Antimicrobial prophylaxis in canine surgery

In 1961, Burke showed that antibiotics affect primary wound infections favourably only if they are administered before or shortly after bacterial contamination. The effect is optimal if there is already an effective tissue concentration at the time of contamination. During surgery the animal's resistance is strongly reduced, and consequently an infection may be caused by an inoculum present in a rather low concentration, at least lower than in normal circumstances. This reduced resistance lasts until only a few hours after operation. Prophylactic use of antibiotics therefore needs to be continued only for a short time after the final stage of the operation. A great number of clinical trials in human surgery have shown that short term peri-operative prophylactic use of antibiotics causes a reduction in the incidence of post-operative septic complications, in certain categories of operations and in selected groups of patients. Until properly designed, prospective, randomized and controlled clinical trials have been done in small animal clinics, it seems sensible to apply the abundant results from research with experimental animals and from clinical trials in human medicine to small animal surgery. Prophylactic use of antibiotics is indicated if the infection risks or dangers of possible complications are greater than the disadvantages of regular use of antibiotics. The risk factors in the development of wound infections and the choice of antibiotics are discussed.