Prevention of Surgical Site Infections

Post-operative surgical site infections (SSI's) are an unfortunate complication of surgery. Although it is unrealistic to think that all surgical site infections are preventable, there is increasing evidence that many might be preventable by observance of optimal infection prevention practice.

Factors that are known to increase the risk of post-operative infection include the nature of the surgery (some are more apt to be complicated by infection - for example, those that involve entry to into bowel), extended duration of surgery, and underlying patient medical conditions.

Rather than accepting the inevitability of surgical site infections, recently there has been emphasis on preventing many SSI’s. Several means of prevention are well established. Surgeon hand cleansing was demonstrated as helpful in preventing surgical site infections in the mid-nineteenth century when Ignaz Semmelweis, a Hungarian physician, demonstrated decreased puerperal sepsis after use of chlorinated lime as a hand cleanser. Much more recently there has been demonstrated the benefit of preoperative antibiotics, maintenance of blood sugars in the near normal range, and maintenance of normothermia. Other measures likely beneficial include use of preoperative surgical site skin preparation antisepsis, avoidance of use of razors for hair removal, and possibly “decolonization” of persons colonized with Staphylococcus aureus.

It is exciting to realize that rates of post operative infection can be favorably impacted by simple adherence to good infection prevention practices even in a time of ever more complex surgeries.

Influenza

Genetically unstable, influenza A viruses change from season to season through a process of “drift” or “shift” of hemaglutinin (H) and neuraminidase (N) antigens. The 2009-2010 influenza season saw the more dramatic “shift” to a novel H1N1 strain of influenza A to which there was very little pre-existing immunity – in other words, a pandemic strain of influenza A. Because of the constantly changing virus it is necessary to vaccinate annually to provide protection against influenza disease.

In general H3N2 and H1N1 influenza A causes disease in humans (an H5N1 avian influenza A virus has also caused severe human disease but has yet to become highly communicable). Often one strain of influenza A becomes predominant in a given flu season and “crowds out” other strains. This has been evident in recent flu seasons where H3N2 influenza A was predominant in 2007-2008, H1N1 influenza A was predominant in 2008-2009, and pandemic 2009 H1N1 influenza A was predominant in 2009-2010.

Different strains of influenza A also may differ in their susceptibility to available antiviral therapies. For example, “seasonal “ influenza A exhibited 99% resistance to oseltamivir (Tamiflu) in the 2008-2009 flu season while pandemic 2009 influenza A (2009-2010) was nearly universally susceptible to this drug. The table below illustrates how different strains of influenza have differed in their antiviral susceptibilities in recent flu seasons. Influenza B viruses are less unstable genetically and are always resistant to to the adamantane antivirals.

Antiviral
Influenza Viruses
  2009 H1N1 Seasonal H1N1
2008-2009
Seasonal H3N2
2007-2008
Influenza B
Adamantanes1 Resistant Susceptible Resistant Resistant
Oseltamivir (Tamiflu) Susceptible Resistant Susceptible Susceptible
Zanamivir (Relenza) Susceptible Susceptible Susceptible Susceptible

1Rimantadine, Amantadine

It is therefore important to be aware of the predominant circulating influenza A strain of a given flu season and its likely susceptibilities in making choice of antiviral therapy. This information comes from public health authorities on an annual basis.

Click here for more comprehensive influenza information.