Results
One hundred thirteen patients were enrolled with 13 of them excluded before study completion for various reasons including the following: difficulties with returning for drain removal (travel distance/bad weather (6), patient consented but changed their mind on POD 1 (3), patient prescribed antibiotics between time of consent and surgery (2), patient had immediate reconstruction (1), and significant language barrier (1).
The remaining 100 patients with 125 drains completed the study. Forty-eight women (58 drains) were randomized to the control group and 52 women (67 drains) to the antisepsis group. The control and antisepsis groups were similar with respect to age, BMI, American Society of Anesthesiologists (ASA) class, prior chemotherapy or radiation, smoking, preoperative skin prep, operative time, day of drain removal, and drain volume (Table 1). Total mastectomy with or without sentinel node biopsy axillary node dissection, and modified radical mastectomy were performed in 66, 6, and 28 patients, respectively. Median duration of drain use was 7 days (range, 4–19 days), with a median output of 23 mL (range, 3–136 mL) for the preceding 24 hours at the 1-week visit and a median of 19 mL (range, 3–57 mL) for the 24 hours before drain removal.
Colonization of Drain Fluid at 1 Week
Cultures of drain bulb fluid at 1 week in the treated group showed significantly less bacterial growth than those in the control group. At the cutoff of 1+ or greater growth for drain fluid cultures, 21% (14/67) of treated drains were positive compared with 66% (38/58) of control drains (P = 0.0001). Analysis performed on a per patient basis showed a similar result with 13 of 52 (25%) patients on the antisepsis arm experiencing 1+ or greater colonization on any drain compared with 31 of 48 (65%) patients on the control arm (P < 0.0001). To examine an analysis not dependent on the choice of cutoff, the ordinal quantification result was also compared between the 2 groups (Table 2) and again demonstrated strong statistical significance (P < 0.0001). In drains removed after the 1-week visit, a second culture was obtained at drain removal. All drains positive (>=1+) at 1 week were also positive at drain removal, with at least 1 organism in common between the 2 cultures for 11 of 14 (79%).
Colonization of Drain Tubing
Drain tubing was cultured at the time of drain removal from 76 subjects (96 drains—43 control and 53 antisepsis). Using a cutoff value of 50 CFU, drain tubing cultures were positive in 0% (0/53) of treated drains compared with 19% (8/43) of control drains (P = 0.004). In a per patient analysis, 0 of 40 patients in the antisepsis group demonstrated greater than 50 CFU colonization for any drain compared with 7 of 36 (19%) patients in the control arm (P = 0.0008). Treating degree of colonization as an ordinal variable (see Table 2) also resulted in a statistically significant difference between the treatment arms (P = 0.04). Subjects in the drain antisepsis group were much less likely to have high levels of bacterial colonization in the drain fluid, and none of them had greater than 50 CFU from drain tubing. Among drains with positive bulb fluid cultures (>=1+) at the time of drain removal, the drain tubing was also positive (>50 CFU) in 28% of control drains versus 0% of antisepsis drains. Conversely, among the 8 drains (7 patients) with positive tubing cultures (all in the control group), all 8 had >=1+ growth in drain fluid, and 7 of 8 had the same organism in both fluid and tubing.
Multiple Drains
Twenty-five patients (10 control, 15 antisepsis) had 2 ipsilateral drains. Regarding fluid cultures, the 2 bulb fluid cultures at 1 week were concordant for 20 drain pairs (12 negative, 8 positive) and discordant for 5; 4 of 5 discordant drain pairs were positive (>=1+) for the mastectomy drain fluid but not for the axillary drain fluid. The difference in positivity rate was not significant (P = 0.38), and the [kappa] agreement statistic was 0.60. Similar results were observed for tubing cultures among the 20 cases with both a mastectomy drain and an axillary drain. The tubing culture results were concordant for 19 pairs (18 with both drain tubing cultures negative, 1 pair with both positive) and discordant for 1 patient who had a positive axillary drain at greater than 100 CFU but a mastectomy drain with growth of only 20 to 50 CFU (below the 50 CFU of positivity and therefore negative).
