How to Calculate the Nitrogen Content of TPN

Patients who are too sick or injured to eat or drink are fed intravenously through "total parenteral nutrition" or TPN. Among other nutrients, TPN provides protein in the form of amino acids, which contain nitrogen. Since protein is important in building new bodily tissues during a patient's recovery, medical staff focus on keeping the patient in "positive nitrogen balance," meaning the patient is retaining more nitrogen (and thus protein) than he is losing. So staff must accurately calculate nitrogen content of TPN.

Instructions

• 1

  Look up the amount of TPN solution the patient is receiving on the patient's chart. Typically a patient receives about 2 liters per day (2000 milliliters).

• 2

  Identify the percentage of amino acids in the TPN solution from the TPN order form. Standard TPN solutions contain 5 percent amino acids, but a doctor may have ordered a special mixture from the pharmacy if the patient's situation necessitates a unique solution.

• 3

  Calculate how many grams of protein the patient is receiving per day. The concentration of amino acids in TPN solution is equal to grams of protein per 100 milliliters of solution. For instance, a 5 percent amino acid solution contains 5 g of protein per 100 ml. Multiply g per 100 ml by the total volume of TPN solution the patient receives in one day. For example, if a patient is receiving 2000 ml of 5 percent amino acid solution, he is getting 100 g of protein per day (2000 ml x (5 g / 100 ml) = 100 g).

• 4

  Calculate grams of nitrogen based on grams of protein. There is 1 g of nitrogen in 6.25 g of protein. Based on this conversion factor, divide the total g of protein per day by 6.25 to get g of nitrogen. For example, a patient receiving 100 g of protein per day is getting 16 g of nitrogen (100 g / 6.25 g = 16 g).