Glycated Haemoglobin (HbA1C) in Cardiac Surgery: A Narrative Review

Background: Perioperative dysglycaemia in cardiac surgery is associated with poor outcomes. Glycaemic variability rather than glucose levels is a predictor of the length of an ICU stay, a rise in creatinine and acute kidney injury after cardiac surgery. Glycated haemoglobin (HbA1C) values correspond closely to average blood glucose levels and cut-off values can be used to define a diabetic and pre-diabetic status. These have been correlated with perioperative events. Methods: In this narrative review, MEDLINE (via PubMed) and the Cochrane Library were used to search for the effects of different preoperative HbA1C levels on the postoperative outcomes after cardiac surgery. HbA1C values correspond closely with average blood glucose levels and cut-off values can be used to define a diabetic and pre-diabetic status; these have been correlated with perioperative events. This narrative review discusses the role of HbA1C in cardiac surgery. Discussion: The scientific data show controversial results: some systematic reviews and randomised control trials demonstrated that a high level of HbA1C seems to be an indicator for postoperative complications in cardiac surgery; other studies dissented and reported that mortality and morbidity cannot be directly attributed to HbA1c levels. Conclusions: The scientific community seems to be in general agreement that high levels of HbA1C are prognostic markers of adverse outcomes post cardiac surgery, but it has also been proved that there could be multiple underlying factors contributing to them.