2008 Abstract : 29

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Authors: Schneiderbauer MM, Trampuz A

Title: Surgical Drains: A Potential Risk Factor for Infection in Orthopaedic Patients

Institution: University Hospital Basel, Basel,Switzerland

Purpose: We investigated the frequency, type, and site of bacterial colonization of surgical drains in orthopaedic surgery to elucidate the potential of drains to cause postoperative infections.

Methods: Adult patients undergoing orthopaedic surgery at our institution during April 2008 were included if 1 or more drains were placed during surgery. The time of drain removal was determined at the discretion of the treating surgeon. Before removal, the skin border of the drain was marked with a sterile marker. The drain was then aseptically removed and the part inside the body was divided into four pieces (distance from the skin border): 0-2 cm, 2-4 cm, 4-6 cm, and remaining part. Individual sterile instruments were used for each drain. Drain pieces were placed in sterile containers and sonicated (40 kHz, 1 min, 0.2 W/cm2) in 10 ml Ringer's solution to dislodge adherent bacteria. The resulting sonication fluid was plated on agar plates and incubated aerobically at 37°C and bacteria were enumerated as colony forming units CFU/ml sonication fluid. We investigated the frequency, type, and site of bacterial colonization of surgical drains to elucidate the potential of drains to cause postoperative infections. In addition, risk factors for microbial drain colonization were investigated.

Results: During the study period 33 drains in 19 patients were included, of whom 18 (95%) had an implanted orthopaedic device. Median patient age was 71 years (range 26?81 years); 12 were females. The mean indwelling time of drains was 1.7 days (range 1?3 days). 4 of 19 patients (21%) demonstrated bacterial growth after sonication of removed drains, of whom 3 were classified as clean surgery (2 patients on the outermost part of the drain, and 1 on the second part with 30, 10, and 20 CFU/ml of coagulase negative staphylococci, respectively). One patient had a surgical site infection with enterococci and showed growth of the same organism on all drain pieces despite adequate antibiotic therapy. The drain was removed 3 days after surgery and showed a decreasing number of bacteria from the inner (>100 CFU/ml) to the outer (50 CFU/ml) pieces of the drain. Of 4 patients with bacterial colonization of the drains, 3 of 5 diabetic patients (60%) showed colonization, compared to only ! 1 of 14 patients (7%) without diabetes (p = 0.037, Fisher's exact test).

Discussion and Conclusion: 21% of patients had colonized drains at the time of removal 1 to 3 days after placement. In patients without surgical site infection, relevant numbers of coagulase negative staphylococci were found on drains within 2-4 cm from the skin border. Therefore, drains might represent a risk factor for orthopaedic infections especially in presence of implants. In case of surgical site infection, sonication of removed drains may help identify the causing organism. Diabetes was a significant risk factor for microbial colonization on drains. Further studies with larger patient numbersand clinical follow up are warranted.