Using an implant containing gentamicin in the groin area following vascular surgery does not significantly reduce the incidence of infected wounds during the postoperative course, according to a new study presented at the European Society for Vascular Surgery annual meeting (ESVS 2019; 24-27 September 2019; Hamburg, Germany). Despite preventative measures, the incidence of surgical site infections (SSIs) is still high, creating further complications such as increased morbidity and mortality, as well as higher costs per patient.
Tiemen van Boxtel (Maastricht, The Netherlands), who presented the findings, underlined how SSIs are a problem faced by many vascular specialists. He said: “A postoperative wound infection is defined as a wound in the postoperative course up to 30 days, or up to one year when a synthetic implant is used. Although the use of the perioperative antibiotic prophylaxis and other antiseptic measures are now part of standard procedure, retrospective analysis still shows an incidence (of SSI) of 4-43%.”
Administrating antibiotics at the incision site by implanting a biodegradable collagen carrier is considered to have significant potential for decreasing the incidence of SSIs, as well reducing systemic side-effects such as nephrotoxicity. “Prior research in this area, including three systematic reviews, has shown that addition of an implant containing gentamicin to standardised, preoperative antiseptic measures may have a benefit,” van Boxtel explained.
The aim of the randomised controlled trial carried out by van Boxtel and colleagues—performed across multiple centres (three hospitals in the Netherlands, one in Belgium)—was to assess the efficacy of implants containing gentamicin for reducing SSI following vascular surgery.
Patients who were eligible for participation included persons over the age of 18 that had undergone vascular surgery with primary longitudinal groin incision, while patients who had received prior surgery to the groin area, or were sensitive to the gentamycin, did not take part. Furthermore, wounds on the left side were excluded in case of a bilateral incision. In terms of power analysis, van Boxtel revealed that the expected incidence of SSI was 15% in the control arm, while a 50% reduction of SSI was anticipated in the gentamycin cohort. Finally, it was calculated that 304 patients per study arm were needed to perform the trial.
Randomisation, as coordinated by an independent, external statistician prior to the investigation, was stratified at each trial centre, with patients blinded before receiving their allocation. As part of the study, the gentamycin arm received a 10cm x 10cm x 0.5cm bovine collagen implant containing 130mg of gentamicin, which was placed on the groin before wound closure and following randomisation.
Postoperatively, patients were followed-up by blinded observers at one day, two weeks, four weeks and six weeks after surgery, with these meetings consisting of an inspection of the groin and photographs being taken. In cases where an infection was suspected, wound cultures were also taken where possible.
The results of the trial, with regard to the primary endpoint of SSIs, showed that of the 151 patients who were ultimately treated and followed-up in the gentamicin group, 11 (7%) developed a wound infection during the postoperative course. In the control group, which included 137 patients, 16 (12%) developed a wound infection, demonstrating that there was no significant difference between the two arms of the study. These findings were reflected in the secondary outcomes, with no significant difference found either in terms of length of stay, allergic reactions, treatment with antibiotics, or mortality.
Moreover, a post-hoc analysis of the results underlined that a significant difference in treatment effectiveness was discovered between study sites. According to van Boxtel, “two study sites had over 10% wound infections in the control arm, and therefore patients included from these sites were marked as high risk”. In these patients, the use of a gentamicin implant did significantly reduce the incidence of post-operative infections, with only 1% of the 72 patients in the gentamycin group developing an SSI, compared to 22% in the control group.
van Boxtel concluded: “Although this is the largest multi-centre randomised controlled trial to date on this particular subject, we were not able to validate the promising effects of using a gentamicin-containing implant in vascular surgery of the groin for decreasing wound infections in the postoperative course. However, centres which experienced a high incidence of wound infections can use the implant as a valuable adjunct to reduce these numbers.”