What is the recommended protocol for initiating and managing continuous intravenous (IV) insulin therapy in a critically ill patient with hyperglycemia?

IV Insulin Protocols for Critically Ill Patients

Initiate continuous IV insulin infusion when blood glucose is persistently ≥180 mg/dL (10 mmol/L) on two consecutive measurements, target a glucose range of 140-200 mg/dL (7.8-11.1 mmol/L), and use a protocol with explicit computerized decision support tools with hourly glucose monitoring during periods of instability. 1

When to Initiate IV Insulin

• Start IV insulin therapy when blood glucose reaches ≥180 mg/dL (10 mmol/L) on two consecutive measurements in critically ill adults 1
• The same threshold of ≥180 mg/dL applies to critically ill children 1
• Before initiating insulin, evaluate and address reversible causes: dextrose-containing fluids, enteral/parenteral nutrition rates, and hyperglycemia-inducing medications (corticosteroids, vasopressors) 1
• Continuous IV insulin infusion is strongly preferred over subcutaneous insulin in hemodynamically unstable patients, those with type 1 diabetes, and any critically ill patient with significant hyperglycemia 1, 2

Target Glucose Range

• Target blood glucose of 140-200 mg/dL (7.8-11.1 mmol/L) for all critically ill adults 1
• Avoid intensive glucose control targeting 80-139 mg/dL (4.4-7.7 mmol/L) as this significantly increases hypoglycemia risk without improving mortality or morbidity outcomes 1
• For critically ill children, the same conventional target of 140-200 mg/dL is recommended with a strong recommendation against intensive control 1

Insulin Preparation and Administration

• Prepare insulin as a 1 unit/mL concentration in 0.9% sodium chloride using polyvinyl chloride infusion bags 1, 3
• Prime new IV tubing with a 20 mL waste volume before connecting to the patient to saturate binding sites in the tubing 1
• Infusion bags prepared with this concentration are stable refrigerated for 48 hours, then at room temperature for an additional 48 hours 3
• Initial infusion rates typically start at 0.1 units/kg/hour for severe hyperglycemia, adjusted according to protocol 4

Glucose Monitoring Frequency

• Monitor blood glucose every 30-60 minutes (≤1 hour intervals) during periods of glycemic instability until glucose stabilizes in target range 1, 2
• Once stable in target range, monitoring intervals can be extended but should remain frequent 1
• Continuous or near-continuous glucose monitoring systems are preferred when available, though current evidence is insufficient to mandate their use over frequent point-of-care testing 1
• Point-of-care glucose meters are acceptable for monitoring, though arterial or venous samples are preferred over capillary samples in critically ill patients with hypotension or peripheral edema 1

Protocol Requirements

• Use a nurse-driven protocol with explicit computerized clinical decision support tools rather than paper-based protocols without decision support 1
• Protocols with explicit decision support tools reduce hypoglycemia risk and improve time in target glucose range compared to protocols without such tools 1, 5
• The protocol should specify insulin dose adjustments based on current glucose, rate of glucose change, and insulin sensitivity 1, 6
• Nurses should have primary responsibility for protocol implementation with clear authority to adjust insulin rates according to the algorithm 6

Hypoglycemia Prevention and Management

• Select protocols that demonstrate low hypoglycemia rates (<1% of measurements <70 mg/dL) in validation studies 1
• Treat any blood glucose <70 mg/dL immediately without delay 1
• Severe hypoglycemia (<40 mg/dL) should trigger protocol review and potential modification 7
• Use extra caution in patients with renal insufficiency (creatinine clearance <70 mL/min) as they have significantly higher hypoglycemia risk 7

Transitioning from IV to Subcutaneous Insulin

• Do not discontinue IV insulin until subcutaneous basal insulin has been administered and absorbed 2, 4
• Calculate total daily subcutaneous insulin requirement as 80% of the total IV insulin used in the previous 24 hours 2
• Administer 50% as once-daily long-acting basal insulin (glargine or detemir) and 50% as prandial rapid-acting insulin divided before meals 2
• Give the first dose of basal insulin 1-2 hours before stopping the IV infusion to ensure adequate overlap 2, 4
• Only transition when the patient is hemodynamically stable, off vasopressors, peripheral edema has resolved, and nutrition intake is predictable 1, 2

Special Monitoring Considerations

• Check serum potassium every 4-6 hours initially as insulin therapy drives potassium intracellularly and can precipitate hypokalemia 4
• Add potassium supplementation to IV fluids when serum potassium is in the low-normal range to prevent dangerous hypokalemia 4
• If glucose remains >300 mg/dL (16.7 mmol/L) despite adequate insulin infusion, check for ketosis (urine ketones ≥2+ or serum ketones ≥1.5 mmol/L) 2, 4
• Presence of ketosis with severe hyperglycemia indicates diabetic ketoacidosis requiring more aggressive insulin therapy (typically 0.1 units/kg/hour) 4

Critical Pitfalls to Avoid

• Never use sliding-scale insulin alone without basal insulin as this approach is ineffective and leads to poor glycemic control 2, 8, 9
• Never abruptly stop IV insulin without overlapping subcutaneous basal insulin as this causes immediate loss of glucose control and rebound hyperglycemia 2, 4
• Avoid targeting glucose <110 mg/dL as this increases hypoglycemia risk 2-fold without mortality benefit 1, 8
• Do not transition to subcutaneous insulin in patients with ongoing hemodynamic instability, hypothermia, significant peripheral edema, or frequent NPO status for procedures 1, 2
• Avoid correcting glucose too rapidly (>50-75 mg/dL per hour) as this may cause neurological complications 4