What is the appropriate fluid replacement calculation for a 70‑kg adult presenting with diabetic ketoacidosis?

Fluid Calculation in Diabetic Ketoacidosis

For a 70-kg adult with DKA, administer isotonic saline (0.9% NaCl) at 15–20 ml/kg/h during the first hour (1,050–1,400 ml), then switch to 0.45% NaCl at 4–14 ml/kg/h (280–980 ml/h) if corrected sodium is normal or elevated, or continue 0.9% NaCl at the same rate if corrected sodium is low. 1

Initial Resuscitation (First Hour)

• Administer 0.9% NaCl at 15–20 ml/kg/h for the first hour in all DKA patients without cardiac compromise 1, 2
• For a 70-kg patient, this equals 1,050–1,400 ml in the first hour (approximately 1–1.5 liters) 1
• This aggressive initial resuscitation expands intravascular and extravascular volume and restores renal perfusion 1

Subsequent Fluid Management (After First Hour)

The choice of fluid after initial resuscitation depends entirely on the corrected serum sodium 1, 2:

Calculate Corrected Sodium First

• Formula: Corrected Na⁺ = Measured Na⁺ + 1.6 × [(glucose - 100)/100] 2
• Add 1.6 mEq to sodium for each 100 mg/dl glucose above 100 mg/dl 1, 3

Fluid Selection Based on Corrected Sodium

If corrected sodium is normal or elevated:

• Switch to 0.45% NaCl at 4–14 ml/kg/h 1, 2
• For a 70-kg patient: 280–980 ml/h 1

If corrected sodium is low:

• Continue 0.9% NaCl at 4–14 ml/kg/h 1, 2
• For a 70-kg patient: 280–980 ml/h 1

Potassium Replacement

• Add 20–30 mEq/L potassium (2/3 KCl and 1/3 KPO₄) to IV fluids once renal function is assured 1, 2
• Never start potassium replacement until serum K⁺ is known and >3.3 mEq/L 2

Total Fluid Deficit and Timeline

• Typical total body water deficit in DKA: 6 liters (approximately 100 ml/kg) 1
• Fluid replacement should correct estimated deficits within 24 hours 1
• For a 70-kg patient with typical deficits, this means replacing approximately 6 liters over 24 hours after initial resuscitation 1

Critical Safety Limits

The induced change in serum osmolality must not exceed 3 mOsm/kg/h to prevent cerebral edema, which carries significant mortality risk 1, 2, 4

Monitoring Requirements

• Check serum electrolytes, glucose, calculated osmolality, venous pH, and urine output every 2–4 hours during initial management 2
• Monitor hemodynamic status (blood pressure improvement), fluid input/output, and clinical examination 1, 4

Special Populations

Patients with renal or cardiac compromise:

• Use more cautious fluid rates with closer monitoring 1, 3
• Perform frequent assessment of cardiac, renal, and mental status during fluid resuscitation to avoid iatrogenic fluid overload 1

Common Pitfalls to Avoid

• Never use measured sodium alone to guide fluid choice—always calculate corrected sodium 2
• Never exceed 3 mOsm/kg/h osmolality reduction 2, 4
• Never start insulin before confirming K⁺ >3.3 mEq/L 2
• Never use dextrose-containing fluids initially in DKA resuscitation, as they cause significant hyperglycemia 5

Transition to Dextrose-Containing Fluids

• Add dextrose (5–10%) to IV fluids when glucose falls below 250 mg/dl in DKA 3
• This prevents hypoglycemia while continuing insulin therapy to clear ketones 3
• Target glucose between 150–200 mg/dl until ketoacidosis resolves 3