What is the appropriate dose of regular insulin for a patient with hyperglycemia (glucose level of 500 mg/dL)?

Regular Insulin Dosing for Severe Hyperglycemia (500 mg/dL)

For a patient with a blood glucose of 500 mg/dL, administer intravenous regular insulin at an initial bolus dose of 0.15 units/kg followed by a continuous infusion at 0.1 units/kg/hour (typically 5-7 units/hour for adults). 1

Approach to Severe Hyperglycemia Management

Initial Assessment

• Determine if the patient has diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS)
• Check for hypokalemia (K+ < 3.3 mEq/L) before starting insulin therapy
• Assess hydration status and initiate appropriate fluid replacement

Insulin Administration Protocol

For Intravenous Administration (Preferred Method):

1. Initial bolus: 0.15 units/kg of regular insulin IV
2. Continuous infusion: 0.1 units/kg/hour (typically 5-7 units/hour for adults)
3. Monitoring and adjustment:
   • If glucose does not decrease by at least 50 mg/dL in the first hour, check hydration status
   • If hydration is adequate, double the insulin infusion rate hourly until achieving a steady glucose decline of 50-75 mg/dL per hour 1

For Subcutaneous Administration (If IV Access Unavailable):

• For mild DKA only: Give "priming" dose of regular insulin at 0.4-0.6 units/kg, with half as IV bolus and half as subcutaneous injection
• Follow with 0.1 unit/kg subcutaneously every hour 1

Special Considerations

Transition to Subcutaneous Insulin

Once blood glucose reaches 250-300 mg/dL:

• Start basal-bolus insulin regimen
• Continue IV insulin for 1-2 hours after first subcutaneous dose to ensure adequate plasma insulin levels
• Avoid abrupt discontinuation of IV insulin 1

Sliding Scale for Subcutaneous Regular Insulin

For patients unable to receive IV insulin with glucose of 500 mg/dL:

• Use 20 units of regular insulin subcutaneously (based on sliding scale of 5 units for every 50 mg/dL above 150 mg/dL) 1
• Monitor glucose every 4-6 hours

Monitoring Parameters

• Check blood glucose every 1-2 hours until stable, then every 2-4 hours
• Monitor electrolytes, especially potassium
• For DKA, monitor resolution of ketosis (preferably using β-hydroxybutyrate measurements)

Pitfalls to Avoid

1. Delayed treatment: Severe hyperglycemia requires prompt intervention to prevent complications
2. Inadequate monitoring: Frequent glucose checks are essential to avoid hypoglycemia
3. Premature discontinuation of IV insulin: Continue IV insulin for 1-2 hours after initiating subcutaneous insulin to prevent rebound hyperglycemia
4. Neglecting fluid status: Adequate hydration is critical for insulin effectiveness and patient safety
5. Relying on urine ketones: Blood β-hydroxybutyrate measurement is preferred for monitoring ketosis resolution 1

Remember that patients with severe hyperglycemia often have significant fluid deficits requiring aggressive rehydration alongside insulin therapy. The goal is to achieve a steady glucose decline while avoiding too rapid correction, which can lead to complications.