Analgesia Standard Treatment Guidelines for Mice

Background:  The avoidance or minimization of discomfort, distress, and pain, when consistent with sound scientific practices, is imperative in animal research. Following conversations with AAALAC evaluators, a campus-wide post-approval monitoring project on analgesia, and a review of the current literature, RARC veterinary staff have updated the standard treatment guidelines on analgesic regimens for rodents. 

Purpose:  The purpose of these analgesia standard treatment guidelines is to describe commonly used analgesic regimens for the management of pain and monitoring parameters for mice used in testing, research, and training at the University of Wisconsin-Madison. Analgesic regimens may need to be modified due to the health status, age, sex, or strain of the mouse and the specific procedure being performed. RARC veterinarians should be consulted to determine an appropriate analgesic regimen for your study.

Pain Levels and Examples

1. Momentary Pain

Description: Brief, transient pain that typically does not require analgesia.

Examples:

• Tail vein injections
• Ear tagging
• Subcutaneous implants with no undermining and no skin incision

2. Mild Pain

Description: Minor discomfort that minimally interferes with normal physiology and requires short-term analgesia.

Examples:

• Minor surgical procedures (e.g., small skin incisions, small biopsies, intracranial injections through small drill sites with minimal tissue undermining, subcutaneous implants with minimal tissue undermining)

3. Moderate Pain

Description: Quantifiable pain that frequently interferes with normal physiology and requires effective analgesia to ensure animal welfare.

Examples:

• Subcutaneous implants with undermining (i.e., large implants/pumps)
• Large biopsies
• Small incision abdominal surgeries (i.e., ovariectomies, castrations, kidney capsule implants)
• Orthopedic procedures (i.e., small joint defects)
• Intracranial injections requiring muscle or bone removal

4. Severe Pain

Description: Quantifiable intense pain that continually interferes with normal physiology and necessitates significant analgesic protocols.

Examples:

• Thoracotomy
• Large incision abdominal surgeries
• Major orthopedic surgeries (i.e., amputations)

Analgesia Standard Treatment Guidelines

Multimodal Analgesia:

• Combination of opioids, NSAIDs, local anesthetics, and supportive care for enhanced pain relief

1. Momentary Pain

• No analgesia typically required.
• Single dose NSAIDs may be used.

2. Mild Pain

• Single dose of either NSAIDs, local anesthetics, or opioids
• Local Anesthetics:
  • Bupivacaine: Injected at incision site (≤ 2 mg/kg diluted appropriately).
• Opioids:
  • Buprenorphine: 0.1-0.5 mg/kg subcutaneously may provide analgesia up to 4-6 hours.
• NSAIDs:
  • Meloxicam: 10 mg/kg subcutaneously may provide analgesia up to 8-12 hours.
  • Carprofen: 5 mg/kg subcutaneously may provide analgesia up to 12 hours; 20 mg/kg subcutaneously may provide analgesia up to 24 hours.

3. Moderate Pain

• NSAIDs, local anesthetics, and opioids should be used in combination (choose at least 2) to provide analgesia for at least 48 hours. Pain scoring must be performed and recorded for 24 hours past the end of the pain management protocol.
• Local Anesthetics:
  • Bupivacaine: Injected at incision site (≤ 2 mg/kg diluted appropriately).
  • Nocita: Injected in all tissue layers at incision site (≤ 0.4 mL/kg diluted appropriately).
• Opioids:
  • Buprenorphine: 0.1-0.5 mg/kg subcutaneously may provide analgesia up to 4-6 hours, so dosing must be repeated before the end of the effective analgesic time period or at the time that an animal begins to show any signs of pain.
  • Extended-Release Buprenorphine:
    • Ethiqa: 3.25 mg/kg subcutaneously may provide analgesia up to 72 hours.
    • Buprenorphine Base ER Lab (compounded): 0.6 mg/kg subcutaneously may provide analgesia up to 48 hours.
• NSAIDs:
  • Meloxicam: 10 mg/kg subcutaneously may provide analgesia up to 8-12 hours, so dosing must be repeated before the end of the effective analgesic time period or at the time that an animal begins to show any signs of pain.
  • Carprofen: 5 mg/kg subcutaneously may provide analgesia up to 12 hours, so must be repeatedly administered; 20 mg/kg subcutaneously may provide analgesia up to 24 hours, so dosing must be repeated before the end of the effective analgesic time period or at the time that an animal begins to show any signs of pain.

