OAR Informational Sheet: Local Analgesia/Anesthesia for Rodents

Informational Sheet: The IACUC has provided a set of guidance documents (Policies, Guidelines, and Informational Sheets) for use when planning animal procedures at the University of Iowa. Informational Sheets provide information about frequently asked questions and represents guidance for best practices. Deviation from the recommendation(s) does not require specific justification.

Purpose:  The purpose of this document is to educate researchers on effective uses of local analgesics and anesthetics in rodents.  When used properly local analgesics and anesthetics can reduce pain and distress in laboratory animals.

Line Blocks
Materials:

  • Lidocaine HCl (without epinephrine) 2% (20 mg/ml) or
  • Marcaine HCl (Bupivacaine) 0.5% (5 mg/ml)
  • Hypodermic needles (25 or 27g, 1/2” or smaller)
  • 1 cc syringes
  • Sterile multi-use injection vials for dilutions
  • Sterile, pyrogen-free water for injection

Formulary: Rats and Mice

Local Anesthetic Dose* Application Notes
Lidocaine (2%) Dilute to 0.5%, do not exceed 7mg/kg total dose; Incisional line block Use Locally before making surgical incision Faster onset than bupivicaine but short (<1hour) duration of action
Bupivicaine (0.5%) Dilute to .25%, do not exceed 8mg/kg total dose; incisional line block Use locally before making surgical incision Slower onset than lidocaine but longer (~4-8 hour) duration of action

* See dilution directions below

Dilutions:

  • Lidocaine
    Dilute the 2% (20 mg/ml) Lidocaine 1:4 to get final concentration of 0.5% (5 mg/ml) (for example: take 1 cc of Lidocaine and add 3 cc of Sterile, pyrogen-free water to an amber, sterile, multi-use vial). Transfer solutions aseptically, carefully label vial with drug name, concentration and date of dilution. Discard diluted solutions in 30 days.
  • Bupivacaine
    Dilute the 0.5% (5 mg/ml) Bupivacaine 1:2 to get final concentration of 0.25% (2.5 mg/kg) (for example: take 1 cc of Bupivacaine and add 1 cc of sterile, pyrogen-free water to an amber, sterile, multi-use vial). Transfer solutions aseptically, carefully label vial with drug name, concentration and date of dilution. Discard diluted solutions in 30 days.

Procedure

1. Weigh animal(s) to be treated.
2. Determine maximum dose that can be used depending on weight of animal (see next page).
3. Inject local anesthetic into the subcutaneous space (“line block”) below the planned incision line prior to surgery (once the animal is anesthetized, fur clipped and the skin prepped for surgery).

Insert needle fully into the subcutaneous space below the planned incision. Gently pull back syringe plunger to make sure there is no blood in the hub of the needle (avoid intravenous injections).

Begin injecting small volumes of the local anesthetic as the needle is withdrawn.

Complete injection of the local anesthetic under the planned incision site. If incision site is longer, re-insert needle further along the planned incision and repeat with remaining calculated volume of local anesthetic.

Maximum Volumes

Weight of Mouse

Maximum Volume Diluted Lidocaine (0.5%) Do not exceed:

Maximum Volume Diluted Bupivicaine (0.25%) Do not exceed:
25g 0.03ml 0.08ml
35g 0.05ml 0.11ml
45g 0.06ml 0.14ml
55g 0.07ml 0.17ml
Weight of Rat Maximum Volume Diluted Lidocaine (0.5%) Do not exceed: Maximum Volume Diluted Bupivicaine (0.25%) Do not exceed:
250g 0.35ml 0.8ml
350g 0.49ml 1.12ml
250g 0.63ml 1.44ml
550g 0.77ml 1.76ml

Local Anesthetics should be used pre-operatively (before the first incision) and can be used in conjunction with opioid analgesics and/or NSAIDs for controlling moderate to severe pain. Intramuscular and intravenous injection of local anesthetics must be avoided. Systemic toxicity (seizures, heart rhythm disturbances and death) results from overdosage or accidental intravenous injection.

 

References

"Local Analgesia/Anesthesia for Rodents." Animalcare.ubc.ca. N.p., n.d. Web. 16 Nov. 2012.

Last Reviewed by Committee 2/10/15