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. His mother reports he has been vomiting since yesterday. On examination: BP 100/62 mmHg, HR 118/min, RR 28/min, temperature 37.2°C. Kussmaul respirations are noted. Laboratory findings: blood glucose 520 mg/dL, arterial pH 7.18, HCO₃⁻ 12 mEq/L, anion gap 18 mEq/L, serum osmolality 310 mOsm/kg, serum ketones strongly positive, urine ketones 4+. What is the most appropriate initial fluid management strategy?

Explanation

## Initial Fluid Resuscitation in DKA **Key Point:** DKA presents with severe dehydration (typically 5–10 L fluid deficit). The initial phase prioritizes aggressive isotonic saline to restore intravascular volume, improve renal perfusion, and dilute glucose and ketones. ### Fluid Management Algorithm ```mermaid flowchart TD A[DKA diagnosis confirmed]:::outcome --> B{Hemodynamic status?}:::decision B -->|Hypotensive/shock| C[0.9% saline 1 L/hr × 1-2 hrs]:::action B -->|Normotensive| D[0.9% saline 500-1000 mL/hr]:::action C --> E{Glucose < 250 mg/dL?}:::decision D --> E E -->|Yes| F[Switch to 0.9% saline + 5% dextrose]:::action E -->|No| G[Continue 0.9% saline, reassess]:::action F --> H[Target: 200-250 mg/dL until pH > 7.3]:::outcome ``` ### Rationale for 0.9% Saline First | Phase | Fluid | Rate | Goal | |-------|-------|------|------| | **Acute (0–4 hrs)** | 0.9% saline | 1 L/hr (or 15–20 mL/kg/hr) | Restore circulating volume, ↓ glucose by dilution | | **Continued (4–12 hrs)** | 0.9% saline ± dextrose | 250–500 mL/hr | Maintain hydration; add dextrose once glucose < 250 | | **Late (> 12 hrs)** | 0.45% saline + 5% dextrose | 150–250 mL/hr | Avoid hypoglycemia; correct remaining deficit slowly | **High-Yield:** In this patient with BP 100/62 (mild hypotension) and HR 118, aggressive 0.9% saline at ~1 L/hr is appropriate. Switching to hypotonic fluids too early risks osmotic complications and worsens hypernatremia. **Clinical Pearl:** Dextrose is added AFTER glucose falls below 250 mg/dL to prevent hypoglycemia while continuing insulin (which drives K⁺ into cells and lowers glucose). Do NOT add dextrose initially — it worsens hyperglycemia and delays ketone clearance. **Warning:** Hypotonic saline (0.2%) in acute DKA is dangerous — it can precipitate cerebral edema by creating a hyperosmolar gradient favoring fluid shift into the brain.