Conference Coverage

ASA: Bowel prep, oral antibiotics cut postop colorectal complications

Key clinical point: A combination of mechanical cleansing and oral antibiotics reduced major colorectal surgery complications by nearly one-half.

Major findings: Mechanical bowel preparation combined with oral antibiotics resulted in reduced colorectal surgery complications, with odds ratios of 0.43 for surgical site infections, 0.71 for ileus, and 0.56 for anastomotic leak; overall mortality was also reduced.

Data source: Retrospective multivariable analysis of data for 8,644 surgical patients undergoing elective colorectal resection in 2012; targeted colectomy data drawn from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database.

Disclosures: The authors reported no conflicts of interest.




SAN DIEGO – A combination of bowel cleansing and oral antibiotics nearly halved the risk of common and troublesome complications in colorectal surgery. Infections, leaks, and postsurgical ileus were all significantly less likely with the combined regime, according to a study reported at the annual meeting of the American Surgical Association.

Patients preparing for colorectal surgery routinely received mechanical bowel preparation in combination with oral antibiotics in the 1970s. However, since then, the availability of IV antibiotics combined with concerns about complications from bowel preparation have contributed to a decline in use of the regime. Consensus is lacking about best practices for preparation for colorectal surgery.

Dr. P. Ravi Kiran
Dr. P. Ravi Kiran

Dr. P. Ravi Kiran, chief and program director of Columbia University Medical Center’s division of colorectal surgery, presented findings from a large retrospective study that addressed whether oral antibiotics and mechanical bowel preparation reduced the risk of complications from colorectal surgery. Drawing from targeted colectomy data, available from 2012 onward through the large American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database, Dr. Kiran and associates compared three groups of patients undergoing elective colectomy. Of the total 8,644 patients, 2,498 (28.9%) received no preparation, 3,822 (44.2%) received mechanical bowel preparation alone, and 2,324 (26.9%) received both oral antibiotics and mechanical bowel preparation.

Primary outcome measures included the presence of anastomotic leak from the surgery, surgical site infections, ileus, and all-cause mortality. The patients were well matched by age and gender, and surgery type; case complexity and degree of resident physician involvement in the surgical procedures were also similar between arms.

On multivariable analysis, patients who received mechanical bowel preparation and oral antibiotics were significantly less likely to have surgical site infections (odds ratio, 0.43), to sustain ileus (OR, 0.71), or to have anastomotic leak (OR, 0.56). Postoperatively, those who had received no bowel preparation were also significantly more likely to have pneumonia, to require reintubation, and to fail to wean from the ventilator. They also were more likely to have deep vein thrombosis and sepsis. All-cause 30-day mortality was also significantly less likely in the group receiving both bowel preparation and oral antibiotics.

Dr. Kiran noted that investigators were not able to determine the type of mechanical bowel preparation patients received, and likely could not control for all confounders.

Discussant Dr. Heidi Nelson of the Mayo Clinic, Rochester, Minn., noted that despite the study’s strengths, including its large size and the real-world nature of the investigation, she doubts that the study will be considered definitive. Limitations that critics might point out, she noted, are the retrospective nature of the study and the possibility that the three groups studied were not really comparable because of subtle selection biases on the part of the treating surgeons. Dr. Kiran conceded that though multivariable analysis attempted to account and control for as many between-group differences as they could identify, differences probably did persist.

Dr. Hiram Polk of the University of Louisville (Ky.) commented that studies such as these using massive databases, though they may show what is true, may not always point to what is clinically relevant. Overall, it’s been shown that about one in four patients given systemic antibiotics are given the wrong drug, he said; further, “the only place you can truly sterilize a colon is in an autoclave.” Dr. Kiran did note that the combined oral preparation regime was successful in reducing the incidence of the most common complications by about 50%.

Following with more real-world observations, Dr. Mary Otterson of the Medical College of Wisconsin, Milwaukee, commented that the effective dose of preoperative erythromycin is very close to doses that cause significant nausea and vomiting. In her experience, “If we went any higher, they vomited. We also had unplanned admits with electrolyte abnormalities.” The best-tolerated and most effective regime, she said, should be identified by a prospective, randomized, controlled trial.

The authors reported no conflicts of interest.

The complete manuscript of this study and its presentation at the American Surgical Association’s 135th Annual Meeting, April 2015, in San Diego, California, are anticipated to be published in the Annals of Surgery pending editorial review.

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