Relationship between Chlorhexidine Gluconate Skin Concentration and Microbial Density on the Skin of Critically Ill Patients Bathed Daily with Chlorhexidine Gluconate

OBJECTIVE AND DESIGN. Previous work has shown that daily skin cleansing with chlorhexidine gluconate (CHG) is effective in preventing infection in the medical intensive care unit (MICU). A colorimetric, semiquantitative indicator was used to measure CHG concentration on skin (neck, antecubital fossae, and inguinal areas) of patients bathed daily with CHG during their MICU stay and after discharge from the MICU, when CHG bathing stopped. PATIENTS AND SETTING. MICU patients at Rush University Medical Center. METHODS. CHG concentration on skin was measured and skin sites were cultured quantitatively. The relationship between CHG concentration and microbial density on skin was explored in a mixed-effects model using gram-positive colony-forming unit (CFU) counts. RESULTS. For 20 MICU patients studied (240 measurements), the lowest CHG concentrations (0-18.75 mu g/mL) and the highest gram-positive CFU counts were on the neck (median, 1.07 log(10) CFUs; P = .014). CHG concentration increased postbath and decreased over 24 hours (P < .001). In parallel, median log(10) CFUs decreased pre- to postbath (0.78 to 0) and then increased over 24 hours to the baseline of 0.78 (P = .001). A CHG concentration above 18.75 mu g/mL was associated with decreased gram-positive CFUs (P = .004). In all but 2 instances, CHG was detected on patient skin during the entire interbath (approximately 24-hour) period (18 [90%] of 20 patients). In 11 patients studied after MICU discharge (80 measurements), CHG skin concentrations fell below effective levels after 1-3 days. CONCLUSION. In MICU patients bathed daily with CHG, CHG concentration was inversely associated with microbial density on skin; residual antimicrobial activity on skin persisted up to 24 hours. Determination of CHG concentration on the skin of patients may be useful in monitoring the adequacy of skin cleansing by healthcare workers.