High mean fasting glucose levels independently predict poor outcome and delayed cerebral ischaemia after aneurysmal subarachnoid haemorrhage

Background: Hyperglycaemia has been related to poor outcome and delayed cerebral ischaemia (DCI) after aneurysmal subarachnoid haemorrhage (aSAH). Objective: This study aimed to assess whether in patients with aSAH, levels of mean fasting glucose within the first week predict poor outcome and DCI better than single admission glucose levels alone. Methods: Data on non-diabetic patients admitted within 48 h after aSAH with at least two fasting glucose assessments in the first week were retrieved from a prospective database (n=265). The association of admission glucose or mean fasting glucose, dichotomised at the median levels, with outcome was assessed using logistic regression, and for DCI using Cox regression. To explore whether the association between glucose levels and outcome was mediated by DCI, we adjusted for DCI. Results: The crude and multivariable adjusted odds ratios and 95% confidence intervals for poor outcome were 1.9 (1.1 to 3.2) and 1.6 (0.9 to 2.7) for high admission glucose and 3.5 (2.0 to 6.1) and 2.5 (1.4 to 4.6) for high mean fasting glucose. The crude and adjusted hazard ratios for DCI were 1.7 (1.1 to 2.5) and 1.4 (0.9 to 2.1) for high admission glucose and 2.0 (1.3 to 3.0) and 1.7 (1.1 to 2.7) for high mean fasting glucose. After adjusting for DCI, the odds ratios on poor outcome for high mean fasting glucose decreased only marginally. Conclusions: Compared with high admission glucose, high mean fasting glucose, representing impaired glucose metabolism, is a better and independent predictor of poor outcome and DCI. DCI is not the key determinant in the relationship between high fasting glucose and poor outcome.