Comparison of Aqueous and Alcohol-based Agents for Presurgical Skin Preparation Methods in Mice

Abstract

Preparing the skin of rodents for surgery often involves multiple applications of antiseptic agents. However, fewer applications may achieve the same antiseptic outcome. We evaluated the antimicrobial efficacy and effects on intraoperative body temperature of various surgical scrub agents, including novel waterless alcohol-based (WAB) options. Prior to ventral laparotomy, female C57BL/6 mice were treated with 0.9% saline (control); 70% ethanol; 10% povidone-iodine alternated with saline or 70% ethanol; 2% chlorhexidine digluconate alternated with saline or 70% ethanol; or 1 of 3 WAB products-commercial surgical scrub A, commercial surgical scrub B, or a common commercial hand sanitizer. Core temperatures were recorded, and aerobic culture swabs were collected from the surgical site at multiple time points. Intraoperative temperature trajectories for animals treated with scrub B, 10% povidone-iodine with saline, or hand sanitizer did not differ from saline (control). Temperature trajectories of mice treated with other scrub agents did differ significantly from saline. Bacteria were not detected at the operative site after 3 scrubs of 70% ethanol or 10% povidone-iodine alternated with ethanol, 2 scrubs of scrub A or B, 1 scrub of hand sanitizer, and both 1 and 3 scrubs of 2% chlorhexidine alternated with ethanol. Scrub B and 2% chlorhexidine-ethanol demonstrated prolonged antibacterial efficacy. Histology of corresponding haired skin sections revealed no differences in postoperative healing between groups, and no postoperative infections occurred. These results indicate that various novel WAB disinfectants, particularly scrub B (61% ethanol and 1% chlorhexidine gluconate), mitigate intraoperative temperature effects associated with several traditional agents and combinations. Furthermore, reduction of skin bacterial load without adverse effects on healing was seen with fewer than triplicate applications of most tested agents. Ultimately effective skin preparation can be achieved by using only 1 or 2 applications of scrub, thus rendering the triplicate skin-prep method unnecessary in laboratory mice.

Figure 1.

Histograms of intraoperative core body temperature by prep group. The y-axis represents the number of readings of a given temperature that were obtained during the indicated procedural phase for mice in the designated agent group.

Figure 2.

The trajectories of body temperature (°C) over time (minutes) for each agent group. Each mouse's trajectory is displayed as a gray line. The average group temperatures at each time point are connected by the black line. The expected growth trajectory, represented by the blue line, was nonlinear and differed by treatment condition. All treatment group trajectories differed from that for the saline group. The temperature trajectories of the 70% ethanol (linear and quadratic, P < 0.0001), chlorhexidine with saline (linear, P = 0.0317; quadratic, P = 0.0404), povidone–iodine with ethanol (linear, P = 0.0049; quadratic, P = 0.0010), chlorhexidine with ethanol (linear, P = 0.0014; quadratic, P = 0.0131), and Scrub A (linear and quadratic, P < 0.0001) groups were significantly different from that of the saline control.

Figure 3.

Photomicrographs of representative skin sections. (A and B) Score, 1. Note the mild patchy mature fibrosis; low numbers of inflammatory infiltrates; and the overlying intact, mildly hyperplastic epidermis, which is lined by basket weave keratin layers. (C and D) Score, 2. Note the extensive granulation tissue, dense inflammatory infiltrates, segmental superficial ulceration, and lining serocelluar crust containing intralesional bacteria. Adjacent intact segments of epidermis are markedly hyperplastic. Skin sections in panels A and C are artifactually tented due to surgical closure. Hematoxylin and eosin stain; magnification: 12.5× (A, C); 100× (B, D).