High Blood Sugar Levels Increase Infection Risk From General Surgery

TUESDAY Sept. 21, 2010 -- High blood sugar levels can increase the risk of surgical site infections in patients having general surgery, researchers report.

Doctors have long been aware that people with diabetes are more prone to surgical infections, and the relationship between high blood sugar and increased risk of infection after surgery is well known in heart and intensive care unit surgery, where blood sugar is carefully monitored. But this appears to be the first study to quantify the risk after general surgery, noted the study authors, from Albany Medical College in New York.

"We wanted to find out how much increased glucose in your blood had a role in infection in general surgery," said lead researcher Ashar Ata, from the College's Department of Surgery. "Surprisingly, we did find that by the time your glucose is higher than 140 milligrams per deciliter, the infection went from 1.8 percent to almost 10 percent."

When blood sugar levels reach that point, medical staff should intervene to control them, Ata said, adding, "We found the higher the blood glucose, starting at about 110 milligrams per deciliter, the more likely you are to have an infection."

The report is published in the September issue of the Archives of Surgery.

The procedures Ata's group looked at included appendectomy, colon surgery, hemorrhoid removal and gallbladder removal, he said. These operations all fall under the definition of general surgery.

For the study, Ata's team looked at medical records of 2,090 patients who had had general or vascular surgery between Nov. 1, 2006, and April 30, 2009.

Among these patients, the researchers studied the blood sugar levels of 1,561 patients, including those who had vascular surgery, colorectal surgery and other types of general surgery.

Of the patients, 7.42 percent developed surgical site infections, including 14.1 percent of those who underwent colorectal surgery, 10.3 percent who underwent vascular surgery and 4.3 percent who had other operations, the researchers found.

Among the well-known risk factors the researchers took into account, including age, overall health, and diabetes, none were found to be significant predictors of overall surgical site infection after adjusting for postoperative blood sugar levels, Ata's group reported.

In fact, a blood sugar level above 140 milligrams per deciliter following an operation was the only significant predictor of surgical site infection among patients who underwent colorectal surgery, the researchers found.

Among those undergoing vascular surgery, however, the length of time the operation took and diabetes were the only significant predictors of infection, not high blood sugar levels after surgery, they noted.

The reason for the association between high blood sugar levels and post-surgical infection is not clear, Ata said.

He and his group speculated that high blood sugar may increase the risk for infection by compromising the immune system, or that insulin may have anti-inflammatory and other anti-infective activities.

But it is also possible that high blood sugar is simply associated with infection risk without being a cause. Other risk factors for infection may cause high blood sugar rather than the other way round, the researchers said.

Surgical site infections make up 14 percent to 17 percent of hospital-acquired infections, which can cause serious and even life-threatening illnesses, prolong hospital stays, increase rates of patient return and drive up the use of emergency services and health-care costs. In fact, they are the third most common type of infections in health-care facilities and the most common in patients having surgery, according to the researchers.

Because this study was based on a retrospective review of patient charts, the results may not hold up, Ata said. He noted that a prospective study needs to be done, one that looks at current patients and, specifically, at their blood sugar and risk for infection.

"This study needs to be followed up by more prospective and closely monitored studies," he said.

Dr. Fahim Habib, an assistant professor of clinical surgery at the University of Miami Miller School of Medicine, said that "the problem is controlling the blood glucose so tightly while preventing the adverse effects of hypoglycemia, which is when the blood glucose level goes too low."

"We do recognize that controlling blood sugar tightly would result in better outcomes and decrease the risk of infection. However, we have to be cautious that we do it in a manner that avoids the development of hypoglycemia, because the consequences of that could outweigh any benefits that we saw from tight glycemic control," he said.

Habib thinks that hospitals need to commit, however, to a program of controlling blood sugar in surgical patients to help bring down surgical site infection rates.

"There needs to be an institutional commitment to carefully monitoring the blood glucose and recognizing the nuances that lead to hypoglycemia," so that surgery units can get the benefit of controlling high blood sugar without the risk of patients developing low blood sugar, he said.

More information

For more information on high blood sugar, visit the U.S. National Library of Medicine.

Posted: September 2010


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