[en] BACKGROUND: Dexamethasone prevents postoperative nausea and vomiting but may increase blood glucose. We compared blood glucose concentrations after dexamethasone in non-diabetic and type 2 diabetic patients undergoing surgery and looked for any association with preoperative glycosylated haemoglobin [HbA (1c)] and BMI. METHODS: Sixty three patients were enrolled: 32 were non-diabetic (Group ND) and 31 type 2 diabetic (Group D) without insulin treatment. Anaesthesia was induced using i.v. anaesthetic agents and maintained with sevoflurane. All patients received 10 mg dexamethasone at induction. Blood glucose concentrations were measured at induction and then every 60 min for 240 min. Data were analysed using anova. Effects of HbA (1c) and BMI were investigated using linear correlation and logistic regression. RESULTS: Blood glucose concentrations increased significantly over time and peaked at 120 min after 10 mg dexamethasone in both groups. The magnitude of increase was comparable between the groups [mean (SD) 29 (19) and 35 (19)% of baseline in Group D and Group ND, respectively]. Maximum concentrations were higher in Group D [8.97 (1.51) mmol litre(-1), range 6.67-12.94 mmol litre(-1)] than in Group ND [7.86 (1.00) mmol litre(-1), range 5.78-10.00 mmol litre(-1)]. There was a significant correlation between the maximum concentrations and BMI (R(2)=0.21) or HbA (1c) (R(2)=0.26). Logistic regression analysis revealed that the higher the BMI, the lower the HbA (1c) threshold associated with an increased probability (>0.5) of observing blood glucose levels higher than 8.33 mmol litre(-1) during 240 min after dexamethasone administration. Similarly, the higher the HbA (1c), the lower the BMI threshold associated with the same probability. CONCLUSIONS: After 10 mg dexamethasone, blood glucose levels increase in non-diabetic and type 2 diabetic patients undergoing abdominal surgery. Poorly controlled diabetes and severe obesity can influence the development of hyperglycaemia.