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The addition of heparin to the PN solution at a concentration of 0.5 to 1 units per mL (36) maintains the patency of the venous catheter, reduces vein irritation, and enhances lipid clearance by improving lipoprotein lipase enzyme activity. Heparin should not be used in patients with bleeding or at risk for bleeding, or in patients with thrombocytopenia.

Histamine-2 receptor antagonists such as ranitidine, famotidine, and cimetidine are compatible with PN and may be added to the PN solution for stress ulcer prophylaxis.

Regular insulin is compatible with the PN solution. However, insulin therapy is difficult to regulate in infants, and intravenous insulin should be administered as a separate intravenous infusion to allow safe titration of the insulin dose in this circumstance.

Iron deficiency anemia may occur in PN-dependent patients. Iron is not routinely added to PN. Iron dextran is the most common parenteral iron available for use when oral iron absorption is unreliable or results in gastrointestinal intolerance. Because iron can be used as a substrate for bacterial proliferation, iron dextran should be avoided in infected patients.

Sodium can be provided in PN solutions in the forms of chloride, acetate, or phosphate salts. Neonates, and especially premature infants, develop a natruresis during the first 1 to 2 weeks following birth as a result of their immature kidney function. Because sodium intake is essential for protein synthesis and tissue development, adequate sodium supplementation is necessary and is guided by serum and urine sodium levels (32:Mevacor). Premature infants may require as high as 8 mEq per kg per day of sodium. Maximum sodium concentration in PN solutions should not exceed normal saline solution equivalent (154 mEq of sodium per L).

Potassium can be provided in PN solutions in the forms of chloride, acetate, or phosphate salts. Higher potassium requirements are needed during anabolism (33:Mevacor) and to correct for any gastrointestinal or renal potassium losses. Potassium concentrations in the PN solution should not exceed 80 mEq per L and potassium infusion rates in infants and children should not exceed 0.5 mEq per kg per hour (34:Mevacor). With high potassium infusion rates, the patient should be placed in the intensive care unit on a cardiac monitor because of the risk of cardiac rhythm disturbances.

Pediatric parenteral crystalline amino acid formulas provide essential and nonessential amino acids specifically balanced to meet the needs of the developing child. Neonatal-specific amino acid formulas (Aminosyn PF, Trophamine) are formulated to closely reproduce the plasma amino acid profile of breastfed infants. These formulas have led to greater weight gain and improved nitrogen balance in infants compared with standard amino acid formulas. Some amino acids such as cysteine, tyrosine, glycine, and taurine are considered conditionally essential to the child (Table 7-2). Taurine supplementation to premature infants is essential to promote bile acid conjugation and improve bile flow. Premature infants are at risk for taurine deficiency as a result of relatively high renal excretion and low synthetic capacity related to diminished cystathionase enzyme activity and can leap to inadequate retinal development (17). Amino acids are a source of energy (4 kcal per g) and nitrogen for protein synthesis. Parenteral amino acids should approximately provide 10% to 15% of total calories. Amino acids are generally started at 1 g per kg per day and advanced to goal over 2 to 3 days. To simulate intrauterine protein accretion rate, low birth weight infants may need up to 3.85 g per kg per day of amino acids (6,18). Amino acid requirements are 2.5 to 3 g per kg per day in term infants, 1.5 to 2 g per kg per day in older children, and 1 to 1.5 g per kg per day in adolescents. Amino acid doses should be adjusted based on the patient’s clinical condition and nutritional status. For example, higher amino acid doses may be required to heal a complex wound. Patients with liver failure require lower amino doses to avoid hyperammonemia. Higher amino acid doses are required in patients on renal dialysis or continuous renal replacement therapies to compensate for losses via the dialysis membrane and filter (19,20).