Metformin is not associated with lactic acidosis in patients with diabetes undergoing coronary artery bypass graft surgery: a case control study

Society for Ambulatory Anesthesia Updated Consensus Statement on Perioperative Blood Glucose Management in Adult Patients With Diabetes Mellitus Undergoing Ambulatory Surgery

This consensus statement is a comprehensive update of the 2010 Society for Ambulatory Anesthesia (SAMBA) Consensus Statement on perioperative blood glucose management in patients with diabetes mellitus (DM) undergoing ambulatory surgery. Since the original consensus guidelines in 2010, several novel therapeutic interventions have been introduced to treat DM, including new hypoglycemic agents and increasing prevalence of insulin pumps and continuous glucose monitors. The updated recommendations were developed by an expert task force under the provision of SAMBA and are based on a comprehensive review of the literature from 1980 to 2022. The task force included SAMBA members with expertise on this topic and those contributing to the primary literature regarding the management of DM in the perioperative period. The recommendations encompass preoperative evaluation of patients with DM presenting for ambulatory surgery, management of preoperative oral hypoglycemic agents and home insulins, intraoperative testing and treatment modalities, and blood glucose management in the postanesthesia care unit and transition to home after surgery. High-quality evidence pertaining to perioperative blood glucose management in patients with DM undergoing ambulatory surgery remains sparse. Recommendations are therefore based on recent guidelines and available literature, including general glucose management in patients with DM, data from inpatient surgical populations, drug pharmacology, and emerging treatment data. Areas in need of further research are also identified. Importantly, the benefits and risks of interventions and clinical practice information were considered to ensure that the recommendations maintain patient safety and are clinically valid and useful in the ambulatory setting. What Other Guidelines Are Available on This Topic? Since the publication of the SAMBA Consensus Statement for perioperative blood glucose management in the ambulatory setting in 2010, several recent guidelines have been issued by the American Diabetes Association (ADA), the American Association of Clinical Endocrinologists (AACE), the Endocrine Society, the Centre for Perioperative Care (CPOC), and the Association of Anaesthetists of Great Britain and Ireland (AAGBI) on DM care in hospitalized patients; however, none are specific to ambulatory surgery. How Does This Guideline Differ From the Previous Guidelines? Previously posed clinical questions that were outdated were revised to reflect current clinical practice. Additional questions were developed relating to the perioperative management of patients with DM to include the newer therapeutic interventions.

A comparison of postoperative blood lactate concentrations and kinetics in cardiac surgical patients being and not being administered metformin

Aim. Early discontinuation of metformin before cardiac surgery is advised by several national societies but no hard evidence exist supporting this practice. This precaution is mostly extrapolated by data on different clinical settings. The aim of this study is to investigate the impact of preoperative metformin use on lactate concentrations and lactate clearance during the first postoperative day after cardiac surgery.Methods. Among 367 consecutive patients who underwent elective on-pump cardiac surgery from January 2019 to October 2019, 109 were diabetics, 74 of which were treated with metformin. Data on lactate concentrations and clearance during the first postoperative day were prospectively collected on arrival, H6, H12 and H24 in the ICU and compared. A subgroup analysis focusing only on diabetic patients was also performed. Repeated measures multivariate analysis of variance (MANOVA) was used to investigate the data based on group, time and their interaction effects.Results. Lactate concentrations were the same for both groups upon arrival in the ICU. Interestingly, metformin users had lower lactate concentrations than non-users on the following measurements (p = 0.003 at 6 h and p = 0.01 at 24 h). No significant interaction was found between the two groups (p = 0.76). No difference was found between the two groups in terms of lactate clearance (p = 0.53). In the subgroup analysis no difference was found between metformin users and non-users neither on lactate concentrations (p = 0.61) nor on lactate clearance (p = 0.86).Conclusions. In a post cardiac surgery ICU setting, using metformin up until the night before surgery was not associated with increased postoperative lactate concentrations or impaired lactate clearance.

