What is the appropriate insulin dose for a patient with hyperglycemia (high blood sugar) exceeding 500 mg/dL?

Management of Severe Hyperglycemia (Blood Glucose >500 mg/dL)

For patients with blood glucose exceeding 500 mg/dL, immediate treatment with intravenous regular insulin is recommended, starting with an intravenous bolus of 0.15 units/kg followed by continuous infusion at 0.1 unit/kg/hour (typically 5-7 units/hour in adults). 1, 2

Initial Assessment and Treatment Approach

For Critically Ill Patients:

• Assess for hyperglycemic hyperosmolar state (HHS) if glucose ≥600 mg/dL 1
• Start IV fluid resuscitation with 0.9% sodium chloride at 10-20 mL/kg/hour for the first hour 2, 3
• Begin IV regular insulin:
  • Adults: Initial IV bolus of 0.15 units/kg followed by continuous infusion at 0.1 unit/kg/hour 1, 2
  • Pediatric patients: No initial bolus; start continuous infusion at 0.1 unit/kg/hour 1, 2
• Monitor blood glucose hourly using arterial or venous samples (not capillary) 2
• Target glucose range: 140-180 mg/dL for most patients 1, 2

For Non-Critically Ill Patients:

• If clinically stable with mild symptoms, subcutaneous insulin may be considered 2
• Use basal-bolus insulin regimen (not sliding scale alone) 2
• Calculate total daily dose (TDD) at 0.3-0.5 units/kg/day 2
• Divide as 50% basal insulin (glargine or detemir) and 50% prandial insulin 2

Monitoring and Adjustments

• Check blood glucose every 1-2 hours until stable, then every 4-6 hours 1, 2
• Monitor electrolytes, especially potassium, every 2-4 hours 2
• If glucose does not fall by 50 mg/dL in the first hour:
  • Verify hydration status
  • If adequate, double insulin infusion rate hourly until achieving steady glucose decline of 50-75 mg/dL/hour 1
• Add 5-10% dextrose infusion when glucose falls below 250 mg/dL to prevent hypoglycemia 1

Special Considerations

For Hyperglycemic Hyperosmolar State (HHS):

• Calculate serum osmolality: 2[Na⁺] + glucose/18 + BUN/2.8
• HHS criteria: glucose >600 mg/dL, osmolality >320 mOsm/kg, pH >7.3, bicarbonate >15 mEq/L 3
• Target gradual osmolality decline (3-8 mOsm/kg/hour) 3
• Continue IV fluids until hypovolemia corrected (urine output ≥0.5 mL/kg/hour) 3

For Diabetic Ketoacidosis (DKA):

• Check for ketonemia/ketonuria
• If present, follow DKA protocol with more aggressive insulin therapy 1
• Continue insulin until ketosis resolves 1

Transitioning to Subcutaneous Insulin

• Calculate subcutaneous insulin dose based on 60-80% of 24-hour IV insulin requirement 2
• Administer first subcutaneous dose 1-2 hours before stopping IV insulin 2
• Use basal-bolus regimen with:
  • 50% as basal insulin (glargine or detemir)
  • 50% as prandial insulin divided between meals 2

Common Pitfalls to Avoid

1. Relying solely on sliding scale insulin - This approach is ineffective and increases glycemic variability 2, 4

2. Inadequate monitoring - Failure to check glucose and electrolytes frequently enough during initial treatment 1

3. Rapid correction of hyperglycemia - Too aggressive correction can lead to cerebral edema, especially in children 1

4. Overlooking potassium replacement - Insulin therapy drives potassium into cells, risking hypokalemia 2

5. Premature discontinuation of IV insulin - Ensure overlap when transitioning to subcutaneous insulin 2

6. Inaccurate glucose readings - Point-of-care glucose meters may be inaccurate in critically ill patients; use laboratory values when possible 1, 2

By following this structured approach to managing severe hyperglycemia, clinicians can effectively reduce blood glucose levels while minimizing the risks of complications such as hypoglycemia, electrolyte disturbances, and cerebral edema.