A 42-year-old woman with type 2 diabetes presents with nausea, vomiting, and rapid shallow breathing. ABG: pH 7.22, PaCO₂ 28 mmHg, HCO₃⁻ 12 mEq/L, anion gap 18 mEq/L. Serum glucose 380 mg/dL, serum ketones positive. What is the most appropriate immediate next step?

Explanation

## Clinical Diagnosis: Diabetic Ketoacidosis (DKA) **Key Point:** This patient has **high anion gap metabolic acidosis** with positive serum ketones, hyperglycemia, and respiratory compensation (Kussmaul breathing). The diagnosis is diabetic ketoacidosis. **High-Yield:** DKA diagnostic criteria: - Arterial pH < 7.30 - Serum HCO₃⁻ < 15 mEq/L - Anion gap > 12 mEq/L - Positive serum/urine ketones - Elevated blood glucose (usually > 250 mg/dL) ## Management Algorithm for DKA ```mermaid flowchart TD A[DKA Confirmed]:::outcome --> B[Assess severity]:::action B --> C{Mild/Moderate vs Severe?}:::decision C -->|Mild-Moderate| D[IV insulin 0.1 U/kg/hr]:::action C -->|Severe| E[IV insulin 0.15 U/kg/hr]:::action D --> F[NS 500-1000 mL/hr]:::action E --> F F --> G[Monitor K⁺ closely]:::action G --> H[Recheck ABG in 2-4 hrs]:::action H --> I{pH improving?}:::decision I -->|Yes| J[Continue current regimen]:::action I -->|No| K[Increase insulin rate]:::action ``` ## Step-by-Step Management 1. **Fluid resuscitation** (first priority) - Normal saline 500–1000 mL/hr IV - Corrects hypovolemia and dilutes hyperglycemia - Improves renal perfusion and ketone clearance 2. **Insulin therapy** - Regular insulin 0.1 U/kg/hr IV infusion (or 0.15 U/kg/hr if severe) - Suppresses ketone production and promotes glucose utilization - Do NOT give bolus; continuous infusion is safer 3. **Electrolyte monitoring** - Serum K⁺ falls as insulin drives K⁺ intracellularly - Add KCl to IV fluids once K⁺ < 5.5 mEq/L 4. **Reassess ABG** in 2–4 hours ## Why NOT the Other Options | Option | Why Wrong | |--------|----------| | **50% Dextrose** | Contraindicated; glucose is already 380 mg/dL. Dextrose worsens hyperglycemia and osmotic stress. Used only for hypoglycemia. | | **Sodium bicarbonate** | NOT routinely recommended in DKA. Reserved only for pH < 6.9 with severe symptoms (arrhythmias, shock). Bicarbonate delays ketone clearance and causes hypokalemia. | | **Lactate + metformin** | Lactate measurement is not the immediate priority. Metformin is contraindicated in acute DKA (risk of lactic acidosis) and in renal dysfunction. | ## Clinical Pearl **Warning:** Do NOT give dextrose or bicarbonate reflexively in DKA. The primary defect is insulin deficiency and ketone overproduction, not hypoglycemia or severe acidemia alone. **Mnemonic: DKA Management = FIKE** - **F**luids (NS 500–1000 mL/hr) - **I**nsulin (0.1 U/kg/hr IV infusion) - **K**⁺ monitoring (add when K⁺ < 5.5) - **E**lectrolytes and ABG (recheck q2–4h)