Monitoring Guidelines.
   1. Concurrent positive pressure ventilation is required. Reversal of NMBAs with neostigmine and glycopyrrolate is possible under specific conditions. Please consult the ULAM veterinarians for instructions on NMBA reversal.
3. Table 5: Neuromuscular Blocking Agents Used in Rabbits                                                                                                                                                                                  
   

   Drug	Dose (mg/kg)	Route	Duration of Effect	Notes
   Cisatracurium	0.12	IV	34 – 46 (38 average) minutes	Onset in 1.5 minutes. Less variability in response than pancuronium.
   Pancuronium	0.1	IV	42 – 70 (55 average) minutes	Onset in 1.5 minutes.

1. Appropriate for minimally invasive procedures such as skin biopsy, or as a supplement to sedation, anesthesia, and analgesia.
   1. Local anesthetics are excellent analgesics for use in minor procedures or as “splash blocks” for post-operative incision pain.
2. Table 6: Local Anesthetic Agents Used in Rabbits
   

   Drug	Dose (mg/kg)	Route	Duration of Effect	Notes
   Lidocaine	<4 (<0.4 mL/kg of a 1% solution)	Infiltrate	<1 hour (quick onset)	May need to dilute to achieve appropriate volume for infiltration.
   Bupivacaine	<2 (<0.8 mL/kg of a 0.25% solution)	Infiltrate	4 – 8 hours (slow onset)	May need to dilute to achieve appropriate volume for infiltration.

1. Signs of pain in rabbits include but are not limited to the following:
   1. Anxiety
   2. Apprehension
   3. Restlessness
   4. Decreased appetite
   5. Dullness
   6. Elevated respiratory rate
   7. Inactivity
   8. Increased aggression
   9. Immobility
   10. Hunched posture
   11. Tooth grinding
   12. Salivation
   13. Scratching/licking painful area
   14. Social isolation
   15. Vocalization
2. Preferred opioid analgesics are buprenorphine (including buprenorphine hydrochloride and Ethiqa), hydromorphone, and transdermal fentanyl.
   1. Buprenorphine and other narcotic agonists can be completely reversed with naloxone.
3. The preferred non-steroidal anti-inflammaties (NSAID) are carprofen and meloxicam  because they are generally well tolerated by the gastrointestinal tract, have good duration of effect, and do not appear to adversely affect platelet function.
4. Opioids and NSAIDs can be combined for their additive or synergistic analgesic effects.
5. Table 7: Analgesic Agents Used in Rabbits
   

   Drug	Dose (mg/kg)	Route	Duration of Effect	Notes
   Buprenorphine	0.01 – 0.05	SQ, IM, IV	6 – 12 hours
   Ethiqa XR® (buprenorphine extended-release injectable suspension)	0.15	SC	72 hours
   Hydromorphone	0.05 – 0.2	SC, IM	6 – 8 hours
   Fentanyl (transdermal patch)	25 mcg/hr	Transdermal	72 hours (from time of placement)	Hair should be clipped in the area of placement -the back of the neck and outer ear are recommended locations. Do not shave or use depilatory cream as it changes the pharmacokinetics of the drug. Analgesia onset is 12 hours. The patch should be placed 12 hours prior to the procedure or, if placed during the procedure, another opioid analgesic should be employed until efficacy.
   Carprofen	2 – 4	SC, IM, PO	24 hours	Use high end of dose range for PO administration.
   Meloxicam (injectable solution	0.3 – 0.6	SC	24 hours
   Meloxicam (oral solution)	0.3 – 1	PO	24 hours
   Ketoprofen NOT RECOMMENDED	1-3	SC, IM, PO	24 hours	Poor water solubility may influence drug absorption and bioavailability

6. Pre-emptive analgesia, particularly opioids like buprenorphine, can reduce the dose of anesthetics required for surgical anesthesia and increase the respiratory depression associated with anesthetics. When preemptive analgesia is used, consider reducing the dose of anesthetic (whether inhalant or injectable) to the low end of the recommended range. Anesthetic depth must be carefully monitored and drug doses may need to be titrated to maintain appropriate levels. With new projects, sexes, strains or anesthetic/ analgesic combinations, assess a subset of animals before expanding to use in a larger cohort.

