• Ketamine (5–8 mg/kg i.m.) plus medetomidine (80–100 μg (micrograms)/kg i.m.) or dexmedetomidine (40–50 μg (micrograms)/kg i.m.) to which can be added butorphanol (0.1–0.2 mg/kg i.m.) or buprenorphine (0.02 mg/kg i.m.) ab.
• Ketamine (5–20 mg/kg i.m.) plus midazolam (0.25–0.5 mg/kg i.m.) or diazepam (0.25–0.5 mg/kg i.m.) will provide immobilization or, at the higher doses, a short period of anaesthesia.
• Ketamine (7–10 mg/kg i.m., s.c.) plus medetomidine (20 μg (micrograms)/kg i.m., s.c.) plus midazolam (0.5 mg/kg i.m., s.c.) will provide anaesthesia; concurrent oxygenation is recommended.

aKo JC, Heaton-Jones TG, Nicklin CF (1997) Evaluation of the sedative and cardiorespiratory effects of medetomidine, medetomidine-butorphanol, medetomidine-ketamine and medetomidine-butorphanol-ketamine in ferrets. Journal of the American Animal Hospital Association 33(5), 438–448

bScherntjamer A, Lendl CE, Hartmann K, Pragst I, Preissel AK and Henke J (2011) Medetomidine/midazolam/ketamine anaesthesia in ferrets: effects on cardiorespiratory parameters and evaluation of plasma drug concentrations. Veterinary Anaesthesia and Analgesia 38(5), 439–450

• Ketamine (3–5 mg/kg i.v. or 5–10 mg/kg i.m., s.c.) in combination with medetomidine (0.05–0.1 mg/kg i.v. or 0.1–0.3 mg/kg s.c., i.m.) or dexmedetomidine (0.025–0.05 mg/kg i.v. or 0.05–0.15 mg/kg s.c., i.m.) and butorphanol (0.05–0.1 mg/kg i.m., i.v., s.c.) or buprenorphine (0.02-0.05 mg/kg i.m., i.v., s.c.).
• Fentanyl/fluanisone (0.1–0.3 ml/kg i.m.) plus diazepam (0.5–1 mg/kg i.v., i.m. or 2.5–5.0 mg/kg intraperitoneal) or midazolam (0.25–1.0 mg/kg i.v., i.m., intraperitoneal).
• The combinations above will provide immobilization/light anaesthesia, usually sufficient to allow intubation for maintenance with a volatile agent.
• Ketamine (15 mg/kg i.m.) in combination with medetomidine (0.25 mg/kg i.m.) and buprenorphine (0.03 mg/kg i.m.) will provide general anaesthesia abc, but use of lower doses followed by intubation and use of a volatile agent is recommended.

aGrint NJ and Murison PJ (2008) A comparison of ketamine-midazolam and ketamine-medetomidine combinations for induction of anaesthesia in rabbits. Veterinary Anaesthesia and Analgesia 37(3), 113–121

bMurphy KL, Roughan JV, Baxter MG and Flecknell PA (2010) Anaesthesia with a combination of ketamine and medetomidine in the rabbit: effect of premedication with buprenorphine. Veterinary Anaesthesia and Analgesia 37(3), 222–229

cOrr HE, Roughan JV and Flecknell PA (2005) Assessment of ketamine and medetomidine anaesthesia in the domestic rabbit. Veterinary Anaesthesia and Analgesia 32(5), 271–279

• Medetomidine (50 μg (micrograms)/kg i.m.) or dexmedetomidine (25 μg (micrograms)/kg i.m.) plus, if needed, ketamine (2–4 mg/kg i.m.) abcdef.
• Other combinations as for rabbits. Combinations can also be administered intraperitoneal in small rodents.

