Prevention of postoperative wound infections by covering the surgical field with iodine-impregnated incision drape (Ioban 2).

The literature is used to analyse the significance of the use of iodine-impregnated incision drape (Ioban(®) 2) for the prevention of postoperative wound infections (SSI). The drape has a microbiocidal effect in vitro. Consequently an antiseptic effect also occurs under the incision drape when it is applied to the skin; at the same time, bacterial wound contamination is reduced. Overall, based on the efficacy strength of the antiseptic incision drape, a reduction of the SSI rate can, however, be confirmed only with a large sample size. A meta analysis which evaluated four prospective studies and one retrospective study was able to provide significant confirmation of a reduction in the SSI rate. There are no limitations in terms of the biocompatibility of the iodine-impregnated incision drape.

Introduction

Most postoperative wound infections (SSI) result from endogenic conditions. Therefore the prevention of bacterial contamination in the region of the surgical incision is an important task.

After preoperative skin antiseptics, an average of 1 log CFU (i.e. one 10x potency of microorganisms) remains on the skin. This consists of the resident skin flora, with S. epidermidis in the foreground. From the remaining skin flora, pathogens can intraoperatively enter the surgical wound and become causative factors of SSI.

The localisation of a large part of the bacteria in the hair follicles [1], in which – due to anatomical conditions – they are only incompletely reached by the alcoholic skin antiseptics, is to be regarded as a significant cause of the restricted efficacy of skin antiseptics. Since iodine has good penetration abilities, it can be assumed that it also penetrates the hair follicles and the bacteria which are located there are at least partly reached.

In addition to skin antiseptics, the use of antimicrobially impregnated incision drapes [2] and skin sealing [3], [4], [5] with the purpose of killing pathogens which have floated up or suppressing their upward movement out of the follicles provide options to minimise the potential dangers of this reservoir of pathogens. Around the incision one can reduce the level of SSI trough the use of antiseptic impregnated sutures [6], [7], [8], [9], [10], [11]. For future applications it appears promising to introduce into the practice liposomal products for skin antiseptics which penetrate the hair follicles and exercise an antiseptic effect there [12].

The following overview will evaluate the literature on the efficacy of iodine-impregnated incision drapes in order to assess their value in the prevention of SSI.

Microbiocidal efficacy in vitro

In accordance with ASTM E2315-0 [13], the coated side of the iodine-impregnated incision drape was contaminated. After 30, 60 and 90 min, the test organisms (MRSA, S. epidermidis, E. faecalis (VRE), E. faecium (MDR), S. pyogenes, E. cloacae, E. coli, K. pneumoniae, P. aeruginosa, S. marcescens, C. albicans, C. parapsilosis) were washed off in neutralisation solution, and the reduction factor (RF) was determined [14]. For comparison, two further drapes without antiseptic impregnation were tested. While the control drapes were ineffective, the iodine-impregnated incision drape obtained a reduction by up to 1 log after 30 min, depending on the species. After 60 min, the reduction as compared to MRSA was slightly more than 2 log; it amounted to approximately 3.5 log as compared to MRSE. After 90 min, the RF against both species exceeded 5 log. The RF differed between 1 and >6 log as compared to the other test organisms. The efficacy of the antiseptic drape was directed primarily against staphylococci, i.e. the main target of preoperative skin antiseptics.

Conclusion

After direct inoculation onto the iodine impregnated incision drape it shows a clinically relevant reduction of the microbial count.

Effects on the skin flora and wound contamination

When comparing the efficacy of skin antiseptics with PVP iodine to the use of the iodine-impregnated drape without preceding skin antiseptics, the skin antiseptics with PVP iodine were more effective than the drape, though the drape also had an antiseptic effect. At the same time, the iodine-impregnated drape reduced wound contamination [15]. Analogous results were shown by the comparison between preoperative antiseptics with PVP iodine/alcohol (betadine), identical antiseptics with subsequent use of the antiseptic incision drape and use of the drape alone [16].

