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Nutrition, acid-base status and growth in early childhood
Insights
Incipient late metabolic acidosis (ILMA) in premature infants is linked to impaired growth. Modifying infant formula to reduce renal acid excretion effectively prevented ILMA and supported healthy development.
Area of Science:
- Neonatology
- Pediatric Nephrology
- Biochemistry
Background:
- Premature infants are susceptible to metabolic acidosis due to immature renal function and high acid load from standard formulas.
- Incipient late metabolic acidosis (ILMA) is an early stage characterized by maximal renal acid stimulation (MRAS) with compensated acid-base status.
Purpose of the Study:
- To investigate the association between ILMA and impaired growth in low birth-weight infants.
- To evaluate the efficacy of sodium bicarbonate (NaHCO3) and sodium chloride (NaCl) supplementation, and formula modification in managing ILMA.
Main Methods:
- Screened 452 low birth-weight infants for ILMA over 50 months.
- Conducted randomized controlled trials (Protocols I and II) with NaHCO3 or NaCl supplementation.
- Modified preterm formula mineral content to reduce renal net acid excretion (NAE).
Main Results:
- ILMA was associated with higher serum creatinine, increased urinary sodium, aldosterone, and nitrogen excretion, and slightly lower blood pH and base excess.
- Alkali therapy (NaHCO3) normalized weight gain, hormonal stimulation, mineralization, and nitrogen assimilation.
- Modified formula significantly reduced ILMA incidence to 1% and decreased renal NAE.
Conclusions:
- ILMA is linked to impaired growth in premature infants, potentially due to homeostatic mechanism activation.
- Alkali therapy and formula modification are effective in managing ILMA and improving growth outcomes.
- Developing formulas with reduced renal NAE is a key preventive strategy for early childhood acid-base disorders.
Abstract:
Optimal growth is only possible in a well-balanced "inner milieu". Premature infants are especially vulnerable for disturbances of acid-base metabolism with a predisposition to metabolic acidosis due to a transient disproportion between age-related low renal capacity for net acid excretion (NAE) and an unphysiologically high actual renal NAE on nutrition with standard formulas. During a 50 month period, 452 low birth-weight infants were screened for spontaneous development of incipient late metabolic acidosis (ILMA), an early stage during the development of retention acidosis, characterized by maximum renal acid stimulation (MRAS, urine-pH < 5.4) on two consecutive days but still compensated systemic acid-base status. Compared with controls, patients with ILMA showed higher serum creatinine values, an increased urinary excretion of sodium, aldosterone and nitrogen, but only slightly lower blood pH (7.38 vs 7.41) and base excess (-2.8 vs. 0.2 mmol/l) with respiratory compensation (PCO2 35 vs 37 mm Hg). Patients with altogether 149 episodes of ILMA were subsequently randomly allocated to either treatment with NaHCO3 2 mmol/kg/d for 7 days or no special therapy in protocol I, or NaHCO3 vs NaCl each 2 mmol/kg/d for 7 days in protocol II. Patients of protocol I with persistent MRAS for 7 days showed lowest weight gain and a tendency for a further increase in urinary aldosterone and nitrogen excretion. NaCl supplementation (protocol II) seemed to promote weight gain without affecting either impaired mineralization or suboptimal nitrogen retention. Patients with alkali therapy under both protocols showed normal weight gain and normalization of hormonal stimulation, mineralization (protocol II) and nitrogen assimilation. Modification of the mineral content of a standard preterm formula decreased renal NAE to the low level seen on alimentation with human milk and reduced the incidence of ILMA in preterm and small-for-gestational-age infants to 1%. The data show that ILMA is associated with impaired growth. Activation of secondary homeostatic mechanisms (extracellular volume contraction, depletion of disposable net base pools) might be important for impaired growth. Production of new formulas for reduced renal NAE could be an effective general preventive measure to reduce the clinical importance of one component of mixed acid-base disorders in early childhood.