Parenteral Fluid Composition for 1 kg ELBW Infant
With 90 ml/kg/day available for parenteral fluids (and 150 ml/kg/day total intake), concentrate amino acids at 2.5-3 g/kg/day, provide sodium primarily as sodium acetate at 3-5 mmol/kg/day, potassium as acetate/phosphate at 2-3 mmol/kg/day, and minimize chloride to maintain Na + K - Cl = 1-2 mmol/kg/day to prevent hyperchloremic metabolic acidosis. 1, 2
Fluid Volume Strategy
Your 1 kg ELBW infant is receiving appropriate total fluid intake at 150 ml/kg/day during stable growth, which aligns with guideline recommendations of 140-160 ml/kg/day for infants <1000g in phase III (stable growth). 3 With 90 ml/kg/day allocated to parenteral fluids and 60 ml/kg/day from other products (likely enteral feeds or medications), this distribution is reasonable. 3
Critical Electrolyte Composition
Sodium Management
- Provide 3-5 mmol/kg/day of sodium, predominantly as sodium acetate rather than sodium chloride. 1, 2 This is higher than the 2-5 mmol/kg/day range for general preterm infants <1500g because ELBW infants often have significant urinary sodium losses. 3
- If urinary sodium losses are high (which is common in ELBW infants), sodium requirements may exceed 5 mmol/kg/day. 3 Monitor serum sodium daily and adjust accordingly.
Potassium Management
- Provide 2-3 mmol/kg/day of potassium as potassium acetate or potassium phosphate. 3, 1, 2 Using potassium phosphate has the added benefit of providing needed phosphorus for bone mineralization.
- Watch carefully for non-oliguric hyperkalemia, which occurs in 37% of AGA ELBW infants, though treatment is rarely required. 4 Defer potassium if oliguria is present initially.
Chloride Restriction - Critical Point
- Limit chloride to the minimum necessary amount, targeting Na + K - Cl = 1-2 mmol/kg/day. 1, 2 This prevents hyperchloremic metabolic acidosis, which increases the risk of intraventricular hemorrhage in ELBW infants. 1
- Late metabolic acidosis occurs in 84.6% of AGA ELBW infants when chloride is not carefully restricted. 4
- Never use equal amounts of sodium chloride and potassium chloride - this creates excessive chloride load. 1
Amino Acid and Glucose Provision
- Concentrate amino acids at 2.5-3 g/kg/day within your 90 ml/kg/day parenteral volume to prevent protein catabolism. 1 This is achievable with concentrated amino acid solutions.
- Provide glucose to maintain normoglycemia, monitoring blood glucose every 4-6 hours. 1 You may need to supplement glucose via other IV lines if the 90 ml/kg/day is insufficient for full caloric needs.
- Add lipid emulsion separately to complete nutritional requirements. 5
Monitoring Protocol
Daily Assessments
- Serum electrolytes daily (sodium, potassium, chloride, bicarbonate) during this critical period. 1, 2
- Daily weights corrected for fluid balance to assess adequacy of intake and growth. 1
- Acid-base status monitoring to detect hyperchloremic metabolic acidosis from excessive chloride. 1, 2
- Urine output >1 ml/kg/hour to ensure adequate renal function. 1
Frequent Assessments
- Blood glucose every 4-6 hours to prevent hypoglycemia or hyperglycemia. 1
Common Pitfalls to Avoid
Do not attempt to provide full caloric needs in only 90 ml/kg/day - focus on preventing protein catabolism with adequate amino acids and supplement calories through other routes. 1
Avoid excessive chloride administration - hypernatremia occurs in only 8% of ELBW infants, but hyponatremia occurs in 33.3%, suggesting that sodium (not chloride) is the limiting factor. 4 Use acetate-based salts preferentially.
Do not ignore high urinary sodium losses - ELBW infants <1000g can have massive urinary sodium losses requiring >5 mmol/kg/day, especially at the end of phase I and beginning of phase II. 3
Monitor for the 21.6% weight loss that is typical in AGA ELBW infants, which is associated with large urine volumes rather than insensible water loss when nursed in high humidity environments. 4 Adjust fluid intake to maintain normal serum sodium while allowing physiologic weight loss.