Pilot Study for Antibiotic Impregnated Calcium Sulfate Beads as Prophylaxis for Surgical Site Infection in Vascular Surgery Patients

The initial pilot will consist of 30 patients per arm and will provide estimates of effect size, event rates, and recruitment rates. It will mirror the final study in terms of methodology. This will occur at the Hamilton General Hospital (Hamilton, ON. Canada)

Patients will be randomized to either the exposure group or control group by the study coordinator. Patients will be block randomized among surgeons (6), so that each surgeon has an equal number of patients in the control and exposure arms. Randomization will occur once an operative date has been booked for a patient. The arm they are assigned to will be how the patient is treated, regardless of if they are cancelled and re-booked. Should patients be done as an emergency procedure, prior to their index procedure (when the beads would be implanted), they will be excluded from the study. As no intervention has occurred at this point, there will be no informative loss to follow-up or censoring and therefore this will not impact validity of the design. We are unable to provide beads for emergency procedures, as the research pharmacy is not open.

The research coordinator will inform the research pharmacy to produce calcium sulfate beads impregnated with Vancomycin (1g) and Tobramycin (240mg) for the exposure arm. The control arm will receive standard care. The only difference between standard care and the treatment arm is the use of the antibiotic calcium sulfate beads. Beads will be delivered in a sterile manner to the OR. For each patient half of a standard 10cc kit will be delivered (5cc of Stimulan Calcium Sulfate). As the beads are being applied only to a groin incision(s) this will provide an adequate volume of beads. It will also prevent insertion of excess beads.

Surgeons will insert the beads loosely within the soft tissue of groin incisions, so as not to distort the normal anatomy. This technique will be discussed with all surgeons prior to pilot initiation as a group. This will aim to standardize the method among involved surgeons. At the end of the study we will complete a focus group with surgeons to discuss their experience using the beads to better inform the protocol for the final RCT. Patients are randomized as a unit and therefore, if there are bilateral groin incisions, both will be treated as per their randomization.

Patients will be blinded to which treatment they receive. The beads are believed to be non-detectable to the patient. Only by means of wound dehiscence would a patient be expected to determine their treatment group. For practical reasons the surgeon cannot be blinded to treatment. Nurse assessors and study authors conducting review of patient records will be blinded to patient treatment.