What is the proper protocol for preparing an insulin infusion?

How to Prepare an Insulin Infusion

Prepare insulin infusions at a standardized concentration of 1 unit/mL using regular human insulin in 0.9% normal saline, and prime the tubing with 20 mL of waste volume before connecting to the patient. 1, 2

Standard Preparation Protocol

Insulin Selection and Concentration

• Use only regular human insulin for all continuous IV infusions—never use rapid-acting analogs, long-acting insulins, or any other insulin formulation for IV administration. 1, 2
• Mix regular insulin to achieve a final concentration of 1 unit/mL in 0.9% normal saline (NS). 1, 2
• This standardized concentration minimizes dosing errors and allows for consistent titration across all critically ill patients. 1

Visual Inspection Before Preparation

• Inspect the insulin vial immediately before use—regular insulin should appear completely clear and colorless. 2, 3
• Do not use the insulin if you observe any clumping, frosting, precipitation, cloudiness, thickening, discoloration, or visible particles. 2, 3
• Any visual changes indicate loss of potency and the vial must be replaced. 2

Tubing Preparation (Critical Step)

• Prime new IV tubing with at least 20 mL of the prepared insulin solution as waste before initiating therapy. 1, 2
• This priming step is essential because insulin adheres to the plastic tubing, and without adequate priming, the initial delivered dose will be unpredictably lower than intended. 1
• Discard this 20 mL waste volume—do not deliver it to the patient. 1, 2

Storage and Handling

Temperature Management

• Store unopened insulin vials refrigerated at 36-46°F (2-8°C) to prevent loss of potency. 2
• Avoid exposing insulin to extreme temperatures (<36°F or >86°F) or excess agitation, as these conditions cause loss of potency. 2
• Once opened and in use, insulin infusions can remain at room temperature during active administration. 2

Mixing and Compatibility

• Never mix other medications with insulin in the same solution unless specifically approved by pharmacy. 2
• Insulin infusions should run through dedicated IV tubing to avoid compatibility issues and ensure accurate dosing. 1

Clinical Context for IV Insulin Use

When to Use IV Insulin Infusion

• Hemodynamically unstable patients with hyperglycemia requiring vasopressor support. 1, 2
• Patients with type 1 diabetes in critical care settings, particularly those with DKA or HHS. 1, 2
• Any situation requiring rapid titration and immediate flexibility for tight glycemic control. 1, 2
• Patients with changing clinical status including hypothermia, peripheral edema, or frequent interruptions of dextrose intake. 1

When NOT to Use IV Insulin

• Stable patients without critical illness can be managed with subcutaneous insulin regimens. 1
• Delay subcutaneous insulin initiation until the patient is off vasopressors, peripheral edema has resolved, and there are no planned interruptions of nutrition. 1

Common Pitfalls to Avoid

• Failing to use regular human insulin—only regular insulin is appropriate for IV administration; using rapid-acting analogs or other formulations can cause unpredictable pharmacokinetics. 1, 2
• Skipping the tubing prime—without the 20 mL waste prime, insulin adherence to tubing causes underdosing during the critical initial period. 1, 2
• Using non-standardized concentrations—concentrations other than 1 unit/mL increase the risk of dosing errors and make protocol-driven titration impossible. 1, 2
• Mixing insulin with incompatible solutions—this can cause precipitation or inactivation of insulin. 2
• Using cloudy or discolored insulin—any visual abnormality indicates the insulin is no longer potent and must be discarded. 2, 3

Dosing Initiation (Brief Overview)

For diabetic ketoacidosis (DKA), start with 0.1 units/kg/h as a continuous infusion after ensuring adequate potassium levels (>3.3 mmol/L). 1

For general critical care hyperglycemia, most protocols use initial rates of 0.5-1 unit/hour with titration based on hourly glucose monitoring, though specific rates should follow your institution's nurse-driven protocol. 1

Human studies from the 1970s established that continuous low-dose insulin infusions (4-7 units/hour) achieve physiologic insulin levels of 55-75 microU/mL and effectively control hyperglycemia without the risks of high-dose regimens. 4, 5

A priming bolus is not necessary if you use an adequate continuous infusion rate (approximately 0.14 units/kg/h or about 10 units/hour in a 70-kg patient), as this achieves therapeutic insulin levels within 45-60 minutes. 6