September 29, 2016

Dr. Naeem Khan - Consultant Surgeon   |   JPMC Karachi

Surgical Site Infections


Surgical site infections (SSI) have played a major role in the evolution of medical care throughout history. Wound complications contributed significantly to the historical surgical mortality rates before the development of Lister’s aseptic approach in the nineteenth century. The impact of the antiseptic/aseptic techniques was readily apparent in its adaptation to battlefield medicine. During the civil war in America, surgeons operated bare handed, with wound suppuration considered to be beneficial aspect of wound healing. With the gradual acceptance of the principles of antisepsis, and the usage of sterile dressings and aseptic surgical techniques, there was a dramatic reduction in mortality from wounds to 7.4% in the Spanish American war.

Despite nearly 2 centuries of medical progress, the management of surgical infections remains a pressing concern, and SSIs continue to be a leading component of nosocomial morbidity and mortality. In this article, the epidemiology, pathogenesis, risk factors and approach to prevention of SSI are reviewed.






Infections occur in 30 days after the operation procedure and involves only skin and subcutaneous tissue of the incision and patient has at least one of the following:

  1. Purulent drainage from the superficial incision.
  2. Organisms isolated from an aseptically obtained culture of fluid or tissue from the superficial incision.
  3. At least one of the following signs and symptoms of infection: pain or tenderness, localized swelling, redness, or heat, and superficial incision is deliberately opened by surgeon and the culture is positive or not cultured. A culture negative finding does not meet this criterion.
  4. Diagnosis of superficial incisional SSI by the surgeon or attending physician.



Infection occurs within 30 days after the operative procedure if no implant is left in place or one year if implant is in place and the infection appears to be related to the operative procedure and  involves deep soft tissue ( e.g., fascial and muscle layer) of the incision and patient at least one of the following:

  1. Purulent drainage from the deep incision but not from the organ/space component of the surgical site.
  2. A deep incision spontaneously dehisces or is deliberately opened by a surgeon and is culture positive or not cultured when the patient has at least one of the following signs or symptoms: fever (>38.C) or localized pain and tenderness. A culture negative finding does not meet this criterion.
  1. An abscess of other evidence of infection involving the deep incision is found on direct examination, during the reoperation, or by histopathologic or radiologic examination.
  1. Diagnosis of a deep incision from a surgeon or an attending physician.



Infection occur within 30 days after the operative procedure if no implant is left in place or within one year if implant is in place and the infection appears to be related to the operative procedure and the infection involves any part of the body, excluding the skin incision, fascia, or the muscle layers, that is opened or manipulated during the operative procedure and the patient has at least one of the following:

  1. Purulent discharge from the drain that is opened through a stab wound into the organ/space.
  2. Organisms isolated from an aseptically obtained culture of fluid or tissue in the organ/space.
  3. An abscess or other evidence of infection involving the organ/space that is found on direct examination, during reoperation, or by histopathologic or radiologic examination.
  4. Diagnosis of an organ/space SSIs by a surgeon or attending physician.



From a general perspective, the microbes responsible for infection of surgical wounds originate from either the surrounding skin or associated structured that are contiguous with the regions of surgical procedure. The logical extension of this principle is that the risk of wound contamination and subsequent SSI depends on the location, the nature of the surgical wound/ incision, and he procedure performed.

Appropriately risk stratification for SSI cannot be limited to the wound alone. There are a variety of patient related factors and perioperative factors that can significantly affect the risk of SSI in a surgical patient.



The predominant source of microbes involves in SSIs originate from either the skin or the surrounding tissues of the incision, or from deeper structures involved in the operative procedure (e.g., enteric organisms in the bowel related surgeries). In the most recent NHSN surveillance report on 21,100 isolates from 2009 to 2010, the most frequently identified pathogens were, in order, staphylococcus aureus, Coagulase negative staphylococci, Escherichia coli, and enterococcus faecalis and pseudomonas aeruginosa.



    Patient factors:

  •                Age
  •                Nutritional status
  •                Diabetes
  •                Smoking
  •                Obesity
  •                Coexistent infections at a remote body site
  •                Colonization with micro organisms
  •                Altered immune response
  •                Length of preoperative stay


    Operative Factors:

  •                Duration of surgical scrub
  •                Skin antisepsis
  •                Preoperative shaving
  •                Preoperative skin preparation
  •                Duration of operation
  •                Antimicrobial prophylaxis
  •                Operating room ventilation
  •                Inadequate sterilization of instruments
  •                Foreign material in the surgical site
  •                Surgical drains
  •                Surgical techniques
  •                         Poor hemostasis
  •                         Failure of obliterate dead space
  •                         Tissue trauma

In a Japanese study of 702 isolates, methicillin resistance in S.aureus was 72.0%. Community acquired MRSA is increasing in prevalence, with the prevalence of nasal colonization with MRSA in the general population increasing from, 8% to 1.5% from 2002 to 2002 to 2003 to 2004. Studies have attempted to clarify the relationship between colonization and risk of MRSA SSI.



