What dose of Human Actrapid (insulin) should be administered to an adult patient with diabetes and severe hyperglycemia (capillary blood glucose level of 480)?

Immediate Insulin Dosing for Severe Hyperglycemia (CBG 480 mg/dL)

For a capillary blood glucose of 480 mg/dL (26.6 mmol/L), administer an immediate intravenous bolus of 0.15 units/kg of regular insulin (Human Actrapid), followed by a continuous intravenous infusion at 0.1 units/kg/hour until blood glucose falls to 250-300 mg/dL. 1, 2

Critical Initial Assessment

Before administering insulin, you must:

• Exclude hypokalemia (K+ <3.3 mEq/L) - if present, correct potassium first before giving insulin to avoid life-threatening cardiac arrhythmias 1, 2
• Check for ketosis - in patients with type 1 diabetes or insulin-treated type 2 diabetes with glucose >300 mg/dL (16.5 mmol/L), measure urine or blood ketones to rule out diabetic ketoacidosis 3
• Assess for hyperosmolarity - measure serum sodium and calculate effective osmolality (2[Na] + glucose/18) to exclude hyperosmolar hyperglycemic state if osmolality >320 mOsm/kg 3, 1

Insulin Dosing Protocol

For Diabetic Ketoacidosis or Severe Hyperglycemia:

• Initial IV bolus: 0.15 units/kg of regular insulin (Human Actrapid) 1, 2
• Continuous infusion: 0.1 units/kg/hour (typically 5-7 units/hour in adults) 1, 2
• Target glucose reduction: 50-75 mg/dL per hour 1, 2
• If glucose fails to drop by 50 mg/dL in the first hour: double the insulin infusion rate every hour until steady decline achieved 1

Transition to Subcutaneous Insulin:

• When glucose reaches 250 mg/dL: decrease IV insulin to 0.05-0.1 units/kg/hour and add 5-10% dextrose to IV fluids 1, 2
• Before stopping IV insulin: give subcutaneous basal insulin, with total subcutaneous dose = half of the 24-hour IV insulin amount 3
• Split subcutaneous dose: 50% as basal insulin (given once in evening), 50% divided among three meals as rapid-acting insulin 3

Alternative Approach for Mild Cases Without Ketoacidosis:

If the patient has mild hyperglycemia without ketosis, adequate hydration, and can take subcutaneous insulin:

• Initial subcutaneous dose: 0.4-0.6 units/kg as total daily dose, with half given as intravenous bolus and half as subcutaneous/intramuscular injection 1
• Maintenance: 0.1 units/kg/hour subcutaneously or intramuscularly 1

Critical Monitoring Requirements

• Check glucose every 1-2 hours during IV insulin infusion 1, 2
• Monitor serum potassium every 2-4 hours - add 20-40 mEq/L potassium to IV fluids once urine output established and K+ >3.3 mEq/L 1, 2
• Check venous pH and anion gap every 2-4 hours if ketoacidosis present 1

Essential Pitfalls to Avoid

• Never give insulin if potassium <3.3 mEq/L - correct hypokalemia first to prevent cardiac arrest 1, 2
• Never use sliding scale insulin alone for glucose of 480 mg/dL - this reactive approach leads to dangerous glucose fluctuations and is explicitly condemned by all major guidelines 4, 5
• Never give rapid-acting insulin at bedtime for correction - this significantly increases nocturnal hypoglycemia risk 5
• Do not stop IV insulin abruptly - overlap with subcutaneous basal insulin by 1-2 hours to prevent rebound hyperglycemia 3

Fluid Resuscitation (Concurrent with Insulin)

• Initial fluid: 0.9% normal saline at 15-20 mL/kg/hour (1-1.5 L) in the first hour 1, 2
• Subsequent fluid: 250-500 mL/hour based on hydration status and corrected sodium 1, 2
• Average requirement: 9 liters over 48 hours for hyperosmolar states 6