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

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Postoperative surgical site infection (SSI) represents the third most common hospital infection and contributes substantially to postoperative morbidity and mortality. In addition, SSI increase treatment costs and length of hospital stay. Following visceral abdominal surgery, SSI rates are especially high (14-25%). Prophylactic intraoperative wound irrigation (IOWI) of the subcutaneous tissue before skin closure with saline or antiseptic solutions, hypothetically represents an easy and economical option to reduce SSI rates and is already frequently used in clinical practice. However, there are currently no official recommendations on its use and clinical practice varies largely. Formerly common irrigation solutions based on iodine or containing antibiotics are no longer approved for this indication, due to potentially negative effects like tissue toxicity or the risk of increasing microbial resistances. New antiseptic polyhexanide-based solutions are approved for soft-tissue wound irrigation in surgery, and were shown to be tissue tolerable and promote wound healing. However, they have not been evaluated in randomized clinical trials in visceral surgery. Therefore, in March 2017 the multicenter, randomized, observer-blinded IOWISI trial was initiated to investigate the efficacy of IOWI with polyhexanide solution or saline before skin closure after laparotomy. Based on the results of a meta-analysis on 41 clinical trials a sample-size of 540 patients was calculated for a 3-armed study design (polyhexanide- vs. saline irrigation vs. control group without wound irrigation). The trial is currently conducted in 13 centers within the German surgical trial network CHIRNET. All patients undergoing elective or emergency visceral surgery by laparotomy are screened for the trial. The primary endpoint of the trial is the SSI-rate 30 days postoperatively. Based on the experience from previous trials, the recruitment period was initially set to 24 months. However, after 18 months of recruitment it became clear that this would not be sufficient to reach the goal of 540 analyzable endpoints. On the one hand, this was due to a delay of the initiation of some study centers because of regulatory hurdles. On the other hand, the number of emergency revision surgeries in the patient population was much higher than expected. Therefore, the sample size has to be increased to 700 patients to obtain 540 analyzable endpoints and ensure the statistical power of the trial results. In addition, more study centers have been recruited and local recruitment problems have been successfully resolved. Hence, the recruitment period has to be extended for another 21 months. The results of this trial will provide evidence for definite clinical recommendations regarding the use of IOWI and influence current guidelines. Moreover, they will provide all participating patients the opportunity of an improved treatment.