We hypothesized that revision clean head & neck surgery may have a higher rate of wound infection that may be lowered with prophylactic antibiotic treatment.

Surgical wound infection (SWI) is a common complication in many operations, including head and neck (H&N) surgery, with reported rates ranging between 3.5 to 87%. While prophylactic antibiotic use has been shown to decrease SWI in clean-contaminated and contaminated surgery, its use in clean surgery is debatable. In most types of clean surgery the value of prophylactic antibiotics is minimal, however in some cases it might be justified, including in radical neck dissections, in a previously irradiated neck, those with a tracheostomy and immunosuppressed patients - although there is no consensus regarding these risk factors.

Previous research has shown that adherence to guidelines regarding prophylactic antibiotic use is lacking, with one study showing a greater than 40% rate of inappropriate antibiotic administration. This may be partially attributed to some patients having other risk factors, not covered by existing guidelines.

One such risk factor is previous H&N surgery. While there are no studies addressing this issue in H&N surgeries, a study in clean neurosurgical operations has shown an almost trice-fold increase in SWI rates in some operations (4% vs. 13%).

The purpose of this study is to investigate the effect of prophylactic antibiotic use in repeat clean H&N surgery.

This is a double-blind, randomized, placebo-controlled study. The study will be conducted at the Otolaryngology department in Rabin Medical Center, Petah Tikva.

Patients will be randomly assigned to 2 groups, with each group composed of 50 patients: a study group which will receive 1 dose of intravenous Cefazolin 1 gram/2 gram if body mass index > 40 or a control group which will receive 1 dose of placebo. The drug/placebo will be given 30-60 minutes prior to incision. Previous studies have shown no benefit for longer duration of prophylactic antibiotic coverage. Both the study drug and placebo will be prepared by a designated nurse from the department. The nurse will use a randomization site (www.random.org with min set to 1 and max set to 1000) to give each participant a number. A predefined Excel table will contain an assignment of each number to one of the groups. Only this nurse will know the assignment of each patient and she will not be assessing the patient post-operatively. The patients, surgeons and researchers will be blinded to the patients' assignments.

The status of the surgical wound will be assessed daily during hospitalization and again on the planned follow-up visit 3-4 weeks after discharge. During the follow-up visit, patients will be questions regarding symptoms and signs of SWI and antibiotic prescriptions given during the post-operative period.

SWI diagnosis will be according to the Center for Disease Control's "guideline for surgical site infection". Treatment of SWI will be according to regular department protocols (with no regard to study allocation).

Inclusion Criteria:

• Previous H&N surgery.
• Planned second H&N clean surgery (the definition of a second H&N surgery is a surgery which will include the same skin incision as the previous operation).

Exclusion Criteria:

• Previous neck irradiation.
• Tracheostomy status.
• Immunosuppression.
• Concurrent infection which requires antibiotic use.
• Any other factor during the surgery which the surgeon estimates requires prophylactic antibiotic use.
• Allergy to cephalosporins and allergy to penicillin which precludes the use of cephalosporins (e.g. anaphylaxis).