What is the best management approach for an elderly male patient with type 2 diabetes, A1c (glycated hemoglobin) of 10.1%, weight 81 kg, BMI (body mass index) 24, admitted with foot gangrene, currently on Jardiance (empagliflozin) 25 mg daily, metformin 1000 mg twice daily, and Amaryl (glimepiride) 4 mg twice daily, with impaired renal function (creatinine 1.11, GFR (glomerular filtration rate) 71) and potential need for surgery?

Immediate Medication Management for Diabetic Patient with Foot Gangrene Requiring Surgery

Stop metformin and Jardiance (empagliflozin) immediately, hold Amaryl (glimepiride) on the morning of surgery, and transition to intravenous insulin therapy for perioperative glycemic control. 1, 2, 3

Critical Medication Discontinuations

Metformin - STOP NOW

• Metformin must be discontinued immediately given the patient's foot gangrene, impending surgery, and borderline renal function (GFR 71 mL/min/1.73 m²). 2, 3
• The risk of metformin-associated lactic acidosis (MALA) is dramatically increased by multiple factors present in this patient: potential volume depletion from fasting, surgical stress, tissue necrosis (gangrene), and possible hemodynamic instability during surgery. 2, 3
• Metformin should be stopped the evening before surgery and withheld for at least 48 hours post-operatively, with resumption only after confirming stable renal function and adequate oral intake. 1, 2
• The mortality rate for MALA ranges from 30-50%, making this a critical safety priority. 2, 3

Jardiance (Empagliflozin) - STOP NOW

• SGLT2 inhibitors like Jardiance must be discontinued immediately due to the severe risk of Fournier's gangrene in patients with existing genital/perineal infections or tissue necrosis. 4, 5
• This patient already has gangrene of the foot, placing him at extremely high risk for progression to more severe necrotizing infections, particularly given his poor glycemic control (A1c 10.1%). 4
• SGLT2 inhibitors also increase the risk of euglycemic diabetic ketoacidosis (euDKA) in the perioperative period, which can be misdiagnosed due to normal glucose levels and lead to catastrophic outcomes including limb loss from vasopressor use. 5
• The medication should remain discontinued throughout hospitalization and recovery. 1, 5

Amaryl (Glimepiride) - HOLD Morning of Surgery

• Sulfonylureas should be held on the morning of surgery due to hypoglycemia risk, particularly with NPO status and surgical stress. 2
• The evening dose before surgery can be given at the usual dose. 1
• Do not resume until the patient has stable oral intake post-operatively. 2

Perioperative Insulin Management

Transition to IV Insulin Protocol

• Insulin is the preferred therapy for persistent hyperglycemia (>180 mg/dL) in hospitalized patients, and this patient's A1c of 10.1% indicates severe hyperglycemia requiring aggressive management. 1
• In the critical care or perioperative setting, continuous intravenous insulin infusion is the best method for achieving glycemic targets, administered via validated protocols. 1
• Target glucose range of 140-180 mg/dL for most hospitalized patients, which balances infection risk reduction with hypoglycemia avoidance. 1, 6

Subcutaneous Insulin Regimen Post-Operatively

• Once stable and eating, transition to basal-bolus insulin regimen (basal, nutritional, and correction components), which is the preferred treatment for patients with good nutritional intake. 1
• Sliding-scale insulin alone is strongly discouraged and should never be used as the sole regimen. 1
• When transitioning from IV to subcutaneous insulin, give subcutaneous basal insulin 1-2 hours before discontinuing IV insulin, using 60-80% of the daily IV insulin dose. 1

Renal Function Monitoring

Current Status Assessment

• With GFR 71 mL/min/1.73 m², the patient has Stage 2 CKD, which requires medication adjustments. 1
• At this GFR level, metformin dose should have already been reduced to maximum 1000 mg/day, but the patient is on 2000 mg/day, increasing MALA risk. 1, 7
• Empagliflozin can be continued at 10 mg daily at this GFR level per FDA labeling, but the clinical context (gangrene, surgery) mandates discontinuation. 1

Perioperative Monitoring

• Monitor serum creatinine within 48 hours post-operatively to assess for acute kidney injury. 2
• Maintain adequate hydration and mean arterial pressure >60 mmHg to preserve renal perfusion during surgery. 8, 2
• Avoid nephrotoxic agents and contrast exposure if possible; if contrast is required, ensure metformin remains discontinued for 48 hours after with confirmed stable renal function before restarting. 2, 3

Infection and Wound Management Priorities

Gangrene-Specific Considerations

• The presence of foot gangrene requires multidisciplinary wound care, and diabetic foot wounds without soft tissue or bone infection do not require antibiotics. 1
• However, given the severity (gangrene requiring potential surgery), assume high infection risk and coordinate with surgical team for debridement planning. 1, 9
• Blood glucose <180 mg/dL before intervention decreases risk of death, infection, and duration of stay. 1

Post-Operative Glycemic Targets

• Maintain glucose 140-180 mg/dL to optimize wound healing and reduce infection risk while avoiding hypoglycemia. 1, 6
• Tighter control (110-140 mg/dL) may be considered if achievable without significant hypoglycemia, as some data suggest benefit in surgical patients. 1, 10

Common Pitfalls to Avoid

• Never continue metformin through surgery - the combination of NPO status, surgical stress, potential contrast exposure, and tissue necrosis creates perfect conditions for fatal lactic acidosis. 2, 3
• Do not restart SGLT2 inhibitors during hospitalization - the risk of Fournier's gangrene and euDKA in this clinical context far outweighs any glycemic benefit. 4, 5
• Avoid sliding-scale insulin as sole therapy - this outdated approach leads to poor glycemic control and increased complications. 1
• Do not overlook vitamin B12 deficiency - with long-term metformin use at high doses, check B12 levels as deficiency can worsen diabetic neuropathy. 7, 3

Long-Term Medication Plan

• After hospital discharge and wound healing, consider restarting metformin at reduced dose (≤1000 mg/day) given GFR 71 mL/min/1.73 m². 1, 7
• Do not restart empagliflozin - consider alternative SGLT2 inhibitor only after complete wound healing and with extreme caution, or preferably switch to GLP-1 receptor agonist for cardiovascular/renal benefits without infection risk. 1
• Reassess need for sulfonylurea given high hypoglycemia risk in elderly patients; consider discontinuation in favor of safer agents. 1
• Optimize basal insulin dosing for long-term glycemic control targeting A1c <7% to prevent further microvascular complications. 8