Early aggressive Amino Acids in TPN in ELBW infants and how it affects Ca, P balance

  A higher early Amino Acid (AA) intake may prevent non-oliguric hyperkalemia in very low birth weight infants by inhibiting cellular catabolism and promoting growth [Standardized parenteral nutrition in preterm infants:early impact on fluid and electrolyte balance.Iacobelli S, Bonsante F, Vintéjoux A, Gouyon JB; Neonatology. 2010 Jun; 98(1):84-90.]. The metabolism of phosphorus and its plasma concentration may also be influenced by this new nutritional approach. Phosphate content is very abundant in the cell, as it represents the main anion in the intracellular space and it enters into the composition of the nucleic acids, the ATP and the cell membrane. The phosphate role in bone development and mineralization, but also in cellular growth, may cause dramatic variations in its serum concentration during early aggressive PN.  Mizumoto et al. [Refeeding syndrome in a small-for-dates micro-preemie receiving early parenteral nutrition. Mizumoto H, Mikami M, Oda H, Hata D; Pediatr Int. 2012 Oct; 54(5):715-7] have observed a severe condition of hypophosphatemia and hypokalemia triggered by early aggressive PN in an extremely low birthweight infant (ELBWI). In a small retrospective cohort, Ichikawa et al. have shown that higher parenteral AA administration facilitated a condition of hypophosphatemia and hypercalcemia in ELBWI at the end of the first week of life [Hypophosphatemia in small for gestational age extremely low birth weight infants receiving parenteral nutrition in the first week after birth. Ichikawa G, Watabe Y, Suzumura H, Sairenchi T, Muto T, Arisaka O; J Pediatr Endocrinol Metab. 2012; 25(3-4):317-21]. In both studies the plasma phosphate levels in infants receiving PN were inversely associated to the AA intake. One study published by Moltu and colleagues in 2012 has further shown that enhanced feeding in very low birth weight infants may induce electrolyte imbalances (hypokalemia, hypophosphatemia and hypercalcemia) during the first week of life [Enhanced feeding in very-low-birth-weight infants may cause electrolyte disturbances and septicemia--a randomized, controlled trial. Moltu SJ,et al Clin Nutr. 2013 Apr; 32(2):207-12.]. Indeed, phosphate concentration disturbances will also induce variations in calcium plasma levels and urinary excretion, due to the metabolic interactions of these two micronutrients during the bone resorption and formation process.