aBakker J, Uilenreef JJ, Pelt ER, Brok HP, Remarque EJ and Langermans JA (2013) Comparison of three different sedative-anaesthetic protocols (ketamine, ketamine-medetomidine and alphaxalone) in common marmosets (Callithrix jacchus). BMC Veterinary Research 9(1), 113

bBuchanan KC, Burge RR and Ruble GR (1998) Evaluation of injectable anaesthetics for major surgical procedures in guinea pigs. Contemporary Topics in Laboratory Animal Science 37(4), 58–63

cDang V, Bao S, Ault A et al. (2008) Efficacy and safety of five injectable anesthetic regimens for chronic blood collection from the anterior vena cava of guinea pigs. Journal of American Association of Laboratory Animal Science 47(6), 56–60

dHedenqvist P, Roughan JV and Flecknell PA (2000) Effects of repeated anaesthesia with ketamine/medetomidine and of pre-anaesthetic administration of buprenorphine in rats. Laboratory Animals 34(2), 207–211

eJang HS, Choi HS, Lee SH, Jang KH and Lee MG (2009) Evaluation of the anaesthetic effects of medetomidine and ketamine in rats and their reversal with atipamezole. Veterinary Anaesthesia and Analgesia 36(4), 319–327

fNevalainen T, Pyhälä L, Voipio HM and Virtanen R (1989) Evaluation of anaesthetic potency of medetomidine-ketamine combination in rats, guinea pigs and rabbits. Acta Veterinaria Scandinavica 85, 139–143

Note: Reduce doses if animal is debilitated. For all small mammals, for deeper anaesthesia, intubation (if possible) and use of a volatile agent is recommended, rather than using higher doses of injectable agents.

Injectable anaesthesia is best avoided unless in field situations (i.e. no gaseous anaesthesia available) or for the induction of large (e.g. swans/ratites), diving (e.g. ducks) or high-altitude birds. Even in these species, gaseous induction and maintenance (e.g. with isoflurane/sevoflurane) would still be the normal recommendation wherever possible. Sedation and premedicants are rarely used, as extra handling will add to the general stress of the situation. On occasions, diazepam (0.2–0.5 mg/kg i.m.) or midazolam (0.1–0.5 mg/kg i.m.) may be used; alternatively, either drug may be used at 0.05–0.15 mg/kg i.v. Parasympatholytic agents (such as atropine) are rarely used as their effect is to make respiratory excretions more viscous, thus increasing the risk of tube blockage.

• Propofol: 10 mg i.v. by slow infusion to effect; supplemental doses up to 3 mg/kg ab.
• Alfaxalone (2–4 mg/kg i.v.) is an alternative to propofol for the induction of anaesthesia in large birds or those with a dive response.
• Ketamine/diazepam combinations can be used for induction and muscle relaxation. Ketamine (30–40 mg/kg) plus diazepam (1.0–1.5 mg/kg) are given slowly i.v. to effect. May also be given i.m. but this produces different effects in different species and specific literature or specialist advice should be consulted. Ketamine (10 mg/kg i.m.) and diazepam (0.2–0.5 mg/kg i.m.) can be used as premedication/sedation (pigeons, Amazon parrots) prior to the administration of sevoflurane/isoflurane cd.
• Raptors: Ketamine (2–5 mg/kg i.m.) plus medetomidine (25–100 μg (micrograms)/kg) (lower dose rate i.v.; higher rate i.m.). This combination can be reversed with atipamezole at 65 μg (micrograms)/kg i.m. Ketamine should be avoided in vultures.

aFitzgerald G and Cooper JE (1990) Preliminary studies on the use of propofol in the domestic pigeon (Columba livia). Research in Veterinary Science 49(3), 334–338

bHawkins MG, Wright BD, Pascoe PJ, Kass PH, Maxwell LK and Tell LA (2003) Pharmacokinetics and anesthetic and cardiopulmonary effects of propofol in red-tailed hawks (Buteo virginianus) and great horned owls (Bubo virginianus). American Journal of Veterinary Research 64(6), 677–683

cAzizpour and Hassani Y (2012) Clinical evaluation of general anaesthesia in pigeons using a combination of ketamine and diazepam. Journal of the South African Veterinary Association 83(1), 12

dPaula VV, Otsuki DA, Auler Júnior JO, Nunes TL, Ambrósio AM and Fantoni DT (2013) The effect of premedication with ketamine, alone or with diazepam, on anaesthesia with sevoflurane in parrots (Amazona aestival). BMC Veterinary Research 9, 142

