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NRC procedure classification is the clipped just before . Preoperative primary determinant of whether showering with chlorhexidine soap, while prophylaxis in surgery prophylaxis is warranted. reducing colony counts, has not been shown to reduce risk. Infection is the most common Patient risk of surgery. Surgical site (SSIs) occur in approximately 3 - 6% of patients Pre-existing infections increase the risk Bacteriology and prolong hospitalisation by an average and should be resolved before surgery The organisms involved in SSIs are acquired of 7 days, which in the USA has a direct where possible. Diabetic patients have an either endogenously or exogenously annual cost of 5 - 10 billion dollars. increased risk, especially if preoperative (from contamination during the surgical glucose exceeds 11 mmol/l. Smoking has procedure). For the majority of SSIs the Prophylactic administration of been identified as an independent risk source of the is the endogenous decreases the risk of infections after factor for infections as nicotine has a flora from skin/mucous membrane/ many surgical procedures and represents deleterious effect on wound healing. The hollow viscera. The commonest organisms an important component of care for the preoperative use of immunosuppressants, involved are Gram-positive cocci, surgical population. including corticosteroids, may increase notably Staphylococcus aureus. Based on Antibiotics administered before the infection risk. Other factors shown to this knowledge and the risk of SSI the contamination of previously sterile tissues increase the risk of infection include age, appropriate antibiotic choices should be are deemed prophylactic antibiotics. length of preoperative hospital stay and made. The goal of therapy is to prevent the obesity. S. aureus, coagulase negative staphylo- development of an infection. Two large epidemiological studies have cocci, enterococci, Escherichia coli and Presumptive antibiotic therapy is been published that quantify the infection Pseudomonas aeruginosa are the path- administered when an infection is risk based on specific patient- and ogens most commonly isolated. With suspected, but not yet proven. The clinical procedure-related factors. The Study on the the widespread use of broad-spectrum areas where this is employed include acute Efficacy of Nosocomial Infection Control antibiotics, however, Candida spp. cholecystitis, open compound fractures (SENIC) assessed more than 100 000 and methicillin-resistant S. aureus are and acute appendicitis of less than 24 surgery cases to identify and validate risk becoming more prevalent. hours’ duration. In these situations, if factors for infection. Abdominal surgery, Factors that affect the ability of an organism signs of perforation or infection are absent operations lasting longer than 2 hours, to induce SSI depend on organism load, during surgery, then routine prophylactic contaminated procedures, and more than virulence and host immune competency. rather than presumptive therapy is three underlying medical conditions, were Opportunistic organisms are usually kept warranted. However, an operative finding each associated with an increase in the in ‘check’ by normal flora and are rarely of a gangrenous gallbladder or a perforated infection incidence. problematic unless they are found in appendix is suggestive of an established The National Nosocomial Infections large numbers. Loss of these protective infection process, and therefore a Surveillance (NNIS) system was an flora, through the use of broad-spectrum therapeutic antibiotic regimen is required. analysis of 84 000 surgical cases. It antibiotics, may allow pathogenic bacteria SSIs can be categorised as incisional (i.e. attempted to simplify the SENIC system to proliferate and infection to occur. If wound infection) or organ/space (e.g. by quantifying intrinsic patient risk using normal flora are transferred to a normally peritoneal cavity). By definition these SSIs the American Society of Anesthesiologists sterile tissue or site during a surgical must occur within 30 days of surgery; (ASA) preoperative assessment score. procedure, they can become pathogenic. however, if a prosthetic implant is involved, An ASA score of ≤ 3 was found to be a For example, S. aureus or S. epidermidis an organ/space infection can be reported strong predictor of the development of an may be transferred from the skin surface up to 1 year from the date of surgery. infection. to deeper tissue or E. coli from the colon All hospitals should implement a to the peritoneal cavity, bloodstream, or Risk factors comprehensive infection control urinary tract. These depend on both procedure- programme to minimise infections. Impaired host defence reduces the and patient-related factors. The risk Although antibiotic prophylaxis is most number of bacteria needed to establish an traditionally has been stratified by surgical commonly relied upon, other measures infection. A breach of normal host defence procedure in a classification system also reduce the risk of infection. through a surgical intervention may developed by the National Research Length of hospital stay is associated with potentiate the ability of organisms to cause Council (NRC) in the USA. The NRC increased colonisation and infection with infection. The loss of specific immune classification system proposes that the nosocomial bacteria and leads to a higher factors, e.g. complement activation, risk of an infection depends on the incidence of infection. Surgery should be cell-mediated response and phagocytic of the surgical site, presence postponed if a patient is hospitalised for function, can greatly increase the risk of a pre-existing infection, likelihood of an unrelated medical problem. Shaving of SSI development. Hypovolaemia can contaminating previously sterile tissue the incision site with a razor the day before affect flow to the surgical site, thus during surgery, and drains during and surgery is associated with a higher infection diminishing host defence mechanisms after the surgical procedure. A patient’s rate; therefore, the site should instead be against microbial invasion.

