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BACKGROUND: Many surgeons fear closed-suction drains serve as a portal for bacterial entry into surgical spaces. Despite a lack of supporting evidence, postoperative antibiotics are often prolonged while drains are in place. We therefore examined potential risk factors for drain colonization and surgical site infection (SSI) in the presence of closed-suction drains.
METHODS: The medical records of all patients who underwent intraoperative closed-suction drain placement by a single surgeon over a 12-month period were prospectively analyzed. Only patients whose drains were present for at least 5 days and removed as an outpatient by the same surgeon under sterile conditions were included. An identical segment of each drain was sent to microbiology for culture and sensitivity testing. Patient demographics, procedures, and drain locations/durations were recorded, as well as the selection and duration of perioperative and postoperative antibiotics. The duration of postoperative drainage was compared between patients with culture-positive and culture-negative drains and analyzed with a two-sample independent measures t-test. Binary logistic regression was conducted to assess the relationship between these factors and both drain colonization and SSI. Binary logistic regression was similarly performed to characterize the relationship between SSI and the microbiology of drain colonization.
RESULTS: Fifty-five patients with 101 drains were included. Drains were placed in the abdominal wall most frequently (46.5%), followed by the back (27.7%), and chest (18.8%). Drains remained in situ postoperatively for an average of 13.2±5.9 days (range 5-43 days), including a mean of 4.9±3.7 inpatient days (range 0-15 days) and 8.4±4.7 outpatient days (range 2-35 days). The duration of postoperative drainage of the culture-positive group (13.8±6.3 days, range 6-43 days) was not significantly different from that of the culture-negative group (12.2±5.1 days, range 5-25 days). Sixty-four drains (63.4%) had positive cultures, including coagulase-negative Staphylococcus (24.8%), MSSA (8.9%), and Enterococcus faecalis (6.9%). Forty-three drains (42.6%) were placed in the presence of hardware or prosthetic material. Of these, 23 were culture-positive upon removal. All patients received perioperative antibiotics. Thirty-nine (70.9%) received postoperative antibiotics (range 2-42 days, mean 12.9±13.0 days). There were 2 cases of cellulitis. One patient required reoperation. Risk factors for colonization included abdominal wall location, p=0.008 (OR 3.14 [95% CI: 1.35-7.32]), and number of outpatient drainage days, p=0.048 (OR 1.16 [95% CI: 1.00-1.34]). Location in the back, p=0.028 (OR 0.37 [95% CI: 0.15-0.90]), the presence of prosthetic material, p=0.003 (OR 0.17 [95% CI: 0.06-0.54]), and duration of postoperative antibiotics, p=0.039 (OR 0.92 [95% CI: 0.85-0.99]), were protective against colonization.
CONCLUSIONS: In our series, drains were left in situ for a relatively extended duration, after which almost two-thirds were colonized with bacteria. Despite this, there was no statistical correlation between the duration of drainage and SSI, and our wound infection rate was low (5.5%). Therefore, drains may be left in place for an extended period without increasing the risk of infection, even in the presence of prosthetic material. Furthermore, these data suggest that use of antibiotics to “cover” drains is unnecessary.