What are the guidelines for managing a patient on intravenous (IV) insulin infusion, specifically Humulin R (regular insulin)?

Managing IV Insulin Infusion in Hospitalized Patients

Continue the IV insulin infusion using a nurse-driven protocol targeting blood glucose 140-180 mg/dL, monitoring glucose every 1-2 hours until stable, then transition to subcutaneous basal-bolus insulin before discontinuing the infusion. 1

Immediate Management of IV Insulin Infusion

Target Blood Glucose Range

• Maintain blood glucose between 140-180 mg/dL (7.8-10.0 mmol/L) for most ICU and non-ICU patients. 1, 2
• More stringent targets of 110-140 mg/dL may be considered only for cardiac surgery patients or those with acute ischemic cardiac/neurological events, but this increases hypoglycemia risk without proven mortality benefit. 1
• Avoid targeting glucose <110 mg/dL as this significantly increases hypoglycemia without improving outcomes. 2

Monitoring Frequency

• Check blood glucose every 1-2 hours while on IV insulin infusion until glucose stabilizes in target range. 1, 2
• Once stable at target for 24 hours, glucose checks can be spaced to every 2-4 hours. 1
• If hyperglycemia persists >180 mg/dL after initial bolus, check glucose every 30-60 minutes and adjust infusion rate accordingly. 2

IV Insulin Administration Details

• Use regular insulin (Humulin R U-100) at concentrations of 0.1-1 unit/mL in 0.9% sodium chloride via polyvinyl chloride infusion bags. 3
• Prepared infusion bags are stable refrigerated for 48 hours, then at room temperature for an additional 48 hours. 3
• Most patients achieve glucose <150 mg/dL within 3-4 hours of starting IV insulin. 4, 5

Protocol-Driven Approach

• Use a standardized, nurse-driven protocol with explicit decision support tools rather than ad-hoc dosing. 1, 2
• Computer-based algorithms can reduce hypoglycemia rates and glucose variability, though they haven't shown mortality benefit over standard protocols. 1
• Variable-rate infusions based on current glucose values are more effective than fixed-rate infusions. 2

When to Continue IV Insulin vs. Transition to Subcutaneous

Indications to Continue IV Insulin

• Type 1 diabetes patients (always prefer IV insulin in acute settings). 1
• Hemodynamically unstable patients or those on vasopressors. 1
• Patients with significant peripheral edema (impairs subcutaneous absorption). 1
• Planned interruptions of nutrition for procedures. 1
• Hourly insulin requirements >5 units/hour (indicates severe insulin resistance). 1
• Presence of diabetic ketoacidosis with glucose >300 mg/dL (16.5 mmol/L). 1, 2

When to Transition to Subcutaneous Insulin

• Blood glucose stable <180 mg/dL for at least 24 hours. 1, 2
• Patient has resumed oral feeding or has consistent enteral/parenteral nutrition. 1
• No vasopressor support. 1
• Peripheral edema resolved. 1
• Hourly insulin requirement ≤0.5 units/hour. 1

Transitioning from IV to Subcutaneous Insulin

Critical Timing

• Administer the first dose of long-acting basal insulin (glargine or detemir) immediately before or simultaneously with stopping the IV insulin infusion—never stop IV insulin first. 1, 2
• Abruptly discontinuing IV insulin without overlapping subcutaneous basal insulin leads to rapid recurrence of hyperglycemia. 2
• Optimal timing for basal insulin injection is 8:00 PM (20:00 hours). 1

Calculating Transition Doses

Use the Avanzini method: 1, 2

• Basal insulin dose = 50% of total IV insulin used in previous 24 hours, given as single daily injection of long-acting insulin (glargine/detemir). 1, 2
• Prandial insulin dose = remaining 50% of total IV insulin, divided equally among three meals as rapid-acting insulin (lispro/aspart). 1, 2
• Alternative approach: Give 80% of 24-hour IV insulin total as basal insulin, then add rapid-acting insulin at first meal. 1

Example calculation: If patient received 48 units IV insulin over 24 hours:

