Intraoperative wound irrigation to prevent surgical site infection after laparotomy - IOWISI

Intra-operative wound irrigation with 0.04% Polyhexanide solution did not show the anticipated reduction of SSI rates after laparotomy for surgical procedures (LOC II-IV) compared to wound irrigation with simple saline solution or no wound irrigation. This result was unexpected as a reduction from previously available evidence was assumed. In the meantime, a single center trial (RECIPE) showed a significant reduction of SSI in colorectal surgery (high risk population) by prophylactic wound irrigation with PHX compared to saline. However, the IOWISI trial is the first multicenter RCT investigating the use of intraoperative irrigation with PHX in a large and standardized manner. The overall SSI rate of 10.4% was lower than in previous multicenter SSI trials (BaFO, PROUD), but still reflects the relevance of this frequent postoperative complication. However, it has to be taken into account that over 90% of the procedures in this trial were elective laparotomies classified as LOC II “clean-contaminated”, which was not anticipated when the trial was designed. Compared to numbers from the European surveillance data this is a coherent SSI rate for this type of procedure. The inclusion criteria of IOWISI were LOC>1, and it was anticipated that the percentage of LOC 3 and 4 patients would be higher. Only 48 (6.9%) patients undergoing procedures with LOC 3 and only 2 with LOC 4 (0.3%) were successfully randomized into the trial. The main reason for this was the difficulty of recruiting patients in the emergency setting. Regarding the secondary endpoints of the trial, there were no differences between the trial groups either. The fact that the prevalence of non-infectious wound complications as well as the rates of SAEs were equally distributed between the groups showed that application of PHX solution was safe for this indication. The IOWISI Study group managed to recruit almost 700 patients in the timeframe of 52 months despite the COVID-19 pandemic and the ever more serious staff shortages in the German hospital sector. High internal validity was ensured by standardization of surgical technique and the blinded assessment of outcome parameters. External validity and generalizability were achieved because of the multicenter approach with 12 study centers across Germany, and the broad inclusion of all types of abdominal surgical procedures. Prevention of SSI after laparotomy remains a relevant and improvable issue and future clinical trials focusing on procedures with level of contamination III and IV are needed to determine the efficacy of prophylactic PHX wound irrigation at the end of surgery. For procedures with level of contamination II wound irrigation to prevent SSI cannot be recommended based on the outcomes of the present IOWISI trial.