Preoperative Management of Endocrine, Hormonal, and Urologic Medications: Society for Perioperative Assessment and Quality Improvement (SPAQI) Consensus Statement

Perioperative medical management is challenging due to the rising complexity of patients presenting for surgical procedures. A key part of preoperative optimization is appropriate management of long-term medications, yet guidelines and consensus statements for perioperative medication management are lacking. Available resources utilize the recommendations derived from individual studies and do not include a multidisciplinary focus or formal consensus. The Society for Perioperative Assessment and Quality Improvement (SPAQI) identified a lack of authoritative clinical guidance as an opportunity to utilize its multidisciplinary membership to improve evidence-based perioperative care. SPAQI seeks to provide guidance on perioperative medication management that synthesizes available literature with expert consensus. The aim of this Consensus Statement is to provide practical guidance on the preoperative management of endocrine, hormonal, and urologic medications. A panel of experts with anesthesiology, perioperative medicine, hospital medicine, general internal medicine, and medical specialty experience was drawn together and identified the common medications in each of these categories. The authors then utilized a modified Delphi approach to critically review the literature and generate consensus recommendations.

Metformin Use Is Associated with Fewer Complications in Patients with Type-2 Diabetes Undergoing Total Knee Arthroplasty: A Propensity Score-Matched Analysis

BACKGROUND

Diabetes is a well-established risk factor for complications following total knee arthroplasty (TKA), and the incidence of type-2 diabetes is increasing. Metformin is considered first-line therapy for type-2 diabetes and has been shown to reduce all-cause mortality and to possess anti-inflammatory properties. The impact of metformin use as it relates to outcomes following TKA is unknown. The purpose of this study was to investigate this relationship.

METHODS

This is a retrospective cohort study using the Truven MarketScan database. Adult patients undergoing unilateral, primary TKA were identified. We included only patients with a preoperative diagnosis of type-2 diabetes and established 2 cohorts based on metformin status. Propensity score matching was performed to match patients who used metformin to those who did not (1-to-1). Patients were matched on factors including age, sex, insulin status, other diabetic medications, comorbidities, complexity of diabetes, and smoking status. Regression analysis was then performed on matched cohorts to examine 90-day outcomes. A subgroup analysis was performed on 1-year revision rates.

RESULTS

After matching, there were 32,186 patients in both the metformin group and the no-metformin group, resulting in a total of 64,372 included patients. Baseline characteristics were similar between groups. Regression analysis, performed on matched cohorts, demonstrated that the no-metformin group had increased odds of readmission (odds ratio [OR], 1.09 [95% confidence interval (CI), 1.04 to 1.15]; p < 0.001), emergency department presentation (OR, 1.09 [95% CI, 1.04 to 1.14]; p < 0.001), extended length of stay (OR, 1.12 [95% CI, 1.06 to 1.15]; p < 0.001), periprosthetic joint infection (OR, 1.30 [95% CI, 1.13 to 1.50]; p < 0.001), deep vein thrombosis (OR, 1.17 [95% CI, 1.09 to 1.26]; p < 0.001), acute kidney injury (OR, 1.21 [95% CI, 1.09 to 1.33]; p < 0.001), hypoglycemic events (OR, 1.25 [95% CI, 1.01 to 1.54]; p = 0.039), and 1-year revision (OR, 1.16 [95% CI, 1.01 to 1.33]; p = 0.033).

CONCLUSIONS

Metformin use in patients with type-2 diabetes undergoing TKA appears to be associated with lower odds of multiple complications and resource utilization parameters, including periprosthetic joint infection and 1-year revision rates. Given the frequency with which TKA is performed in patients with type-2 diabetes, this knowledge has the potential to improve optimization protocols and outcomes in this group of patients.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

[Metformin Therapy During Surgical Interventions and Iodinated Contrast Agent Use]

