Does Tight Blood Glucose Control during Cardiac Surgery Improve Patient Outcome?

Intensive insulin therapy to maintain normal levels of blood glucose (4.4 to 6.1 mmol/L [80 to 110 mg/dL]) during intensive care improves survival and reduces morbidity of critically ill patients after complicated, high-risk, or extensive surgery or trauma (1). Clear benefit from this intervention requires maintenance of tight blood glucose control for at least a few days (2). The mechanism by which maintaining normoglycemia prevents adverse outcomes is not fully understood. One possibility is that avoiding sustained cellular glucose overload and toxicity in certain cell types reduces the likelihood for vital organ dysfunction (3). Avoiding glucose toxicity seems to prevent damage to the mitochondrion, the organelle that generates energy for cellular functions (4).

The first observation of this clinical effect took place in a randomized trial performed in Belgium (1) in which a large number of the study patients were admitted to the intensive care unit (ICU) after high-risk cardiac surgery. These cardiac patients had a mean EuroSCORE of 6.0 and thus a high “predicted risk of death” (9.9%) (5); few were known to have diabetes before the operation. This subgroup of cardiac patients had substantially better outcomes when randomly assigned to tight blood glucose control, with an in-hospital mortality rate of 3.4% (vs.7.5% in control patients) and lower morbidity (5). These results were consistent with an observational study (6) in which patients had a history of diabetes mellitus (6). The short-term mortality rate …