ABSTRACT: This article aims to highlight the current guidelines for antibiotic use during soft tissue surgery. Nursing staff are invaluable in terms of practical antibiotic use – often it is the nurses who administer antibiotics, and they can prompt the vets to think about how and when they are being used. If all practices are aware of the guidelines, we can minimise our usage of antibiotics, reserving them for necessary cases, and thereby reduce the selection pressure for resistant bacteria. It is the combined responsibility of all vets and nurses to ensure we can continue to use effective antibiotics in the future.


There are clear guidelines set out in the literature for how and when we should use antibiotics. Unfortunately, very few practices are following them. In this, we are not alone. Both human and veterinary hospitals have been evaluated, and in many cases the conformity has been shown to be around 50 per cent, or less.1, 2 & 3

My own undergraduate research showed an overall conformity of 34.7 per cent in a veterinary teaching hospital. In general, non-conformity refers to either an overuse of antibiotics (using them where they are not required, or using a broader spectrum or longer period of treatment) or incorrect timing of use. Few cases lack antibiotic therapy where it is indicated. There are several reasons for this poor conformity. In some cases, it is simply a lack of knowledge – if vets and nurses are unaware of the guidelines and how best to use antibiotics, then they cannot be expected to conform. In other cases, it may be a lack of confidence in aseptic technique – the staff may know that antibiotics are not required but they are given ‘just in case. Where the doses are given at the wrong time, this is often an organisational problem.

Associated problems

The main problems associated with overuse of antibiotics are increased costs, possible side effects (for example gastrointestinal upset), and increasing resistance. Resistance to antimicrobials has been recognised as a major problem recently, with the emergence of multi-drug resistant bacteria, such as methicillin- resistant Staphyloccus aureus (MRSA).

However, the less obvious signs of resistance are often ignored – the cases where antibiotics are simply less effective, or take longer to achieve a clinical cure, or where antibiotics have to be changed in order to clear up an infection. In many cases, the practice staff simply don’t think of these cases in terms of resistance. Problems of resistance can be worse where multiple antibiotics are used, leading to multiple resistance and the potential for inter-drug reactions or increased toxicity, where broad spectrum drugs are used, and where dosage is inadequate, for example, where weight is estimated rather than measured.

Resistance can also be induced via the normal bacteria of the gut, for instance, when prolonged oral treatment is used; and is an important consideration, especially when considering zoonotic infections and the risk of resistant bacteria transferring to the human population.

For more information on resistance refer to the Federation of Veterinarians in Europe’s publication on Antibiotic Resistance (FVE, Resistance).4

Logical process

The first thing to consider when facing a soft tissue surgery is whether or not antibiotics are warranted. The National Research Council (NRC) has produced a system of wound classification which can help to determine when antibiotics are needed (Table 1).

Clean wounds (NRC classification) are not considered to require antibiotics. This will include simple neutering and uncomplicated lump removals. The immune system of the patient is generally capable of dealing with the small numbers of bacteria which inevitably contaminate the surgical site from the skin or airborne bacteria.

The exceptions to this rule are lengthy procedures (90 minutes or more, where bacterial contamination will be at a higher level through time) and procedures where the consequences of infection are considered potentially disastrous (for example, when using a prosthetic implant which can act as a focus for infection).

In these cases prophylactic antibiotics may be given. 

If antibiotics are, in fact, warranted, the next question is for how long should they be given? Antibiotic administration can be categorised as either prophylactic or therapeutic.

Prophylactic administration is appropriate when some bacterial contamination is expected but no prior bacterial infection is encountered. This applies to Clean Contaminated and Contaminated wounds, including cystotomy or gastrotomy.

Therapeutic antibiotics are warranted for Dirty wounds – where prior bacterial infection is established, or for contaminated traumatic wounds.

Figure 1 is intended to be a quick reference guide to help determine how to apply the guidelines to each case. Cut it out and keep it along with Table 1.

Figure 1: Quick reference guide to the application of guidelines for antibiotic use

Strategic use

Prophylactic antibiotic administration involves giving antibiotics before and during the procedure, and for no longer than 24 hours following surgery. Studies have shown that there is no benefit to the patient – in terms of postoperative infection rates – in continuing antibiotics for longer than 24 hours.9 & 10 Indeed, a link has been shown between prolonged antibiotic prophylaxis and increased resistance.11

Therapeutic antibiotic administration involves giving antibiotics before and during surgery, and for an extended period afterwards. The period of administration of therapeutic antibiotics should be sufficient to reduce bacterial contamination to a level with which the immune system can cope – premature withdrawal of treatment can allow the infection to re-establish.

Owner compliance is a key issue here and owners should be educated to understand the importance of completing a course of antibiotics.

