Conventional Glycaemic Control May Not Be Beneficial in Diabetic Patients Following Cardiac Surgery

Introduction Stress hyperglycaemia is common following cardiac surgery. Its optimal management is uncertain and emerging literature suggests that flexible glycaemic control in diabetic patients may be preferable. This study aims to assess the relationship between maximal postoperative in-hospital blood glucose levels (BSL) and the morbidity and mortality outcomes of diabetic and non-diabetic cardiac surgery patients. Methods A retrospective cohort analysis of all patients undergoing cardiac surgery at a tertiary single centre institution from 2015 to 2019 was undertaken. Early management and outcomes of hyperglycaemia following cardiac surgery were assessed via multivariable regression modelling. Follow-up was assessed to 1 year postoperatively. Results Consecutive non-diabetic patients (n=1,050) and diabetic patients (n=689) post cardiac surgery were included. Diabetics with peak BSL <= 13.9 mmol/L did not have an increased risk of morbidity or mortality compared to non-diabetics with peak BSL <= 10.0 mmol/L. In non-diabetics, stress hyperglycaemia with peak BSL >10.0 mmol/L was associated with overall wound complications (5.7% vs 8.8%, OR 1.64 [1.00-2.69], p=0.049) and postoperative pneumonia (2.7% vs 7.3%, OR 2.35 [1.26-4.38], p=0.007). Diabetic patients with postoperative peak BSL >13.9 mmol/L were at an increased risk of overall wound complication (7.4% vs 14.8%, OR 2.47 [1.46-4.16], p,0.001), graft harvest site infection (3.7% vs 11.8%, OR 3.75 [1.92-7.30], p,0.001), and wound-related readmission (3.1% vs 8.8%, OR 3.11 [1.49-6.47], p=0.002) when compared to diabetics with peak BSL <= 13.9 mmol/L. Conclusion In non-diabetics, stress hyperglycaemia with peak BSL >10.0 mmol/L is associated with morbidity. In diabetic patients, hyperglycaemia with peak BSL <= 13.9 mmol/L was not associated with an increased risk of morbidity or mortality compared to non-diabetics with peak BSL <= 10.0 mmol/L. Further investigation of flexible glycaemic targets (target BSL <= 13.9 mmol/L) in diabetic patients is warranted.