Bacterial Colonization and Drain Duration
In the control group, bacterial colonization was a time-dependent phenomenon and increased in frequency with longer duration of drain presence, both for bulb fluid and drain tubing (Fig. 2). In the antisepsis group, positive fluid cultures also increased in frequency over time but were less frequent than those in the control group at all time intervals. Tubing cultures in the antisepsis group remained negative at all time points.
(Enlarge Image)
Figure 2.
Frequency of bacterial growth in surgical drain fluid and tubing as a function of time. A, Drain fluid cultures. B, Drain tubing cultures. Positive culture was defined as 1+ or greater growth from fluid and greater than 50 CFU from tubing.
Microbiology
A wide variety of microorganisms were identified in bulb fluid, with 35% of cultures demonstrating multiple organisms (Table 3). Staphylococci were the most common recovered (71%), predominantly coagulase-negative staphylococcus with some Staphylococcus aureus. Gram-negative rods and anaerobes were identified with lower frequency. Drain tubing showed less variation in types of microorganisms, with Staphylococcus species the most common.
Drain Site Erythema and Colonization
The extent of erythema in the skin around the drain exit site as a radial measurement was significantly less among subjects in the antisepsis group than in the control group (mean 1.1 mm vs 2.6 mm, P = 0.001) at 1 week. Although drains with positive (>50 CFU) tubing cultures on average had greater drain site erythema (mean 4.4 mm vs 1.1 mm, P = 0.86), as did patients with SSI (mean 3.0 mm vs 2.1 mm, P = 0.41), neither of these comparisons reached statistical significance.
Surgical Site Infections
SSI was diagnosed in 6 patients—5 in the control group and 1 in the antisepsis group (Table 4). Of the 5 patients with SSIs in the control group, 2 had abscesses that required incision and drainage, and a third demonstrated cellulitis with a positive culture. The remaining 2 patients with SSIs had cases of cellulitis without cultures, but at the time of treatment they were judged by a physician blinded to the study group to represent infection, were treated with antibiotics, and improved on antibiotic therapy, thus on final review these were deemed to be SSIs.
There was only 1 case of SSI that occurred in the drain antisepsis group, presenting with symptoms on POD 31. That patient started chemotherapy on POD 21 and developed fever of unknown origin on POD 31, with localized signs of axillary infection developing over the next week leading to incision and drainage of an axillary abscess. Because the patient's symptoms began just outside the standard 30-day time frame of the Centers for Disease Control and Prevention definition, it is debatable whether this SSI should be included or not, but we included it for a conservative assessment of the differences between the control and antisepsis groups. Therefore, with 5 SSIs among 48 women in the control group and 1 SSI among 52 subjects in the antisepsis group, the difference in the SSI rate between the 2 groups (10.4% vs 1.9%) was not statistically significant but showed a strong trend (P = 0.06). If this case of SSI in the antisepsis group is excluded because of its occurrence after 30 days, then the SSI rate in the control group (10.4%) is significantly higher than that in the antisepsis group (0%),P = 0.01.
Correlation of SSI and Degree of Drain Colonization
Although the analysis was limited by a small number of SSIs, the trend was that SSI occurred more frequently among subjects with greater bacterial colonization, in either drain fluid or drain tubing, compared with those with less or no bacterial colonization. Among patients with heavy (4+) bacterial growth in drain fluid from any drain at 1 week, the SSI rate was 2 of 9 (22%) compared with those with less heavily colonized fluid or no growth (4/91 = 4%, P = 0.08). Similarly, the SSI rate was 2 of 7 (29%) for subjects with tubing growth greater than 50 CFU in any drain compared with 3 of 69 (4%) for those with fewer CFU or no growth (P= 0.05).
Intervention Toxicity and Compliance
There were no allergic reactions to the chlorhexidine disc. Compliance with the antiseptic interventions was excellent based upon subjects' reports; at the 1-week follow-up visit and beyond, there were no subjects who reported any compliance failures with the interventions. Two subjects felt unsure about their ability to perform the chlorhexidine disc dressing change. Both of these subjects returned to the clinic for study coordinator assistance with the first dressing change; one performed dressing changes independently after that, and the other subject elected to return for study coordinator assistance with the remaining dressing changes.