Parenteral nutrition concentrations

Along with a disturbance in fluid volume (eg, loss of plasma, blood, or water) or a need for providing parenteral nutrition with the previously discussed solutions, an electrolyte imbalance may exist. An electrolyte is an electrically charged substance essential to the normal functioning of all cells. Electrolytes circulate in the blood at specific levels where they are available for use when needed by the cells. An electrolyte imbalance occurs when the concentration of an electrolyte in the blood is either too high or too low. In some instances, an electrolyte imbalance may be present without an appreciable disturbance in fluid balance For example, a patient taking a diuretic is able to maintain fluid balance by an adequate oral intake of water, which... 

Concentrate intravenous medications ° Evaluate maintenance fluids ° Concentrate parenteral nutrition 0 Use concentrated enteral nutrition products Avoid and/or discontinue nephrotoxins wherever possible... 

Solutions for PPN have lower final concentrations of amino acid (3% to 5%), dextrose (5% to 10%) and micronutrients as compared to central parenteral nutrition (CPN). 

Serum amylase and triglyceride concentrations in patients with history of elevated amylase, pancreatitis, ethanol abuse, or receiving parenteral nutrition... 

Hyperammonemia has occurred during parenteral nutrition as a component of therapy for renal insufficiency (905). The hyperammonemia presented as a change in mental status, developing about 3 weeks after initiation of parenteral nutrition therapy in most cases the episodes are of increasing duration and paroxysmal. In three of the patients, serum amino acid analysis in the acute phase showed reduced concentrations of ornithine and citrulline (the respective substrate and product of condensation with carbamyl phosphate at its entry into the urea cycle). Concentrations of arginine, the precursor to ornithine, were raised. 

Linoleic acid and alpha-linoleic acid are essential fatty acids that are provided in any long-term parenteral nutrition by administering fat emulsions at least twice a week. Fatty acid deficiency is a common complication of severe end-stage liver disease. The ability of short-term intravenous lipid supplementation to reverse fatty acid deficiencies has been studied in patients with chronic liver disease and low plasma concentrations of fatty acids (914). Shortterm supplementation failed to normalize triglycerides. 

Choline deficiency developed in a 41-year-old woman with advanced cervical cancer who underwent prolonged parenteral nutrition (915). Her liver function tests became abnormal and she became jaundiced and complained of nausea and vomiting. The serum choline concentration was 5.77 mmol/1 and there was histological evidence of hepatic steatosis. There was steady improvement with oral choline supplementation, 3 g/ day, and with oral glutamine 15 g/day. There was a 45% improvement in serum choline concentration over baseline. 

Chromium deficiency is characterized by glucose intolerance but also may include neuropathy, increased free fatty acid concentrations, and a low respiratory quotient. Chromium deficiency has been identified in the setting of long-term, chromium-free parenteral nutrition. 

Selenium deficiency has been described in patients receiving long-term selenium-free total parenteral nutrition. Myopathy and abnormal glutathione peroxidase concentrations are most... 

Physicochemical incompatibilities are of particular concern when parenteral administration is planned. For example, when calcium and phosphate ion concentrations are excessively high in a total parenteral nutrition (TPN) solution, precipitation will occur. Similarly, the simultaneous administration of antacids or products high in metal content may compromise the absorption of many drugs in the intestine, eg, tetracyclines. The package insert and the Handbook on Injectable Drugs (Trissel 2003) are good sources for this information. 

Peripheral PN (PPN) is a relatively safe and simple method of nutritional support. PPN candidates do not have large nutritional requirements, are not fluid restricted, and are expected to begin enteral intake within lOto 14days. Thrombophlebitis is a common complication this risk is greater with solution osmolarities greater than 600 to 900 mOsm/L (Table 60-2). Solutions for PPN have lower final concentrations of amino acid (3% to 5%), dextrose (5% to 10%) and micronutrients as compared to central parenteral nutrition (CPN). 

The activity of propionyl CoA carboxylase in lymphocytes falls, and the activation of the apoenzyme on incubation with biotin rises, in patients receiving total parenteral nutrition before there is any change in the plasma concentration of biotin (Velazquez et al., 1990). In experimental animals, the activity of lymphocyte propionyl CoA carboxylase falls early during biotin depletion, at the same time as the activity of the hepatic enzyme. There is not the expected increase in urinary excretion of hydroxypropionic acid, presumably because propionyl CoA carboxylase is not rate-limiting for propionate metabolism (Mock and Mock, 2002). 

Bowy er, B. A., Miles, J. M ilayntond, M. W-, and Fleming, C. R. (1988), L-Carnitino therapy in home parenteral nutrition patients with abnormal liver tests and low plasma carnitine concentrations. CastToentetolcg)t 94,434-436. 

The best way to monitor excessive exposure to manganese includes serum manganese concentration measurement in combination with brain MRI scanning and perhaps a battery of neurofunctional tests (7). Studies have concentrated on manganese in patients on parenteral nutrition (8) and occupational exposure (9). 

In a series of neonates on total long-term parenteral nutrition, cholestatic disorders were associated with high manganese concentrations (over 360 nmol/1) (21). 

The chnical differentiation of chylothorax from leakage of parenteral nutrition fluid into the pleural space can be difficult. However, in one case the diagnosis of leakage of parenteral nutrition fluid was made by additional tests of electrolytes, showing very high concentrations of potassium (11.3 mmol/1) and glucose (128 mmol/1), mhng out chylothorax (13). 

---