Saturday, September 29, 2012

Prevention of Surgical Site Infection




The NNIS guidelines recommend preoperative prophylactic antimicrobial therapy for procedures
with an estimated SSI risk >1% based upon the NNIS score.

Prophylactic antimicrobial therapy should be strongly considered for:
(i) any clean-contaminated procedure,
(ii) any clean procedure in a patient with an NNIS score >1
(iii) an immunocompromisedpatient,
(iv) when any prosthetic material is inserted,
(v) when the operative area contains high bacterial counts, such as the axilla or scrotum.

NNIS Score Risk of SSI (%)
0: 1.5
1: 2.9
2: 6.8
3: 13.0

Note: Because it is difficult to estimate an individual patients risk of SSI based on traditional risk factors
the NNIS score was developed to consider the interaction between multiple
risk factors and provide individualized SSI risk assessments. Estimates are based on over 84,000
procedures with 2376 documented SSIs. To calculate NNIS score, contaminated and dirty wounds are
given 1 point, an ASA score of III or greater is given 1 point, and length of procedure >75th percentile
is given 1 point.
Abbreviations: NNIS, National Nosocomial Infection Surveillance System; SSI, surgical site infection.

Timing of antimicrobial prophylaxis administration is critical. A large study by Stone et al. found that the lowest SSI risk occurred when therapy was initiated within one hour of surgery.
Patients who received therapy after the incision had nearly the same risk as patients who
did not receive prophylaxis. More recent data corroborate the conclusion that timely preoperative
antimicrobial administration can reduce SSI rates. These and other observations
demonstrate the importance of obtaining therapeutic serum antimicrobial levels before the surgical
incision and exposure to bacteria.

Current guidelines suggest that prophylactic antimicrobials should be redosed appropriately for lengthy procedures and should stop within 24 hours of surgery.

Recent data support prophylactic antimicrobial therapy for trans-scrotal surgery based on
high bacterial counts on the scrotum and perineum. In a retrospective review of 131 outpatient
scrotal procedures, Kiddoo et al. found a 9.3% overall SSI rate among patients who did not receive
prophylactic therapy. In contrast, Swartz et al. found a 4% SSI rate in over 100 trans-scrotal procedures with a mean follow-up of 36 months (Swartz M, Urology, University of Washington).
Although the precise benefit of prophylactic antimicrobials cannot be ascertained by comparing
such retrospective studies, these data do suggest that scrotal wounds merit consideration as
clean-contaminated wounds that may warrant prophylaxis.

Prophylactic antimicrobial agents should be selected based on the most likely organisms
encountered. Beta-lactam antibiotics, such as the cephalosporins, are the most common agents
used for prophylaxis.
Recommendations include cefazolin for clean abdominal procedures or cefotetan for clean-contaminated abdominal procedures involving the gastrointestinal tract.
Clindamycin or vancomycin regimens are recommended alternatives for patients with
documented beta-lactam allergies. Other possible regimens include combinations of either
metronidazole or clindamycin with gentamicin or a floroquinolone. Currently, there is no
evidence supporting the use of prophylactic vancomycin rather than other agents, even in hospitals with perceived high rates of bacterial resistance.

Recommendations for specific urologic procedures are described next
Special consideration must be given to preventing bacteremia in surgical patients with
prosthetic joints who are at risk for joint infections or patients with certain cardiac anomalies
who are at risk for life-threatening endocarditis. The American Urological Association (AUA)
and the American Heart Association (AHA) have published specific guidelines for antibiotic
prophylaxis in these patient populations (as outlined previously).

Transient bacteremia can occur after a variety of urologic procedures, especially if patients
are instrumented during active UTI. Identification and treatment of active infections is strongly
recommended prior to any elective procedure. Bacteremia is commonly associated with urologic
procedures, with rates of 31% for patients undergoing TURP, 24% among patients undergoing
urethral dilations, 44% in patients having prostate needle biopsy, and 7% in patients having
office urodynamics. The AHA recommends endocarditis prophylaxis for patients undergoing prostatic surgery, urethral dilations, cystoscopy, or ureteroscopy.

Prophylaxis is not necessary for urethral catheterization or circumcision in the absence of clinical infections.

Perioperative ampicillin or vancomycin with gentamicin is recommended for high-risk patients while moderate-risk patients can be treated with single-agent ampicillin or vancomycin. High risk patients are defined by having prosthetic heart valves, previous histories of endocarditis, or complex congenital anomalies. Currently, the AUA recommends assessing patients overall risk for artificial joint infection based on a combination of patient-related and procedure-related factors.

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