Introduction

Optimal glucose control improves surgical outcomes. Post-operative hyperglycemia in the first 24 hours increase the risk of delayed wound healing and recovery, postoperative complications and prolonged length of stay.

Given that periods of fasting will disrupt the usual schedule of diabetes medications and insulin, plan the procedure for the morning so that this is minimized and glucose levels can remain stable. Patients with diabetes may have complications and comorbidities that increase their risk of surgical complications, so optimize these pre-operatively to minimize this risk.

These guidelines are derived from the Australian Diabetes Society and aim to provide specific and practical guidance to ensure your patient is safe and their procedure will not be cancelled.

Key points from the Australian Diabetes Society Guidelines

1. Optimal peri-operative glucose targets = 5 – 10 mmol/L and HbA1c <8.0%
2. Consider postponing elective surgery if HbA1c >9.0%
3. Elective surgery should be performed in the morning to minimize the disruption to usual diabetes care
4. Commence insulin & Dextrose infusion for patients with:
   
   • Type 1 Diabetes
   • Insulin-treated Type 2 Diabetes
   • Pre-operative glucose levels are out of range (<4 mmol/L or >12 mmol/L)
   • Major surgery where fasting is expected to be prolonged
   • Unstable underlying medical comorbidities eg. sepsis, organ dysfunction, acute coronary syndrome
5. For elective surgery, commence insulin infusion prior to induction of anaesthesia
   
   • Earlier than 6am for morning procedures
   • Earlier than 10am for afternoon procedures
   • Continue until patient is eating and drinking post-operatively, then resume subcutaneous insulin
6. Consider admitting patients pre-operatively for glucose stabilization who:
   
   • Experience frequent hypoglycemic episodes
   • Have persistent hyperglycemia (>15 mmol/L)
   • Have unstable medical comorbidities eg. angina, claudication from PVD
   • Are unable to attend the hospital early in the morning for commencement of insulin infusion
7. Surgery should only be cancelled if the patient is very unstable:
   
   • Diabetic emergencies eg. DKA, HHS, severe hypoglycaemia
   • Sepsis
   • Medical emergency eg. aMI, cardiac arrhythmia, CCF

Pre-admission clinic

Pre-operative workup

Diabetes increases the risk of perioperative complications and a prolonged length of stay. This is due to three features of diabetes:

• Poor glucose control (<4 mmol/L and >12 mmol/L) increases the risk of perioperative complications,
• Underlying diabetic complications and comorbidities increase their risk of surgical complications
• Side effects of diabetes medications are more likely during acute illness, organ dysfunction and fasting.

So, a good pre-operative workup that aims to optimize your patient’s diabetes control and overall health status can minimize this risk.

Investigations recommended

• HbA1c
• Electrolytes and liver function tests
• Full blood count
• Thyroid function tests
• B12 if patient taking Metformin >12 months
• 12-lead ECG

Glucose monitoring and ideal targets

• HbA1c <8.0%
• Pre-meal glucose levels 5 – 8 mmol/L
• Post-meal glucose levels 5 – 10 mmol/L (if being monitored)

Medical optimization

Clinical assessment, looking for signs of vascular disease that can increase the risk of perioperative complications:

• Cardiac failure
• Peripheral vascular disease
• Peripheral neuropathy

Pre-operative admission

Consider elective admission to improve glycaemic control only in patients who are at high risk of peri-operative complications:

• Frequent hypoglycemic episodes
• Persistent hyperglycemia (>15 mmol/L)
• Unstable medical comorbidities eg. angina, claudication from PVD
• Social disadvantage that may affect their ability to attend the hospital early for commencement of insulin infusion

Postponing surgery

Should only be considered in high-risk situations where your patient is very unstable:

• Diabetic emergencies eg. DKA, HHS, severe hypoglycaemia
• Sepsis
• Medical emergency eg. aMI, cardiac arrhythmia, CCF
• HbA1c >9.0% is a relative contraindication to surgery, being a marker of poor glucose control

Insulin pumps

Patients who manage their diabetes with an insulin pump

Aim to keep the insulin pump running when:

• The patient is undergoing a minor procedure (period of fasting is no more than one meal)
• The pump is clear of the surgical field
• The patient can manage their pump independently after surgery

The pump should be removed and replaced by an insulin infusion when the patient is:

• Undergoing major surgery, where the expected period of fasting is at least 2 meals
• Undergoing a Caesarean section
• Undergoing emergency surgery
• Medically unstable eg. hypoglycaemia, hyperglycaemia, DKA, sepsis
• Unable to self-manage their pump post-operatively
• The pump site is in the surgical field

Radiological procedures eg. IV contrast, PET scans

Radiological investigations that require the patient with diabetes to fast should be scheduled for the morning, so that the disruption to the diabetes medications and/or insulin is minimized.

For your patient with diabetes, you may need to make special considerations for these situations:

• MRI
  
  • Insulin pumps, continuous glucose monitoring devices should be removed before entering the MRI suite.
  • A plastic cannula can remain in situ for the MRI, but a metal cannula must be removed
  • Resume insulin pump as soon as the MRI study is complete
  • Unless the investigation is expected to take more than 1 hour, patient does not require subcutaneous insulin during the MRI
• Metformin
  
  • Intravenous contrast can induce nephropathy and lactic acidosis.
  • Although this is rare, it is more likely in people with acute or chronic renal impairment. Metformin can increase this risk.
  • If your patient is taking Metformin:
    
    • Check their renal function
    • If eGFR >30ml/min/1.73m2 and stable:
      
      • Your patient should continue Metformin
      • Check creatinine the following morning
    • If eGFR =30ml/min/1.73m2, or there is an acute kidney injury:
      
      • Withhold the Metformin 24 hours before the IV contrast load if the imaging is elective
      • Withhold the Metformin for 48 hours after the dose is given
      • Give IV 0.18 Normal Saline for 24 hours after dose has been given
      • Check the creatinine to ensure it is stable before the Metformin is restarted
• Fasting for investigations
  
  • These investigations should be scheduled in the morning to minimize the disruption to diabetes medications and/or insulin
  • Adjust the doses of morning medications and insulin, according to the timing of the fast (Table below)
  • Patient should monitor glucose levels every 2 hours during the fast
  • For inpatients, consider an insulin infusion if glucose levels are <4 mmol/L or above 12 mmol/L to optimize glycaemic control