Adding Oral to IV Antibiotics Likely Curbs Wound Infection in Elective Colorectal Surgery

By Marilynn Larkin

November 08, 2021

NEW YORK (Reuters Health) - In patients undergoing elective colorectal surgery, adding oral antibiotics (OAs) to intravenous (IV) antibiotics preoperatively reduced incisional surgical site infection (SSI) by more than 50% in a network meta-analysis.

"There are differences in opinions and international guidelines on whether OAs should be given preoperatively in addition to IV antibiotics as part of the bowel preparation in elective colorectal surgery," Dr. John Woodfield of the University of Otago in Dunedin, New Zealand told Reuters Health by email.

"A number of the randomized studies have compared IV antibiotics that do not have good aerobic and good anaerobic antibiotic cover against IV and OAs that, when combined, do have good aerobic and good anaerobic antibiotic cover," he said. "So we did not know if the improved outcome with OAs was due to the addition of OAs or to the overall better antibiotic cover."

"This network meta-analysis shows, for the first time, that when we summarize all the randomized controlled trial (RCT) data with good aerobic and anaerobic cover in all groups being compared, that adding OAs improved incisional SSI rates," he said. "It also shows that when we use RCT data, IV and OAs combined are as good as (and ranked first) full mechanical bowel preparation (MBP) and IV and OAs (ranked second)."

"MBP+IV+OA is widely used, but IV+OA is not," he added. "The option of IV+OA appears to combine the advantage of using OAs without the disadvantage of taking a full MBP. This option should be more widely used."

As reported in JAMA Surgery, Dr. Woodfield and colleagues analyzed data from 35 RCTs that included 8,377 patients. Treatments compared were IV antibiotics alone (33%); IV antibiotics with enema (3%); IV antibiotics with OA with or without enema (7%); MBP with IV antibiotics (32%); MBP with IV antibiotics with OA (with good IV antibiotic cover in 11% and with good overall antibiotic cover in 4%); MBP with OA (3%); and OA alone (6%).

The likelihood of incisional SSI was significantly lower for those receiving IV antibiotics with OA with or without enema (rank 1) and MBP with adequate IV antibiotics with OA (rank 2) compared with all other treatments.

The addition of OA to IV antibiotics, both with and without MBP, was associated with a reduction in incisional SSI by greater than 50%. There were minimal differences between treatments in anastomotic leak and in the secondary outcomes.

Study limitations include, among others, the small number of studies and patients included to assess the various bowel preparation options.

Dr. Olle Ljungqvist of Orebro University in Sweden, coauthor of a related editorial, commented in an email to Reuters Health, "MBP before colorectal surgery has been debated many years and the definitive answer if and how this treatment should be used is still not clear because the original studies that the meta-analysis is based on are heterogenous."

"The treatment is uncomfortable for the patient and causes several potentially unwanted effects, including disturbed fluid balance; (yet), some surgeons argue it facilitates surgery," he noted. "What has dimmed the picture about its potential value has been the use of an additional antibiotic treatment given orally on top of the standard IV antibiotics given preoperatively."

"When combining MBP with the two antibiotics, some studies report fewer postoperative infections," he said. "The current study suggests that it is the OAs alongside the IV antibiotics that have the positive effect on infections, and hence bowel preparation may not be necessary."

"What we feel is still missing is a large randomized trial that determines the effects of bowel preparation with or without OAs and of OAs alone," Dr. Ljungqvist concluded.

SOURCE: and JAMA Surgery, online October 20, 2021.