Peri‐operative continuation of metformin does not improve glycaemic control in patients with type 2 diabetes: A randomized controlled trial

Abstract

Historically, metformin was withheld before surgery for fear of metformin-associated lactic acidosis. Currently, however, this risk is deemed to be low and guidelines have moved towards the continuation of metformin. We hypothesized that continuing metformin peri-operatively would lower postoperative serum glucose level without an effect on plasma lactate levels. We performed a single-blind multicentre randomized controlled trial in people with type 2 diabetes mellitus scheduled for non-cardiac surgery and continued (MF+ group) or withheld (MF- group) metformin before surgery. The main outcome measures were the differences in peri-operative plasma glucose and lactate levels. We randomized 70 patients (37 MF+ group and 33 MF- group) with type 2 diabetes mellitus. Postoperative glucose levels were similar in the MF+ and the MF- groups (8.2 ± 1.8 vs 8.3 ± 2.3 mmol/L P = .95) Although preoperative lactate levels were slightly higher in the MF+ group compared with the MF- group (1.5 vs 1.2 mmol/L; P = .02), the postoperative lactate levels were not significantly different (1.2 vs 1.0 mmol/L; P = .18). In conclusion, continuation of metformin during elective non-cardiac surgery does not improve glucose control or raise lactate levels to a clinically relevant degree.

Metformin for the management of peri‐operative hyperglycaemia

“…20,21 The safety profile of metformin is further supported by a subsequent Cochrane review that found no clear association between the use of metformin and an increase in the development of lactic acidosis. 20 It was reassuring to see that no significant changes in lactate were observed by Hulst et al 9 and is consistent with previous reports. 14,15 Thus, the continuation of metformin peri-operatively appears to be both a viable and safe intervention.…”

“…Taken together, the potential benefits of metformin on peri‐operative glycaemic control in patients undergoing non‐cardiac surgery should not yet be discounted. Although the trial by Hulst et al failed to detect any changes in glucose control, this was not an unexpected result given the large number of patients in the study who underwent metabolic surgery, which could have significantly confounded the results. If the metformin and control groups were not balanced in terms of the number of patients who underwent metabolic surgery, this would also have had an impact on the glycaemic outcomes.…”

In response to: Metformin for the management of peri‐operative hyperglycaemia

“…While continuation of metformin during this period is considered to be safe, there was little evidence of benefit in doing so, and therefore, we designed the respective randomized controlled trial. 1 As pointed out by Dr Brown and Dr Paul, a possible limitation of our study is the high proportion of cases of bariatric surgery (46%) included. They suggest that early metabolic changes, observed after bariatric surgery independently of weight loss, may have had an impact on our results.…”

“…We thank Dr Brown and Dr Paul for their insightful commentary on our study and the subject of perioperative continuation of metformin, stressing again the importance of perioperative hyperglycaemia and treatment of diabetes mellitus (DM). The mentioned guidelines indeed suggest considering continuation of metformin in the perioperative period, despite previous concerns about metformin‐associated lactic acidosis.…”

“…The mentioned guidelines indeed suggest considering continuation of metformin in the perioperative period, despite previous concerns about metformin‐associated lactic acidosis. While continuation of metformin during this period is considered to be safe, there was little evidence of benefit in doing so, and therefore, we designed the respective randomized controlled trial …”