Summary

A Clinical Practice Improvement study was conducted at a hospital in the Rocky Mountain West to determine the optimal administration time for prophylactic antibiotics to prevent surgical wound infection.  Data were collected on 2,847 surgical patients who received prophylactic antibiotics.  Results show that patients who received prophylactic antibiotics within two hours before surgical incision had the lowest rate of subsequent surgical wound infections; patients who received prophylactic antibiotics either before or after such a two-hour window had higher infection rates.

Primary Objective

Determine the optimal administration time for prophylactic antibiotics to prevent surgical wound infection.

1.         Data were collected on 2,847 surgical patients who received prophylactic antibiotics.

2.         Of these patients, 1,708 received them preoperatively (within two hours before surgical incision), 369 received them early (more than two but less than 24 hours before incision), 488 received them post-operatively (more than three but less than 24 hours after incision), and 282 received them perioperatively (during the three hours after incision.) 

3.      Stepwise logistic regression analysis was performed on all data.

Results

1.      The 1,708 surgical patients who received prophylactic antibiotics preoperatively had the lowest rate of subsequent surgical wound infections (0.6%), the 369 patients who received them early had the highest rate of such infections (3.8%), the 488 who received them post-operatively had the next highest rate of such infections (3.3%), and the 282 who received them perioperatively had the next lowest rate of such infections (1.4%).

2.      The rate of surgical wound infection increased with each hour that passed after surgical incision, until prophylactic antibiotics were administered.

3.      When the study was first conducted, the rate of preoperative administration of prophylactic antibiotics was found to be 60%.  Four years after the results of the first study were reported, the study was repeated, and the rate of administration was found to be 96%.

4.      The overall surgical wound infection rate fell from 1.8% during the first study to 0.9% in the year immediately following the first study.

Impact

If the overall surgical wound infection rate had remained at its first study level, more than 50 additional patients would have developed surgical wound infections in the year of the second study. The estimated additional cost for diagnosis and treatment of these 50 patients would have been $250,000, not including post-hospitalization costs (New England J. Medicine, 326, January 30, 1992:281-286).