['surgical site infection']
['cefuroxime 4 hourly bolus']

        Inclusion criteria

          -  Undergoing colorectal surgery (incision, excision or anastomosis of the large bowel,
             including anastomosis of small to large bowel)

          -  Age >18.

          -  Expected duration of surgery > 2hours

          -  Creatinine clearance > 40 ml/min

          -  Cefuroxime/metronidazole are appropriate antibiotic prophylaxis regimens.

          -  Patient capable of giving informed consent

          -  Patients undergoing colorectal surgery plus additional surgery e.g. plastic surgery,
             urological surgery, gynaecological surgery.

          -  If it is not possible to obtain intra-operative blood samples e.g. difficult vascular
             access, or pre-operative swabs e.g. anatomy makes it difficult to obtain, patients
             will be included and this information treated as missing data. Patients on antibiotic
             treatment for an existing infection (except SSIs) can be included in the study

        Exclusion Criteria:

          -  Unable to consent

          -  Pregnancy

          -  Expected duration of surgery <2hours

          -  Creatinine clearance <40ml/min

          -  Individual level microbiological advice for non cefuroxime based prophylaxis

          -  Cephalosporin allergy

          -  Penicillin allergy (hypersensitivity reaction only)

          -  Coumarin (warfarin and acenocoumarol) treatment

          -  Active blood borne virus infection e.g. HIV, hepatitis.

          -  Seizure history

          -  Concurrent use of probenecid

          -  Current participation in a research project aimed at reducing SSIs

          -  Antibiotics for treatment of a systemic Gram negative infection within 2 hours of
             initiation of surgery (Vancomycin, Teicoplanin, Daptomycin, Linezolid, Flucloxacillin.
             Nitrofurantoin and Clarithromycin would be permissible antibiotics without systemic
             Gram negative antibiotics).

          -  A current diagnosis of a SSI at the time of study entry.
      