Additives to Parenteral Nutrition
Posted by Surgery on Sep 9, 2008
Additives to Parenteral Nutrition
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.
Heparin should not be used in patients with bleeding or at risk for bleeding, or in patients with thrombocytopenia.Histamine-2 Receptor Antagonists
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.
Parenteral Nutrition Components and Requirements
Posted by Surgery on Sep 9, 2008
Composition of Parenteral Nutrition
PN is a source of macronutrients (amino acids, dextrose, lipid emulsions), micronutrients (multivitamins, trace minerals), fluids, and electrolytes.
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).
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).Complications of Enteral Feeding
Posted by Surgery on Sep 9, 2008
The gastrointestinal tract generally tolerates feedings quite well once any postoperative ileus is resolved. Not uncommonly, however, a critically ill child will sustain a loss of a significant portion of the absorptive function, often due to acquired lactase deficiency. Symptoms are generally manifested by cramping, diarrhea, or emesis.:Pravachol Symptoms will often improve with the initiation of a lactose-free diet. Other alterations in the administration of the diet can also improve feeding tolerance. 
First, the gastrointestinal tract generally tolerates increased volume more readily than increased osmolarity. Therefore, adverse symptoms can be avoided by initiating 1/8 or 1/4 strength formula and slowly advancing the formula concentration. Second, administration of formula by continuous drip may be better tolerated than bolus feedings. The risk of gastroesophageal reflux and dumping symptoms are thereby greatly reduced. Third, care must be taken to ensure the enteral formula does not become contaminated, either during preparation or at the bedside. Expiration dates should be carefully observed. Finally, pectin, Metamucil, lomotil, paregoric, or Imodium may be required for those who have lost a significant amount of their bowel length (see the Short Bowel Syndrome section:Pravachol). Assessment of absorptive capacity can be done most readily by testing stool for the absorption of carbohydrates. This is done by measuring stool pH and checking for reducing substances. Stool pH less than or equal to 5.5, or a reducing substance of greater than one-half percent, indicates the passage of unabsorbed carbohydrates into the stool. Once demonstrated, these findings are best treated by decreasing the formula concentration of carbohydrate.
Tags: Metamucil, Nutrition Support in the Pediatric Surgical Patient, PARENTERAL NUTRITION, Pravachol, TraumaFirst, the gastrointestinal tract generally tolerates increased volume more readily than increased osmolarity. Therefore, adverse symptoms can be avoided by initiating 1/8 or 1/4 strength formula and slowly advancing the formula concentration. Second, administration of formula by continuous drip may be better tolerated than bolus feedings. The risk of gastroesophageal reflux and dumping symptoms are thereby greatly reduced. Third, care must be taken to ensure the enteral formula does not become contaminated, either during preparation or at the bedside. Expiration dates should be carefully observed. Finally, pectin, Metamucil, lomotil, paregoric, or Imodium may be required for those who have lost a significant amount of their bowel length (see the Short Bowel Syndrome section:Pravachol). Assessment of absorptive capacity can be done most readily by testing stool for the absorption of carbohydrates. This is done by measuring stool pH and checking for reducing substances. Stool pH less than or equal to 5.5, or a reducing substance of greater than one-half percent, indicates the passage of unabsorbed carbohydrates into the stool. Once demonstrated, these findings are best treated by decreasing the formula concentration of carbohydrate.
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