What is the insulin infusion protocol for Total Parenteral Nutrition (TPN)?

From the Guidelines

The insulin infusion protocol for Total Parenteral Nutrition (TPN) should involve adding regular insulin directly to the TPN solution, starting with a dose of 1 unit of insulin for every 10 g of carbohydrate, as recommended by the most recent guidelines 1.

Insulin Dosing for TPN

When initiating TPN, it is crucial to consider the carbohydrate content of the solution to determine the appropriate insulin dose.

• The insulin dose can be calculated based on the total daily carbohydrate content of the TPN solution.
• For example, if the TPN solution contains 250 grams of carbohydrate per day, the initial insulin dose would be 25 units of regular insulin added to the TPN bag, based on the guideline recommendation of 1 unit of insulin per 10 grams of carbohydrate 1.

Monitoring and Adjustments

• Blood glucose levels should be monitored every 6 hours initially, with insulin adjustments made daily based on these readings.
• If glucose levels remain above 180 mg/dL despite insulin in the TPN, a separate insulin infusion may be required, starting at 0.05-0.1 units/kg/hour and titrated according to blood glucose levels.

Special Considerations

• For patients with pre-existing diabetes, higher initial insulin doses may be needed, and the protocol should be adjusted accordingly.
• The protocol should also include a plan for hypoglycemia management, typically involving temporary reduction of insulin and administration of dextrose if glucose falls below 70 mg/dL.

Rationale

This approach is necessary because TPN provides continuous glucose infusion, which requires insulin to prevent hyperglycemia, as uncontrolled blood glucose can increase infection risk and worsen outcomes in critically ill patients, as highlighted in recent guidelines 1.

From the FDA Drug Label

The intravenous administration of Humulin R U-100 was tested in 21 patients with type 1 diabetes The patients' usual doses of insulin were temporarily held, and blood glucose concentrations were maintained at a range of 200 – 260 mg/dL for one to three hours during a run-in phase of intravenous Humulin R U-100 followed by a 6-hour assessment phase. During the assessment phase patients received intravenous Humulin R at an initial dose of 0. 5 U/h, adjusted to maintain blood glucose concentrations near normoglycemia (100 to 160 mg/dL).

The insulin infusion protocol is to start with an initial dose of 0.5 U/h and adjust to maintain blood glucose concentrations near normoglycemia (100 to 160 mg/dL) 2.

• Key points:
  • Initial dose: 0.5 U/h
  • Target blood glucose range: 100 to 160 mg/dL
  • Adjustment of dose based on blood glucose levels is necessary.

From the Research

Insulin Infusion Protocol for Total Parenteral Nutrition (TPN)

• The blood glucose target for hospitalized patients on parenteral nutrition is 7.8 to 10.0 mmol/L (140 to 180 mg/dL) 3
• Insulin can be delivered via the subcutaneous or intravenous route or, alternatively, added to parenteral nutrition admixtures 3
• For stable patients, insulin can be added directly to the parenteral nutrition bag 3
• If parenteral nutrition is infused continuously over 24 hours, the subcutaneous injection of a long-acting insulin combined with correctional bolus insulin may be adequate 3

Transition from Intravenous Insulin to Subcutaneous Long-acting Insulin

• The optimal initial dose of subcutaneous (SC) insulin after intravenous (IV) infusion is controversial, especially in patients receiving continuous enteral nutrition (EN) or total parenteral nutrition (TPN) 4
• The initial dose of SC insulin was estimated as 50% of the daily IV insulin requirements, extrapolated from the previous 12h 4
• A corrective dose of short-acting insulin (lispro) was used when necessary 4

Insulin Protocol for Management of Hyperglycemia

• An insulin protocol for parenteral nutrition (PN)-induced hyperglycemia is superior to conventional management relying primarily on sliding-scale insulin 5
• The protocol determined insulin doses based on carbohydrate delivery and capillary blood glucose (CBG) if half or more of CBG measurements in the first 24 hours after initiation of PN exceeded 140 mg/dL 5
• Linking insulin to carbohydrate in PN leads to improved glycemic control with a low rate of hypoglycemia 5

Addition of Insulin to Parenteral Nutrition

• Administration of parenteral nutrition (PN) may result in hyperglycemia in patients with preexisting diabetes or disease-related insulin resistance 6
• Insulin can be administered subcutaneously, intravenously via a variable rate sliding scale, or by adding it directly to the PN 6
• The available literature suggests that, at least in the short term, insulin addition to PN can achieve reasonable glycemic control with low rates of hypoglycemia 6

Standardized Subcutaneous Insulin Protocols

• Standardized subcutaneous insulin protocols for diabetic patients on general medical and surgical floors have been developed 7
• The recommended starting subcutaneous insulin protocol for patients receiving meals is a basal-bolus approach using 0.5 U/kg basal insulin and 0.1 U/kg rapid analog at each meal 7
• A variation on this approach is used with total parenteral nutrition (TPN), with a portion of the insulin placed in the TPN bag and the remainder given as "q 8 hour 70/30" insulin 7