Postoperative dysglycemia in elective non-diabetic surgical patients: a prospective observational study

Elevated glycosylated hemoglobin (HbA1c) is often found in surgical patients with no history of diabetes. The purpose of this prospective observational study was to determine if elevated preoperative HbA1c is associated with postoperative hyperglycemia in non-diabetic surgical patients and to identify predictors of elevated HbA1c.

This study included 257 non-diabetic adults scheduled for inpatient surgery. Preoperatively, capillary blood glucose (CBG) and HbA1c were measured and patients completed the Canadian Diabetes Risk Questionnaire (CANRISK). Capillary blood glucose was measured for two days or until hospital discharge at the following time points: postoperatively, before all meals, and at 22:00 hr. The mean CBG and incidence of hyperglycemia were compared between HbA1c levels: Group I < 6.0%, Group II 6.0-6.4%, and Group III ≥ 6.5%.

The mean postoperative glucose levels at all time points were significantly higher in Group III compared with Groups I and II (P < 0.01). At least one episode of hyperglycemia (CBG ≥ 10.0 mMol·L^-1) occurred in 61% (11/18) of patients in Group III vs 11% (23/209) of patients in Group I (relative risk, 5.55; 95% confidence interval [CI], 3.26 to 9.47; P < 0.001). Elevated glycosylated hemoglobin ≥ 6.0% was found in 31% (33/107) of those with a high CANRISK score. The best predictors of postoperative hyperglycemia were preoperative CBG > 6.9 mMol·L^-1 [diagnostic odds ratio (OR) (reference < 6.0 mMol·L^-1), 4.16; 95% CI, 1.57 to 10.98; P = 0.004], HbA1c ≥ 6.0% [OR (reference < 6.0%), 3.00; 95% CI, 1.39 to 6.49; P = 0.005], and HbA1c ≥ 6.5% [OR (reference < 6.5%), 13.45; 95% CI, 4.78 to 37.84; P <0.001].

Elevated HbA1c is associated with higher mean postoperative glucose levels in patients with no diabetic history. The CANRISK score is a strong predictor of elevated HbA1c, while CBG and HbA1c are both predictors of postoperative hyperglycemia.