Patient comorbidities can contribute significantly to the potential risk of SSIs. These factors include age, obesity, smoking, diabetes mellitus, malnutrition, dyslipidemia and immunosuppression. These factors are not directly accounted for in the NNIS classification scheme but can contribute significantly to the risk of SSIs. Identification of these risk factors with appropriate preoperative history and physical examination is critical. The core principle for management of these patients relates risk factors is preoperative optimization.

Smoking results in significantly increased risk of SSIs because of its effects on local tissue perfusion. Large numbers of studies have consistently shown that smoking, additional studies and in meta-analysis of trial data. Recommendations are for smoking cessation at least 30 days before operation.



Preventative measures in the preoperative period have changes rapidly over the past few decades. A large volume of research has established the importance of a host of preventive measures in the operative period. Examples include skin decontamination, perioperative warming, and antimicrobial prophylaxis. As additional studies have been conducted with increasing methodological rigor, from observational studies to randomized controlled trials, refinements of existing preventative measures have further improved the efficacy of these measures. This review focuses on areas of prevention Those are the focus of significant active research or have seen recent change in key guidelines or recommendations.


Skin Decontamination:

The use of antiseptic agents topically has long been recommended for use in skin decontamination. The 2 broad classes of topical agents including chlorhexidine based preparations and iodophor based agents. In addition, these agents can be combined with isopropyl alcohol (IPA) in solution. Several studies have sought to address potential differences in efficacy between the various available agents, although there have been significant inconsistency of results, which have been also been confounded by methodological differences between the studies.

In the systemic review and meta-analysis conducted by Lee and colleagues, chlorhexidine based agents were found to reduce the risk of SSIs significantly.

In the most recent published cohort study by Hakkarainen and colleagues, there were no significant differences between 4 different preparations of skin antisepsis agents (chlorhexidine/IPA, chlorhexidine, providone-iodine, and iodine-povacrylex/IPA) in a cohort of primarily clean contaminated general surgical cases.


Antibiotic Prophylaxis:

From a historical perspective, routine antibiotic prophylaxis was questioned for the usefulness. With demonstrated clinical benefit in the clinical trials conducted separately by Polk and Lopez-Mayor and Stone and colleagues, there has been tremendous improvement in SSIs as an outcome. From the ontset, the development of antibiotic prophylaxis has undoubtedly led to a clear reduction in rates of SSIs. The complexity and nuance of clinical practice guidelines has continued to become more complex and refined.

Clinical practice guidelines for antimicrobial prophylaxis were recently updated in 2013 in a joint publication by the American Society of Health-System Pharmacists, focuses including timing of preoperative dosing, weight-based dosing, and duration of postoperative prophylaxis should be made with the primary consideration of the spectrum of coverage required. Current guidelines emphasize prophylaxis administration within 60 minutes of incision, or within 120 minutes for antibiotics requiring longer.

In the updated clinical practice guidelines, weight based dosing is an additional focus particularly in obese patients.

Adequate redosing of antibiotics for longer operative procedures is necessary for risk reduction. With longer procedures, serum and tissue concentration can drop below adequate levels, particularly in antibiotics with shorter half-lives(e.g. cefazolin, cefixitin, gentamicin)

Additional route of antibiotic administration have been investigated in the past and have been historically ruled out. Topical routes of antibiotic prophylaxis have been considered for some time. With the recent guidelines, there are no recommendations describing a role for topical routes of antibiotic administration.


Additional Measures:

Several additional measures have been investigated for implementation in the prevention of SSI. In many circumstances, recommendations have been equivocal due to the lack of evidence or the presence of often contradictory evidence. In these cases, guidelines are directed by expert opinion and experience. Further research is as a prime example, perioperative oxygenation was shown in 2 early trials to lead to the reduction of SSI rates with the use of 80% oxygen intraoperatively with immediately post operatively.


Perioperative measures with considerably less controversy include perioperative warming, hair removal, and optimization of the operating room environment. Perioperative hypothermia is associated with significantly increased risk of SSI. With regards to hair removal, the lowest risk of SSI is always associated with not removing hair. If hair needs to be removed because of interference of procedure, then hair removal should be done immediately before the surgery with a clipper or a razor.



The economic costs of SSIs are significant because of the volume of cases that were seen, with the annual 2.7 million operative procedures performed in the United States. Even with a conservative estimate of more than 290,000 cases of SSI. There is a substantial economic cost to the management of SSI. There is wide variance in estimates of the attributable costs of SSI infection that depends heavily on the type of surgical procedure and the geographic region studied.



SSIs remain the very important component of patient outcome, contributing to substantial patient morbidity. From a historical perspective, there has been a significant improvement in postsurgical outcomes, but these incremental gains have slowed in the recent decades. The translation of basic and clinical research has expanded the complexity of evidence based guidelines for SSI prevention. The importance of SSI prevention has been heightened because of its association with institutional and regulatory quality control measures. Sustained research in multiple aspects of SSI prevention needs to continue to realize further gains in SSI prevention. A multidisciplinary and multifactorial approach to SSI is absolutely necessary to continue to improve these critical outcomes of surgery.



Pang Y. Young, Rachel G. Khadaroo

Surgical Clinics of North America

Volume 94, Issue 6, Pages 1135-1378 (December 2014)