4. Severe Pain

• MULTIMODAL ANALGESIA IS REQUIRED! Opioid and NSAID +/- local anesthetic (if appropriate) should be provided for 48-72 hours. Pain scoring is required to be performed and recorded for 24 hours past the end of the pain management protocol.
• Local Anesthetics:
  • Bupivacaine: Injected at incision site (≤ 2 mg/kg diluted appropriately).
  • Nocita: injected in all tissue layers at incision site (≤ 0.4 mL/kg diluted appropriately).
• Opioids:
  • Buprenorphine: 0.1-0.5 mg/kg subcutaneously may provide analgesia up to 4-6 hours, so dosing must be repeated before the end of the effective analgesic time period or at the time that an animal begins to show any signs of pain.
  • Extended-Release Buprenorphine:
    • Ethiqa: 3.25 mg/kg subcutaneously may provide analgesia up to 72 hours.
    • Buprenorphine Base ER Lab (compounded): 0.6 mg/kg subcutaneously may provide analgesia up to 48 hours and may need to be repeated.
• NSAIDs:
  • Meloxicam: 10 mg/kg subcutaneously may provide analgesia up to 8-12 hours, so dosing must be repeated before the end of the effective analgesic time period or at the time that an animal begins to show any signs of pain.
  • Carprofen: 5 mg/kg subcutaneously may provide analgesia for up to 12 hours, so must be repeatedly administered; 20 mg/kg subcutaneously may provide analgesia up to 24 hours, so dosing must be repeated before the end of the effective analgesic time period or at the time that an animal begins to show any signs of pain.

Additional Considerations

• Preemptive Analgesia: Administer analgesics before the onset of pain is required.
• Monitoring: Regularly assess pain levels and adjust analgesic protocols as needed (see below).

Any administration of substances must be documented. In addition, all monitoring (intra- and post-procedurally) must be documented.

If a lab performs research with quantifiable outcomes that would be adversely affected by these standard analgesia guidelines, robust justification (including references) for NOT following these requirements must be included in the animal use protocol.

Recognition of Pain

Monitoring for and recognizing signs of pain and distress is essential for providing adequate analgesia. Researchers must be able to identify signs of pain and distress for the species they are working with. The RARC Trainers provide species-specific training on signs of pain and distress. RARC veterinarians are also able to consult on pain and distress recognition in unique models.

The grimace scale is a useful method of assessing pain in laborator rodents by observing changes in their facial expressions.

Pain Scoring Using the Grimace Scale

The website https://nc3rs.org.uk/3rs-resources/grimace-scales has posters of grimace scales in mice.

Key Facial Action Units for Mice:

1. Orbital Tightening: Squinting or closing of the eyes.
2. Nose Bulge: Bulging of the nose.
3. Cheek Bulge: Bulging of the cheeks.
4. Ear Position: Ears pulled back or flattened.
5. Whisker Change: Whiskers pulled back or forward.

Scoring:

• 0: Feature is absent.
• 1: Feature is moderately present.
• 2: Feature is obviously present.

Monitoring:

• Pre-Procedure: Observe and assess the animal’s baseline condition.
• Post-Procedure: Regularly observe and assess pain levels and adjust analgesic protocols as needed.
• Frequency of monitoring is based on pain severity.
  • Mild:
    • Day of procedure (day 0): Immediately after the procedure and 1 check prior to end of day.
    • Post-procedure (days 1-3): 1 check daily for 72 hours.
  • Moderate:
    • Day of procedure (day 0): Immediately after the procedure and 1 check prior to end of day.
    • Post-procedure (days 1-3): 2 checks a day with a minimum of 6 hours in between for 72 hours.
  • Severe:
    • Day of procedure (day 0): Immediately after the procedure and 1 check prior to end of day.
    • Post-procedure (days 1-3 or 1-4): 2 checks a day with a minimum of 6 hours in between for 72-96 hours.

Monitoring may need to be modified based on the specific procedure being performed and possible post-procedural complications. Monitoring frequency must be performed as stated in the protocol and must be documented. Observations can be documented using the Non-USDA Surgery Record. Additional information on medical records can be found here: Medical Records for Non-USDA Covered Species.