• Alfaxalone provides deep sedation/anaesthesia in chelonians (preferable to perform intermittent positive pressure ventilation with 100% oxygen after administration to prevent hypoxia). Can be used at 2–4 mg/kg i.v. or intraosseously for induction but effects are dependent on species and temperature.
  • Chelonians: Red-eared sliders, Horsfield tortoises: 10 mg/kg i.m. (light sedation) up to 20 mg/kg i.m. for surgical anaesthesia ab; Macquarie river turtles: 9 mg/kg i.v. c.
  • Lizards, Snakes: <9 mg/kg i.v. d; Green iguanas: 10 mg/kg i.m. (light sedation) up to 30 mg/kg i.m. for surgical anaesthesia e or 5 mg/kg i.v. f (for sufficient sedation to allow intubation); Veiled chameleons: 5 mg/kg i.v. (for sufficient sedation to allow intubation) g.
• Propofol (5–10 mg/kg i.v. or intraosseously) will give 10–15 minutes of sedation/light anaesthesia )preferable to perform intermittent positive pressure ventilation with 100% oxygen after administration to prevent hypoxia).
  • Red-eared sliders: 10–20 mg/kg i.v. (higher doses required for successful intubation).
  • Green iguanas: 5–10 mg/kg iv., intraosseous.
  • Brown tree snakes: 5 mg/kg i.v.
• Ketamine as sole agent: Ketamine alone may result in variable sedation, poor muscle relaxation and prolonged recovery at higher dose rates. Usually combined with alpha-2 agonists and/or opioids/midazolam to provide deep sedation/light anaesthesia (see below).
• Alpha-2 agonists as sole agents: Although single agent use has been reported, it is generally preferable to use medetomidine or dexmedetomidine in combination with opioids and/or ketamine and/or midazolam for more reliable sedation (see below).
• Benzodiazepines as sole agents: Although single agent used has been reported, it is generally preferable to use midazolam in combination with opioids and/or ketamine and/or alpha-2 agonists for more reliable sedation (see below).
• Ketamine/alpha-2 agonist mixtures:
  • Ketamine (5–10 mg/kg i.m., i.v.) plus medetomidine (100–200 μg (micrograms)/kg i.m., i.v.) (deep sedation to light anaesthesia in gopher tortoises h and red-eared sliders i); may reverse medetomidine with atipamezole at 5 times the medetomidine dose (i.e. 0.5–1.0 mg/kg atipamezole)
  • Ketamine (2 mg/kg s.c.) plus dexmedetomidine (100 μg (micrograms)/kg s.c.) and midazolam (1 mg/kg s.c.) (moderate sedation in red-eared sliders j)
  • The addition of an opioid (e.g. morphine) to the mixture should be considered for potentially painful procedures (see monograph).
• Ketamine/benzodiazepine mixtures:
  • Chelonians, Snakes: Sedation to light anaesthesia: Ketamine (20–60 mg/kg i.m.) plus midazolam (1–2 mg/kg i.m.) or diazepam (Chelonians: 0.2–1 mg/kg i.m.; Snakes: 0.2–0.8 mg/kg i.m.) has been recommended for sedation.
• Ketamine/opioid mixtures:
  • Ketamine (10–30 mg/kg i.m.) plus butorphanol (0.5–1 mg/kg i.m.) has been recommended for sedation.
• Opioid/midazolam mixtures:
  • Butorphanol (0.4 mg/kg i.m.) plus midazolam (2 mg/kg i.m.) maybe administered for pre-anaesthetic sedation.

