Complete parenteral nutrition: indications, monitoring, complications

Parenteral nutrition is by definition administered intravenously. Partial parenteral nutrition only provides part of the daily nutritional needs, reinforcing its intake through the mouth. Many of the hospitalized patients receive this solution of dextrose or amino acids. Complete parenteral nutrition (PPP) meets all daily food needs. Complete parenteral nutrition can be administered at the hospital or at home. Since solutions for total parenteral nutrition are concentrated and can cause peripheral vein thrombosis, a central venous catheter is usually used.

[1], [2], [3]

Indications for complete parenteral nutrition

Complete parenteral nutrition is prescribed for patients who do not have GIT. A widespread but still insufficiently researched indication is the prevention of malnutrition (less than 50% of metabolic needs) lasting more than 7 days. Complete parenteral nutrition is prescribed before and after treatment of patients with severe malnutrition who can not consume large amounts of food orally and are preparing for surgery, radiation therapy or chemotherapy. Complete parenteral nutrition can reduce the risk of complications and mortality after major surgical interventions, severe burns, head trauma, especially in patients with sepsis. Patients with disorders requiring significant reduction in bowel function (certain stages of Crohn's disease, ulcerative colitis, severe pancreatitis), or children with disorders (congenital malformations, prolonged diarrhea regardless of cause) often also respond well to complete parenteral nutrition.

Nutrient content

For complete parenteral nutrition, water (30-40 ml / kg / day), energy (30-60 kcal / kg / day, depending on energy expenditure), amino acids (1-2.0 g / kg / day, depending on the degree catabolism), essential fatty acids, vitamins and minerals. In children who need complete parenteral nutrition, the fluid requirements may differ, and the energy requirements (120 kcal / kg / day) and amino acids (2.5-3.5 g / kg / day) are significantly higher.

Basic solutions for complete parenteral nutrition are prepared in sterile conditions, in liter packages according to standard formulas. Usually 2 liters of a standard solution are needed per day. Solutions can be changed based on laboratory data, the presence of major disorders, hypermetabolism, or other factors. Often, commercially available lipid emulsions are added to provide essential fatty acids and triglycerides; 20-30% of the total energy is replenished with lipids. However, the rejection of lipids and their energy can help obese patients mobilize endogenous fat stores, thereby increasing their sensitivity to insulin.

Solutions for total parenteral nutrition

Usually, various solutions are used. Electrolytes can be added to meet the patient's needs for them.

Patients who have renal failure and who are not on dialysis, or who have hepatic insufficiency, need solutions with a reduced protein content and a high percentage of essential amino acids. In patients with cardiac or renal failure, the volume (liquid) to be administered should be limited. For patients with respiratory failure, the lipid emulsion should provide most non-protein calories to minimize CO ₂ production in carbohydrate metabolism. Newborns need lower concentrations of dextrose (17-18%).

The beginning of the procedure for complete parenteral nutrition

Since the central venous catheter should remain in place for a long time, strict sterility measures during installation and maintenance are necessary. The system for complete parenteral nutrition should not be used for any other purpose. The outer tube must be replaced every 24 hours from the time the first bag is installed. The use of built-in filters is controversial and, perhaps, does not help. The laundry should be stored sterile and usually replaced every 48 hours with complete sterility. If full parenteral nutrition is carried out outside the hospital, then patients should be taught to recognize the symptoms of the infection, and they should be given good home care.

The solution is started slowly, at a rate of 50% of the calculated requirements, using a 5% dextrose solution to compensate for fluid balance. Energy sources and nitrogen must be given simultaneously. The number of standard units of insulin added directly to the solution for total parenteral nutrition depends on the level of glucose in the blood; if the level is normal and the final solution contains the usual 25% concentration of dextrose, the usual starting dose is 5-10 standard units of insulin / liter of liquid for total parenteral nutrition.

Monitoring of total parenteral nutrition

The dynamics of the procedure should be accompanied by a flowchart. A team of nutritionists, if any, should constantly monitor the patient. Body weight, a general blood test, electrolytes should be checked repeatedly (for inpatients on a daily basis). Blood glucose should be checked every 6 hours until it stabilizes. The intake and removal of liquid must also be checked regularly. After stabilizing the patient, blood tests can be done less often.

