What's in a bag of PN?

The contents and size of a bag of PN vary, and depend on what each person needs. The hospital clinical team will calculate fluid (liquid) and nutrient needs, and the results of this will be converted into an individual’s prescription. It’s very much like making a meal from a recipe that’s tailored to a person’s specific body needs. In this case however, the ‘meal’ is in liquid form and the ingredients have to be ones that are suitable to go in a bag together and into a person’s veins.

PN bags come in different types and what is prescribed for a person depends on their nutrient and fluid needs. Some people may be prescribed a PN bag that has been developed to cater for a group of people with similar needs, and has been assessed by the organisation that regulates medicines in the UK (the MHRA - Medicines and Healthcare Regulatory Agency). These types of PN bags are called 'licensed' medicines and are made on an industrial scale. If someone has very specific or complex needs however, a licensed PN bag might not be suitable, and an individual PN formulation will be calculated just for that individual. These types of PN bags are known as 'unlicensed' and are made in a special unit under highly controlled aseptic conditions.

A bag of PN can contain more than 50 ingredients

Because every individual is... individual, the size and contents of a PN bag will vary from person to person. Some people may have different PN bags on different days of the week, and the number of days a week PN is infused will also vary from person to person.

Find out more about the specific ingredients in a PN bag by clicking through the sections below:

Fluid

This is the amount of liquid in the bag. Every human needs a certain amount of liquid every day to keep working properly, but the amount of fluid in a PN bag can vary depending on medical conditions. The hospital clinical team will carefully calculate how much fluid each person needs in their PN. You’ll know how much is in your bag as it will say on the label and will be a number followed by ‘ml’ or ‘millilitres’ (e.g. 2500ml).

Electrolytes

Electrolytes are salts and minerals, such as sodium, potassium, calcium and chloride, which are found in the blood. They are vitally important in making sure the human body works properly. As is the case with fluid, the hospital clinical team will work out the needs of an individual person.

Carbohydrate

Carbohydrate is one type of macronutrient (macro means large) in PN and is provided as glucose, a form of sugar that gives us energy. Glucose typically makes up about 60% of the total energy (measured in calories, kcal) in a PN bag. This is because it’s important to have enough, but not too much glucose as the energy source.

Amino acids

Amino acids are a second type of macronutrient, amino acids are the molecules that combine to make proteins. Proteins play lots of critical roles in the human body, including growth in children, recovering from illness and general day to day functioning. Amino acids are different from some of the other types of molecules that are needed to power a human partly because they contain nitrogen. You may hear your clinical team talking about ‘nitrogen’ requirements rather than ‘amino acids’, but this is really a different way to talk about the same thing.

Lipid (or fat)

Lipid is the technical term for fat, another macronutrient which not only provides a source of energy, but is part of the structure of all cells – so it’s very important. You’ll know if your PN bag contains lipid, as it will look like a thick white liquid. Some people on PN find they will have a few ‘fat-free’ days a week – this is normal and just means some bags won't contain the thick white liquid.

Vitamins and trace elements

Together these are known as micronutrients (micro meaning extremely small) and are also needed for the human body to function properly, but only in very small quantities. These are usually added to the PN bag before it’s dispensed and delivered. Most people will receive a standard dose but in some circumstances more or less may be needed – again this is all down to the individual and is decided by the hospital clinical team.

How PN is made

Making a bag of PN has to be carried out under special conditions. At Calea, the PN is made in a type of pharmacy department known as an aseptic services unit (ASU), where the environment is tightly controlled, and there are lots of checks and calculations carried out. The Calea pharmacy is made up of a team of more than 70 pharmacists and technicians, who are all specialists in making PN. This team oversee every part of the manufacturing process; from checking the ingredients are correct, to mixing them together, and running final checks on the PN bag before it can be delivered to a patient.

Did you know?

It's important anyone who is on PN is monitored regularly by their hospital team. This is to make sure the PN is working and isn't causing any unwanted complications. Given there are so many combinations of ingredients, if there are any concerns, the hospital team can adjust the recipe (prescription) as needed. Usually, when someone is started on PN they will have frequent checks, but once they are stable these checks aren't usually as often. You can ask your hospital team for more information.