Metformin as first-line treatment in type 2 diabetes mellitus (T2 D) shows benefits in terms of reducing cardiovascular events, but the risk of a lactic acidosis as a serious adverse event especially in patients with decreased renal function is still relevant. Since the perioperative management of Metformin or its use in diagnostic procedures with contrast agents is inconsistent in literature and different in practice, the results of various guidelines are reviewed below showing the current state of evidence. Despite many guidelines, the evidence on both issues is low, as they are mainly based on consensus recommendations. The guidelines are still based on weak data and many international recommendations have clearly different statements. A fundamental problem with drugs is that expert information does specify eGFR limits for dose reduction, but not the method to be used. Depending on the formula, this can then lead to different treatment decisions. At present, it is not possible to give reliable recommendations for practice with the aim of minimising the interruption of therapy. For this reason, only a strictly conservative approach with 48-hour breaks before and after both measures can be recommended at present. For the situations mentioned in this overview, the question of the right approach has not yet been conclusively and definitely answered, therefore further studies should be carried out.

Prognostic impact of elevated lactate levels on mortality in critically ill patients with and without preadmission metformin treatment: a Danish registry-based cohort study

BACKGROUND

Lactate is a robust prognostic marker for the outcome of critically ill patients. Several small studies reported that metformin users have higher lactate levels at ICU admission without a concomitant increase in mortality. However, this has not been investigated in a larger cohort. We aimed to determine whether the association between lactate levels around ICU admission and mortality is different in metformin users compared to metformin nonusers.

METHODS

This cohort study included patients admitted to ICUs in northern Denmark between January 2010 and August 2017 with any circulating lactate measured around ICU admission, which was defined as 12 h before until 6 h after admission. The association between the mean of the lactate levels measured during this period and 30-day mortality was determined for metformin users and nonusers by modelling restricted cubic splines obtained from a Cox regression model.

RESULTS

Of 37,293 included patients, 3183 (9%) used metformin. The median (interquartile range) lactate level was 1.8 (1.2-3.2) in metformin users and 1.6 (1.0-2.7) mmol/L in metformin nonusers. Lactate levels were strongly associated with mortality for both metformin users and nonusers. However, the association of lactate with mortality was different for metformin users, with a lower mortality rate in metformin users than in nonusers when admitted with similar lactate levels. This was observed over the whole range of lactate levels, and consequently, the relation of lactate with mortality was shifted rightwards for metformin users.

CONCLUSION

In this large observational cohort of critically ill patients, early lactate levels were strongly associated with mortality. Irrespective of the degree of hyperlactataemia, similar lactate levels were associated with a lower mortality rate in metformin users compared with metformin nonusers. Therefore, lactate levels around ICU admission should be interpreted according to metformin use.

Insight Into the Perioperative Management of Type 2 Diabetes

Diabetic people are at risk of developing acute complications when exposed to stress. Surgery brings a stressful period when the patient is exposed not only to surgical stress but also the effects of medications used during that particular period. The patient's comorbidities can influence the perioperative management of diabetes. Poorly controlled diabetes can complicate the hospital course. The literature was searched through PubMed and the articles of the last 5 years, from 2014 to 2019, were looked into. The studies available as a free text, in the English language and related to humans, were included. Inclusion criteria also included adults with type 2 diabetes undergoing surgery. The perioperative management of diabetes is a challenging one. Apart from the diabetes control; comorbidities, general health, intake, and interaction of medications both anti-diabetic and non-diabetic, type and duration of surgery, are some of the factors that influence the outcome of the surgery. With a variety of options available to manage diabetes currently, it is important to have a good insight into their effects to prevent complications to occur and ensure safe discharge from the hospital. The good control of diabetes is essential in bringing favorable outcomes. The perioperative management of diabetes should be individualized. Oral anti-hyperglycemic medications, other than sulfonylureas and SGLT2 inhibitors, provide a reasonable alternative to insulin and can be continued safely perioperatively depending upon the type of surgery and the patient is expected to resume oral intake soon postoperatively.

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

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.

Recent advances in diabetes treatments and their perioperative implications

PURPOSE OF REVIEW

The implications for perioperative management of new oral antihyperglycemic medications and new insulin treatment technologies are reviewed.

