Companion animal surgery guidelines

The surgical guidelines have been developed for all veterinarians, to inform clinical decisions, in response to a survey we completed in 2016 that identified a need for widely accessible antimicrobial guidelines for surgical prophylaxis.

The results of this survey have been published and the paper can be found at this link.

We suggest you download the VPG guidelines poster, display it in your clinic and record your protocols for surgical prophylaxis in the space provided.

Measuring compliance with the guidelines, or your clinic policy, is a powerful tool in improving appropriate antimicrobial use. Periodic review of clinical records, or review of surgical checklists, with regular reporting will motivate all staff to improve appropriate antimicrobial use for surgical prophylaxis.


To provide guidance on need for antimicrobials for surgical prophylaxis to mitigate the risk of surgical site infections and where antimicrobials are indicated guidance on antimicrobial selection, timing and duration of therapy. We aim to provide guidance for common surgical conditions in dogs and cats, however some conditions may not be covered and clinicians are advised to use their best judgement in these instances.

National Research Council’s risk index for surgical infection:

Clean Non-traumatic, uninfected. No break in aseptic technique, no inflammation encountered. Elective, closed primarily and no drain used.

Eg. Routine spey or castration

Exploratory laparotomy (not entering viscus)

Clean-contaminated Controlled entering of a hollow muscular viscus, minor break in aseptic technique Eg. Exploratory laparotomy for foreign body removal, cystotomy (no abdominal contamination)
Contaminated Open, fresh traumatic wound. Incision into a site with acute, non-purulent inflammation. Major break in aseptic technique.

Eg. Cystotomy/laparotomy with significant abdominal contamination,

pyometra, closure of contaminated traumatic wound (<4h duration).

Dirty Pus encountered during surgery. Perforated viscus found. Traumatic wound with devitalised tissue, foreign material or faecal contamination, or of more than 4-hour duration. Eg. Peritonitis, necrotic traumatic wound (>4h duration) undergoing primary closure.

Guidelines for surgical prophylaxis in dogs and cats:

Surgical contamination level Complicating factors Likely pathogens Antimicrobial recommendation Duration of therapy Level of evidence
Clean None1 None N/A Strong

Only if surgical site infection would be a major

threat to the patient (ie central nervous system surgery)

Stop within 24 hours*2 Medium



Surgical duration >90mins3, 4


Obese dogs5


Endocrine disorder6


Bacterial dermatitis





or 1st generation cephalosporin

Stop within 24 hours* Medium
Stop within 24 hours*
Stop within 24 hours*
Stop within 24 hours*
Treat till infection cured
Implant1, 7 Orthopaedic: Staphylococcus intermedius Perioperative only**7
Clean contaminated Gastrointestinal Coliforms, anaerobes if caudal GI tract


or 1st generation cephalosporin

Stop within 24 hours* Medium
Contaminated Pyometra, prostatic abscess E. coli, Streptococcusspecies, Anaerobes


or 1st generation cephalosporin & gentamicin & metronidazole

No evidence, 24-48 hours is common in human medicine Weak
Significant bowel leakage Coliforms Amoxycillin & gentamicin
Dirty Choose appropriate for infection (ideally based on culture and susceptibility testing) Treat till infection cured
Dental None None N/A Medium

Geriatric patients

Heart disease

Systemic illness


Bacteraemia expected for duration of procedure8, 9. If cannot tolerate this: clindamycin or amoxycillin. Stop within 24 hours* Weak


* Stop within 24 hours indicates administration prior to and during surgery, and doses after surgery up till 24 hours. Inter-dosing interval after surgery is described below.

**Perioperative only indicates administration prior to and during surgery, but no further doses after surgery


Timing of prophylactic antimicrobials:

Tissue levels of antimicrobials are required at the time of first incision to confer protection from surgical site infection.

Intravenous antimicrobials: administer 30-60 mins prior to surgery

Subcutaneous amoxycillin / clavulanate: 2 hours prior to surgery

Tmax for individual drugs given by different routes can be used to assess optimal timing to achieve peak serum levels at the time of first incision.


Repeat dosing:

Dosing interval should be measured from the time of the preoperative dose. The dosing interval during surgery can be calculated as twice the elimination half-life of the antimicrobial. For example, the dosing interval during surgery for common intravenous antimicrobials used in surgery for dogs and cats are:

Cefazolin: Maintains concentrations above MIC for common skin pathogens (Staphylococcal  & Streptococcal species) for 4 hours (10), however 2 hourly administration (twice elimination ½ life) may be required for E.coli. (11)

Amoxycillin: 2 hours


Following surgery, if antimicrobials continue to be indicated, the dosing interval returns to that used for non-surgical indications.


Other factors to consider:

Clip hair less than 4 hours before surgery4

Minimise number of people in surgical theatre5

Consider use of surgical safety checklist. Use of these tools has reduced surgical complications from 17% to 7% (SSIs from 5% to 1.4%).11

(Based on World Health Organisation surgical safety checklist)


A special mention – Surgical treatment of Cranial Cruciate Ligament disease:

Tibial tuberosity advancement (TTA): Peri-operative prophylaxis only, no evidence for post-operative therapy12.

Tibial plateau leveling osteotomy (TPLO): Peri-operative prophylaxis only13, 14. Studies that have shown reduced post-operative surgical site infections have had protocols that were unlikely to lead to necessary serum antimicrobial levels at the time of the first incision15, or did not report timing and in which antimicrobial therapy was given at the surgeons discretion16-18 thereby introducing unacceptable confounding bias. Careful attention should be paid to timing of prophylactic antimicrobial therapy.

TightRope: Peri-operative prophylaxis only14.

See the evidence