Timing of antibiotic doses before and during surgery is important in order to ensure adequate tissue concentrations throughout the procedure. The best results are achieved when antibiotics are given before contamination.8

Following surgery, oedema around the wound hinders the penetration of antibiotics. Antibiotics given prophylactically up to two hours before the first incision, and continued for up to 24 hours, have been shown to reduce the risk of postoperative wound infections.10

Commonly used i.v. include cefuroxime (Zinacef – GlaxoSmithKline), lincomycin (Lincocin – Pfizer Ltd) and clavulanate- potentiated amoxicillin (Augmentin – GlaxoSmithKline). These have similar pharmacokinetic properties. It is recommended that the first dose is given 30 to 60 minutes before the first incision, and that repeat doses are given every two hours until the end of surgery.

It is worth noting that neither Zinacef nor Augmentin is a veterinary licensed product.

More commonly, systemic antibiotics given perioperatively are administered by subcutaneous injection. These preparations will have varying pharmacokinetics, but in general antibiotics administered between 30 and 120 minutes before the first incision will achieve the hig
hest tissue concentrations during surgery. In practical terms, it may be best to give antibiotics (where they are necessary) with premedication.

Spectrum choice

Antibiotic selection should consider the spectrum of action (Gram-positive or Gram-negative), and the mode of action (bacteriostatic or bacteriocidal). Bacteriostatic drugs prevent reproduction of the bacteria but rely on the immune system to kill those bacteria present. Bacteriocidal drugs kill bacteria, and therefore may be more suitable for certain cases, for example immunocompromised patients.

The spectrum of action determines which bacteria are likely to be susceptible, and therefore in which cases the antibiotic is likely to be effective. In most cases in general practice, the antibiotic is chosen based on commonly encountered bacteria at the site of surgery, and their likely susceptibility. However, best practice dictates that, wherever possible and particularly when dealing with pre-existing infections or vulnerable patients (very young or elderly patients, or those with concurrent disease), culture and sensitivity testing should determine the antibiotics chosen.

Culture and sensitivity gives accurate information about which antibiotics will be effective against the bacteria encountered in vitro, but should be considered alongside knowledge of pharmacokinetic properties in vivo – for example, if a drug does not pass into the prostate it will not be useful for prostatic infections.

In all cases, antibiotic treatment should be considered alongside husbandry, nutrition and nursing care, to ensure that our patients have the best chance of avoiding bacterial infection. Antibiotics should never be a substitute for simple practical measures such as aseptic technique during surgery, temperature regulation, nutritional support and good hygiene.


Of course, as with all rules and guidelines, there are exceptions. Antibiotic administration should be tailored to suit the individual. For example, patients with a compromised immune system may be given antibiotics for a Clean procedure.

Clinical discretion should be used in each case to determine the most appropriate treatment, in conjunction with published recommendations for storage, handling, dosing and administration, and always with the guidelines in mind, varying from these only when it is necessary. 


Charly McGahan BVetMed mrcvs

Charly McGahan graduated from the Royal Veterinary College, London, in July 2009. She is now working in small animal practice in North Wales, where she says she is fortunate enough to find time to keep up with Guiding.


1.   Weese, J. S. & Hailing, K. B. (2006) Perioperative administration of antimicrobials associated with elective surgery for cranial cruciate ligament rupture in dogs: 83 cases (2003-2005). J Am Vet Med Assoc 229: 92-95.

2.   Fennessy, B. G., O'Sullivan, M. J., Fulton G. J., Kirwan, W. O. & Redmond, H. P. (2006) Prospective study of use of perioperative antimicrobial therapy in general surgery. Surg Infect (Larchmt) 7: 355-360.

3.   Thouverez, M., Lallemand, S., Bailly, P, Bertrand, X. & Talon, D. (2002) [Determination of indicators for non¬compliance with guidelines for surgical antimicrobial prophylaxis]. Pathol Biol (Paris) 50: 547-551

4.   Federation of Veterinarians in Europe (FVE) – Antibiotic Resistance & Prudent Use of Antibiotics ir Veterinary Medicine. http://www.fve.org/news/publications/pdf/antibioen.pdf

5.   Slatter (2003) Textbook of Small Animal Surgery, Saunders.

6.   Vasseur, P. B., Levy, J., Dowd, E. & Eliot, J. (1988) Surgical wound infection rates in dogs and cats. Data from a teaching hospital. Vet Surg 17: 60-64

7.   DEPTSURGED (2006) Antibiotic P rophylaxis in Surgery – Guidelines from the Department of Surgical Education. Orlando Regional Medical Centre

8.   Fry, D. (1995) Surgical Infections. Little, Brown & Co.

9.   Bratzler, D. W. & Houck, P. M. (2005) Antimicrobial prophylaxis for surgery: an advisory statement from the National Surgical Infection Prevention Project. Am J Surg 189: 395-404

10.   Brown, D. C., Conzemius, M. G., Shofer, F. & Swann, H. (1997) Epidemiologic evaluation of postoperative wound infections in dogs and cats. J Am Vet Med Assoc 210: 1302-1306

11.   Harbarth, S., Samore, M. H., Lichtenberg, D. & Carmeli, Y. (2000) Prolonged antibiotic prophylaxis after cardiovascular surgery and its effect on surgical site infections and antimicrobial resistance. Circulation 101: 2916-2921.

Veterinary Nursing Journal • VOL 25 • No9 • September 2010 •