RECENT FINDINGS

The preoperative period represents an opportunity to optimize glycemic control and potentially to reduce adverse outcomes. There is now general consensus that the optimal blood glucose target for hospitalized patients is approximately 106-180 mg/dl (6-10 mmol/l). Recommendations for the management of antihyperglycemic medications vary among national guidelines. It may not be necessary to cease all antihyperglycemic agents prior to surgery. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are associated with higher rates of ketoacidosis especially in acutely unwell and postsurgical patients. The clinical practice implications of new insulin formulations, and new systems for insulin delivery, are not clear. The optimal perioperative management of these will vary depending on local institutional factors such as staff skills and existing clinical practices. Improved hospital care delivery standards, quality assurance, process improvements, consistency in clinical practice, and coordinated multidisciplinary teamwork should be a major focus for improving outcomes of perioperative patients with diabetes.

SUMMARY

Sulfonylureas and SGLT2i should be ceased before moderate or major surgery. Other oral antihyperglycemic therapies may be continued or ceased. Complex patients and/or new therapies require specialized multidisciplinary management.

Diabetes Mellitus: Preoperative Concerns and Evaluation

Diabetes is an important cause of morbidity in the adult population resulting in blindness, renal dysfunction, cardiovascular events, and amputation. Such morbidities may have an impact on perioperative anesthetic care and outcomes. In this review, the authors discuss the preoperative considerations in managing patients with diabetes as well as those without diabetes albeit hyperglycemic. They propose a plan for managing preoperative diabetes pharmacotherapy, including the use of a subcutaneous insulin pump to avoid both hypoglycemia and hyperglycemia. The authors also discuss the decision whether to proceed or cancel surgery for a given hemoglobin A1c percentage or blood glucose concentration.

Liver enzyme trends in patients taking uninterrupted metformin before and after coronary surgery

Background

Metformin is an oral antidiabetic agent belonging to the biguanide class of antidiabetics. Possible novel applications for metformin in cardiovascular disease might exist. The aim of this study was to verify a possible association between pre-operative metformin administration and protection against ischemia-induced liver injury in diabetic patients undergoing coronary artery bypass grafting (CABG) surgery.

Methods

A retrospective case-control series was conducted at a single center. Two hundred consecutive diabetic patients underwent isolated on-pump CABG during a 12-month span (July 2015 - July 2016). Metformin was uninterrupted in patients who took this drug prior to CABG; 68 patients were metformin users (34%) while 132 patients were taking other antidiabetic agents (66%). Liver enzymes and other organ markers were consecutively recorded daily for 7 days after surgery and expressed as medians with interquartile range (IQR).

Results

Both the metformin and non-metformin group of patients had similar pre-operative demographic characteristics. The median (IQR) post-operative cardiac enzyme creatinine kinase (CK) MB fraction was significantly lower in the metformin group [46.4 U/L (35.8-66.5) vs. 66.5 U/L (44-94.5), P=0.005]. Total bilirubin [0.58 (0.48-0.82) mg/dL vs. 0.67 (0.56-0.95) mg/dL, P=0.021], the transaminase aspartate aminotransferase (AST) [32.5 U/L (25.0-42.0) vs. 37.5 U/L (28.5-56), P=0.011], the transaminases alanine aminotransferase (ALT) [48.5 U/L (40.0-64.0) vs. 57.0 U/L (44.0-77.0), P=0.040] and lactate dehydrogenase (LDH) [320.0 U/L (273.5-367.2) vs. 356.5 U/L (289.5-427), P=0.014] were significantly lower in the metformin group. No differences were noted in clinical outcomes.

Conclusions

In this limited retrospective study, the diabetic patients who took metformin before and after undergoing CABG appeared to have a reduced post-operative surge in the total bilirubin and transaminase liver enzymes. Metformin's role in mitigating oxidative stress in liver cells might explain this observation. Further experimental studies are warranted to verify this possible effect.