Recommendations
It is difficult to make firm recommendations concerning which analgesics to use routinely, and how often to give them, because of the various factors outlined above. Nevertheless, as a general guide, the following techniques are used routinely in the author’s research facility.
When carrying out any surgical procedure, buprenorphine is administered either pre-operatively or immediately following the induction of anaesthesia, if a volatile anaesthetic is used. If neuroleptanalgesic regimens are used, or mu opioids are given as part of a balanced anaesthetic technique, then administration of buprenorphine is delayed until completion of surgery. If the procedure is relatively minor, for example, jugular or carotid cannulation, then only a single dose of analgesic is administered. In some circumstances, a potent NSAID, such as meloxicam or carprofen, may be used as an alternative to buprenorphine.
Following more invasive surgical procedures, such as laparotomy, orthopaedic surgery or craniotomy, opioid administration is continued for 8–48 hours, depending upon the species and the expertise of the surgeon (since this has a major influence on the degree of tissue trauma). When undertaking major surgery, particularly in larger species when the degree of tissue trauma tends to be greater, analgesic administration may continue for 72 hours. In addition, local anaesthetics (e.g. bupivacaine combined with lidocaine) may be infiltrated into the wound margins, or used to provide a localized nerve block of the area. Frequently, the technique chosen consists of an opioid (buprenorphine) in combination with an NSAID for 8–24 hours, followed by NSAID alone for further 24–36 hours.
In rats, the major signs of pain are present for only 6–8 hours following laparotomy, although more subtle effects persist for longer in both rats and mice. This suggests that a single dose of a long-acting opioid such as buprenorphine, combined with a longer-acting NSAID, may provide sufficient pain relief after mild and moderate surgical procedures in some species. In all instances, it is important to establish the intensity and the duration of pain, and the efficacy of analgesic therapy by the use of pain assessment systems. Suggested dose rates of analgesics are given in the tables below.
Dose Rates for Non-steroidal Anti-inflammatory Drugs
Table: Suggested Dose Rates for Non-steroidal Anti-inflammatory Drugs in Laboratory Animals| Drug | Mouse | Rat | Guinea pig | Rabbit | Ferret |
|---|---|---|---|---|---|
| Carprofen | 5 mg/kg sc | 5 mg/kg sc | 4 mg/kg sc once daily | 1.5 mg/kg per os u.i.d., 4 mg/kg sc u.i.d. | 4 mg/kg sc u.i.d. |
| Meloxicam | 5 mg/kg sc or per os | 1 mg/kg sc or per os | 0.1–0.3 mg/kg sc or per os every 24 h | 0.6–1 mg/kg sc or per os | 0.1–0.2 mg/kg sc or per os |
| Note that considerable individual and strain variation in response may be encountered and that it is therefore essential to assess the analgesic effect in each individual animal | |||||
| Drug | Pig | Sheep | Primate | Dog | Cat |
|---|---|---|---|---|---|
| Carprofen | 2–4 mg/kg iv or sc, once daily | 2–4 mg/kg sc or iv, once daily (? 2–3 days) | 3–4 mg/kg sc u.i.d. | 4 mg/kg iv or sc, once daily 1–2 mg/kg b.i.d. per os, for 7 days | 4 mg/kg sc or iv |
| Meloxicam | 0.4 mg/kg sc, once daily | 0.5 mg/kg iv, sc up to b.i.d. for 1 day, then 0.5 mg/kg per os u.i.d. for 5 days | 0.1–0.2 mg/kg u.i.d. sc or per os | 0.2 mg/kg u.i.d. sc or per os, then 0.1 mg/kg sc or per os | 0.2 mg/kg u.i.d. sc or 0.3 mg/kg per os, then 0.1 mg/kg sc or per os |
| Note that considerable individual and strain variation in response may be encountered, and that it is therefore essential to assess the analgesic effect in each individual animal. | |||||
Suggested Dose Rates for Opioid Analgesics
Table: Suggested Dose Rates for Opioid Analgesics in Laboratory Animals| Drug | Mouse | Rat | Guinea pig | Rabbit | Ferret |
|---|---|---|---|---|---|
| Buprenorphine | 0.05–0.1 mg/kg sc 12 hourly | 0.01–0.05 mg/kg sc or iv, 8–12 hourly 0.1–0.25 mg/kg per os, 8–12 hourly | 0.05 mg/kg sc, 8–12 hourly | 0.01–0.05 mg/kg sc or iv, 8–12 hourly | 0.01–0.03 mg/kg iv, im or sc, 8–12 hourly |
| Morphine | 2.5 mg/kg sc, 2–4 hourly | 2.5 mg/kg sc, 2–4 hourly | 2–5 mg/kg sc or im, 4 hourly | 2–5 mg/kg sc or im, 2–4 hourly | 0.5–2 mg/kg im or sc, 6 hourly |
| Tramadol | 5 mg/kg sc, ip ? | 5 mg/kg sc, ip ? | – | – | – |
| Note that considerable individual and strain variation in response may be encountered, and that it is therefore essential to assess the analgesic effect in each animal. ? 5 duration of action uncertain. | |||||
Conclusions
Attention to the suggestions made above concerning post-operative care can have a dramatic effect on the speed with which animals return to normality following surgical procedures. It has been repeatedly demonstrated in humans that the provision of effective analgesia reduces the time taken for post-operative recovery. The provision of good post-operative care should be considered essential both because of a concern for the animal’s welfare and also because it is good scientific practice.
Additional reading and references can be found in Flecknell, P.A., (2015) “Laboratory Animal Anaesthesia”, 4th Edition, Elsevier