Prophlactic Use of Antibiotics on Prevention of Wound Infections

INTRODUCTION:

Prophylactic use of antibiotics can decrease the incidence of infections, especially at the surgical wound site. According to the principles of antibiotic prophylaxis, antibiotics should be effective against the expected type of contamination, used only if the risk of infection justifies doing so, given in appropriate doses and at appropriate times, and stopped before the risk of side effects outweighs benefits. Moreover, antibiotics for preventive use must not be highly toxic and should not be the "first-line" antibiotics used for treatment of an established infection. This is because resistance to antibiotics may develop quickly. Furthermore, agents that have been used frequently for prophylaxis are likely to lose their effectiveness for later treatment. Nonetheless, prophylactic agents should be chosen for cost-effectiveness and safety as well as for efficacy.

Prophylactic antibiotics should be selected to target the organisms most likely to be encountered in the anticipated operative procedure. A first-generation cephalosporin (eg, cefazolin) is preferred for most procedures since it is effective against common gram-positive and gram-negative bacteria and has a moderately long serum half-life. However, antibiotics such as vancomycin for prophylaxis use has been discouraged since the emergence of vancomycin-resistant organisms, especially with enterococcus and staphylococcus. Agents with better gram-negative and anaerobic bacterial activity (eg, cefoxitin, cefotetan) are preferred for colorectal and gynecologic procedures. A single dose of antibiotic given 30 minutes prior to making the skin incision should provide adequate tissue concentrations for most procedures. Additional doses are advisable for longer procedures (over 4 hours) or those that require large volumes of resuscitative fluids. Nonetheless, postoperative doses of prophylactic antibiotics are usually not necessary.

Prevention and treatment for complications of surgical wound healing should be included in surgical decision making for all procedures. The surgical site infections (SSIs) increase the overall mortality and morbidity and increase hospital length of stay along with overall costs. However, the use of prophylactic antibiotics is one method of preventing surgical site infections. This is especially indicated for patients who are at high risk or in contaminated surgical procedures. Nonetheless, the degree of contamination in the surgical site has long been recognized as an independent risk factor for SSI. This lead to the development of the wound classification system which consist of four classes. For example, class I (Clean) includes uninfected wounds without contamination. Class II (Clean contaminated) includes uninfected wounds in procedures where the respiratory, gastrointestinal, or genitourinary tracts are entered in a controlled fashion without gross spillage. Class III (Contaminated) involves an operation with major breaks in sterile technique, gross spillage, incisions into inflamed but not suppurating infections or fresh accidental wounds. And finally, Class IV (Dirty/infected) includes wounds with necrotic or devitalized infected tissue.

Patients undergoing class I (clean) procedures have a very low infection rate and generally do not benefit from prophylactic antibiotics, unless there is some suspicion at the start of the procedure that some contamination may occur. In addition, many surgeons prefer to use antibiotic prophylaxis in class I procedures when a prosthesis is implanted. For examples, procedures such as hernia repair in which a mesh is used and in vascular bypass surgeries where synthetic grafts are used, prophlactic antibiotics are usually given. In these settings, the risk of SSI is low, but the morbidity and mortality of an infected prosthesis are great, and prophylaxis may decrease this risk. However, to date, large prospective trials have not shown benefit of antibiotic prophylaxis in preventing prosthetic infections, but smaller trials have suggested a decrease in site infection without change in implant infection rate. Therefore, there is no strict guideline for the use of systemic antibiotics for implant surgery, and the surgeon should tailor the use of antibiotics to the individual patient's risk.

Patients with class II (clean contaminated) surgical wounds do benefit from systemic antibiotic prophylaxis. The most studied example of this class is elective colon resection. Most current guidelines recommend