Studies on perioperative skin flora.

Chlorhexidine in spirit is used to reduce the skin bacterial load before surgery; and recently prewashing with chlorhexidine scrub has been advocated. We describe three studies on cardio-thoracic surgical patients--particularly those having coronary artery grafts with long leg and sternal wounds. Two studies compared prewashes with chlorhexidine scrub (Hibiscrub-ICI) or soap. Study Number One (250 patients per group) was of wound infections; and Number Two (25 patients per group) was of alterations in skin flora for 10 days postoperation. Chlorhexidine scrub failed to reduce overall wound infection rates in Study 1, although leg wounds healed more quickly with less inflammation. Study Two showed that the scrub had a significant effect on skin flora that lasted at least 3 days postoperation. Study Number Three was of 100 patients (no chlorhexidine scrub) examined for methicillin-resistant coagulase-negative staphylococci (MRSE) by cultures of swabs from the leg, sternum and chest drain site before and after operation on methicillin agar. Three per cent of patients had MRSE preoperation (1 doctor) and 23% postoperation. One thousand strains were tested by agar dilution against methicillin and chlorhexidine. MRSE had a 2-8-fold increased resistance to chlorhexidine compared to a greater than 256-fold to methicillin. Thus although chlorhexidine has a marked persistent effect on skin flora, emergence of major resistance is unlikely. Use of postoperative chlorhexidine should be investigated further.