Negative pressure therapy – How many dressing changes are enough?

Objectives: Negative pressure wound therapy is a promising tool in the treatment of deep sternal wound infections. The aim of this therapy is to remove infectious materials and to promote the formation of granulation tissue. Usually the dressing should be changed after about three to four days. But the question arises how many changes are enough.

Methods: Therefore we have retrospectively analyzed our negative pressure wound therapy protocol over the last three years. In case of deep sternal wound infection we removed osteosynthetic material, installed negative pressure wound therapy and took wound swab cultures regularly. In case of negative bacteriological culture findings and sufficient granulation tissue we stopped the negative pressure therapy and did the sternal reosteosynthesis and wound closure. We counted the number of changes of the dressing. Negative endpoint of the study was the reoccurrence of deep sternal wound infection.

Results: From January 2009 until August 2011 we treated 98 patients with deep sternal wound infection. In all the patients we installed negative pressure therapy. The number of dressing changes ranged between 1 and 15 with a mean of 5.3. The reinfection rate was 19%. There was a statistical significant decrease from 7.15±2.88 changes of the dressing in 2009 to 4.07±2.65 in 2011. But there was no rise in the percentage of reinfections. There was also no correlation between the number of changes and the success rate of the negative pressure wound therapy.

Conclusions: It is still challenging to determine the optimal time to stop negative pressure wound therapy. We use a combination of indications: formation of granulation and negative wound swab culture. Usually we accept now a wound colonisation with Staphylococcus epidermidis to stop negative pressure therapy. In conclusion, four to five changes of the dressing are usually enough.