Patients scheduled to undergo ambulatory surgery are usually made non per os (NPO) at
midnight on the day prior to surgery. In the case of patients with type 2 diabetic mellitus
(DM) on treatment with oral hypoglycemic agent (OHA), patients are instructed to temporarily
discontinue treatment on the day prior to surgery. This advice is based on the concern for
intraoperative and postoperative hypoglycemia in this group of patients. Metformin , a
dimethylbiguanide, is widely used as an oral antihyperglycemic drug in the long term
treatment of type 2 DM. This instruction to withhold treatment may be imprudent given that
metformin by virtue of its mechanism of action does not cause hypoglycemia. Another concern
often cited as a reason to withhold metformin is the reported adverse effect of lactic
acidosis. However, a recent metanalysis by the Cochrane group found no cases of fatal or
nonfatal lactic acidosis in 70,490 patient-years of metformin use, or in 55,451 patient-years
for those not on metformin. Furthermore, discontinuing OHA treatment can result in disruption
of established glycemic control and intraoperative and postoperative hyperglycemia all of
which can be deleterious to the patient.
We hypothesize that uninterrupted treatment with OHA in type 2 DM patients undergoing
ambulatory surgery will not result in intraoperative and postoperative hypoglycemia (defined
as blood glucose < 60mg/dl) compared to patients withholding OHA treatment on the day of
surgery.