1. Abou-Taleb HA, Shoman ME, Makram TS, Abdel-Aleem JA, Abdelkader H. 2023. Exploration of the safety and solubilization, dissolution, analgesic effects of common basic excipients on the NSAID drug ketoprofen. Pharmaceutics 15(2):713.
2. Andrews DD, Fajt VR, Baker KC, Blair RV, Jones SH, Dobek GL. 2020. A comparison of buprenorphine, sustained release buprenorphine, and high concentration buprenorphine in male New Zealand white rabbits. J Am Assoc Lab Anim Sci 59(5):546-56.
3. Ayub S, Parnia S, Poddar K, et al. 2023. Xylazine in the opioid epidemic: a systematic review of case reports and clinical implications. Cureus 15(3):e36864.
4. Bradley MP, Doerning CM, Nowland MH, Lester PA. 2019. Intramuscular administration of alfaxalone alone and in combination for sedation and anesthesia of rabbits (Oryctolagus cuniculus). J Am Assoc Lab Anim Sci 58(2):216-22.
5. Carpenter JW. 2018. Exotic Animal Formulary, Fifth Edition. St Louis (MO):Elsevier.
6. Diaz LL, Zhang J, Heerdt PM. 2014. Comparative pharmacodynamics of pancuronium, cisatracurium, and CW002 in rabbits. J Am Assoc Lab Anim Sci 53(3):283-9.
7. Farkas MR, Dorn S, Muller L, Singh VP, et al. 2024. Pharmacokinetics, fecal output, and grimace scores in rabbits given long-acting buprenorphine or fentanyl for postsurgical analgesia. J Am Assoc Lab Anim Sci 63(3):303-9.
8. Flecknell PA, Roughan JV, Hedenqvist P. 1999. Induction of anaesthesia with sevoflurane and isoflurane in the rabbit. Lab Anim 33(1):41-6
9. Flecknell P. 2015. Laboratory Animal Anaesthesia, Fourth Edition. San Diego (CA):Elsevier-Academic Press.
10. Foley PL, Henderson AL, Bissonette EA, Wimer GR, Feldman SH. 2001. Evaluation of fentanyl transdermal patches in rabbits: blood concentrations and physiologic response. Comp Med 51(3):239-44.
11. Fredholm DV, Carpenter JW, KuKanich B, Kohles M. 2013. Pharmacokinetics of meloxicam in rabbits after oral administration of single and multiple doses. Am J Vet Res 74(4):636-41.
12. Gaertner DJ, Boschert KR, Schoeb TR. 1987. Muscle necrosis in Syrian hamsters resulting from intramuscular injections of ketamine and xylazine. Lab Anim Sci 37(1):80-3
13. Harkness JE, Turner PV, VandeWoude S, and Wheler CL. 2010. Harkness and Wagner’s Biology and Medicine of Rabbits and Rodents, Fifth Edition. Ames(IA):Wiley-Blackwell.
14. Lester PA, Moore RM, Shuster KA, Myers DD. 2012. Anesthesia and analgesia, p33-56. In: Suckow MA, Stevens KA, Wilson RP, editors. The Laboratory Rabbit, Guinea Pig, Hamster, and Other Rodents. San Diego (CA):Elsevier-Academic Press.
15. Lester PA, Martin TL, Myers DD. 2023. Anesthesia and analgesia in rabbits, p357-391. In: Dyson MC, Jirkof P, Lofgren J, Nunamaker EA, Pang D, editors. Anesthesia and Analgesia in Laboratory Animals, Third Edition. London (UK): Academic Press
16. Maguire S, Hawk CT. 2012. Formulary, p1193-1229. In: Suckow MA, Stevens KA, Wilson RP, editors. The Laboratory Rabbit, Guinea Pig, Hamster, and Other Rodents. San Diego (CA):Elsevier-Academic Press.
17. Mirschberger V, von Deimling C, Heider A, Spadavecchia C, Rohrbach H, Zeiter S. 2020. Fentanyl plasma concentrations after application of a transdermal patch in three different locations to refine postoperative pain management in rabbits. Animals (Basel) 10(10):1778
18. Muir WW, Hubbell JAE, Bednarski RM, Lerche P. 2013. Handbook of Veterinary Anesthesia, Fifth Edition. St Louis (MO):Elsevier-Mosby.
19. Murphy KL, Roughan JV, Baxter MG, Flecknell PA. Anaesthesia with a combination of ketamine and medetomidine in the rabbit: effect of premedication with buprenorphine. Vet Anaesth Analg 37(3):222-9.
20. Plumb DC. 2015. Plumb’s Veterinary Drug Handbook, Eighth Edition. Ames (IA):Wiley-Blackwell.
21. Quesenberry KE, Carpenter JW. 2012. Ferretts, Rabbits, and Rodents Clinical Medicine and Surgery, Third Edition. St Louis (MO):Elsevier-Saunders.
22. Schroeder CA, Smith LJ. 2011. Respiratory rates and arterial blood-gas tensions in healthy rabbits given buprenorphine, butorphanol, midazolam, or their combinations. J Am Assoc Lab Anim Sci 50(2):205-11.
23. Smiler KL, Stein S, Hrapkiewicz KL, Hiben JR. 1990. Tissue response to intramuscular and intraperitoneal injections of ketamine and xylazine in rats. Lab Anim Sci 40(1):60-4