9.4 Indications for peri-operative antibacterial prophylaxis

The need for prophylaxis depends on the type of intervention and the individual risk for each individual patient. Risk factors, such as chronic debility, metabolic dysfunction (e.g. diabetes mellitus), immunosuppression, poor surgical condition, re-operation and special risk factors (e.g. artificial cardiac valves) have to be considered (Table 17). A review of factors of importance for the prevention of surgical site infections was recently published (24).

Table 17: General factors increasing the risk of post-operative infection following urological intervention due to the patient's condition and/or increased bacterial load

Risk factors due to:
Patient's Condition	Increased Bacterial Load
• Reduced general condition, e.g. debility • Metabolic dysfunction, e.g. diabetes mellitus • Immunosuppression • Re-operation • Special risk, e.g. artificial cardiac valve	• Surgery using bowel segments • Transrectal biopsy of the prostate • Long-term urinary drainage • Urinary obstruction

Increased exposure to endogenous bacteria can be expected in procedures that include bowel segments and transrectal biopsy of the prostate with a thick needle. Furthermore, bacterial contamination of the urinary tract is often associated with long-term drainage (catheter, etc.) or with obstruction. Even short-term hospitalization may lead to colonization with multi-resistant strains, which may require a change in antibiotic policy.

In the absence of risk factors and with sterile urine, prophylaxis may not be necessary. However, if the anticipated risk changes during the operation (e.g. accidental perforation of the intestine or the infected urinary tract), intra-operative administration of antibiotics should be considered. In the pre-operative work-up of the patient, any infection, especially of the urinary tract, should be identified. If there is an infection present and the intervention cannot be delayed, antibiotic therapy should be given on an empirical basis before surgery and continued afterwards, preferably according to sensitivity testing, when it becomes available.

From a microbiological viewpoint, any peri-operative antibiotic prophylaxis represents a compromise. It has to be balanced between a reduction in bacterial load on one hand and an increased risk of adverse events and the selection of resistant strains on the other hand.

9.5 Timing and duration of peri-operative antibacterial prophylaxis

Basic studies have shown that wound infections are usually prevented by the administration of an antibiotic before contamination takes place (16,25,26). High blood levels are needed at the start of the surgical procedure

and, therefore, timing and dosing are important factors (27). In clinical practice, the best time for administration is 30-60 minutes prior to the start of an operation, i.e. when anaesthesia is initiated, if the antibiotic is given intravenously. If intra-operative complications occur, the antibiotic should be given immediately. This approach has been particularly effective in emergency general surgery (28).

Clinical studies have shown a significant increase in post-operative infections if a single prophylactic dose of antibiotic is given > 1 hour before the start of the operation (25). Any antibiotic given after wound closure will not alter the rate of wound infection. There are, however, no studies demonstrating such a correlation in endoscopic procedures.

Generally, a single full dose of a suitable antibiotic is as effective as multiple dosing. Only in the case of prolonged intervention (> 3 hours) is an additional dose required, the size and timing of which are dictated by the pharmacokinetics of the antibiotic. Antibiotic prophylaxis should not be continued for > 24 hours (13,29-31). The administration of antibiotics for > 1 day is not considered to be prophylaxis, but therapy. This may become necessary if the focus of infection cannot be eliminated by the operation or in case of severe contamination.