Equine surgical 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
Clean-contaminated Controlled entering of a hollow muscular viscus, minor break in aseptic technique
Contaminated Open, fresh traumatic wound. Incision into a site with acute, non-purulent inflammation. Major break in aseptic technique.
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

Guidelines for surgical prophylaxis:

Surgical contamination level Mitigating factors Antimicrobial recommendation Duration of therapy
Clean None None N/A
Field castration1,2 None N/A
Routine elective arthroscopy3-5 None N/A

Only if surgical site infection would be a major

threat to the patient (ie central nervous system surgery)

No evidence, in other species preoperative only
If surgical duration >90mins6 Penicillin & Gentamicin No evidence, in other species preoperative only
Implant No evidence, 7 days recommended for companion animals
Clean contaminated Penicillin & Gentamicin Stop within 24h

Colic – no intestinal ischaemia

– Ischaemic damage to GI tract

 Penicillin & Gentamicin

Penicillin & Gentamicin

Stop within 24h

Some evidence for 3 days7, 3-5 days common8, 9

Contaminated Likely anaerobic Penicillin & Gentamicin & metronidazole No evidence, 24-48h is common in human medicine
Significant bowel leakage Penicillin & Gentamicin & metronidazole
Dirty Choose appropriate for site of infection and likely causative agent Treat till infection cured

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

Intramuscular procaine penicillin: 3.5h prior to surgery10


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 can be calculated as twice the elimination half-life of the antimicrobial.

Benzyl penicillin: 80 mins

Oxytetracycline: 7 hours


Other factors to consider:

Clip hair less than 4 hours before surgery11

Minimise number of people in surgical theatre12

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

(Based off World Health Organisation surgical safety checklist)


Other considerations:

Local or regional antibiograms: If you work in a hospital that performs culture and susceptibility frequently you may consider using summarised sensitivity data (antibiogram) when selecting empiric therapy. You should consider the inherent bias in most of this data however. Most cases that have samples cultured are not reflective of the general bacteria that present in the equine community. These cases are often refractory to antimicrobials or have had previous antimicrobial therapy, thus we are testing a more resistant population of bacteria. Unless culture and susceptibilty testing is performed routinely on a large number of cases at admission/first visit, and prior to any antimicrobial therapy, this information is not useful in determining appropriate empiric therapy.

See the evidence