The widespread practice of aggressively controlling blood sugar levels in intensive care unit patients may be helping kill some patients, researchers reported on Tuesday.

Medicating patients to bring down their blood sugar levels may raise the overall death rate by 10 percent, the researchers reported in the New England Journal of Medicine.

"Our results should be incorporated into practice guidelines as a matter of urgency," Dr. John Myburgh of the George Institute for International Health in Sydney, Australia, who led the study, said in a telephone interview.

"There's been debate for many years as to what level of control is appropriate. What we have done is to determine that a very low level is, in fact, harmful."

The researchers in the NICE-SUGAR study estimated that for every 38 ICU patients aggressively treated for high blood sugar, one would die.

In general, doctors believe that tight blood sugar control is beneficial. Among diabetics, it reduces the risk of kidney disease, blindness and other complications. But the question is more complicated for critically ill patients, who often only develop high blood sugar under the stress of their illness.

Hospitalized patients with high blood sugar levels tend to fare worse than other patients.

But it was never clear if the high blood sugar levels, called glycemia, were a symptom or a cause of the most dangerous conditions, wrote Silvio Inzucchi and Mark Siegel of the Yale University School of Medicine in Connecticut in a commentary on the findings.

STRESS RESPONSE

Myburgh believes they are a symptom. "High blood sugar levels are a common phenomenon in sick people. It is part of the normal response to stress and illness," he said.

Myburgh said the new study, involving 6,104 people in Australia, New Zealand, Canada and the United States, only 20 percent of whom had a history of any type of diabetes, is the largest to look at high blood sugar in acutely ill patients, and should make it clear that doctors need to be less extreme.

Ninety days after being admitted into intensive care, 27.5 percent of those whose sugar levels were kept below 108 milligrams per deciliter of blood had died, compared to 24.9 percent whose sugar levels were kept under 180. The group with tighter glucose controls suffered more fatal heart attacks.

In addition, dangerously low blood sugar was seen in 6.8 percent of the patients who received aggressive treatment, compared to 0.5 percent for those who had less aggressive control. Both groups had their glucose levels controlled with intravenous insulin.

Inzucchi and Siegel said doctors should still control blood sugar in their ICU patients. However, "there is no additional benefit from the lower of blood glucose levels below the range of approximately 140 to 180," they said.

The concept of tight control over diabetes is being revised as new studies suggest that it may not be as beneficial for some people as once believed.

Last year, the so-called ACCORD study of adult-onset diabetics with a high risk of heart disease found that lowering their blood sugar to levels regarded as normal did not prevent heart attacks and strokes.

In fact, people whose blood sugar levels were brought down to the lowest level were more likely to die if they did have a heart attack.