How to Calculate the TPN

Total Parenteral Nutrition (TPN) is normally customized based on the patient's needs. TPN nutritional formulas contain different percentages of carbohydrates, fat and protein in order to supply the appropriate amount of nutrition to the patient based on her condition. A TPN solution can be designed by determining the patient's fluid, carbohydrate, protein, fat, dextrose, energy and electrolyte needs. You can add vitamins, electrolytes and other additives to the solution once you have added in the calculated amount of carbohydrates, proteins and fats.

• 1

  Determine the patient's energy needs. 25 to 30 kcal/kg/day is usually indicated for normal patients. Add 5 kcal/kg/day to that number for patients who have undergone elective surgery. Add 10 kcal/kg/day to the number for patients with a severe injury and 20 kcal/kg/day for patients with extreme trauma. As an example, a patient with extreme trauma could require 45 kcal/kg/day of energy, which totals 2,700 kcal (45 X 60) for a patient weighing 60 kg (133.8 lb.).

• 2

  Calculate the grams of protein for the TPN solution by using 0.83 gm/kg/day for normal patients. Add 1 to 2 gm/kg/day to that number, depending on the severity of the patient's condition. A patient with a severe condition weighing 60 kg (133.8 lb.) might require 2.83 gm/kg/day or 169.9 gm (2.83 X 60), for example.

• 3

  Calculate the patient's fluid needs by using 30 cc/kg for normal patients. Add 40 to 70 cc/kg to number if the patient is in a catabolic state, during which body tissues and components are breaking down.

• 4

  Calculate the number of kilo calories provided by lipids based on the patient's energy needs. Multiply a 10 percent lipid volume (lipid percentage for patients with lower energy needs) by 1.1 kcal/cc, or a 20 percent lipid volume (lipid percentage for patients with higher energy needs) by 2.0 kcal/cc.

• 5

  Calculate the amount of carbohydrates to be used in the solution based on the amount of lipids used. Subtract the total number of kilo calories provided by proteins and lipids from the patient's total energy needs. Use this number for the percentage of carbohydrates in the solution.