MONDAY, Oct. 18, 2010 (HealthDay News) -- People with diabetes who had normal blood sugar levels before non-heart surgery had a higher risk of death in the year following surgery compared to people without diabetes, researchers have found.
And, patients who hadn't been diagnosed with diabetes but had high blood sugar readings before surgery had a higher risk of death in the year after a surgical procedure compared to people with lower blood sugar readings, they noted.
"When we looked at blood sugar levels and the likelihood of complications after surgery, we didn't see a significant difference between diabetics and non-diabetics. But, when we looked at the long-term outcomes, we found significant differences between diabetics and non-diabetics," said Dr. Basem Abdelmalak, director of anesthesia for bronchoscopic surgery at the Cleveland Clinic in Ohio.
Findings from the study were scheduled to be presented Monday at the Anesthesiology 2010 meeting in San Diego.
The researchers collected information from one preoperative blood test to assess fasting blood sugar levels before 61,536 non-cardiac surgeries. Abdelmalak said the surgeries were varied, and included all surgeries that weren't related to the heart.
From this large sample, about 16 percent of the surgical patients had either type 1 or type 2 diabetes.
The average age of the patient population overall was 57, according to Abdelmalak. The average age of the non-diabetic patient was 56, and the diabetic group was slightly older, with an average age of 63, he said.
The researchers compared the one preoperative blood sugar reading to short- and long-term postoperative complications and death.
The investigators found that people with diabetes had between an 8 percent and 11 percent risk of dying in the year following surgery. But those with lower blood sugar levels before surgery -- in the range of about 60 milligrams to 90 milligrams per deciliter (mg/dL), according to Abdelmalak -- had a risk of death between 10 percent and 18 percent.
In people without diabetes, another interesting relationship emerged. Those with a blood sugar level of more than 200 mg/dL had more than an 11 percent risk of death in the year after surgery compared to just 3 percent to 5 percent for non-diabetics with lower blood sugar levels.
Abdelmalak said that one reason the non-diabetics with high blood sugar levels had an increased risk of death might be because they have undiagnosed diabetes. Diabetes, especially type 2 diabetes, can go unrecognized for long periods, but at the same time is still causing damage to the body. So, these people may have already been at a higher risk from complications related to undiagnosed diabetes.
As for the finding that people with a low blood sugar level are more likely to die in the year after surgery, Abdelmalak hypothesized that the body may get used to living with higher blood sugar levels -- in essence, resetting the body's metabolism. If you then try to maintain "normal" blood sugar levels, these may then be too low for you.
"We are still looking for the best way to give advice for managing diabetes during surgery. We're hoping that this study will stimulate further research, and that hopefully, we'll reach agreement on what is the better, or even optimal level of blood glucose," said Abdelmalak.
"We have abundant data that achieving good blood sugars without causing hypoglycemia has many benefits that are still worth striving for," explained Dr. Richard Bergenstal, president of medicine and science for the American Diabetes Association.
"Initially, it seemed that the lower the blood sugars could be recommended for everybody. But, now it looks as if we might need to individualize target blood sugars. However, we are still trying to sort out what are the right targets for which patients," said Bergenstal.
In the meantime, both experts suggested that people who haven't been diagnosed with diabetes, but who have high blood sugar levels before surgery, may need to be followed more closely after surgery since they have a higher risk of death. And, the same holds true for people with diabetes who have lower blood sugar levels.
To learn more about managing diabetes well, visit the U.S. National Diabetes Education Program.