A 28-year-old man with type 1 diabetes mellitus presents to the emergency department with a 2-day history of polyuria, polydipsia, and progressive lethargy. He admits to missing insulin injections for the past 3 days due to financial constraints. On examination, he is drowsy, respiratory rate 28/min with deep, laboured breathing (Kussmaul respiration), and blood pressure 110/70 mmHg. Laboratory investigations reveal: blood glucose 520 mg/dL, arterial pH 7.18, HCO₃⁻ 12 mEq/L, serum Na⁺ 132 mEq/L, serum K⁺ 5.8 mEq/L, and serum osmolality 310 mOsm/kg. Urine dipstick shows 3+ ketones and 2+ glucose. What is the most appropriate initial management step?

Explanation

## Diagnosis and Pathophysiology **Key Point:** This patient has diabetic ketoacidosis (DKA) with severe metabolic acidosis (pH 7.18), elevated anion gap, ketonuria, and altered mental status. ## Initial Management Algorithm ```mermaid flowchart TD A[DKA Diagnosis Confirmed]:::outcome --> B{Assess Fluid Status}:::decision B -->|Hypovolemia present| C[Aggressive IV Fluid Resuscitation]:::action C --> D[0.9% NS: 15-20 mL/kg in first hour]:::action D --> E[Monitor glucose q1h]:::action E --> F{Glucose < 250 mg/dL?}:::decision F -->|No| G[Continue NS + Insulin 0.1 U/kg/hr]:::action F -->|Yes| H[Switch to 0.45% NS with 5% glucose + Insulin]:::action G --> I[Reassess K+ before insulin]:::decision I -->|K+ > 5.5| J[Hold K+ supplementation initially]:::action I -->|K+ < 3.5| K[Add 20-40 mEq/L KCl to fluids]:::action ``` ## Rationale for Correct Answer **High-Yield:** In DKA, fluid deficit averages 100 mL/kg. Aggressive isotonic saline (0.9% NS) in the first 1–2 hours achieves three goals: 1. Restores intravascular volume and improves renal perfusion 2. Dilutes serum glucose and reduces osmolality 3. Allows safer insulin initiation once glucose begins to fall **Clinical Pearl:** Insulin should NOT be started until: - Serum K⁺ is confirmed ≥3.5 mEq/L (this patient has K⁺ 5.8, so safe to start) - Adequate fluid resuscitation has begun (prevents worsening hypokalemia from insulin-driven K⁺ shift into cells) **Key Point:** Once serum glucose falls below 250 mg/dL, switch to 0.45% saline with 5% dextrose to prevent hypoglycemia while continuing to lower ketone production. ## Electrolyte Management | Electrolyte | Finding | Action | |---|---|---| | K⁺ (5.8 mEq/L) | High initially | Do NOT add KCl yet; insulin will shift K⁺ intracellularly | | Na⁺ (132 mEq/L) | Pseudohyponatremia | Corrects with fluid resuscitation and glucose lowering | | Osmolality (310) | Elevated | Improves with IV fluids and insulin | **Mnemonic: DKA Fluid First (DFF)** — Aggressive Fluids, then Insulin, then Potassium supplementation (once K⁺ drops).