CHICAGO – Oral antibiotics alone or in combination with mechanical bowel preparation were independently associated with reduced surgical site infections after elective colorectal resection in a large national patient sample.
Oral antibiotics (OA) alone significantly reduced the rate of any surgical site infection (SSI) by 44% (odds ratio, 0.56; 95% confidence interval, 0.36-0.87) and wound SSI by 59% (OR, 0.41; 95% CI, 0.23-0.72), compared with no bowel preparation in propensity-adjusted multivariate analysis.
OA combined with mechanical bowel preparation (MBP) was independently associated with significant reductions of 54%, 58%, and 41%, respectively, for any SSI (OR, 0.46; 95% CI, 0.38-0.55), wound SSI (OR, 0.42; 95% CI, 0.33-0.53), and organ space SSI (OR, 0.59; 95% CI, 0.44-0.78).
In contrast, MBP, which was used in 40.8% of cases, was not independently associated with reduced rates of any SSI (OR, 0.95; 95% CI, 0.82-1.10), wound SSI (OR, 0.91; 95% CI, 0.76-1.09), or organ space SSI (OR, 1.0; 95% CI, 0.79-1.27), according to Dr. Sarah Koller of Temple University Hospital in Philadelphia and her associates.
A limitation of the study was the lack of information on type of OA or MBP used, patient compliance, and use of parenteral antibiotic prophylaxis.
“Randomized clinical trials are needed to determine the true benefits of oral antibiotics alone versus combined oral antibiotics and mechanical bowel prep prior to elective colorectal resection,” Dr. Koller said at the American College of Surgeons/National Surgery Quality Improvement Program National Conference.
Session comoderator Dr. E. Patchen Dellinger, of the University of Washington in Seattle, commented, “Logically, it’s hard for me to believe that oral antibiotics would affect a couple of kilograms of stool in the colon and yet here are these tantalizing data. So we do need the prospective trial you mention.
“But, the other thing that blows my mind every time I see these data is 49% of people getting a mechanical bowel prep without oral antibiotics, which has conclusively been shown to be useless for anything but torture of the patient.”
Significant variability in the use of bowel preparation exists within the surgical community, with a recent survey of colorectal surgeons revealing that 76% routinely used MBP and only 36% routinely used oral antibiotics, Dr. Koller observed.
In the current analysis, just 3.3% of patients received OA, 30.4% OA plus MBP, 40.8% MBP, and 25.5% no bowel preparation.
Physicians have been slow to abandon MBP, despite multiple studies showing that MBP alone does not reduce SSIs in elective colon and rectal surgery. There also have been reports of higher rates of anastomotic leak, increased cardiac or metabolic complications, and a slower return of bowel function with MBP.
Several studies, including a recent Cochrane Database Review, have shown that oral or intravenous antibiotic prophylaxis reduces surgical wound infection after colorectal surgery. The comparison groups are not uniform across the studies, however, and the controversy persists as to which type of bowel prep best reduces SSI after colorectal surgery, she said.
To explore this issue, the investigators identified all patients who underwent elective, nonemergent colorectal resections in both the ACS NSQIP Participant Use Data File (PUF) and the Procedure Targeted PUF for colectomy from 2012 to 2013. The cohort included 19,372 patients with complete preoperative bowel preparation data. Patients who were ventilator dependent or had infections or open wounds at the time of surgery were excluded.
The overall rates of any SSI, wound SSI (superficial and/or deep), and organ space SSI were 9.5%, 6.4%, and 3.5%, respectively.
With regard to adverse outcomes cited in previous studies, only OA plus MBP was shown to independently reduce anastomotic leak (OR, 0.57; 95% CI, 0.42-0.78) and postoperative ileus (OR, 0.79; 95% CI, 0.68-0.92), compared with no bowel prep, Dr. Koller reported.
Both OA and OA plus MBP, however, decreased length of stay by 0.83 days.
None of the bowel preparations were independently associated with increased rates of cardiac or renal complications, she said.
The investigators were not able to track rates of Clostridium difficile colitis after administration of the oral antibiotics. Dr. Koller acknowledged this is a concern when using oral antibiotics and may contribute to why they aren’t used frequently.
Dr. Koller reported having no conflicts of interest. A coauthor disclosed consulting for Intuitive Surgical.