Comparison of Two Antiseptic Solutions To Disinfect the Skin for Blood Cultures

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The summary below is from the full report titled "Chlorhexidine Compared with Povidone-Iodine as Skin Preparation before Blood Culture. A Randomized, Controlled Trial." It is in the 7 December 1999 issue of Annals of Internal Medicine (volume 131, pages 834-837). The authors are O. Mimoz, A. Karim, A. Mercat, M. Cosseron, B. Falissard, F. Parker, C. Richard, K. Samii, and P. Nordmann.

What is the problem and what is known about it so far?

Blood cultures are tests for infection in the blood, a serious condition. Bacteria (germs) are always present on the skin surface. Skin bacteria that get into the blood sample while it is being drawn can make it look as though patients have a blood infection when they really do not. To prevent contamination of blood cultures, it is important to disinfect the skin thoroughly before drawing blood for these tests. The cleaning solutions used most commonly for this purpose are chlorhexidine and povidone-iodine. It is not known, however, whether one solution is better at preventing contamination than the other.

Why did the researchers do this particular study?

The researchers wanted to find out if chlorhexidine was associated with fewer contaminated blood cultures than povidone-iodine.

Who was studied?

403 adult patients who needed at least one blood culture drawn while hospitalized in intensive care units in a teaching hospital in France.

How was the study done?

When patients had blood drawn for culture, the researchers randomly assigned each situation to have the skin cleaned with either chlorhexidine or povidone-iodine. They then measured the frequency of contamination in the cultures done with the two cleaning solutions.

What did the researchers find?

Contamination occurred in 14 of the 1019 cultures done with chlorhexidine and in 34 of the 1022 cultures done with povidone-iodine. Cleaning the skin with chlorhexidine was therefore somewhat better at preventing contamination.

What were the limitations of the study?

This study was done at a single hospital and only with patients in intensive care units. The same results may not be found at different hospitals or with other types of patients. Chlorhexidine solution is clear, and povidone-iodine is brown; the nurses who drew the blood culture samples could therefore tell which solution they were using. It is possible that they cleaned the skin differently with the two solutions. Lastly, we do not know whether patients who had blood cultures done using chlorhexidine had better outcomes, such as shorter hospital stays, less unnecessary treatment with antibiotics, and fewer complications. The study also did not determine whether use of one cleaning solution was less expensive than use of the other.

What are the implications of the study?

This study suggests that using chlorhexidine instead of povidone-iodine to clean the skin before blood cultures better prevents contamination of the cultures with skin bacteria. Other studies are needed to find out whether lower blood culture contamination rates also mean better patient outcomes or save money.