Low blood sugar danger for critically ill

By Eleanor McDermid, Senior medwireNews Reporter

Further analysis of the NICE-SUGAR trial shows a dose-response relationship between the degree of hypoglycemia and the risk for death in critically ill patients.

Simon Finfer (George Institute for Global Health, Sydney, Australia) and team assessed blood sugar levels for 6026 patients enrolled in the NICE-SUGAR (Normoglycemia in Intensive Care Evaluation‑Survival Using Glucose Algorithm Regulation) trial.

In all, 223 developed severe hypoglycemia (≤40 mg/dL; 2.2 mmol/L) and 35.4% of this group died. Almost all patients who developed severe hypoglycemia had been randomly assigned to receive intensive glucose control (target range 81-108 mg/dL; 4.5-6.0 mmol/L).

By contrast, 28.5% of 2714 patients with moderate hypoglycemia (41-70 mg/dL; 2.3-3.9 mmol/L) died, as did 23.5% of 3089 patients who maintained normoglycemia.

After adjustment for baseline and postrandomization variables, the risk for death was increased 1.41-fold among patients with moderate hypoglycemia and 2.10-fold among those with severe hypoglycemia, relative to those with normoglycemia. The findings did not differ according to whether patients had received intensive or conventional glucose control.

The risk for death was present if patients had hypoglycemia on just 1 day, but was stronger if they experienced it on more than 1 day. It was further increased if patients were not receiving insulin at the time of the episode.

In an editorial accompanying the paper in The New England Journal of Medicine, Irl Hirsch (University of Washington School of Medicine, Seattle, USA) says: "These observations raise the most obvious question - is hypoglycemia simply a biomarker for severe underlying disease? The NICE-SUGAR study does not presume to answer this question, nor can it support a causal relationship between hypoglycemia and death."

He also notes that although blood sugar was measured about every 2.5 hours, and hourly for patients taking insulin, blood sugar levels can change very rapidly, so the reported frequency of hypoglycemia may not be accurate.

"Although it is tempting to criticize the NICE-SUGAR [intensive care unit] teams for inadequate monitoring of glucose levels, it is difficult to imagine many hospitals doing better," he comments.

Hirsch says that more advanced monitoring technology is needed, to pin down hypoglycemia and make insulin use safer. But in the meantime, he says: "In many hospitals, maintaining blood glucose at levels similar to those in the conventional-control group of the NICE-SUGAR population is safe and similar to other recommendations. The use of more conservative glucose targets is unacceptable, and older, nonchalant attitudes need to be abandoned."

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