• The use of EN and PN poses challenges in managing blood glucose levels.
• EN- Basal insulin requirements should be provided along with sliding scale coverage while feedings are being advanced. If the feeding is providing 25% of usual intake, then 15% to 25% of usual insulin can be given, with increases in daily insulin dose based on feeding rate and blood glucose levels.
• Oral diabetic agents can be appropriately used in stable patients with type 2 diabetes who have normal hepatic and renal function and are receiving EN.
• Gastroparesis can make glucose control difficult due to the mismatching of insulin action and nutrient absorption. Post pyloric feeding along with prokinetics can be used if glucose control is a significant problem. Further if EN is used, it should be fiber free with low fat (<30% of total calories) as both fat and fiber prolongs gastric emptying.
• Special diabetic formulas (low CHO and high fat) are available; however, there is not sufficient evidence to recommend routine use of these formulas for patients with DM.

Discuss parenteral nutrition in diabetes mellitus?

• PN should not be initiated until glycemic control is achieved (< 11mmol/l).
• For diabetic patients or patients with a fasting glucose concentration of11 mmoles/l, no more than 100 grams of dextrose per day should be administered. A basal amount of regular insulin should also be added to the PN formulation to keep blood glucose concentrations less than 8.5mmol/l.  A common initial regimen is 0.1 units of insulin per gram of dextrose in the PN infusion.
• Obese patients with type 2 diabetes may require as much as 0.1 units of insulin for every 0.5 grams of dextrose whereas thin, type 1 diabetics may require only 0.1 units of insulin per 2 grams of dextrose. If hyperglycemia persists when 0.3 units of insulin per gram of PN dextrose is exceeded, a separate iv insulin infusion should be used to achieve glycemic control.
• A separate intravenous infusion is preferred in a patient whose insulin needs are dynamic or difficult to predict (e.g. infection, inflammatory response).
• It is important to know that the insulin dose may need adjustments because there is a variable amount of insulin binding to PN bags and tubing, depending on materials used.
• Monitor capillary glucose levels every 6 hours. Once glucose concentrations are stable, the frequency of measuring capillary glucose concentrations often can be reduced.
• The insulin dosage in the PN formulation ratio is modified daily based on the amount of insulin given with sliding-scale insulin coverage over the previous 24 hours.

Ref

1. ASPEN guidelines