What pre‑operative assessment and peri‑operative management should be used for a diabetic patient undergoing anesthesia to minimise complications?

Preoperative Assessment and Perioperative Management of Diabetic Patients for Anesthesia

All diabetic patients undergoing anesthesia require a structured preoperative assessment focusing on HbA1c, recent glycemic control, and screening for three life-threatening complications: gastroparesis (aspiration risk), silent myocardial ischemia (cardiac death risk), and autonomic neuropathy (hemodynamic instability risk). 1

Minimum Preoperative Assessment

Every diabetic patient requires the following baseline evaluation 1:

• HbA1c measurement to assess glycemic control over the preceding 3 months and guide therapeutic optimization 1
• ECG at rest to detect silent ischemic changes 1
• Urinary test strip to identify proteinuria (marker of nephropathy and cardiovascular risk) 1
• Serum creatinine to assess renal function and guide medication adjustments 1
• Recent blood glucose patterns from the past week to identify hypoglycemic episodes and glycemic variability 2
• Screening for ketosis with urinary or blood ketones, as presence mandates surgery postponement except for emergencies 2

Critical Diabetes-Specific Complications Assessment

Gastroparesis (30-50% of diabetic patients)

Question specifically about abdominal bloating, early satiety, postprandial fullness, nausea, or vomiting 1, 3, 2. Gastroparesis represents delayed gastric emptying without mechanical obstruction and dramatically increases aspiration risk during intubation 1. If suspected based on these symptoms, treat as full stomach and plan for rapid sequence intubation 1.

Silent Myocardial Ischemia (30-50% of asymptomatic Type 2 diabetics)

Approximately 75% of diabetic patients die from atherosclerotic complications, and myocardial infarction is frequently silent in this population 1, 3. Screen asymptomatic patients with cardiovascular risk factors for silent myocardial ischemia if they have:

• Other arterial damage (peripheral vascular disease, cerebrovascular disease) 1
• Proteinuria or renal failure 1
• Multiple cardiovascular risk factors (hypertension, dyslipidemia, smoking, family history) 1

For major surgery with Lee score ≥2 and reduced functional capacity (<4 METs), obtain stress testing (exercise tolerance test, myocardial scintigraphy, stress echocardiography) 1. Coronarography reveals significant stenosis in 30-70% of patients with positive stress tests 1.

Cardiac Autonomic Neuropathy

Measure orthostatic blood pressure after 10 minutes supine, then at 1,2, and 3 minutes standing 1. Orthostatic hypotension is defined as systolic BP drop ≥20 mmHg (≥30 mmHg if hypertensive) or diastolic BP drop ≥10 mmHg 1. Also ask about postprandial hypotension and exercise intolerance 2. Presence of autonomic neuropathy increases risk of intraoperative hemodynamic instability and sudden cardiac death 2.

Preoperative Glycemic Optimization

If HbA1c indicates poor control during the anesthesia consultation, intensify diabetes treatment before elective surgery 1. For Type 2 diabetes on oral agents, consider treatment intensification or initiation of insulin 1. For insulin-treated patients (Type 1 or Type 2), review auto-surveillance records to identify timing of hyperglycemia and adjust insulin doses accordingly 1. If ketosis is detected, propose insulin therapy and postpone elective surgery 1, 2.

Preoperative Medication Management

Evening Before Surgery

Administer all insulin at usual doses the evening before surgery, including both basal insulin and prandial insulin with the evening meal 2. Maintain insulin pumps at usual settings until arrival at the surgical unit 2. Continue all oral agents (sulfonylureas, DPP-4 inhibitors, GLP-1 agonists) with the evening meal 2.

Critical exceptions:

• Stop metformin from the evening before surgery to reduce lactic acidosis risk, particularly with perioperative renal stress 2, 4
• Discontinue SGLT2 inhibitors 3-4 days prior to surgery due to euglycemic ketoacidosis risk 2, 4

Patients should eat their normal evening meal without restriction, and no preoperative glucose infusion is necessary the night before 2.

Morning of Surgery

Give 50% of usual morning NPH insulin dose 2. Give 75-80% of usual long-acting analog dose (glargine, detemir, degludec) 2. Hold all rapid-acting/prandial insulin on the morning of surgery 2. Hold all remaining oral hypoglycemic agents on the morning of surgery 2, 4.

Fasting and Glucose Management

If the insulin-treated patient requires prolonged fasting, establish glucose infusion starting at 7:00 AM, which should be stopped if blood glucose exceeds 16.5 mmol/L (297 mg/dL) 1. Patients taking sulfonylureas or glinides before emergency surgery also require glucose infusion if remaining NPO 1. Non-insulin-treated patients do not require glucose infusion during fasting 1.

Insulin Pump Management

For ambulatory or short-duration surgery, retain the pump and continue basal delivery 1. Understand the patient's "total basal delivery" to prescribe long-acting insulin if pump must be stopped 1. The main risk is ketoacidosis if insulin continuation is not immediate after stopping the pump—either by subcutaneous basal-bolus injection or continuous intravenous insulin 1.

Anesthetic Technique Considerations

No specific anesthetic agent provides superior outcomes in diabetic patients 1. Neither general anesthesia nor regional anesthesia demonstrates clear superiority, though regional anesthesia slightly increases preoperative glycemia while spinal/epidural reduces hyperglycemic injury but increases hemodynamic risk 1. Choose technique as for non-diabetic patients 1.

Peripheral nerve blocks are not contraindicated but require documentation of:

• Preoperative clinical examination for dysautonomia 1
• Assessment for pre-existing polyneuropathy 1

Difficult Intubation Assessment

Evaluate for difficult intubation using the palm print test in long-term diabetics 1. Tracheal intubation may be difficult due to densification of periarticular collagen structures affecting temporomandibular and atlanto-occipital joints from non-enzymatic glycosylation 1. These metabolic collagen disorders simultaneously affect interphalangeal joints, making the palm print test a useful screening tool 1.

Perioperative Glycemic Targets

Target blood glucose 140-180 mg/dL (7.8-10 mmol/L) during surgery and in the perioperative period 4, 5, 6. This range balances infection risk reduction with hypoglycemia avoidance 4. For critically ill patients, use continuous intravenous insulin infusion via validated protocol 4, 6. For non-critically ill patients in the operating theater, use rapid-acting insulin analogs subcutaneously 5.

Common Pitfalls to Avoid

Never allow insulin deficiency in insulin-treated patients, as ketoacidosis develops within hours, particularly critical in Type 1 diabetes 2. Do not use sliding-scale insulin alone postoperatively—transition to basal-bolus regimen for patients with good nutritional intake 4, 6. Do not proceed with elective surgery if blood glucose exceeds 250 mg/dL or HbA1c exceeds 8.5-9% to minimize severe complications 5. Monitor serum creatinine within 48 hours postoperatively to assess for acute kidney injury 4.