aHansen LL and Bertelsen MF (2013) Assessment of the effects of intramuscular administration of alfaxalone with and without medetomidine in Horsfield’s tortoises (Agrionemys horsfieldii). Veterinary Anaesthesia and Analgesia 40(6), 68–75

bKischinovsky M, Duse A, Wang T and Bertelsen MF (2013) Intramuscular administration of alfaxalone in red-eared sliders (Trachemys scripta elegans) – effect of dose and body temperature. Veterinary Anaesthesia and Analgesia 40(6) 68–75

cScheelings TF (2013) Use of intravenous and intramuscular alfaxalone in Macquarie river turtles (Emydura macquarii). Proceedings of the Association of Reptilian and Amphibian Veterinarians pp. 71

dScheelings TF, Baker RT, Hammersley G et al. (2011) A preliminary investigation into the chemical restraint with alfaxalone of selected Australian squamate species. Journal of Herpetological Medicine and Surgery 21, 63–67

eBertelsen MF and Sauer CD (2011) Alfaxalone anaesthesia in the green iguana (Iguana iguana). Veterinary Anaesthesia and Analgesia 38(5), 461–466

fKnotek Z, Hrda A, Knotkova Z, Barazorda Romero S and Habich A (2013) Alfaxalone anaesthesia in birds. Acta Veterinaria Brno 82, 109–114

gKnotek Z, Hrda A, Kley N and Knotkova Z (2011) Alfaxalone anesthesia in veiled chameleon (Chamaeleo calyptratus). Proceedings of the Association of Reptilian and Amphibian Veterinarians, pp. 179–181

hDennis C and Heard DJ (2002) Cardiopulmonary effects of a medetomidine-ketamine combination administered intravenously in gopher tortoises. Journal of the American Veterinary Medical Association 220(10), 1516–1519

iGreer LL, Jenne KJ and Diggs HE (2001) Medetomidine-ketamine anesthesia in red-eared slider turtles (Trachemys scripta elegans). Journal of the American Association for Laboratory Animal Science 40(3), 8–11

jMans C, Drees R, Sladky KK, Hatt JM and Kircher PR (2013) Effects of body position and extension of the neck and extremities on lung volume measure via computed tomography in red-eared slider turtles (Trachemys scripta elegans). Journal of the American Veterinary Medical Association 243(8), 1190–1196

All anaesthetics are administered by immersion and the stage of anaesthesia reached is determined by the concentration used and the duration of exposure, since absorption continues throughout the period of immersion. There are significant species differences in their response to the drugs and it is advised that the lower dose rates are used for unfamiliar species, marine and tropical fish. Many products and stock solutions should be kept in a dark bottle and protected from light. Ideally, the anaesthetic solution should be made up using water from the tank or pond of origin to minimize problems due to changes in water chemistry. It should be used on the day of preparation and well aerated during use. Food should be withheld for 12–24 hours before anaesthesia to reduce the risk of regurgitation, which may cause damage to gill tissues. Monitoring heart rate during prolonged procedures using a Doppler probe or ultrasound scanner is advisable since this is a direct reflection of the level of anaesthesia. Following the procedure, anaesthetized fish should be returned to clean water from their normal environment to allow recovery.

• Tricaine mesilate (MS-222) (50–250 mg/l by immersion) produces an acidic solution and should be buffered with sodium bicarbonate to maintain the same pH as the original environmental water conditions. The dry powder is very soluble in water and can be added directly or a stock solution can be made up to facilitate accurate dosing.
• Benzocaine (25–200 mg/l by immersion) is insoluble in water and must be dissolved in acetone or ethanol. For example, a stock solution of 100 g benzocaine/l of ethanol produces 100 mg/ml to facilitate accurate dosing.
• 2-Phenoxyethanol (0.1–0.5 ml/l by immersion) must be whisked vigorously into the water to improve solubility.