For a 30‑kg child with diabetic ketoacidosis and hyperglycemia, how should I calculate the 48‑hour IV fluid replacement (deficit plus maintenance) using corrected serum sodium to decide between 0.9% sodium chloride and 0.45% sodium chloride?

Calculating 48-Hour IV Fluid Replacement in Pediatric DKA Using Corrected Sodium

For a 30-kg child with DKA, use 0.9% sodium chloride (normal saline) for the entire 48-hour rehydration period, calculating total fluid as deficit plus maintenance, with corrected sodium serving primarily as a monitoring parameter rather than a determinant of fluid tonicity. 1

Initial Fluid Resuscitation (First 1-4 Hours)

• Administer 0.9% NaCl at 10-20 mL/kg/hour for the first hour to restore intravascular volume and renal perfusion 1
• For a 30-kg child, this equals 300-600 mL in the first hour 1
• In severely dehydrated patients, this bolus may be repeated, but total initial reexpansion should not exceed 50 mL/kg over the first 4 hours (maximum 1,500 mL for this child) to minimize cerebral edema risk 1

Calculating the 48-Hour Fluid Plan

Step 1: Calculate Corrected Sodium

• Use the formula: Corrected Na = Measured Na + [1.6 × (glucose - 100) ÷ 100] 1
• This correction accounts for the dilutional effect of hyperglycemia on measured sodium 2
• The corrected sodium helps predict the degree of free water deficit from osmotic diuresis but does NOT determine whether to use 0.9% or 0.45% saline 2

Step 2: Calculate Total Fluid Requirement

Maintenance fluid calculation for 30-kg child:

• First 10 kg: 100 mL/kg/day = 1,000 mL/day
• Second 10 kg: 50 mL/kg/day = 500 mL/day
• Remaining 10 kg: 20 mL/kg/day = 200 mL/day
• Total maintenance = 1,700 mL/day × 2 days = 3,400 mL over 48 hours 1

Estimated deficit:

• Typical water deficit in DKA is approximately 60-100 mL/kg 1
• For a 30-kg child: 60-100 mL/kg = 1,800-3,000 mL deficit 1
• Use clinical assessment (degree of dehydration, vital signs, perfusion) to estimate actual deficit 1

Total 48-hour fluid = Maintenance (3,400 mL) + Deficit (e.g., 2,400 mL for moderate dehydration) = 5,800 mL

Step 3: Subtract Initial Bolus Volume

• If 600 mL was given as initial bolus, subtract this from total: 5,800 - 600 = 5,200 mL remaining over 48 hours 1

Step 4: Calculate Infusion Rate

• 5,200 mL ÷ 48 hours = 108 mL/hour of 0.9% NaCl 1
• This rate represents 1.5 times the 24-hour maintenance requirement, which accomplishes smooth rehydration with osmolality decrease not exceeding 3 mOsm/kg/h 1

Why Use 0.9% NaCl Throughout (Not 0.45% NaCl)

The evidence strongly supports isotonic saline for pediatric DKA rehydration:

• Guideline recommendation: Continue 0.9% NaCl at 1.5 times maintenance for the full 48-hour period 1
• Research evidence: Use of 0.45% saline resulted in significant decrease in corrected serum sodium (P < 0.01), while 0.9% saline maintained stable sodium levels 3
• Clinical rationale: Sodium concentration in rehydration fluids behaves as an independent factor that positively influences serum sodium trends during DKA treatment (P < 0.008) 4
• Corrected sodium is NOT used to select fluid tonicity—it serves as a monitoring parameter to track the degree of hypertonicity from osmotic diuresis 2

Potassium Supplementation

• Once renal function is assured (adequate urine output) and serum potassium is known, add 20-40 mEq/L potassium to the IV fluid 1
• Use 2/3 KCl (or potassium acetate) and 1/3 KPO₄ 1
• For 108 mL/hour rate, this equals approximately 2-4 mEq/hour of potassium 1
• If serum K⁺ < 3.3 mEq/L, delay insulin therapy until potassium is restored 5

Monitoring Parameters

• Check serum sodium, potassium, glucose, and venous pH every 2-4 hours during treatment 1
• Recalculate corrected sodium with each measurement to monitor the trend 2
• Ensure the induced change in serum osmolality does not exceed 3 mOsm/kg/h 1
• Monitor for signs of cerebral edema (headache, altered mental status, bradycardia) 1

Critical Pitfalls to Avoid

• Do NOT use 0.45% saline based on corrected sodium values—this can cause dangerous hyponatremia 3, 4
• Do NOT use normal saline if corrected sodium is low—the adult guideline recommendation for 0.45% saline when corrected sodium is normal/elevated does NOT apply to pediatric DKA 1
• Do NOT exceed 50 mL/kg in the first 4 hours—this increases cerebral edema risk 1
• Do NOT add potassium before confirming adequate urine output—this risks life-threatening hyperkalemia 1
• Hyperchloremic non-anion gap acidosis from 0.9% saline is transient and self-limited, requiring no specific treatment 1, 3

Special Considerations

• In cases of extreme hypernatremia (corrected Na > 160 mEq/L), the rate of sodium correction becomes critical—aim for decrease of no more than 8-10 mEq/L per day 6
• If corrected sodium rises during treatment despite appropriate fluid therapy, consider occult ongoing losses or inadequate free water replacement 2
• The corrected sodium may change during treatment due to ongoing osmotic diuresis and should be recalculated frequently 2, 7