[Skin disinfectants for nerve blocks and their long-lasting antimicrobial effects]

Although epidural catheterization has many advantages in anesthesia and in the treatment of acute pain, spinal epidural abscess is a serious complication after the procedure. Since it is presumed that the epidural space is contaminated by bacteria on the skin via the space around the catheter, it seems important to clarify bacterial re-growth after application of skin disinfectant. Therefore, bacterial growths on human back 1, 2 days, and 1 week after application of disinfectants were studied in summer and winter to elucidate whether there are differences between the two seasons. Four disinfectants, 0.5% chlorhexidine in 80% ethyl alcohol (CA), 0.2% benzalkonium in 80% ethyl alcohol (BA), 10% povidone iodine (PI), and 80% ethyl alcohol (EA) were applied on the back of 76 adult healthy volunteers, and the specimens were taken by agar-contact method. The frequencies of positive cultures for bacteria were higher in summer than in winter. The frequencies of positive culture in summer after the applications of CA, BA, PI, and EA were as follows, respectively: 50%, 20%, 5%, and 40% after 1 day; 47%, 50%, 60%, and 50% after 2 days; and 82%, 82%, 70%, and 64% after 1 week. In winter, these frequencies after the application of CA, BA, PI, and EA were as follows, respectively: 0%, 0%, 18%, and 18% after 1 day; 5%, 26%, 32%, and 58% after 2 days; and 21%, 21%, 32%, and 42% after 1 week. We conclude that when an epidural catheter is in situ, more frequent skin disinfection has to be carried out, preferably by CA, in summer than in winter, since the presence of sweat on the back seems to hasten the re-growth of bacteria.