A 28-year-old woman with Type 1 diabetes mellitus on insulin therapy develops severe hyperglycemia (blood glucose 450 mg/dL) with ketonemia and arterial pH 7.18. She is in diabetic ketoacidosis (DKA). Which is the drug of choice for immediate management of her hyperglycemia and ketosis?

Explanation

## Immediate Management of DKA **Key Point:** Intravenous rapid-acting insulin is the definitive drug of choice for diabetic ketoacidosis. It is the ONLY agent that directly suppresses lipolysis, halts ketone production, and corrects hyperglycemia simultaneously. ## Pathophysiology of DKA ```mermaid flowchart TD A[Absolute insulin deficiency]:::urgent --> B[Uncontrolled lipolysis] A --> C[Hyperglycemia] B --> D[Free fatty acid release] D --> E[Hepatic ketone production] E --> F[Ketonemia + Metabolic acidosis] C --> G[Osmotic diuresis] G --> H[Dehydration + Electrolyte loss] I[IV Insulin]:::action --> J[Suppresses lipolysis] I --> K[Inhibits ketone production] I --> L[Lowers blood glucose] J --> M[Resolves acidosis] K --> M L --> N[Corrects osmotic diuresis] ``` ## Why IV Insulin is the Drug of Choice | Mechanism | Effect on DKA | |-----------|---------------| | **Suppresses hormone-sensitive lipase** | Stops free fatty acid mobilization | | **Inhibits hepatic ketogenesis** | Halts ketone body production | | **Enhances peripheral glucose uptake** | Reduces hyperglycemia | | **Restores anabolic state** | Shifts metabolism from catabolic to anabolic | | **Corrects pH** | Resolves metabolic acidosis as ketone production ceases | **High-Yield:** The insulin regimen in DKA: 1. **Loading dose:** 0.1 U/kg IV bolus (optional, rarely used now) 2. **Maintenance:** 0.1 U/kg/hr IV infusion, titrated to glucose decline of 50–100 mg/dL/hr 3. **Transition:** Switch to subcutaneous insulin once pH >7.3, HCO₃⁻ >18 mEq/L, and patient can tolerate oral intake **Clinical Pearl:** Insulin is the ONLY agent that addresses the root cause of DKA (absolute insulin deficiency) and stops ketone production. All other supportive measures (fluids, electrolyte replacement, bicarbonate) are adjunctive. ## Concurrent Management (Not Alternatives) - **IV fluids (0.9% saline):** Correct dehydration and restore renal perfusion - **Potassium replacement:** Monitor and replace as insulin drives K⁺ intracellularly - **Phosphate:** Replace if severely depleted - **Bicarbonate:** Reserved for severe acidosis (pH <6.9); NOT first-line **Warning:** Do NOT use metformin in acute DKA — risk of lactic acidosis. Glucagon worsens hyperglycemia and ketosis by promoting hepatic glucose output and lipolysis. [cite:Harrison 21e Ch 417; Endocrinology Board Review]