عفونت محل زخم جراحی وآنتی بیوتیک پروفیلاکسی عفونت محل زخم جراحی وآنتی بیوتیک پروفیلاکسی دکتر علیرضا شریف متخصص عفونی دانشیار دانشگاه علوم پزشکی کاشان

(3) microbial factors (e.g., tissue adherence and invasion), and PRINCIPLES OF SURGICAL SITE INFECTION PREVENTION Determinants and Pathophysiology Whether a wound infection occurs after surgery depends on a complexinteraction between the following: (1) patient-related factors (e.g., hostimmunity, nutritional status, comorbid conditions), (2) procedurerelated factors (e.g., implantation of foreign bodies, degree of traumato the host tissues), (3) microbial factors (e.g., tissue adherence and invasion), and (4) use of preventive measures (e.g., perioperative antimicrobialprophylaxis).

Although numerous sources of bacterial contamination of surgical wounds have been described, it is virtually impossible to identify with certainty the source(s) and route(s) of contamination. The direct inoculation of a patient’s endogenous flora at the time of surgery is believed to be the most common mechanism; however, others undoubtedly occur. Transmission from contaminated surgical instruments or surgical material, hematogenous seeding from preexisting infection of a nonwound site, and contamination from either the skin, mucous membranes, or clothing of operating room staff have been implicated as potential sources of microbial contamination

Antimicrobial Prophylaxis: Timing of Administration and Redosing Initial Dose Timing The initial dose of systemic antibiotics must be administered in a timely fashion so that antibiotic levels in the tissue at the time of the incision are adequate. Administration too early before or too late after the time of incision will result in suboptimal tissue levels and potentially increased risk of postoperative wound infection. Guidelines and studies have traditionally varied on the exact timing, ranging from 2 hours to no more than 30 minutes before incision, but the new consensus guideline defines appropriately timed antibiotic prophylaxis as delivery of the antibiotic within 60 minutes before incision, with theexception that vancomycin and the fluoroquinolones should be givenwithin 120 minutes before incision because of the need for a longer infusion time. This definition has become widely used as a metric that indicates delivery of standard, high-quality surgical care

The use of higher doses of antibiotic is needed for obese patients. The 2013 consensus guidelinenotes that, given the low cost and favorable safety profile of cefazolin,using a 2-g dose for patients weighing 80 kg and a 3-g dose for those weighing more than 120 kg is justified

Special Considerations with Prophylaxis in Colorectal Surgery For colorectal procedures, three approaches to antimicrobial prophylaxis have generally been used: (1) use of oral (often nonabsorbable)agents, (2) use of intravenous (IV) agents, and (3) combination therapy using both types of agents. Many surgeons use combination IV and oral therapy, with the rationale to decrease intraluminal flora as well as to provide adequate subcutaneous tissue concentrations

The addition of oral antimicrobials does appear to slightly increase the risk of development of nausea and vomiting, and patients should be advised of these symptoms. Mechanical bowel preparation (MBP) to cleanse the bowel lumen before incision has also been used for some time in colorectal surgery patients, but there has been debate regarding the optimal approach and utility of MBP, with some studies noting a higher rate of anastomotic leakage with MBP The 2013consensus guideline on surgical prophylaxis now recommends use ofMBP combined with oral and IV antimicrobials for most colorectal procedures

Novel Methods of Antibiotic Prophylaxis: Local and Topical Compounds Newer methods for delivery of antimicrobial prophylaxis, such as antimicrobialwashes, cement, sutures, and other compounds, have been increasingly used for the prevention of SSIs. First introduced in 1939, antibiotic-impregnated cement placed directly into the operative wound (as a local antimicrobial “brachytherapy”) has been used as a method of antibiotic prophylaxis and treatment, particularly inprocedures involving the replacement of infected prosthetic joints. Brachytherapy uses powdered antibiotic mixed with a cement polymer, such as polymerized polymethylmethacrylate, to form a compound that may be directly applied onto prosthetic material or manufactured into beads, usually 3 to 10 mm in diameter, that are placed into the wound.

Candidate antibiotics for use as brachytherapy must be availableas a pharmaceutical-grade powder, must be heat stable (becauseof the exothermic reaction induced with polymerization), and must have an appropriate microbiologic spectrum of activity for the predominant pathogens at the operative site. The aminoglycosides and vancomycin are the compounds most commonly used for brachytherapy; oxacillin and cefazolin have comparable elution characteristicsbut are less frequently used because of concerns regarding β-lactam allergy. The majority of antibiotic elution occurs in the first days afterimplantation, but elution from impregnated cement has been detected years after surgery