Diabetes is a common condition related to insulin deficiency or increased tissue insulin resistance.
Precipitation
- Diabetes can be precipitated in a variety of situations:
- Pregnancy
- Sepsis
- Certain medications, e.g. Steroids
- Post-surgery, e.g. Pancreatic resection
Types
- Two main types:
Type 1: Most common in young people as a result of insulin deficiency
- Can lead to keto-acidosis and is usually managed with insulin injections Type 2: Most common in adults as a result of insulin resistance
- Much less likely to lead to keto-acidosis and can be managed by diet, medications and insulin
Nutritional Considerations in Diabetic Patient
Source: Dogra P, Jialal I. Diabetic perioperative management. StatPearls.
Intro
- In both diabetic and non-diabetic populations, hyperglycaemia in peri-op period is an independent marker of poor surgical outcomes – i.e. delayed wound healing, increased rate of infection, prolonged hospital stay, higher post-op mortality
- Stress of surgery, anaesthesia and illness ⇒ Increases secretion of counter-regulatory hormones, i.e. cortisol, glucagon, growth hormone, catecholamines ⇒ Decreases insulin secretion, increased insulin resistance, decreased peripheral utilization of glucose, increased lipolysis and proteolysis
- Gluconeogenesis and glycogenolysis increase ⇒ Worsening hyperglycaemia ⇒ Osmotic diuresis, ketogenesis, increased generation of pro-inflammatory cytokines with mitochondrial injury, endothelial dysfunction, immune dysregulation
Pre-operative management A) History:
- Diabetes specific info: type of diabetes, current management – incl. current regimen details and medication adherence, current glycaemic control, related complications, susceptibility to hypoglycaemia including hypoglycaemic unawareness B) HbA1c
- Should check pre-op HbA1c if not tested in preceding 3 months
- No evidence proving better outcomes by deferring surgery for better glycaemic control
C) Oral anti-hyperglycaemic and non-insulin injectable
- Metformin – risk of lactic acidosis in cases of renal dysfunction or with use of IV contrast
- Sulfonylureas and other secretagogues – risk of hypoglycaemia
- [Sodium-glucose co-transporter-2 ] inhibitors (E.g. Empagliflozin)– risk of euglycaemic ketoacidosis in fasting
- GLP-1 agonists – worsen nausea and vomiting by delaying gastric emptying
- Current recommendations: withhold these meds on day of surgery except for SGLT-2 inhibitors – should be withheld for a minimal of 3 days before surgery
- If acute operation or illness, meds should be stopped immediately
D) Insulin Therapy
- If on home insulin, pts should reduce dose of long-acting basal insulin by 20-25% the evening before surgery
- If routinely take basal insulin in morning only, pt should use reduced dose on the morning of surgery
- If take BD dose, then both the dose the evening before and on the morning of the surgery need to be reduced
- If pts on high doses of basal insulin or total daily insulin > 80 units or at high risk of hypoglycaemia (e.g. elderly, renal or hepatic insufficiency, prior hypoglycaemic episodes) then the basal insulin dose should be reduced by 50-75% to minimize hypoglycaemic risk
- If ultra-long-acting insulin – dose reductions should be made 3 days before surgery
- During fasting: nutritional (or prandial) insulin is with-held – subcutaneous correctional insulin initiated with blood glucose monitoring every 4-6 hrs
- If critically ill, continuous IV infusion of insulin is the preferred route
- Diabetic pts should preferably be scheduled for surgery early in the day
- Recommendation: check glucose in pre-op
- If hypo, treat with glucose tablets/gels or IV dextrose
- If severe hyper, or metabolic decompensation, e.g. DKA or hyperglycaemic hyperosmolar syndrome, prudent to post-pone surgery by a couple of hours for better glycaemic control
Intra-operative Management
- Hyperglycaemia – in short surgeries (< 4 hrs) with expected haemodynamic stability and minimal fluid shift – can be managed with 2-hrly subcut correctional insulin and blood glucose checks.
- In surgeries involving longer duration (> 4 hrs) haemodynamic fluctuations, massive fluid shifts, use IV insulin infusion and blood glucose checks every 1-2 hrs
Post-operative Management
- In PACU: Review intra-op hyperglycaemic mgmt and continue close glucose monitoring with either IV or subcut insulin
A) Ambulatory
- After recovery, if pts are stable and tolerating oral intake – discharge home with usual regimen
B) Non-critically ill
- If poor or no oral intake, basal insulin + correctional insulin preferred
- If regular oral intake, insulin regimen consists of basal + nutritional + correctional
- Basal: controls hyperglycaemia when pt is not eating and can be given as long-acting insulin once or twice daily
- Nutritional: controls hyperglycaemia related to carb intake with either rapid-acting or short-acting insulin
- Correctional: counteracts hyperglycaemia that is above the goal, with either rapid-acting or short-acting insulin
- Calculating doses:
- Total daily dose: 0.4 – 0.5 units/kg/day
- If insulin sensitive, e.g. type 1 DM, insulin naïve, elderly, malnourished, renal/hepatic insufficiency, frequent hypoglycaemia – reduce to 0.2 – 0.4 units/kg/day
- If insulin resistant, e.g. obese, on high dose steroids, use 0.6 – 0.7 units/kg/day
- Half of total daily dose administered as basal insulin and 1/6 administered as nutritional insulin with each of the 3 meals
- If eating: blood glucose monitored 4 times a day and correctional insulin administered accordingly
- If fasting: blood glucose monitored every 6 hours and correction with regular insulin or every 4 hours for correction with rapid-acting insulin
C) Critically Ill Patient
- Continuous insulin infusion with blood glucose monitoring every 1-2 hrs
- Important to overlap IV and SC insulin by 2-3 hours due to extremely short half-life of IV insulin and delayed onset of action of long/intermediate acting insulin
Other Issues Enteral Nutrition
- Diabetic pts on EN should receive formulas low in carbs, high in mono-saturated fatty acids, and subcut insulin regimen should include basal, nutritional and correctional components.
- If EN is administered continuously, then nutritional and correctional insulin is administered every 4 hrs or every 6 hrs
Parenteral Nutrition
- In TPN pts, insulin given as a separate IV infusion or added to TPN solution
- If added to solution, rough guide: 1 unit of insulin for every 10 grams of dextrose and then adjust every 1-2 days based on glycaemic trends
- Blood glucose monitored with subcut correctional insulin every 4-6 hrs to treat any hyperglycaemia above target range
Hypoglycaemia
- International Hypoglycaemia Study Group classification:
- BG < 70 mg/dl (3.9 mmol/L) = hypoglycaemic alert level
- BG < 54 mg/dl (3.0 mmol/L) = clinically significant hypoglycaemia
- Cognitive impairment with no BG threshold = severe hypoglycaemia
- Risk factors for hypoglycaemia:
- Inappropriate insulin dosing
- Aggressive glycaemic target
- Insulin admin not aligned with meal-time
- Insulin stacking
- Unforeseen changes in caloric intake
- Poor communication between staff
- Failure to recognize glycaemic trends