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Wishing and Hoping

November 11, 2010

There is no benefit to prolonged courses of prophylactic antibiotics, and there are some serious things wrong with them.

It is standard practice to give antibiotics prior to a surgical operation, especially those with a suspected or certain risk of bacterial contamination.  It has been demonstrated that doing so will reduce the risk of a subsequent wound infection.  Timing, dosing, and antibiotic selection are all critical in optimizing the outcome. 

The practice of giving antibiotics in this manner is called prophylaxis, because we expect it to prevent some of those infections.  A critical concept behind prophylactic administration is that it is given to patients who currently have no evidence of an active infection.

What has also been demonstrated is that there is absolutely no benefit to a prolonged course of prophylactic antibiotics.  The concept underlying the practice is that antibiotics should be in the tissue at the time bacteria land in the tissue as a result of the skin incision.  Once bacteria are no longer landing in tissue, further antibiotic use will be futile as those bacteria that are surviving are in some microscopic area where the antibiotics cannot get to them, such as a fluid collection or a hematoma or a piece of suture material or debris.

Continuing to administer “prophylactic” antibiotics after the wound has been closed cannot reduce the risk of subsequent, but it can select out for resistant strains of bacteria.  On a practical level, it becomes problematic to manage a patient who develops a fever and other signs of infection at 5 or 6 days following surgery while still receiving a putative prophylactic regimen.  None of the available options are satisfactory:

  • switching blindly to some other antibiotic(s) (difficult to choose appropriate without culture results),
  • stopping antibiotics and reculturing (not optimal while the patient is becoming more ill), or
  • continuing the current antibiotic regimen (not likely to work as the infection developed while on that regimen).

However, if the patient has been off “prophylactic” antibiotics when (and if) signs of infection develop,cultures could then be obtained and presumptive antimicrobials can be started with reasonable expectations that the offending organism(s) will be covered.  This practice would reduce costs and deter the emergence of resistance without increasing the rate of surgical infections.

It would be a true paradigm shift in medicine to realize that knowing and doing works better than wishing and hoping.

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