In a comparison of the skin flora at the end of surgery after skin antiseptics with PVP iodine (n=107) and after the use of the iodine-impregnated incision drape 24 h before the start of surgery to the end of surgery (n=122), the wound contamination rate was 15% and 1.6% respectively [17].

The iodine-impregnated drape does not only significantly reduce the resident skin flora, but its use also clearly reduces intraoperative wound contamination.

Influence on the SSI rate

Retrospective studies

After the removal of liver cancers, the influence of the iodine-impregnated drape on the SSI rate was compared to skin antiseptics without using the drape (n=296). The SSIs were defined as purulent drainage from superficial incisions with or without laboratory confirmation and one or more of the following symptoms: pain, local swelling, redness, heat. SSIs occurred in 25 patients. The regression analysis showed that risk factors consisted of low BMI, smoking, long preoperative hospital stays and no use of the antiseptic drape. Using a multivariant regression analysis, the BMI, smoking and no use of the antiseptic drape were independent risk factors. The SSI rate with use of the antiseptic drape was 3.1%; without use of the adhesive drape, it was 12.1%. Based on the sample size, the difference was not significant [18].

In hip endoprosthesis implantations, no significant influence on the SSI rate was found after the use of the antiseptic drape (n=649) as compared to use of skin antiseptics alone with PVP iodine [19].

Prospective randomised controlled studies

In a comparison of preoperative skin antiseptics for 1 min with 70% ethanol or 2% iodine in 90% ethanol and subsequent application of the antiseptic drape vs. 10 min of skin antiseptics with iodophor without drape, the SSI rate did not show a difference (in clean interventions, 1.3% vs. 1.3%; in a comparison of all interventions, 2.5% vs. 2.3%, n=1,324) [20].

The use of the antiseptic drape in comparison to standard skin antiseptics without using the drape (n=1,102) did reduce wound contamination in abdominal and cardiac surgery; however the SSI rate did not differ significantly [15].

In cardiac surgery, the use of the antiseptic drape also showed only a tendential reduction in the rate of SSIs (6.3% vs. 14.8%) [21].

No SSI occurred in 616 patients after fusing of the frontal cervical vertebrae without using the antiseptic drape. This led to the conclusion that the use of antiseptic drape is dispensable for this intervention [22].

Meta analyses

The scope of a Cochrane analysis comparing iodine-impregnated incision drape vs. no incision drape, no significant difference in the rate of SSIs was shown in an evalu-ation of 2 studies with 1,113 patients [23].

Parks [2] calculated that a sample size of at least 10,000 is required in order to confirm the efficacy of iodine-impregnated incision drape due to the low rate of SSI in clean and clean-contaminated surgery. In the evaluation of SSI rates (clean or clean-contaminated cardiovascular and abdominal interventions and liver resection) of four prospective studies and one retrospective study with the Mantel-Haenszel-Cochrane (MHC) statistics, he calculated an OR of 0.34 with a lower confidence interval 95% of 0.222 and an upper confidence interval of 0.702; i.e. the reduction of the SSI rate through the use of iodine-impregnated incision drape was significant.

The use of iodine-impregnated incision drape as compared to the use of incision drape with no antiseptic impregnation was not associated with negative consequences in any of the studies. Overall, based on the efficacy strength of the antiseptic incision drape, a reduction of the SSI rate can, however, be confirmed only with a large sample size. From a surgical perspective, the indication range for iodine-impregnated incision drape can therefore not be precisely defined at this time.

Biocompatibility

In experimental wounds in rats, 2% PVP iodine did not have any influence on wound healing, while 5% already inhibited wound healing [24]. Therefore no negative influence on wound healing is to be feared due to the utilised concentration of 2% in the antiseptic drape.

Furthermore, the use of the iodine-impregnated incision drape does not mean that a risk to the thyroid gland must be expected [in preparation].