Policy On Analgesia in Animals Undergoing Surgery

Institutional Animal Care & Use Committee
Mar 18, 2024 12:00 am

This policy has been created to minimize pain and distress to animals undergoing surgical procedures for research, teaching and testing by providing the minimum analgesic duration that is acceptable for various surgical procedures.

  • Background

    The USDA Animal Welfare Act Regulations require procedures to “be performed with appropriate sedatives, analgesics or anesthetics, unless withholding such agents is justified for scientific reasons, in writing, by the principal investigator and will continue only for the necessary period of time1”, but the assessment of pain and distress in animals is difficult and can be subjective. As such, and according to the U.S. Government Principles for the Utilization and Care of Vertebrate Animals Used in Testing, Research, and Training, “unless the contrary is established, investigators should consider that procedures that cause pain or distress in human beings may cause pain or distress in other animals2.”

    1 The Animal Welfare Act Regulations (9 CFR, Part 1, Subpart C)    
    2 Published in the Federal Register, May 20, 1985, Vol. 50, No. 97, by the Office of Science and Technology Policy [FR Doc. 85-12059]. (A PDF version can be found here: https://grants.nih.gov/grants/olaw/references/phspolicylabanimals.pdf)
  • Applicability

    This policy is applicable to all animal activities conducted under the auspices of the University and applies to all locations under the purview of the U-M IACUC.

  • Glossary Definitions

    Local Anesthetic

    A local anesthetic is a drug that blocks sensation from a specific area of the body, such as lidocaine or bupivacaine.

  • Policy

    Surgical procedures that require withholding analgesics must be justified for scientific reasons in the IACUC approved animal use protocol.

    The table below, developed by veterinarians as an assessment tool, standardizes pain relief requirements for surgical procedures based on the procedures level of invasiveness. Any surgical analgesic regimen described in the IACUC approved animal use protocol must follow, at a minimum, the expectations outlined in the table.

    Additionally, depending on the nature and invasiveness of a surgical procedure, the ULAM veterinarians may require additional analgesics to be added to the protocol. If pain persists after the required analgesia is provided, or other complications arise, a ULAM veterinarian must be consulted.

  • Minimum Analgesic Duration Based on Surgery Invasiveness


    Type I Surgery

    Surgical procedures that require use of preemptive analgesia, such as single dose of a systemic analgesic or a local anesthetic (i.e., bupivacaine).

    Though some anesthetic agents have analgesic properties, the duration of that analgesia should not solely be relied upon to sufficiently treat post-operative pain.

    Type II Surgery

    Surgical procedures that require use of preemptive analgesia and a minimum of approximately 24 hours of postoperative analgesia.

    Systemic analgesia should be used and can be combined with local anesthesia.

    Type III Surgery

    Surgical procedures that require use of preemptive analgesia and a minimum of approximately 48 hours of postoperative analgesia.

    Multimodal analgesia is recommended.


    Skin incision without deeper tissue manipulation


    • Skin biopsy
    • Tracheal injection

    Skin incision and deeper tissue manipulation


    • Subcutaneous implantation with creation of a pocket such as for a pellet, pump, or tissue
    • Muscle incision
    • Muscle biopsy
    • Vessel cannulation
    • Vessel biopsy
    • Castration
    • Vasectomy
    • Oral soft tissue manipulation
    • Craniotomy with minor soft tissue manipulation and small bone defect or hole
    • Laparotomy with minor flank incisions
    • Laparoscopic surgeries

    Any surgical procedure not included
    as Type I or Type II


    • Thoracotomy
    • Laparotomy with midline or major surgical incision
    • Craniotomy with extensive soft tissue manipulation and bone defects or incisions
    • Direct manipulation of a joint, nerve, or bone (including teeth)
    • Ophthalmic surgery
  • Compliance

    The provisions of this policy are under the direction and oversight of the U-M’s IACUC. The IACUC will, if necessary, suspend research or implement sanctions if policy infractions should occur.


For questions, additional detail, or to request changes to this policy, please contact the Office of the Assistant Vice President for Research, Director of the Animal Care & Use Office at acuoffice@umich.edu or (734) 763-8028.