Sedation
Midazolam 2.5 mg/kg i.m. or i.v.
Diazepam 2.5 mg/kg i.m. or i.v.
Xylazine 5.0 mg/kg i.m.
Medetomidine 0.135 mg/kg i.m.
Azaperon 1.0 mg/kg i.m.
Table 5.2
Anesthesia with alfa2-agonists
A | B |
Ketamine 100 mg/kg i.m. + Xylazine 5 mg/kg i.m. | Ketamine 60–75 mg/kg i.m. or s.c. + Medetomidine 0.25–0.5 mg/kg i.m. or s.c. |
Surgical anesthesia stage lasts 20–30 min. For prolongation, one third of the starting dose can be added. Sleep after anesthesia is lengthy. Diuresis is increased. Danger of hypothermia. The effect can be partially antagonized by atipamezole | The length of surgical anesthesia stage fluctuates from 30 to 90 min. Danger of hypothermia. Polyuria. The partial reversion by atipamezole is possible no earlier than 45 min after anesthesia induction |
C | D |
Tiletamine/zolazepam 20 mg/kg i.p. or i.m. + Xylazine 10 mg/kg i.p. or i.m. | Tiletamine/zolazepam 20–40 mg/kg i.m. |
Surgical anesthesia stage lasts 30–45 min. Recovery may be prolonged. The effect of zolazepam and xylazine can be partially antagonized by specific antagonists | It is used less often because recovery is prolonged |
The opioid anesthetics fentanyl or sufentanil can be combined with neuroleptic azaperone (Table 5.3). Mantell [4] used fully antagonizable general anesthesia in a combination fentanyl + medetomidine + midazolam. The reversion was performed by a combination of atipamezol, flumazenil and naloxone (Table 5.4). Perantoni used partiall agonist of the opioid receptor buprenorfin instead of naloxon to antagonize the above mentioned anesthetic combination. The use of buprenorfin instead of naloxon results in prolongation of analgesic effect even in the postoperative period.
Table 5.3
Anesthesia with opioid components
A | B |
Fentanyl 0.1–0.15 mg/kg i.m. + Azaperon 1.0 mg/kg i.m. | Sufentanil 0.01–0.02 mg/kg i.m. + Azaperon 1.0–2.0 mg/kg i.m. |
After 10–15 min, a stage of surgical analgesia for 30–45 min is reached. The effect of the opioid component can be reversed by naloxone at a dose 0.1 mg/kg | After 10–15 min, the stage of surgical analgesia for 60–120 min is reached. Naloxone (0.1 mg/kg) can be administrated to antagonize the effect of opioid component |
C | |
Hypnorm (fentanyl 0.08 mg/kg – fluanizon 0.25 mg/kg) + Medetomidine 0.25 mg/kg | |
Occasionally Atropin 0.05 mg/kg | |
Therapeutic range is good. Animals can tolerate double of the recommended dose . Anesthesia can be prolonged by half of the initial dose of hypnorm/medetomidine or by combination of fentanyl/medetomidine at a dose as for anesthesia induction or by combination droperidol 1.0–2.0 mg/kg with medetomidine 0.15–0.2 mg/kg. Specific antagonists can reverse the effects of fentanyl and medetomidine | |
Table 5.4
Fully antagonizable anesthesia
Anesthesia | Antagonization |
|---|---|
Fentanyl 0.005 mg/kg i.m. + Midazolam 2.0 mg/kg i.m. + Medetomidine 0.15 mg/kg i.m. | Naloxon 0.12 mg/kg s.c. + Flumazenil 0.2 mg/kg s.c. + Atipamezol 0.75 mg/kg s.c. |
Duration of the anesthesia is 45–60 min. One third of the initial dose can be administered i.m. or i.p. for anesthesia prolongation | Analgesia maintaining in the post-operative period can be achieved by replacing naloxone with buprenorphine at a dose 0.05 mg/kg s.c. |
5.1.5 Post-operative Analgesia
Analgesics should be given in the post-operative period to enhance the recovery of animals and a more rapid return to normal behavior (food and water intake, movement). Adequate pain relief should also be provided from ethical reasons and based on the animal protection act.
Though we are able to provide effective analgesia during surgery, the use of analgesics in the postoperative period of small rodents has not yet became a general rule The post-operative analgesion has still a minor tradition in small rodents. Although general anesthesia produces loss of consciousness, painful stimuli can still be transmitted and processed by the spinal cord and brain and also hypersensitivity can still develop. Administration of analgesics before surgery can prevent these events and also the duration and intensity of post-operative pain is reduced. This approach is known as preemptive analgesia and combines analgesics with different mechanisms of action, such as ketamine and alpha2-agonist. Peri-operative analgesion in laboratory rats use strong analgesics (opioids), mostly centrally acting antipyretic (e.g. pyrazolones) and more peripherally acting weak non-steroidal antiflogistics. Post-operative analgesia is listed in the following table (Table 5.5).
Table 5.5
Post-operative analgesia
Dose | Duration of action | |
|---|---|---|
Opioids | ||
Petidin | 10–20 mg/kg s.c. or i.m. | 2–3 h |
Morphine | 2.5 mg/kg s.c. | 4 h |
Butorphanol | 2.0 mg/kg s.c. | 4 h |
Buprenorphine | 0.01–0.05 mg/kg s.c. or i.v. | 8–12 h |
0.1–0.25 mg/kg per os | 8–12 h | |
Antipyretics | ||
Metamizol | 1–2 drops per os | 4–6 h |
Paracetamol | 200 mg/kg per os | 4 h |
Aspirin | 100 mg/kg per os | 4 h |
NSAIDs | ||
Carprofen | 4 mg/kg i.v., i.m. or s.c. | 12 h |
2 mg/kg per os | 12 h | |
Ibuprofen
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