Modifiable risk factors associated with deep sternal site infection after coronary artery bypass grafting

Randomized, controlled trials have shown that prophylactic antibiotics are effective in preventing surgical-wound infections. However, it is uncertain how the timing of antibiotic administration affects the risk of surgical-wound infection in actual clinical practice. We prospectively monitored the timing of antibiotic prophylaxis and studied the occurrence of surgical-wound infections in 2847 patients undergoing elective clean or "clean-contaminated" surgical procedures at a large community hospital. The administration of antibiotics 2 to 24 hours before the surgical incision was defined as early; that during the 2 hours before the incision, as preoperative; that during the 3 hours after the incision, as perioperative; and that more than 3 but less than 24 hours after the incision, as postoperative. Of the 1708 patients who received the prophylactic antibiotics preoperatively, 10 (0.6 percent) subsequently had surgical-wound infections. Of the 282 patients who received the antibiotics perioperatively, 4 (1.4 percent) had such infections (P = 0.12; relative risk as compared with the preoperatively treated group, 2.4; 95 percent confidence interval, 0.9 to 7.9). Of 488 patients who received the antibiotics postoperatively, 16 (3.3 percent) had wound infections (P less than 0.0001; relative risk, 5.8; 95 percent confidence interval, 2.6 to 12.3). Finally, of 369 patients who had antibiotics administered early, 14 (3.8 percent) had wound infections (P less than 0.0001; relative risk, 6.7; 95 percent confidence interval, 2.9 to 14.7). Stepwise logistic-regression analysis confirmed that the administration of antibiotics in the preoperative period was associated with the lowest risk of surgical-wound infection. We conclude that in surgical practice there is considerable variation in the timing of prophylactic administration of antibiotics and that administration in the two hours before surgery reduces the risk of wound infection.

Elevated blood glucose levels in the postoperative period are associated with an increased risk of deep wound infection in diabetic individuals undergoing open heart operations at Providence St. Vincent Hospital. Of 8,910 patients who underwent cardiac operations between 1987 and 1993, 1,585 (18%) were diabetic. The rate of deep sternal wound infections in diabetic patients was 1.7%, versus 0.4% for nondiabetics. Nine hundred ninety patients had their operation before implementation of the protocol and 595 after implementation. Charts of all diabetic patients were reviewed. Mean blood glucose levels were calculated from documented results of finger-stick glucometer testing. Thirty-three diabetic patients suffered 35 deep wound infections: 27 sternal (1.7%) and eight at the donor site (0.5%). Infected diabetic patients had a higher mean blood glucose level through the first 2 postoperative days than noninfected patients (208 +/- 7.1 versus 190 +/- 0.8 mg/dL; p < 0.003) and had a greater body mass index (31.5 +/- 1.4 versus 28.6 +/- 0.1 kg/m2; p < 0.05). Multivariable logistic regression showed that mean blood glucose level for the first 2 days (p = 0.002), obesity (p < 0.002), and use of the internal mammary artery (p < 0.02) were all independent predictors of deep wound infection. Institution of a protocol of postoperative continuous intravenous insulin to maintain blood glucose level less than 200 mg/dL was begun in September 1991. This protocol resulted in a decrease in blood glucose levels for the first 2 postoperative days and a concomitant decrease in the proportion of patients with deep wound infections, from 2.4% (24/990) to 1.5% (9/595) (p < 0.02). The incidence of deep wound infection in diabetic patients was reduced after implementation of a protocol to maintain mean blood glucose level less than 200 mg/dL in the immediate postoperative period.

Insulin-dependent diabetes mellitus (IDDM) and eating disorders are relatively common among young women in North America. Their coexistence could lead to poor metabolic control and an increased risk of the microvascular complications of IDDM. We studied 91 young women with IDDM at base line and four to five years later to determine the prevalence and persistence of disordered eating behavior (on the basis of self-reported eating and weight-loss practices, including the intentional omission or underdosing of insulin to control weight) and the association of such eating disorders with metabolic control, diabetic retinopathy, and urinary albumin excretion. At base line, the mean age of the young women was 15+/-2 years and the duration of diabetes was 7+/-4 years. At base line, 26 of 91 young women (29 percent) had highly or moderately disordered eating behavior, which persisted in 16 (18 percent) and improved in 10 (11 percent). Of the 65 women with normal eating behavior at base line (71 percent), 14 (15 percent) had disordered eating at follow-up. Omission or underdosing of insulin lose weight was reported by 12 of 88 young women (14 percent) at base line and 30 (34 percent) at follow-up (P=0.003). At base line, the mean (+/-SD) hemoglobin A(1c) value was higher in the group with highly disordered eating behavior (11.1+/-1.2 percent) than in the groups whose eating behavior was moderately disordered (8.9+/-1.7 percent) or nondisordered (8.7+/-1.6 percent, P<0.001). Disordered eating at base line was associated with retinopathy four years later (P=0.004), when 86 percent of the young women with highly disordered eating behavior, 43 percent of those with moderately disordered eating behavior, and 24 percent of those with nondisordered eating behavior had retinopathy. Disordered eating behavior is common and persistent in young women with IDDM and is associated with impaired metabolic control and a higher risk of diabetic retinopathy.