Continuation of Metformin Till Night Before Surgery and Lactate Levels in Patients Undergoing Coronary Artery Bypass Graft Surgery

Tarannum Bano; Sunil Kumar Mishra; Mohammad Shafi Kuchay; Yatin Mehta; Naresh Trehan; Pooja Sharma; Manish Kumar Singh; Ambrish Mithal

doi:10.4103/ijem.IJEM_114_19

Continuation of Metformin Till Night Before Surgery and Lactate Levels in Patients Undergoing Coronary Artery Bypass Graft Surgery

Indian J Endocrinol Metab. 2019 Jul-Aug;23(4):416-421. doi: 10.4103/ijem.IJEM_114_19.

Authors

Tarannum Bano¹, Sunil Kumar Mishra¹, Mohammad Shafi Kuchay¹, Yatin Mehta², Naresh Trehan³, Pooja Sharma⁴, Manish Kumar Singh⁴, Ambrish Mithal¹

Affiliations

¹ Division of Endocrinology and Diabetes, Medanta The Medicity Hospital, Gurugram, Haryana, India.
² Institute of Critical Care and Anesthesia, Medanta The Medicity Hospital, Gurugram, Haryana, India.
³ Department of Cardiothoracic and Vascular Surgery, Medanta The Medicity Hospital, Gurugram, Haryana, India.
⁴ Institute of Education and Research, Medanta The Medicity Hospital, Gurugram, Haryana, India.

Abstract

Background: Lactic acidosis is a rare but serious complication associated with metformin therapy in certain high-risk patients. NICE guidelines and the British National Formulary advise the discontinuation of metformin before surgery. The drug manufacturer's datasheet advises the withdrawal of metformin 48 h before surgery. However, the data regarding perioperative use of metformin is scarce.

Aims: To evaluate the effect of continuation of metformin till night before surgery on lactate levels in patients undergoing coronary artery bypass graft (CABG) surgery.

Materials and methods: In this prospective cohort study, 1,800 consecutive patients who underwent CABG between 1^st November 2015 and 31^st October 2016 were enrolled. Following exclusion criteria, a total of 790 subjects were included for final analysis. Three-hundred and eight seven (48.9%) patients with diabetes received metformin till night before surgery (Met group), 239 (30.3%) patients with diabetes were non-metformin users (Non-Met group), and 164 (20.8%) patients were having no diabetes (Non-Diab group). Lactate levels and arterial pH were measured using arterial blood gas machine. Postoperative morbidity outcome data were obtained by collecting clinical data, routine biochemistry, and chest imaging.

Results: The mean metformin dose was 1,124.6 mg/day (SD: 509.3; range: 500-2,500 mg/day). Mean postoperative lactate levels were 1.91 ± 0.7 in Met group, 2.04 ± 0.79 in Non-Met group, and 2.07 ± 0.78 in Non-Diab group. Lactic acidosis occurred in 41 patients and there was no difference among the groups [Met group = 18 (4.7%); Non-Met group = 14 (5.9%)]. Among secondary outcome measures, acute renal failure occurred more frequently in diabetic patients [Met group = 46 (11.9%) and Non-Met group = 32 (13.4%)] as compared with non-diabetic patients. There were no differences with regard to pneumonia, length of ICU stay, and duration of ventilatory support among the three groups.

Conclusions: Continuation of metformin till night before surgery is not associated with significant changes in lactate levels in patients undergoing CABG.

Keywords: Coronary artery bypass graft; lactate levels; lactic acidosis; metformin; type 2 diabetes.