SAN FRANCISCO – Hypoglycemic episodes were common and largely unnoticed after bariatric surgery, a controlled study of 45 patients found.
During a 3-day period of "normal living," symptomatic hypoglycemias occurred in 22% of 15 patients after gastric bypass surgery, 20% of 15 patients after biliopancreatic diversion with duodenal switch, and in none of 15 obese, nondiabetic control patients matched to the surgical patients by body mass index.
Continuous glucose monitoring showed that patients in both postsurgery groups spent significant amounts of time in hypoglycemia, Dr. Niclas Abrahamsson and his associates reported at the annual scientific session of the American Diabetes Association.
After gastric bypass, patients averaged 42 minutes per day with glucose levels lower than 3.3 mmol/L and 21 minutes per day with levels lower than 2.8 mmol/L. After duodenal switch surgery, patients averaged 85 minutes per day with glucose levels lower than 3.3 mmol/L and 39 minutes per day with levels lower than 2.8 mmol/L. No patients in the control group had glucose levels that low, reported Dr. Abrahamsson of the University of Uppsala, Sweden.
"We were very surprised that they had so many hypoglycemic episodes, especially since the controls had none," he said. Patients were unaware of approximately 80% of the hypoglycemic episodes, he added.
"The clinical significance should be that one should be alert to any hypoglycemia symptoms," Dr. Abrahamsson said.
Patients in the post–duodenal switch group had the lowest mean glucose level (4.6 mmol/L) and mean hemoglobin A1c level (29 mmol/mol), compared with the post–gastric bypass group (mean glucose 5.3 mmol/L and HbA1c 36 mmol/mol) and the control group (mean glucose 5.9 mmol/L and HbA1c 38 mmol/mol).
Glucose curves on continuous monitoring were more variable in the post–gastric bypass group, compared with controls, and less variable in the post–duodenal switch group, compared with controls. That difference between the two surgical groups probably relates to the different glucose absorption capabilities after surgery, he suggested.
Dr. Abrahamsson has been a speaker for Eli Lilly and Sanofi and has held stock in AstraZeneca.
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View on the News: Alarming findings will change practice
Dr. Thomas Barber
Dr. Thomas Barber
The finding that patients with recent duodenal switch surgery spent 85 minutes per day with hypoglycemia, compared with 42 minutes per 24 hours for patients in the gastric bypass group, is quite alarming. Although these hypoglycemias were largely unnoticed, we know that hypoglycemia can affect brain function, cognition, and motor function.
This study has safety and legal implications for things like driving and operating machinery and raises questions of how we can best manage patients in terms of mitigating the effects of hypoglycemia. I think it opens up a whole area of questions at which we need to look.The problem with continuous glucose monitoring is that it’s a research tool, but it’s not very practical to be doing in every single patient who’s had a gastric bypass surgery. The problem with doing blood glucose measurement is that it’s a snapshot and you can potentially miss hypoglycemia. So, this has a lot of clinical implications as to how we investigate such patients.
I think this study will change my practice. It has opened my eyes. I was quite shocked at the data. At my center, we don’t tend to do many duodenal switches. We do many more sleeve gastrectomies than the bypass procedures. But, certainly, following a bypass procedure, I will be much more cognizant of the potential for hypoglycemia and caution our patients regarding driving and about monitoring their sugars closely following the procedure.
Dr. Thomas Barber is an associate professor and honorary consultant endocrinologist at the University of Warwick, England. These comments are excerpted from an interview at the meeting. Dr. Barber reported having no financial disclosures.