The original data file consisted of 3,588 medical records. We excluded 374 patients with multiple admissions and 30 patients aged ≥90 years. The patient population included 3,184 patients, 53.8% female and 46.2% male, with mean ± SD age 56.5 ± 16 years and BMI 27.6 ± 7.3 kg/m2, who underwent noncardiac surgical procedures. shows the clinical characteristics of study patients divided into diabetics and nondiabetic patients. A history of diabetes before admission was known in 643 patients (20.2%). Compared with subjects without a history of diabetes, patients with diabetes were older (61.2 ± 13.2 vs. 55.4 ± 15.9 years, P < 0.001), had higher BMI (29.6 ± 7.8 vs. 26.8 ± 6.9 kg/m2; P < 0.001), were more likely to be male (52.1 vs. 44.8%; P < 0.001), were of minority ethnic groups (African Americans 28.8 vs. 21.4%; P < 0.001), and were more likely to undergo high-risk surgical procedures (8.9 vs. 6%; P = 0.012).
The blood glucose level before surgery in the entire cohort was 120 ± 38 mg/dl. Of note, there were no significant differences in blood glucose concentration between patients included in and those excluded from the analysis. As expected, nondiabetic subjects had lower presurgery blood glucose levels (113 ± 28 mg/dl) than patients with a known history of diabetes (145 ± 51 mg/dl; P < 0.001). The blood glucose level on the 1st day after surgery was 155 ± 42 mg/dl in diabetic patients and 132 ± 28 mg/dl in nondiabetic subjects; both values were higher than those reported during the subsequent hospital stay (139 ± 34 and 115 ± 21 mg/dl, respectively; P < 0.01). After surgery, 40% of patients had mean blood glucose >140 mg/dl; three-fourths of these had mean blood glucose between 141 and 180 mg/dl, and the remainder had blood glucose >180 mg/dl. Clinically significant hyperglycemia (defined as blood glucose >180 mg/dl) was observed in 7.9% of patients before surgery, in 17.2% of subjects on the day of surgery, and in 9.9% of patients during the postoperative period (days 2–10).
Mortality and in-hospital complication rates in patients with and without diabetes are shown in . The overall 30-day mortality was 2.3% (72 of 3,112 patients), with a higher mortality (3.1%) observed in diabetic than in nondiabetic (2.1%) patients, but this difference did not reach statistical significance (P = 0.105). Compared with nondiabetic subjects, diabetic patients had a higher rate of complications including pneumonia (12.1 vs. 5.4%; P < 0.001), wound and skin infections (5 vs. 2.3%; P < 0.001), systemic blood infection (3.6 vs. 1.1%; P < 0.001), urinary tract infections (4.5 vs. 1.4%; P < 0.001), acute myocardial infarction (2.6 vs. 1.2%; P = 0.008), and ARF (9.6 vs. 4.8%; P < 0.001). In addition, diabetic patients had higher length LOS and ICU LOS than nondiabetic subjects (8.8 ± 10.6 vs. 7 ± 10.8 days; P < 0.001 and 2.3 ± 6.2 vs. 1.8 ± 6.5 days; P < 0.01, respectively).
Figure 1 Thirty-day mortality and in-hospital complication rates in patients with and without diabetes: blood infection (combined bacteriemia and sepsis); urinary tract infection (UTI), acute myocardial infarction (AMI), and ARF. *P < 0.001; †NS; (more ...)
The association between glucose levels before and after surgery and mortality odds ratios is shown in . We found a strong association between mortality and glucose levels both before surgery (A) and after surgery (B); however, mortality odds ratios were different between patients with and without diabetes. The risk of death increased in proportion to blood glucose levels in patients without a history of diabetes (P < 0.001), but the association of hyperglycemia and mortality was greater in patients without a history of diabetes before admission (P < 0.001 for both preoperative and postoperative blood glucose) compared with patients with known diabetes (P = 0.78 for preoperative blood glucose and P = 0.51 for postoperative blood glucose). Multivariate analysis adjusted for age, sex, race, and surgery severity showed that before surgery blood glucose may be an independent predictor of mortality with marginal significance (P = 0.063) and likewise with postoperative blood glucose concentration (P = 0.087). To investigate the effect of race on mortality and hospital complications, we included African American race in the multivariate analyses, which adjusted for age, African American race, diabetes status, interaction between African American race and diabetes, sex, severity of surgery, and presurgery blood glucose levels. We observed that African American patients were not at increased risk of mortality compared with other races (P = 0.96), but they were more likely to develop complications including pneumonia (P = 0.0075) and ARF (P = 0.0158) than non–African Americans. We observed no difference in blood glucose concentration between racial groups before or after surgery.
Figure 2 Mean blood glucose concentration before (A) and after surgery (B) and odds ratio for 30-day mortality in patients with and without diabetes. ●, all patients; ■, diabetic patients; , nondiabetic patients.
The clinical characteristics of survivors and nonsurvivors are shown in . Compared with survivors, patients who died had significantly higher blood glucose concentrations before surgery (133.4 ± 40.9 vs. 119.9 ± 37.7 mg/dl; P = 0.002) and after surgery (126.6 ± 23.7 vs. 119.7 ± 26.6 mg/dl; P < 0.001). In addition, compared with survivors, deceased patients were older (P < 0.001), the majority of them were men (P < 0.001), they had longer hospital LOS (18 ± 24 vs. 7 ± 10 days; P < 0.001), and they had higher rates of ARF (30.6 vs. 5.2%; P < 0.001) and bacteremia/sepsis (16.7 vs. 2.2%; P < 0.01). In addition, we found that age, male sex, development of hyperglycemia before or after surgery, blood infections, and acute myocardial infarction were predictors of 30-day mortality.
Clinical characteristics of survivors and nonsurvivors