Post-operative Monitoring and Surgical Closures in Research Animals

Policy

Post-operative monitoring:

IACUC protocols must specify the post-operative monitoring plan, including the frequency, duration, and behavioral/clinical signs that will be monitored. These parameters should be determined in consultation with the veterinary staff.

The following provides broad guidelines for the minimum frequency and duration. Note that these may be increased by the veterinarian depending on the complexity and severity of the surgery.

For non-rodent mammals and birds, once to twice daily monitoring is generally expected for the first three to five days post-operatively followed by daily monitoring until the incision has healed (at least 7-10 days total for major surgery). Daily includes weekends and holidays.

For rodents and other non-mammalian vertebrates, daily (including weekends and holidays) monitoring is generally recommended for at least the first three days followed by monitoring at least 3 times per week on non-consecutive days until the incision has healed.

For rodent surgeries with a potentially higher incidence of complications (e.g., intra-abdominal surgeries with midline incisions), daily (including weekends and holidays) post-operative monitoring for the first 7-10 days is expected.

Any concerns noted during the post-operative period require prompt notification of veterinary services. This includes, but is not limited to: lethargy, inappetence, fever, wound dehiscence, evidence of infection (redness, excessive swelling, or discharge), missing sutures, staples, or wound clips, and wound dehiscence.

Wound dehiscence must be promptly reported to and evaluated by veterinary staff prior to reclosure. Veterinary staff will evaluate if reclosure is clinically indicated and will determine the appropriate method of reclosure when indicated. Reclosure of dehisced wounds is considered a repair surgery and must only be done under explicit veterinary directive unless the IACUC protocol specifically allows for repairs without consultation.

Records of post-operative monitoring must be maintained and readily available upon request.

Surgical and Wound Closures:

Appropriate pre-surgical planning is critical to ensure animal welfare and optimize the likelihood of successful outcomes. Prior to developing or implementing new, challenging, or complex surgical procedures, research staff should consult with veterinary staff and/or other other trained experts with relevant experience to develop a surgical plan. Pre-surgical consultation with veterinary staff is especially important for surgeries that will involve closure of large muscle defects, significant tissue debridement, closure of contaminated wounds, and closures with significant skin deficits (e.g. large cranial explants). Ideally, this consultation should occur during protocol development but may occur during veterinary pre-review of protocols if needed.

At any time, if a surgeon encounters an obstacle outside of or beyond their knowledge or area of expertise, they must contact a veterinarian for immediate assistance.

An understanding of anatomy is required when planning a surgery. Surgical incisions should be made with the intention of preserving the integrity of underlying nerves, blood vessels, and muscles as much as possible. Tissues should be handled gently with appropriate instruments and kept moist to prevent tissues from drying out.

Unanticipated wound closures (e.g., from trauma or dehiscence) should be performed by a veterinarian or under the guidance of a veterinarian. Severely damaged or dead tissue and foreign bodies must be removed, and any signs of pre-existing infection should be addressed and treated. Wound edges should be debrided of all devitalized tissue prior to apposition. Tissues ready for closure should be free of thickened or discolored areas and have evidence of good blood supply (active bleeding from edges). Surgeons must maintain a sterile and aseptic technique during wound closure.

Analgesics, including local anesthetics, must be administered as described in the protocol and are generally given pre-operatively unless contraindicated. Refer to Policy “Analgesia in Research Animals”.

Suture materials

Suture type and needle type must be appropriate for each type of tissue to maximize healing and minimize infection. The smallest suture with sufficient strength should be used. Silk sutures should not be placed in the skin of animals. Absorbable sutures and braided sutures are not recommended for use in the skin of non-primate animals, and any proposed use should be described and justified in the associated IACUC protocol. Absorbable sutures should be used for intradermal closure. When appropriate, tissue adhesive, wound clips, and/or staples may be used for skin closure.

The protocol should indicate the nature of closure (e.g., suture, wound clip, and/or staple) and the type of suture (absorbable versus non-absorbable; monofilament versus braided) but it is generally not recommended to specify brand or exact size of suture as that may vary with availability and size of the animal.

Suturing technique

Suture pattern and spacing of sutures must be appropriate for the species and type of surgery/closure. Multi-layer closures should be performed whenever possible to ensure elimination of subcutaneous dead space. Dead space in the wound may lead to fluid accumulation and result in a seroma and/or infection. Excessive dead space or air in the wound may also impede healing. Skin edges must meet directly for a proper closure. Proper tension should be used when closing incisions, so that wound edges are apposed fully covering underlying tissues, but loose enough to prevent ischemia and tissue necrosis.

After surgery, any blood, debris, and leftover surgical scrub should be gently cleaned from the surrounding tissue and/or hair/fur.

Suture removal

Tissue must be held in apposition until the wound has healed sufficiently to withstand normal stressors. During the healing process, all attempts should be made to keep the area clean and dry. Creams, ointments, or disinfectants should not be used unless the veterinarian prescribes such treatment.

The duration of time before suture removal will vary with each area and will be outlined in the protocol or determined by the veterinarian. In rodents, suture removal is generally done 10-14 days post-surgery. Geriatric or immunocompromised animals may experience delayed healing and require later suture removal. If the wound does not appear adequately healed at the anticipated time of suture/staple removal, consult with veterinary services before removal of sutures/staples.