In Type 2 Diabetics, Discontinuing Oral Hypoglycemics Pre-op Not Necessary

Although adults with type 2 diabetes mellitus who are taking oral hypoglycemic agents are instructed to discontinue their medications on the day of surgery, a study has concluded this strategy may not be necessary. A study found that perioperative blood glucose levels did not differ significantly between patients who did and did not discontinue oral hypoglycemic agents prior to surgery.

“Although patients with type 2 diabetes are ordered to discontinue their medications on the day of surgery due to concerns about perioperative hypoglycemia, such instructions can also lead to perioperative hyperglycemia or interrupt long-term blood glucose control,” said Eric B. Rosero, MD, an assistant professor of anesthesiology and pain management at UT Southwestern Medical Center, in Dallas. “We hypothesized that uninterrupted perioperative treatment with oral hyperglycemic medications will result in improved blood glucose control—but not hyperglycemic episodes—in these patients.”

The researchers enrolled 160 patients into the trial; each was scheduled for elective ambulatory surgery, had an established diagnosis of type 2 diabetes mellitus and was being treated with oral hypoglycemic drugs. Participants were excluded if they were on insulin treatment of any kind.

Reporting at the 2017 annual meeting of the American Society of Anesthesiologists (abstract A1096) on behalf of lead author Irina Gasanova, MD, PhD, Dr. Rosero said 67 participants received oral hypoglycemic agents, of whom 43 were taking metformin and 24 metformin-sulphonylurea. Of the 90 patients whose medications were held, 55 were taking metformin and 35 a metformin-sulphonylurea combination. No patient in either group was taking sulphonylurea alone.

Interestingly, preoperative blood glucose was found to be significantly lower in patients who continued their medications (median, 122.0 mg/dL; interquartile range [IQR], 111.0-151.0 mg/dL) than in those who held theirs (median, 142.0 mg/dL; IQR, 117.0-176.0 mg/dL) (P=0.007). Despite these initial differences, the median blood glucose level intraoperatively (131.5 vs. 140.5 mg/dL; P=0.25) and postoperatively (148.5 vs. 154.5 mg/dL; P=0.634) did not differ significantly between groups. Perioperative hypoglycemia did not occur in either group. Conversely, preoperative hyperglycemia occurred in 13.4% of patients who continued their medications and 25.6% of those who stopped their medications, but the difference was not significant (P=0.07). “With a larger sample size, these results likely would have been significant,” Dr. Rosero said.

The investigators also performed a subgroup analysis of patients who had an HbA_1c value of at least 7% or less than 7%. “This revealed that in patients with good long-term blood glucose control [HbA_1c <7%], there were no intraoperative or postoperative differences in blood sugar levels, whether they continued their medications or stopped their medications,” Dr. Rosero said. By comparison, patients with an HbA_1c value of at least 7% who continued their medications had significantly lower preoperative blood glucose levels (median, 128.0 mg/dL; IQR, 104.0-165.0 mg/dL) than those who stopped their medications (median, 158.5 mg/dL; IQR, 134.0-201.5 mg/dL) (P=0.004).

“This analysis also demonstrated that patients with poor preoperative glucose control [HbA_1c≥7%] had higher intraoperative glucose values than did those with good preoperative glucose control [HbA_1c <7%], whether or not they stopped their medications preoperatively,” he added.

“Given these findings, the study concluded that patients with type 2 diabetes undergoing ambulatory surgery can safely continue their oral hypoglycemic medications in the perioperative period,” Dr. Rosero said.

Proof Not All In

Despite these results, not all audience members seemed convinced that continuing hypoglycemic medications is the best strategy. “I think timing is important,” said Mary Ann Vann, MD, an assistant professor of anesthesia at Harvard Medical School, in Boston. “Personally, I would only ask the patient to hold their oral hypoglycemics from the time they come to the hospital until they return home. So it’s only a couple of hours, and I don’t think that short window will disturb their control.”

“This is the first study that has randomized patients to continue or discontinue their oral hypoglycemics,” said co-investigator Girish P. Joshi, MD, a professor of anesthesiology and pain management at UT Southwestern Medical School, in Dallas. “It seems clinicians’ biggest concern is hypoglycemia, and the [Society for Ambulatory Anesthesia] guidelines published in 2010, recommend that we continue metformin until the day of surgery. So although the sample size here is relatively small, it seems that you can continue to take it safely, and that’s our practice right now; we continue our patients on their oral hypoglycemics.”

“I don’t disagree with that; I just don’t want to say that we’ve proven it,” Dr. Vann replied. “I would emphasize that this study only looked at patients taking these two drugs, and cannot be extrapolated to all type 2 diabetes medications. Nevertheless, I think this is a good start.”

“The other concern with asking patients to discontinue their medications is that we don’t know what happens once they leave the hospital,” Dr. Joshi added. “We hope that they start taking their oral hypoglycemics again, but they don’t always do that. So by having them continue uninterrupted, we are avoiding that possible confusion.”

—Michael Vlessides