SAN FRANCISCO – Oral antibiotics with mechanical bowel preparation significantly reduce surgical site infections, length of hospital stay, and readmissions in both open and laparoscopic elective colorectal surgery, according to a review of 8,415 cases in the National Surgery Quality Improvement Program.
It “should be adopted for elective colorectal surgery,” concluded the investigators, led by colorectal surgeon Melanie Morris of the University of Alabama at Birmingham.
A quarter of the patients had no bowel prep, 45% had mechanical prep alone – GoLytely or another laxative, and 30% received both oral antibiotics and mechanical prep. Partial colectomy and sigmoid resections were the most common procedures, generally for neoplasms or diverticulitis.
Overall, 15% of the no-prep group, 12% of the mechanical prep group, and 6.5% of the oral antibiotic plus mechanical prep group developed subsequent surgical site infections (SSIs), a statistically significant difference. Results were similar when broken down into superficial, deep wound, and organ space infections (J. Am. Coll. Surg. 2014:219;S18-19).
On multivariate analysis and after adjusting for diabetes, smoking, age, and other potential confounders, the antibiotic group was 54% less likely than the no-prep group to develop an SSI (odds ratio 0.46), 26% less likely to be readmitted (OR 0.74), and more likely to leave the hospital earlier, at about 4 days instead of 5 (OR 0.90). SSIs and readmissions were only slightly less likely in the mechanical prep–only group, compared with the no-prep group, and there was no difference in length of stay.
There were fewer anastomotic leaks, fewer cases of sepsis, less significant bleeding, and other benefits for oral antibiotics with mechanical preparation. In addition, there was a protective effect against 30-day mortality in open procedures.
“Even in the minimally invasive group,” about two-thirds of patients, “oral antibiotic prep … was protective for surgical site infections,” Dr. Morris said at the annual clinical congress of the American College of Surgeons.
Still, bowel prep remains “a very controversial topic.” Nationwide some surgeons prep, some don’t. “People have very strong beliefs that may or may not be rooted in the data,” she said.
There are concerns about fluid and electrolyte disturbances, Clostridium difficile overgrowth, and other potential problems. Plus, mechanical preparation hasn’t worked any better than placebo in recent studies, but many of those studies didn’t include oral antibiotics. Effective bowel prep includes both, Dr. Morris said.
It’s possible that confounders might have been at work in the Alabama study. Perhaps surgeons shied away from bowel prep in older, sicker patients, but the rate of acute renal injury was the same in all three study groups at about 0.9%, suggesting similar background comorbidities.
“I don’t think confounding issues” explain the findings. Previously, “we’ve shown the benefit of oral antibiotic bowel prep in a [Veterans Affairs] cohort, and now we’ve shown it in this national cohort,” Dr. Morris said (Dis. Colon. Rectum 2012;55:1160-6).
After a marked reduction in surgical site infections in the VA study, “we changed our practices. We now do mechanical and oral antibiotic preps and have seen a 50% reduction in our SSI rate. We don’t feel like we are doing anything else differently,” she said.
Dr. Morris has no disclosures.