A 28-year-old man with type 1 diabetes mellitus presents to the emergency department with a 3-day history of polyuria, polydipsia, and progressive lethargy. He reports missing insulin injections for the past week due to financial constraints. On examination, he is drowsy, respiratory rate 28/min with deep breathing, blood pressure 110/70 mmHg, and has fruity-smelling breath. Laboratory investigations reveal: blood glucose 580 mg/dL, arterial pH 7.18, HCO₃⁻ 12 mEq/L, anion gap 18 mEq/L, serum sodium 128 mEq/L, serum potassium 5.8 mEq/L, and positive serum and urine ketones. What is the most appropriate immediate management step?

## Diagnosis: Diabetic Ketoacidosis (DKA) This patient presents with the classic triad of DKA: hyperglycemia, metabolic acidosis with elevated anion gap, and ketonemia/ketonuria. ### Diagnostic Criteria Met | Feature | Patient Value | DKA Criterion | |---------|---------------|---------------| | Blood glucose | 580 mg/dL | >250 mg/dL | | pH | 7.18 | <7.30 | | HCO₃⁻ | 12 mEq/L | <18 mEq/L | | Anion gap | 18 mEq/L | >12 mEq/L | | Ketones | Positive | Present | **Key Point:** DKA is characterized by the triad of hyperglycemia, metabolic acidosis, and ketosis. The anion gap of 18 confirms high anion gap metabolic acidosis. ### Immediate Management Algorithm ```mermaid flowchart TD A[DKA Confirmed]:::outcome --> B[Fluid Resuscitation]:::action B --> C[0.9% NaCl 15-20 mL/kg in first 1-2 hours]:::action A --> D[Insulin Therapy]:::action D --> E[0.1 units/kg IV bolus]:::action E --> F[0.1 units/kg/hour continuous infusion]:::action A --> G[Electrolyte Monitoring]:::action G --> H[Check K+, Na+, Cl- every 2-4 hours]:::action A --> I[Avoid Bicarbonate]:::urgent I --> J[Only if pH < 6.9 and life-threatening arrhythmias]:::urgent ``` ### Rationale for Correct Answer **High-Yield:** The standard DKA management protocol is: 1. **Fluid resuscitation** with 0.9% normal saline (15–20 mL/kg in first 1–2 hours) 2. **Insulin therapy**: 0.1 units/kg IV bolus, then 0.1 units/kg/hour continuous infusion 3. **Electrolyte replacement** (especially K⁺ once urine output confirmed) **Clinical Pearl:** Despite serum K⁺ appearing elevated (5.8 mEq/L), total body potassium is depleted due to osmotic diuresis and acidosis-driven transcellular shift. Insulin therapy will shift K⁺ intracellularly, causing dangerous hypokalemia if not monitored. **Key Point:** Insulin is the cornerstone of DKA management. It suppresses lipolysis, reduces ketone production, and promotes glucose utilization. Fluid resuscitation corrects hypovolemia and improves renal perfusion, aiding ketone clearance. ### Why NOT Bicarbonate? **Warning:** Bicarbonate is NOT indicated in DKA unless pH < 6.9 with life-threatening complications (severe arrhythmias, shock). Reasons: - Paradoxically worsens intracellular acidosis - Increases risk of hypokalemia - Impairs oxygen unloading (left-shifts oxyhemoglobin dissociation curve) - Delays resolution of ketosis [cite:Harrison 21e Ch 397]