A 28-year-old man with newly diagnosed type 1 diabetes mellitus presents to the emergency department with a 3-day history of polyuria, polydipsia, and progressive lethargy. On examination, he is tachypneic (RR 28/min) with Kussmaul respirations and fruity-smelling breath. Blood pressure is 110/70 mmHg, heart rate 110/min. Laboratory investigations reveal: blood glucose 520 mg/dL, arterial pH 7.18, HCO₃⁻ 12 mEq/L, anion gap 18, serum osmolality 310 mOsm/kg, serum ketones strongly positive, and urine ketones 4+. What is the most appropriate immediate management step after establishing IV access and beginning fluid resuscitation?

Explanation

## Immediate Management of DKA **Key Point:** In DKA, insulin therapy is the cornerstone of management and should be initiated early, but only AFTER establishing adequate IV access, beginning fluid resuscitation, and correcting severe hypokalemia (if present). ### Pathophysiology DKA is characterized by: - Absolute or relative insulin deficiency - Uncontrolled lipolysis → free fatty acid release - Hepatic ketone body production (acetoacetate, β-hydroxybutyrate) - High anion gap metabolic acidosis with ketonemia and ketonuria ### Insulin Dosing in DKA The standard insulin protocol is: 1. **Initial bolus:** 0.1 units/kg IV (regular insulin) — optional but often used 2. **Continuous infusion:** 0.1 units/kg/hour IV 3. **Goal:** Reduce blood glucose by 50–75 mg/dL/hour 4. **Transition:** When glucose reaches 200–250 mg/dL, switch to 5% dextrose + 0.45% saline + insulin to prevent hypoglycemia and cerebral edema while continuing ketone clearance **High-Yield:** Insulin addresses the root cause (lack of insulin) and promotes: - Glucose uptake into cells - Suppression of lipolysis - Inhibition of ketone production - Correction of acidosis (as ketone production ceases) ### Why NOT the Other Options | Management | Why NOT in DKA | |---|---| | **Sodium bicarbonate** | Contraindicated unless pH < 6.9 and severe hemodynamic instability; may worsen hypokalemia, paradoxically increase intracellular acidosis, and delay ketone clearance | | **Early potassium supplementation** | Serum K⁺ may be normal or high initially (due to acidosis-induced shift); risk of fatal hyperkalemia if given before insulin and fluids lower K⁺; check baseline K⁺ first | | **Dextrose-free fluids without insulin** | Delays insulin initiation; perpetuates ketone production; prolongs acidosis | **Clinical Pearl:** The patient's serum osmolality (310 mOsm/kg) is mildly elevated, consistent with DKA (not HHS, where osmolality typically >320). Kussmaul respirations are the respiratory compensation for metabolic acidosis. ### DKA vs. HHS Comparison | Feature | DKA | HHS | |---|---|---| | **Glucose** | 250–600 mg/dL | >600 mg/dL (often >1000) | | **pH** | <7.30 (often <7.10) | >7.30 | | **HCO₃⁻** | <18 mEq/L | >18 mEq/L | | **Serum osmolality** | <320 mOsm/kg | >320 mOsm/kg | | **Ketones** | Strongly positive | Absent or trace | | **Insulin requirement** | Early, high-dose | Lower dose | | **Mortality** | 1–5% | 5–15% | [cite:Harrison 21e Ch 417]