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Table 2 Summary of the properties of injectable anaesthetics
| Anaesthetic agent | Advantages | Disadvantages | Dosing |
|---|---|---|---|
| Fentanyl/fluanisone (Hypnorm™)-based combination | Good analgesic effect | Cardiovascular and respiratory depression | 10 ml/kg (mouse), 2.7 ml/kg (rat) i.p. mixture Hypnorm™/Hypnovel™ (midazolam)/water mixture (1:1:2 volume) (120 to 140 min sleep time)Hypnorm™ top-up 0.3 ml/kg (mouse), 0.1ml/kg (rat) i.p. (30 to 40 min sleep time) |
| Sedative | Poor muscle relaxation alone | ||
| Possible to top-up for long-term anaesthesia | Risk of enterohepatic recirculation: relapse | ||
| Reversal of sedative effect with buprenorphine to speeds up recovery time | Prolonged recovery time | ||
| Hypersensitivity to noise | |||
| Ketamine-based combination | Analgesic effects | Muscle rigidity +++ unless combined with other agents. | Ketamine + medetomidine 75 mg/kg + 0.5 to 1 mg/kg i.p.(Ketamine + xylazine 75 to 100 mg/kg)/(10mg/kg i.p.)(60 to 120 min sleep time ) (mouse and rats)Atipamezole 1mg/kg i.p. |
| Light sedation | Increases intracranial pressure. | ||
| Wide safety margin | Recovery often involved with ataxia and hyper responsiveness. | ||
| Can increase blood pressure | |||
| Alfaxalone (Alfaxan) | Minimal respiratory or CVS depression | Administration route i.v. (rodents, cats) or i.m. (primates) | 15 to 20mg/kg (mouse), 10 to 12mg/kg (rat) i.v.(10 to 15 min sleep time after bolus)0.25 to 0.75 mg/kg/min i.v. infusion (long term) |
| Rapidly metabolised, repeated doses do not accumulate. | |||
| Suitable for long-term anaesthesia in rodents | |||
| Propofol (Rapinovet®, Diprivan®) | Rapidly metabolised, continuous infusion possible for long-term anaesthesia. | i.v. use only | 26 mg/kg (mouse), 10 to 12mg/kg (rat) i.v.(10 to 15 min sleep time after bolus)2 to 2.5 mg/kg/min i.v. infusion (long-term, mouse) 0.5 to 1 mg/kg/min i.v. infusion (long-term, rat) |
| No analgesic properties | |||
| Rapid recovery | Severe respiratory depression | ||
| Can be used in animals with hepatic or renal impairment. | Apnoea can occur after i.v. bolus | ||
| Barbiturates products | Sedative effect | No analgesic properties | Pentobarbitone, 40 to 50mg/kg i.p. (mouse) (120 to 180 min sleep) |
| Good hypnotic effect | Severe respiratory depression and hypotensive | ||
| Reasonable muscle relaxation | Easy to overdose | Thiopentone, 30 mg/kg i.v. 15 min sleep (rat) | |
| Metabolites accumulate with time | |||
| Caustic substances (thiopentone only i.v. route) | |||
| Chloral hydrate | Sedative effect | No analgesic properties | 300 to 400 mg/kg i.p. (1 to 2 h sleep time) (mouse and rats) |
| Good hypnotic effect | Paralytic ileus noted in rats | ||
| Minimal CVS and respiratory depression | Terminal/non-recovery work only | ||
| α-Chloralose | Sedative effect | No analgesic properties | 50 to 60 mg/kg i.p. (rats), 120 mg/kg i.p. (mouse)(8 to 12 h for non-recovery only)50 mg/kg i.v. bolus followed by 25 to 40 mg/kg/h (rats) |
| Good hypnotic effect | i.v. use only | ||
| Suitable for long-term anaesthesia | Slow induction and recovery associated with involuntary excitement | ||
| Minimal CVS and respiratory depression | Terminal/non-recovery work only | ||
| Urethane | Suitable for long-term anaesthesia. | Carcinogenic: only allowed to be used with special justification | 0.8 to 1.3 g/kg i.p. (mouse and rats)Duration of action 8 to 10 h (non-recovery only) |
| Minimal CVS and respiratory depression | Terminal/non-recovery work only | ||
| Avertin® (tribromoethanol) | Wide safety margin | Local irritation/peritonitis | 0.015 ml/g body wt of 2.5% i.p. |
| Good muscle relaxation | Handling and storage safety issues | 30 min; supplemental doses of anaesthesia: minimum of 1/2 of the initial dose up to 1 ml maximum volume per animal | |
| Rapid induction and recovery | Toxic effects |