• Basal insulin (glargine): 24 units once daily at 8 PM
• Rapid-acting insulin: 8 units before each meal (breakfast, lunch, dinner)

Special Circumstances

• If IV insulin was used <24 hours in non-diabetic patients with persistent hyperglycemia, start with 0.5-1 unit/kg/day total insulin (half basal, half prandial). 1
• Give only half the calculated prandial dose if patient has poor oral intake or light meals. 1
• For patients on total parenteral nutrition (TPN) while NPO, use 60-80% of calculated basal insulin dose to prevent hypoglycemia. 6

Nutritional Considerations

Carbohydrate Intake Management

• Calculate insulin requirements based on amount and timing of carbohydrate intake. 1
• Consistent nutrition simplifies glycemic management during IV insulin infusion. 1
• Provision of 200-300 grams dextrose daily may be needed to prevent hypoglycemia during aggressive insulin therapy. 1

Unplanned Nutrition Interruptions

• Protocols must include explicit instructions for managing sudden discontinuation of enteral feeds, TPN, or dextrose infusions. 1
• If nutrition is interrupted, reduce insulin infusion rate by 50% and check glucose every 30-60 minutes. 1
• Have dextrose 10% or 50% immediately available to treat hypoglycemia. 1

Hypoglycemia Prevention and Management

Risk Factors in Elderly Patients

• Older adults have impaired counterregulatory responses and are at higher risk for severe hypoglycemia. 1
• Renal/hepatic impairment delays insulin clearance, increasing hypoglycemia risk. 1
• Spontaneous hypoglycemia (not insulin-induced) is a marker of severe illness and mortality. 1

Hypoglycemia Thresholds and Treatment

• Treat any glucose <70 mg/dL (3.9 mmol/L) immediately, even without symptoms. 1
• For glucose 60-70 mg/dL with symptoms, administer oral glucose if patient conscious. 1
• For glucose <60 mg/dL or unconscious patient, give IV dextrose immediately. 1
• After treating hypoglycemia, reduce insulin infusion rate by 20-50% and reassess protocol. 1

Monitoring for Hypoglycemia

• Hypoglycemia rates should be <1-2% of all glucose measurements. 4
• Severe hypoglycemia (<40 mg/dL) should occur in <3% of insulin infusion runs. 4

Common Pitfalls to Avoid

Critical Errors

• Never use sliding-scale insulin alone as the sole regimen—it causes dangerous glucose fluctuations and increases complications. 1, 2
• Never stop IV insulin before administering subcutaneous basal insulin—this causes immediate loss of glycemic control. 1, 2
• Never use subcutaneous insulin in hemodynamically unstable patients or those in shock—absorption is unpredictable. 1

Protocol Violations

• Avoid targeting glucose <110 mg/dL outside of specific cardiac surgery protocols. 1, 2
• Don't initiate subcutaneous insulin while patient remains on vasopressors. 1
• Don't transition to subcutaneous insulin if peripheral edema is present. 1
• Don't start long-acting insulin if frequent NPO periods are anticipated for procedures. 1

Monitoring Failures

• Failure to check glucose frequently enough (every 1-2 hours) during active titration leads to dangerous excursions. 1, 2
• Not having a written protocol for nutrition interruptions causes preventable hypoglycemia. 1
• Inadequate overlap between IV and subcutaneous insulin (should be 1-2 hours minimum). 1

Post-Transition Management

Subcutaneous Insulin Monitoring

• Check blood glucose every 4-6 hours after transitioning to subcutaneous regimen. 1, 2
• Adjust insulin doses daily based on glucose patterns. 2
• If glucose control fails (consistently >180 mg/dL), redesign regimen or resume IV insulin. 1

Discharge Planning

• For HbA1c <8%, arrange follow-up with primary care physician within 1-2 weeks. 1, 2
• For HbA1c 8-9%, arrange endocrinology consultation before discharge. 1
• For HbA1c >9% or persistent glucose >200 mg/dL (11 mmol/L), consider endocrinology hospitalization or urgent outpatient follow-up. 1