Randomized Controlled Trial to Evaluate the Optimal Timing of Surgical Antimicrobial Prophylaxis

Additionally, the association between the following pre-defined variables and the occurence of SSI, mortality, morbidity and length of hospital stay (LOS) will be investigated:

• laparoscopy
• tutorial assistance during operation
• obesity (Body Mass Index, BMI)
• preoperative Virtual Reality (VR) training
• Adherence to Enhanced Recovery After Surgery (ERAS) concept
• smoking status
• perioperative blood glucose levels
• preoperative levels of HbA1c
• intensified insulin resistance as measured by Homeostasis Model Assessment (HOMA) and quantitative insulin-sensitivity check index (QUICKI)
• type of diabetes (IDDM vs. NIDDM)
• intraoperative Hypothermia (body core temperature)
• Lack of adherence to the principles of asepsis during surgery
• surgical experience
• patients age
• Malnutrition, measured by Hypalbuminaemia
• emergency operations
• immunosuppression and steroids
• Predictive value of Procalcitonin
• American Society of Anesthesiologists (ASA) classification
• intraoperative blood transfusion
• preoperative wound class

Amendments:

The following changes were made to the study protocol according to amendments approved by the local ethics committee:

• As of April 22nd, 2013, or the 222. patient randomized at the University Hospital Basel, the time the SAP infusion STARTED was recorded instead of the time that it ENDED. The decision to change this important parameter was taken in order to make results of this trial more comparable to those of other published studies.
• In the original study protocol it was planned to provide each randomized patient with a patient's diary to record signs of SSI. This was abandoned for limited benefit and in order to minimize patients' time and effort.
• Patients who undergo combined surgery (by one of the participating surgical specialties plus by a non participating specialty) shall not be included in this trial as outcomes (SSI) could be difficult to correlate to one or another part of surgery. This had not been specified as an exclusion criterion in the original study protocol.
• Patients' information sheets and informed consents in one of the languages other than German were only approved by the local ethics committees by May 15th, 2013.
• As per ethics committees regulations, patients can only be included in more than one clinical trials under specific circumstances. Therefore only a limited percentage of patients that are already included in other studies can still be included for this trial. However, overall, this only excludes a very limited number of potentially includable patients.

The following additional amendments were authorized by the ethics committees on August 9th, 2014:

• Version 4 of the patients' information and the written consent form. In these new versions, patients are specifically asked for permission to review their general practitioners' notes concerning potential SSI, for planned follow up as well as in case of readmission to hospital. This is specified in the study protocol, but had not been specifically mentioned in the patients' information and consent forms. This change is also intended to significantly decrease the number of patients lost to follow up as it proved difficult to contact some patients by telephone.

Inclusion criteria

• Age ≥ 18 years
• Inpatient visceral, vascular and trauma procedures
• SAP indicated according to clinical standards (CDC guidelines for surgical wound classification)
• informed consent

Exclusion criteria

• Contraindication for study drugs
• Pre-existing antibiotic therapy within 14 days of surgery
• Any doubt that patients can make the decision to participate fully informed due to cognitive impairment, such as in critically ill or demented patients.
• Emergency procedures with planned incision within 2 hours after the surgeon indicated the procedure
• Participation in other studies that could potentially interfere with the present one (according to the ethics committee)
• Combined surgery including surgical subspecialties other than the above mentioned