Objective: Ten percent povidone-iodine (PVI) is commonly used as a bactericidal solution before amniocentesis is performed. Warming PVI may increase patient comfort; however, the effect of warming on its bactericidal properties is not known. The objective of this study was to determine the effect of warming 10% PVI on its bactericidal properties.
Study design: Room temperature of PVI was 25 degrees C, and temperature in an ultrasonic gel warmer was 32 degrees C. In vitro experiments were conducted in 25 degrees C and 32 degrees C water baths. Nine milliliters of PVI at each temperature was added to 1 mL of bacteria (10(7) organisms/mL Staphylococcus aureus, Enterococcus species, Escherichia coli, group B Streptococcus). After 0.25, 0.5, 1, 2, 4, and 8 minutes, 1-mL samples were removed and added to 4 mL of 0.5% sodium thiosulfate (to neutralize the iodine and interrupt bactericidal action). The number of viable organisms was determined by plating 0.1-mL samples on trypticase soy agar plates. Plates were incubated at 37 degrees C for 24 hours and colony-forming units (CFUs) were counted. For in vivo experiments in 40 volunteers, a 9-cm2 area of the dorsum of each hand was wiped with a sterile cotton swab to obtain a sample of bacteria for culture. The area was then wiped for 15 seconds with PVI at 25 degrees C or 32 degrees C and recultured. The bactericidal properties of PVI at each temperature were compared. The Mann-Whitney U test was used as appropriate, and P <.05 was considered significant.
Results: In vitro, PVI was bactericidal against E coli, S aureus, Enterococcus species, and group B Streptococcus within 0.25 minutes at both 25 degrees C and 32 degrees C, with median bacterial growth of 0 CFU/plate for each species of bacteria studied (3 replicates at each temperature). Median bacterial growth from skin was 4 CFU/plate (range, 0 to >100). After hands were wiped with PVI at 25 degrees C and 32 degrees C, median bacterial growth was 0 CFU/plate (range, 0-8) and 0 CFU/plate (range, 0-15), respectively (not significant).
Conclusion: PVI is as effective at 32 degrees C as it is at 25 degrees C. Use of PVI at 32 degrees C should be considered to increase patient comfort in procedures performed without the use of anesthetics.