Tests should be done to assess liver function. Plasma proteins (eg, serum albumin, possibly transthyretin or retinol-binding protein); prothrombin time; osmolality of plasma and urine; Ca, Mg and phosphate (not during glucose infusion) should be measured twice a week. A complete assessment of the nutritional status (including calculation of BMI and anthropometric measurements) should be repeated at intervals of 2 weeks.

Complications of complete parenteral nutrition

With careful monitoring by the nutrition team, the level of complications may be less than 5%. Complications can be associated with a central venous catheter or with the provision of nutrients.

Deviations from normal glucose levels are quite characteristic. Hyperglycemia can be avoided by constantly monitoring blood glucose levels by adjusting the insulin dose in the solution for complete parenteral nutrition and injecting insulin subcutaneously as needed. Hypoglycemia can be eliminated by the immediate administration of concentrated dextrose. Treatment, depending on the degree of hypoglycemia, consists of intravenous administration of a solution of 50% dextrose or infusion of 5% or 10% dextrose solution for 24 hours before resuming complete parenteral nutrition through a central venous catheter.

Deviations from normal levels of electrolytes and mineral substances in the blood should be corrected by modifying the subsequent infusion or, if correction is urgently required, starting the appropriate infusion into the peripheral veins. Insufficiency of vitamins and minerals is rare in cases when solutions are administered correctly. Dehydration can be corrected by introducing water and 5% dextrose into the peripheral vein.

Hypervolaemia (its presence can be assumed if weight gain is more than 1 kg / day) can occur when large daily energy requirements require large volumes of fluid.

Metabolic bone damage, or bone demineralization (osteoporosis or osteomalacia), develops in some patients who receive complete parenteral nutrition for more than 3 months. The mechanism is unknown. Progression of the disease can cause severe periarticular pain, pain in the lower limbs and lower back. Temporary or permanent cessation of complete parenteral nutrition is the only known method of treatment.

Adverse reactions to lipid emulsions (including dyspnea, skin allergic reactions, nausea, headache, back pain, sweating, dizziness) are rare, but can quickly appear, especially if lipids are given at a rate of more than 1.0 kcal / kg / h . There may be temporary hyperlipidemia, especially in patients with renal or hepatic insufficiency; treatment is usually not required. Late adverse reactions to lipid emulsions: hepatomegaly, moderate elevation in the blood of hepatic enzymes, splenomegaly, thrombocytopenia, leukopenia and, especially in premature infants with respiratory distress syndrome, pulmonary dysfunction. Temporary or permanent slowing or stopping of lipid emulsion infusion can prevent or minimize these side reactions.

Hepatic complications include liver dysfunction, painful hepatomegaly and hyperammonemia. They can develop at any age, but are most frequent in infants, especially premature babies, whose liver is functionally immature. In the beginning, full parenteral nutrition is also transient liver dysfunction, in which there is an increase in the levels of transaminases, bilirubin, alkaline phosphatase. Late or persistent increases may be due to excessive amounts of amino acids. The pathogenesis is unknown. Their contribution is probably made by cholestasis and inflammation. Sometimes progressive fibrosis develops. Reducing the introduction of protein in such situations can be useful. Painful hepatomegaly indicates the accumulation of fat; the introduction of carbohydrates should be reduced. Infants may develop hyperammonemia. Symptoms include drowsiness, convulsive twitching, general paralysis. Correction is the addition of arginine in an amount of 0.5-1.0 mmol / kg / day. In infants with hepatic complications it is necessary to limit amino acids to 1.0 g / kg / day.

Complications from the gallbladder include cholelithiasis, bile stasis and cholecystitis. These complications can be caused or aggravated by prolonged congestion of bile in the gallbladder. It is assisted by stimulation of its reduction by providing 20-30% of energy from fat and stopping glucose infusion for several hours a day. Also, food through the mouth and enteral nutrition also helps. Some patients with cholelithiasis are helped by the use of metronidazole, ursodeoxycholic acid, phenobarbital, cholecystokinin.

[4], [5], [6]