About This Calculator

The Insulin Infusion Rate Calculator is a clinical support tool designed to help healthcare professionals determine the appropriate initial rates for continuous intravenous insulin therapy. It is intended for managing acute hyperglycemic states, such as Diabetic Ketoacidosis (DKA), Hyperosmolar Hyperglycemic State (HHS), and other critical care situations requiring precise glycemic control.

Outputs Explained

The calculator provides three key outputs for initiating therapy:

• Initial IV Bolus: A one-time dose of insulin given to rapidly lower high blood glucose levels. This is typically calculated for weight-based protocols (e.g., DKA) and may not be recommended for standard sliding scale protocols.
• Initial Infusion Rate (units/hr): The continuous hourly dose of insulin to be administered. This is the primary therapeutic rate that will be titrated based on subsequent blood glucose measurements.
• Pump Rate (mL/hr): The volume of insulin solution to be infused per hour, calculated from the infusion rate (units/hr) and the concentration of the insulin bag (units/mL). This is the value programmed into the infusion pump.

How to Use the Calculator

Follow these steps to obtain an initial dosing recommendation:

1. Select Protocol: Choose between “Weight-Based (DKA/HHS)” for critically ill patients or “Standard Sliding Scale” for general hyperglycemic management.
2. Enter Patient Weight: If using the weight-based protocol, input the patient’s weight and select the appropriate unit (kg or lbs).
3. Enter Current Blood Glucose: Input the patient’s most recent blood glucose reading and select the unit (mg/dL or mmol/L).
4. Select Insulin Concentration: Choose the concentration of your institution’s standard insulin infusion bag (e.g., 100 units in 100 mL for 1 unit/mL) or select “Custom” to input specific values.
5. Set Target Range: Verify or adjust the target blood glucose range according to institutional policy. The units will automatically match the blood glucose units selected.

Dosing Overview

Intravenous insulin therapy is guided by specific protocols to ensure safety and efficacy. The two common approaches supported by this tool are:

Weight-Based Protocol (DKA/HHS)

This is the standard of care for DKA and HHS. It typically involves an initial weight-based bolus (e.g., 0.1 units/kg) followed by a continuous weight-based infusion (e.g., 0.1 units/kg/hr). The goal is a steady, controlled decrease in blood glucose of 50-75 mg/dL per hour. Rapid correction can lead to cerebral edema and must be avoided.

Standard Sliding Scale

This protocol uses predefined ranges of blood glucose to determine the insulin infusion rate. It is often used in non-DKA hyperglycemic patients in the ICU or post-operative settings. An initial bolus is generally not administered with this approach. The rate is adjusted based on hourly glucose checks.

Switching to Subcutaneous Insulin

Transitioning from a continuous IV infusion to a subcutaneous (SQ) insulin regimen is a critical step that must be carefully planned to prevent rebound hyperglycemia. The process typically involves:

1. Assessing Stability: The patient should be clinically stable, eating meals, and have their glycemic levels controlled within the target range on a low, stable insulin infusion rate for several hours.
2. Calculating Total Daily Dose (TDD): Estimate the 24-hour insulin requirement based on the stable infusion rate. For example, a stable rate of 2 units/hr would suggest a TDD of 48 units (2 units/hr × 24 hr). Many protocols recommend using 70-80% of this calculated value for the initial SQ TDD.
3. Administering Subcutaneous Insulin: The TDD is split into basal (long-acting) and prandial (rapid-acting) components. The first dose of basal insulin should be administered 1-2 hours before the IV insulin infusion is discontinued to ensure overlap and prevent a gap in insulin coverage.

Managing Infusion Interruptions

If the insulin infusion must be paused (e.g., for transport or a procedure), frequent blood glucose monitoring is essential. Short interruptions of less than 15-30 minutes may be acceptable, but longer pauses significantly increase the risk of hyperglycemia and ketosis, particularly in patients with Type 1 diabetes. Consult institutional protocols for guidance on managing these interruptions, which may involve providing a corrective SQ insulin dose.

Safety Alerts

• Hypoglycemia: This is the most significant risk of IV insulin therapy. Blood glucose must be monitored frequently (e.g., every hour) and the infusion adjusted promptly. Ensure a protocol for treating hypoglycemia is readily available.
• Electrolyte Imbalance: Insulin drives potassium into cells, which can cause or worsen hypokalemia. Potassium levels must be checked before starting the infusion and monitored regularly throughout therapy, with replacement as needed.
• Calculation Verification: All calculations, especially for custom concentrations, should be independently double-checked by another qualified healthcare professional before administration.
• Cerebral Edema: A rare but devastating complication of DKA treatment, associated with overly rapid correction of glucose and osmolarity. Adherence to guideline-recommended rates of glucose reduction is critical.

Frequently Asked Questions

1. Why is patient weight required for the DKA/HHS protocol?
   The DKA/HHS protocol is weight-based to provide a standardized dose relative to the patient’s size and metabolic needs, which is considered the safest and most effective method for these conditions.
2. What is the difference between mg/dL and mmol/L?
   Both are units for measuring blood glucose concentration. mg/dL is standard in the United States, while mmol/L is the standard in the United Kingdom and many other countries. To convert mmol/L to mg/dL, multiply by 18.018.
3. When should I use a custom insulin concentration?
   Only select “Custom” if your institution uses a non-standard insulin preparation. The most common concentration is 100 units of regular insulin in 100 mL of 0.9% sodium chloride (1 unit/mL). Always verify the concentration on the IV bag.
4. How often should the infusion rate be adjusted?
   Initially, blood glucose should be checked hourly, and the rate titrated based on the patient’s response and institutional protocol until glucose levels are stable within the target range.
5. What should I do if the blood glucose drops too quickly?
   If blood glucose falls by more than 100 mg/dL in one hour, the insulin infusion rate should be reduced. This helps prevent hypoglycemia and reduces the risk of cerebral edema.
6. Why is there no bolus recommended for the Standard Sliding Scale protocol?
   Standard sliding scales are typically for more gradual glucose control in non-DKA/HHS situations. An aggressive initial bolus can increase the risk of hypoglycemia in these patients.
7. Can this calculator be used for children?
   This tool is designed for adult patients. Pediatric DKA management has distinct protocols and fluid management considerations that require specialized pediatric guidelines.
8. What type of insulin is used for an IV infusion?
   Regular human insulin is the standard type of insulin used for intravenous infusions due to its short half-life, which allows for rapid titration.

References

1. Kitabchi AE, Umpierrez GE, Miles JM, Fisher JN. Hyperglycemic crises in adult patients with diabetes. Diabetes Care. 2009;32(7):1335-1343. doi:10.2337/dc09-9032
2. American Diabetes Association. 15. Diabetes Care in the Hospital: Standards of Medical Care in Diabetes—2022. Diabetes Care. 2022;45(Supplement_1):S234-S244. doi:10.2337/dc22-S015
3. Gosmanov AR, Gosmanova EO, Dillard-Cannon E. Management of adult diabetic ketoacidosis. Diabetes Metab Syndr Obes. 2014;7:255-264. ncbi.nlm.nih.gov
4. Umpierrez GE, Korytkowski M. Diabetic emergencies – ketoacidosis, hyperglycaemic hyperosmolar state and hypoglycaemia. Nat Rev Endocrinol. 2016;12(4):222-232. doi:10.1038/nrendo.2016.15
5. Magee MF, Nassar CM, El-Khoury L. Insulin Therapy. In: Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.; 2000-. Updated 2021 Jan 18. Available from: ncbi.nlm.nih.gov