Preop Glycemic Control Decreases Infection Risk


Diabetic patients with good preoperative glycemic control had significantly fewer postoperative infections in a retrospective analysis of data from the Veterans Affairs National Surgical Quality Improvement Program.

“If the association is confirmed in other studies, strategies to improve glycemic control prior to elective surgery can be employed to decrease infections and improve overall outcomes for diabetic surgical patients,” wrote Dr. Annika S. Dronge of Yale University, New Haven, Conn., and her colleagues.

The study included 490 diabetic surgery patients from the National Surgical Quality Improvement Program database, which prospectively collects preoperative, intraoperative, and 30-day outcomes on major noncardiac operations. All patients had a hemoglobin A1c (HbA1c) level recorded within 180 days prior to the surgery, with good glucose control defined as a level of less than 7%. The primary outcome of the study was postoperative infectious complications, including pneumonia, wound infection, urinary tract infection, and sepsis (Arch. Surg. 2006;141:375–80).

After adjusting for several factors known to be associated with postoperative infections, the researchers found that good long-term glycemic control was strongly associated with significantly fewer postoperative infections (odds ratio 2.13). Age, American Society of Anesthesiologists score, operation length, and wound class were also significantly associated with the risk of postoperative infection.

The authors noted that while long-term glycemic control in diabetic patients is widely recognized as decreasing both the incidence and severity of many chronic complications, only three studies have investigated its effect on postoperative infections. Two of these studies had opposite findings, but both used an HbA1c level of 11.5% as the point between what they defined as good and poor glycemic control, a definition not consistent with current recommendations (J. Urol. 1992;147:386–8; J. Urol. 1998;159:1537–9). The third study used an HbA1c level of 8% and showed twice as many postoperative infections in patients with high levels, compared with those with low levels (8% vs. 4%), although this did not reach statistical significance (Infect. Control Hosp. Epidemiol. 2001;22:607–12). However, a highly significant finding of this study was the increased incidence of postoperative hyperglycemia in the poorly controlled group, compared with the well-controlled group (78% vs. 43%).

The reason for the current study's finding of decreased postsurgical infection in association with good preoperative glycemic control could be linked simply to the better likelihood of postoperative glycemic control, as demonstrated by the third study, noted the authors. “Acute hyperglycemia has clearly been shown to be associated with poor outcome in a variety of clinical settings. … Tight control of glucose in the postoperative period results in fewer complications, including infections, and decreased mortality in both diabetic and nondiabetic patients,” they wrote.

Another possible explanation for their findings is simply “the overall improvement in general health and metabolic milieu of the well-controlled diabetic patient.”

They noted limitations of their study, including the fact that all subjects came from a single Veterans Affairs hospital and were predominantly male, making generalizability to a larger diabetic population more difficult. Additionally, the database they used did not control for factors such as smoking, nutritional status, and perioperative antibiotic use.