Clinical studies on a newly devised amino acid solution for neonates

Glutamate in current paediatric amino acid solutions is not toxic

AIM

To discuss the viewpoint article "How much glutamate is toxic in paediatric parenteral nutrition?" Acta Paediatr 2005;94;16-9.

CONCLUSION

There is no doubt that glutamate used at high bolus doses in animal experiments would permanently damage brain cells. However, these effects should not be extrapolated to the condition of parenteral nutrition of newborn infants when much smaller amounts of glutamate are infused constantly during 24 h. Clinical studies proving the maintenance of plasma glutamate concentrations within the reference range during parenteral nutrition were not considered. The authors have alarmed neonatologists with arguments without substance.

Total parenteral nutrition-associated intrahepatic cholestasis in infants: 25 years' experience

BACKGROUND/PURPOSE

There are few long-term chronological reviews examining the incidence of total parenteral nutrition (TPN)-associated intrahepatic cholestasis (TPNAC) in infants. The authors therefore reviewed TPNAC in their 25-year series, and also looked at the current problems associated with TPN in infants.

METHODS

Two hundred seventy-three surgical neonates who received TPN for more than 2 weeks were divided into 3 groups chronologically: group A (1971 through 1982, n = 77), group B (1983 through 1987, n = 72), and group C (1992 through 1996, n = 124). TPNAC was defined as serum direct bilirubin (DB) level greater than 2.0 mg/dL during the neonatal period.

RESULTS

The incidence of TPNAC in groups A, B and C was 57%, 31%, and 25% (P< .01), respectively, and the mortality rate from TPN-associated complications was 13%, 3%, and 3% (P< .05), respectively. Over the last 5 years, severe TPNAC developed in 20 patients (16%). Four of 20 died of TPN-associated sepsis with hepatic failure; 2 had hypoganglionosis with intractable stagnant enteritis and subsequent sepsis, and 2 had fatal respiratory or cardiac disease.

CONCLUSIONS

The incidence of TPNAC in surgical neonates and TPN-associated mortality rates have decreased significantly. The mortality rate, however, still remains at 3%. Two of 4 fatal cases had hypoganglionosis, which were totally dependent on TPN. In patients who require long-term TPN, TPN still has unsolved problems, and small bowel transplantation may be indicated.

Amino acid metabolism in pediatric patients

As with energy requirements, protein requirements are relatively much greater in infants and decline progressively with age. Amino acid metabolism in pediatric patients is characterized by the following differences. The requirement for essential amino acids in neonates is larger than that in adults. Because of low activity of phenylalanine hydroxylase and cystathionase, hyperphenylalaninemia and hypermethioninemia tend to occur, whereas tyrosine and cysteine tend to be deficient. In addition to cysteine and tyrosine, histidine, lysine, arginine and taurine are considered as semiessential amino acids. Nowadays there are different kinds of amino acid formulas to satisfy these specific requirements, and most of these formulas are intended to normalize the plasma aminogram. However, the nutritional benefit of these formulas for growth and development is still not completely proven, and the pharmacological use for specific diseases is expected with some modification of these formulas.

The effect of metronidazole on TPN-associated liver dysfunction in neonates

The effect of metronidazole (MNZ) on hepatic dysfunction associated with total parenteral nutrition (TPN) in neonates was investigated. Neonates receiving TPN for more than 2 weeks were divided into three groups. In group 1, TPN was given alone, in group 2, 25 mg/kg/d of MNZ was administered intravenously for the first 2 weeks of TPN, and in group 3, 50 mg/kg/d of MNZ was given for the first 3 weeks of TPN. Several parameters of liver function tests (LFTs) during the first 4 weeks of TPN were compared among these three groups. There was no significant difference of these parameters between group 1 and group 2. Although there was no significant difference of alkaline phosphatase, gamma-glutamyl transpeptidase, direct bilirubin, and total bile acid between groups 1 and 3, transaminase (glutamic oxaloacetic, glutamic pyruvic) of group 3 remained significantly lower than those of group 1. In conclusion, the administration of MNZ 50 mg/kg/d for 3 weeks, at least, prevented the elevation of transaminase during TPN in neonates, suggesting the possible involvement of intestinal anaerobic flora in the pathogenesis of TPN-associated liver dysfunction.