What is the appropriate dose and administration of rapid-acting insulin, such as NovoLog (aspart), Apidra (glulisine), or Humalog (lispro), for an 80kg patient with severe hyperglycemia (blood sugar level of 300)?

Rapid-Acting Insulin Dosing for Severe Hyperglycemia

For an 80kg patient with blood glucose of 300 mg/dL, administer 4 units of rapid-acting insulin (NovoLog, Apidra, or Humalog) immediately, or alternatively use 10% of the current basal insulin dose if the patient is already on basal insulin therapy. 1

Immediate Correction Dose

• Blood glucose of 300 mg/dL represents significant hyperglycemia requiring prompt intervention with rapid-acting insulin. 1
• The American Diabetes Association recommends an initial correction dose of 4 units of rapid-acting insulin (aspart, glulisine, or lispro) for blood glucose levels at this threshold. 1
• If the patient is already on basal insulin therapy, an alternative approach is to use 10% of the current basal insulin dose as the correction dose. 1
• For blood glucose levels ≥300-350 mg/dL, more aggressive insulin therapy may be warranted, especially if the patient is symptomatic or showing catabolic features. 1

Timing and Administration

• Rapid-acting insulin should be administered within 15 minutes before a meal or immediately after a meal when used for prandial coverage. 2
• For correction of hyperglycemia without concurrent food intake, administer immediately upon recognition of elevated blood glucose. 1
• Subcutaneous injection should be given in the abdominal wall, thigh, upper arm, or buttocks, with rotation of injection sites within the same region to reduce lipodystrophy risk. 2

Pharmacokinetic Considerations

• Rapid-acting insulin analogs (lispro, aspart, glulisine) have onset of action within 15 minutes, peak at 30-90 minutes, and duration of less than 5 hours. 3
• These analogs provide faster subcutaneous absorption, earlier and greater insulin peak, and more rapid postpeak decrease compared to regular human insulin. 3
• Insulin glulisine demonstrates the most rapid onset among rapid-acting analogs, with pharmacokinetics that do not depend on the amount of subcutaneous fat. 4

Critical Monitoring Requirements

• Monitor blood glucose 2-4 hours after administration to assess effectiveness and detect potential hypoglycemia, as this corresponds to peak insulin action. 1
• Be vigilant for hypoglycemia, especially during the 2-4 hour window when insulin action peaks. 1
• Continue monitoring every 2-4 hours until blood glucose stabilizes. 1

Context-Dependent Adjustments

If Patient is NOT on Basal Insulin

• Blood glucose of 300 mg/dL in an insulin-naive patient suggests the need for immediate initiation of basal-bolus insulin therapy, not just correction doses. 1
• For patients with blood glucose ≥300-350 mg/dL and/or HbA1c 10-12% with symptomatic or catabolic features, start basal-bolus insulin immediately rather than basal insulin alone. 5
• Calculate total daily insulin dose as 0.3-0.5 units/kg/day (24-40 units for an 80kg patient), with approximately 50% as basal insulin and 50% as prandial insulin divided among meals. 5, 1

If Patient is Already on Basal Insulin

• The presence of blood glucose at 300 mg/dL despite basal insulin indicates inadequate prandial coverage. 5
• After immediate correction, add scheduled prandial insulin starting with 4 units before the largest meal, increasing by 1-2 units or 10-15% twice weekly based on postprandial glucose readings. 1
• When basal insulin exceeds 0.5 units/kg/day (40 units for an 80kg patient) and glucose remains elevated, adding prandial insulin is more appropriate than continuing to escalate basal insulin alone. 5

Common Pitfalls to Avoid

• Do not rely solely on correction insulin (sliding scale) without addressing basal insulin needs, as this approach is strongly discouraged and ineffective for long-term glycemic management. 1
• Avoid insulin stacking by accounting for previously administered rapid-acting insulin that may still be active (duration up to 5 hours). 1
• Do not administer excessive insulin that could lead to hypoglycemia, especially during overnight hours when hypoglycemia may go undetected. 1
• In the setting of reduced carbohydrate intake, lispro has increased potential for early postprandial hypoglycemia compared to regular insulin, requiring careful meal composition consideration. 6

Special Clinical Situations

• If the patient is hospitalized, target blood glucose ≤180 mg/dL, and for levels significantly above this (such as 300 mg/dL), additional rapid-acting insulin therapy is warranted. 1
• If the patient is on glucocorticoid therapy, higher insulin doses may be required due to steroid-induced insulin resistance. 1
• Evaluate for diabetic ketoacidosis if blood glucose is persistently elevated or if the patient has symptoms of hyperglycemic crisis. 1

Regimen Optimization

• Continue metformin unless contraindicated, as it provides complementary glucose-lowering effects and reduces total insulin requirements. 1
• Discontinue sulfonylureas when advancing to complex insulin regimens beyond basal-only therapy to prevent hypoglycemia. 1
• Consider underlying causes for persistent hyperglycemia, including inadequate basal insulin coverage, uncovered carbohydrate intake, or steroid administration. 1