Anaesthetic management

1. Preoperative assessment and optimization

• Type and duration of diabetes, usual glucose pattern, HbA1c, hypoglycaemic episodes, current insulin regimen or oral agents.
• Check capillary blood glucose on arrival.
• Investigate complications: ECG, renal function and electrolytes, urinalysis if indicated, full blood count and group-and-crossmatch for expected blood loss.
• Look for ischemic heart disease, heart failure, nephropathy, peripheral neuropathy, diabetic foot lesions, and difficult airway from limited cervical or temporomandibular joint mobility.

• Symptoms: postural dizziness/syncope, resting tachycardia, exercise intolerance, early satiety, nausea, vomiting, constipation, urinary retention, and impaired sweating.
• Record supine and standing BP and heart rate. The patient may have supine hypertension but profound hypotension on induction, positioning, neuraxial block, haemorrhage, or positive-pressure ventilation.
• ECG for resting tachycardia, ischemia, QT abnormalities and arrhythmias. Consider echocardiography/cardiology review if symptomatic cardiac disease or poor functional capacity.
• Autonomic neuropathy commonly produces postural hypotension and gastroparesis in diabetes, and diabetes increases postoperative cardiac, renal and surgical-site complications. Miller's Anesthesia, 10e, p. 3964.

• Withhold metformin on the day of surgery.
• Stop SGLT2 inhibitors 3-4 days preoperatively due to risk of euglycaemic ketoacidosis.
• Omit most other oral hypoglycaemic drugs on the morning of surgery.
• Continue basal insulin with dose adjustment. A commonly used approach is 75-80% of long-acting basal insulin or 50% of morning NPH, individualized to glucose control and fasting duration. Never omit basal insulin completely in type 1 diabetes.
• Continue beta-blockers if prescribed. Review antihypertensives and consider withholding ACE inhibitors/ARBs on the day of surgery if significant hypotension is anticipated, according to local policy.
• Correct dehydration, electrolyte abnormalities, infection, ketoacidosis or hyperosmolar state before elective surgery. Defer surgery if metabolic decompensation is present.

2. Aspiration prophylaxis

• Follow standard fasting guidelines only if there are no symptoms of delayed gastric emptying.
• In symptomatic gastroparesis or uncertain gastric emptying, treat as a full stomach.
• Give non-particulate antacid, H2 blocker or proton-pump inhibitor, and metoclopramide if appropriate.
• Consider gastric ultrasound where expertise exists.
• Perform modified rapid-sequence induction with cuffed tracheal intubation if aspiration risk is high.

3. Choice and conduct of anaesthesia

• Standard ASA monitoring plus temperature and frequent glucose measurement.
• Insert an arterial cannula before induction if autonomic dysfunction is significant, haemodynamic instability is anticipated, major blood loss is likely, or frequent blood sampling is needed.
• Two reliable large-bore IV cannulae; group and crossmatch blood.
• Consider central venous access only for a specific indication, such as poor peripheral access or need for vasoactive infusion.
• Measure glucose at induction and at least hourly intraoperatively during major surgery or insulin infusion.
• Do not rely on continuous glucose monitor values alone during anaesthesia.

• Avoid dehydration, prolonged fasting, anaesthetic overdose, abrupt postural changes, and excessive depth of anaesthesia.
• Pre-induction fluid should be judicious, especially if nephropathy or cardiac dysfunction is present. Use balanced crystalloids and replace blood loss promptly.
• Induce slowly and titrate doses to effect. Propofol may cause substantial hypotension; etomidate can be considered if cardiovascular reserve is poor.
• Have vasopressors prepared before induction. Phenylephrine or norepinephrine is often required to maintain perfusion pressure; response may be unpredictable in severe autonomic failure, so titrate to invasive BP.
• Maintain normoxia, normocapnia, normothermia and adequate analgesia. Hypothermia, pain and surgical stress can worsen autonomic instability.
• Anticipate blunted tachycardic response to hypovolaemia or haemorrhage. Do not use heart rate alone to judge volume status.

4. Intraoperative glucose and insulin management

• Target glucose: 100-180 mg/dL (5.6-10 mmol/L).
• For this major abdominal operation, use a variable-rate IV insulin infusion with dextrose-containing fluid when prolonged fasting, type 1 diabetes, poor control, or glucose persistently above target makes it appropriate. Follow the institution’s validated insulin-infusion protocol.
• Check potassium during insulin therapy and replace as required.
• Avoid both hyperglycaemia, which increases infection and poor wound healing risk, and hypoglycaemia, which is masked under general anaesthesia.
• Measure blood or urine ketones and obtain blood gas analysis if unexplained acidosis, nausea, tachypnoea, or high anion gap occurs, especially with recent SGLT2 inhibitor exposure.

5. Hysterectomy-specific considerations

• Anticipate blood loss and ensure blood products are available.
• Carefully pad pressure areas and protect neuropathic limbs.
• Avoid prolonged extreme positioning; reposition slowly because postural hypotension may occur.
• Multimodal, opioid-sparing analgesia: paracetamol, NSAID if renal function and bleeding risk permit, wound infiltration or transversus abdominis plane block, and cautious opioid titration.
• If epidural analgesia is used, use incremental local anaesthetic dosing and close BP monitoring.

6. Postoperative management

• Recover in a monitored setting. Consider HDU/ICU if severe autonomic dysfunction, unstable BP, major blood loss, renal impairment, insulin infusion, or cardiac disease.
• Continue frequent BP, ECG, urine output, temperature, electrolytes, ketones when indicated, and glucose monitoring.
• Maintain glucose 100-180 mg/dL. Continue IV insulin until the patient is eating reliably, then overlap with subcutaneous basal insulin before stopping the infusion.
• Restart oral therapy only when eating, haemodynamically stable, and renal function is satisfactory. Restart SGLT2 inhibitors only after recovery from acute illness and normal oral intake, following local endocrinology guidance.
• Monitor for silent myocardial ischemia, arrhythmia, hypotension, acute kidney injury, infection, ileus, urinary retention, and postoperative nausea/vomiting.
• Mobilize gradually with supervised first ambulation because orthostatic hypotension may be profound.

Key practical summary

1. Treat the patient as high risk for hypotension, silent ischemia and aspiration.
2. Use invasive BP monitoring when autonomic dysfunction is clinically significant.
3. Maintain preload carefully and have a vasopressor infusion immediately available.
4. Treat symptomatic diabetic gastroparesis as a full stomach.
5. Maintain glucose at 5.6-10 mmol/L, checking frequently and using IV insulin for major/prolonged surgery when indicated.
6. Use cautious neuraxial analgesia, opioid-sparing multimodal postoperative pain control, and monitored postoperative care.