A 28-year-old man with newly diagnosed type 1 diabetes mellitus presents to the emergency department with diabetic ketoacidosis (pH 7.18, HCO₃⁻ 12 mEq/L, anion gap 18). After initial fluid resuscitation and electrolyte correction, what is the drug of choice for insulin replacement?

Explanation

## Management of DKA: Insulin Therapy **Key Point:** In acute diabetic ketoacidosis, intravenous regular (short-acting) insulin is the gold standard because it has rapid onset, short half-life (~6 minutes), and allows precise titration in an acute metabolic emergency. ### Why Intravenous Regular Insulin? 1. **Rapid onset and offset** — allows real-time adjustment based on blood glucose and ketone clearance 2. **Predictable pharmacokinetics** — IV route bypasses absorption variability 3. **Reversible with dextrose** — if hypoglycemia occurs, glucose infusion immediately reverses the effect 4. **Titration protocol** — typically 0.1 U/kg bolus, then 0.1 U/kg/hr infusion, adjusted to maintain glucose drop of 50–100 mg/dL/hr ### Why NOT the Other Options? | Agent | Why Inappropriate in Acute DKA | |-------|--------------------------------| | **Insulin glargine** | Long-acting basal insulin; cannot be titrated in acute setting; used for chronic maintenance only | | **Insulin lispro** | Rapid-acting but subcutaneous; slower onset than IV; cannot be titrated as precisely; used after acute phase resolves | | **Insulin NPH** | Intermediate-acting; unpredictable peak; cannot be used IV; unsuitable for acute metabolic crisis | **Clinical Pearl:** Once blood glucose reaches 200–250 mg/dL and ketosis is resolving (pH > 7.30, HCO₃⁻ > 15), transition to subcutaneous insulin (rapid-acting + basal) and then to long-term regimen. **High-Yield:** The transition from IV to subcutaneous insulin must overlap by at least 2–4 hours to prevent rebound hyperglycemia and recurrence of ketosis.