338A CME July 2007 Vol.25 No.7

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be cost-ineffective. Potential sources of Table I. Prophylactic antibiotics for various surgical procedures inappropriate antibiotic use include the use of broad-spectrum antibiotics when a Type of surgery Consensus position narrow-spectrum agent is warranted and extending the duration of prophylaxis. Abdominal or vaginal hysterectomy Cefazolin or cefoxitin. Metronidazole Individualised institutional guidelines monotherapy is also used. that take into account best literature If the patient has a (-lactam allergy, evidence and institution-based antibiotic use clindamycin combined withgen susceptibility data are important tools tamicin to rationalise antibiotic prophylaxis. The use of vancomycin for prophylaxis Hip or knee arthroplasty Cefazolin should generally be discouraged as it has If the patient has a (-lactam allergy to be given by slow infusion and, more use vancomycin or clindamycin importantly, it is the key antimicrobial Cardiothoracic and vascular surgery Cefazolin for resistant Gram-positive infections. If the patient has a (-lactam allergy, Widespread use will select for resistance. use vancomycin or clindamycin Table I provides a guide to the choice Colon surgery Use cefoxitin, or cefazolin plus of prophylactic antibiotic for various metronidazole surgical procedures (evidence-based US guidelines). If the patient has a (-lactam allergy, use clindamycin combined with Further reading gentamicin Bratzler DW, Houck PM for the Surgical Infection Prevention Guidelines Writer Workgroup. Antimicrobial prophylaxis for surgery: An Adapted from: Bratzler DW, et al. Clin Infect Dis 2004; 38. advisory statement from the National Surgical Infection Prevention Project. Clin Infect Dis 2004; The introduction of a foreign body during agent, the current literature evidence to 38: 1706-1715. a surgical procedure reduces the number support its use, and the cost. The most Culver DH, Horan TC, Gaynes RP. Surgical of colony-forming bacteria required important of these factors is the evidence wound infection rates by wound class, operative to cause an SSI. A study examining S. from randomised controlled trials. It is procedure and patient risk index. Am J Med 1991; 91(suppl 3B): 152S-157S. aureus-contaminated wound infections essential that the antimicrobial therapy has demonstrated a 10 000-fold reduction Gram-positive coverage, especially against de Lalla F. Antimicrobial chemotherapy in the control of surgical infectious complications. J in the number of organisms required to the key pathogen S. aureus. The decision to Chemother 1999; 11: 440 – 445. establish a wound infection if sutures are broaden prophylaxis to agents with Gram- Haley RW, Culver DH, Morgan WM, et al. not present. negative and anaerobic activity depends Identifying patients at high risk of surgical on both the surgical site and whether the wound infection: A simple multivariate index of Antibiotic administration operation will transect a hollow viscus patient susceptibility and wound contamination. Am J Epidemiol 1985; 121: 206 - 215. Basic principles for the use of antimicrobial or mucous membrane that may contain surgical prophylaxis include: resident flora. Mitka M. Preventing surgical infection is more important than ever. JAMA 2000; 283: 44 - 45. • the agent should be delivered to the are the most commonly Polk HC, Christmas AB. Prophylactic surgical site before the initial incision prescribed agents for surgical prophylaxis. antibiotics in surgery and surgical wound They have a broad antimicrobial infections. Am Surg 2000; 66: 105 - 111. • bactericidal antibiotic concentrations spectrum, favourable pharmacokinetic must be maintained at the surgical site profile, low incidence of side-effects, and MARC BLOCKMAN throughout the procedure. are relatively cheap. Cefazolin, together MB ChB, BPharm, MMed, Dip Int Res It is usual to administer a single dose with metronidazole for procedures where Ethics of an antibiotic. Subsequent doses may anaerobes are important, is the best Division of Clinical Pharmacology, Univer- be indicated if the surgery is prolonged, studied agent and the preferred choice for sity of Cape Town depending on the half-life of the antibiotic, most surgical procedures. It is interesting e.g. 2 - 5 hours for cefazolin and 6 - 8 hours to note that cefazolin, which is a first- for metronidazole. generation with a relatively hen your patients narrow spectrum of activity, is so effective Wcannot hold back any longer Antibiotics should be administered that it is generally used as the comparator with anaesthesia just before the initial in studies of antimicrobial prophylaxis 00 100 incision. If given too early this may for the prevention of SSIs and is seldom 5 95 result in concentrations below the surpassed. It is also the most commonly 00 100

minimal inhibitory concentration (MIC) recommended antibiotic in national and 5 75 towards the end of the operation, while if international guidelines for the prevention 5 95 administered too late it leaves the patient of SSIs. unprotected at the critical time – the initial 5 75 incision. Allergic reactions are the most common 5 25 side-effects associated with the 5 Antimicrobial choice cephalosporins. The incidence of cross- ® sensitivity to the penicillins is less than 5 25 The choice of agent depends on the surgical 5%. 0 Detrunorm 5 procedure, the most frequent propiverine hydrochloride seen in SSIs associated with the procedure, Inappropriate prophylactic antibiotic S3 Detrunorm Tablets. Each tablet use may induce antibiotic resistance and contains 15 mg propiverine HCl 0 the safety and efficacy of the antimicrobial Reg. No.: 36/5.4/0019 Pharmafrica (Pty) Ltd. Tel: (011) 493-8970

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