The medical world almost has its own language, with many technical terms, unique phrases, and abbreviations that medical students and practitioners need to know. One acronym that you might see often is PN, which stands for parenteral nutrition, and this can also be known as intravenous or IV nutrition.

Parenteral nutrition involves the administration of nutrients directly into a patient’s body via the veins. It can be extremely useful for patients who are unable to consume food normally or meet their body’s dietary and nutritional needs in conventional ways. There are two main types of PN: PPN (partial parenteral nutrition) and TPN (total parenteral nutrition).

Both of these forms of PN involve a patient receiving a nutritional formula directly into their bloodstream, without the need for the usual processes of eating and digesting. However, there are some key differences between total parenteral nutrition and partial parenteral nutrition. In this guide, we’ll look at PPN vs TPN to see the main differences you need to know about.

What Is Parenteral Nutrition (PN)?

Before we look at the specifics of TPN and PPN, it’s important to have a basic understanding of general parenteral nutrition, or PN. Parenteral nutrition is a process in which a patient is fed intravenously, with nutrient solutions passed directly into the bloodstream, without the need for any digestion. Parenteral nutrition is not to be confused with enteral nutrition. We created a guide to clearly differentiate enteral and parenteral nutrition.

Pharmaceutical companies create PN formulas using a mixture of ingredients, and a typical formula usually contains precise amounts of salts, sugars, proteins, lipids, vitamins, and minerals.

Parenteral nutrition is used in many situations when a patient is unable to eat or digest food in the usual way. This could be because of some kind of blockage or problem with the gastrointestinal tract, for example, or a fistula. It can also be used for comatose patients or elderly patients that may have mental or physical problems preventing them from eating sufficient amounts.

What Is Peripheral Parenteral Nutrition (PPN)?

PPN stands for partial parenteral nutrition, and as the name suggests, this is a form of parenteral nutrition that aims to only partially fulfill a patient’s nutritional needs. It is used in situations when the patient is able to consume at least some food or nutrients in other ways, such as with a feeding tube.

With PPN, the nutritional solutions are administered at a peripheral level, with the aid of a peripheral intravenous (IV) line, which can also be known as a hep-lock. PPN is administered into smaller veins than TPN, and the solutions used for PPN are a little different, being thinner and more diluted overall to allow them to flow freely through smaller and narrower vessels.

In general, PPN is used more as a short-term form of nutritional IV therapy. It provides a patient with a supplemental source of nutrients, in addition to the nutrients that they’re able to consume in other ways, giving the body additional strength over a relatively short-term period. This could be used, for example, in a patient who has a temporary blockage in their digestive system.

What Is Total Parenteral Nutrition (TPN)?

Total parenteral nutrition, as the name suggests, is a type of parenteral nutrition that aims to satisfy the totality of a person’s dietary needs. It’s used as the sole source of nutrients for a patient when oral consumption and other methods are not viable, and TPN solutions are rich in all of the key nutrients like proteins, lipids, carbohydrates, and more.

Total parenteral nutrition can also be known as total nutrient admixture, or TNA, and it involves solutions that are of a higher concentration compared to those used for PPN. In addition, it involves delivery of the nutrient solutions into a large vein, typically in an area like the chest or neck of the patient.

Total parenteral nutrition is generally more of a long-term treatment method than PPN. It may be used for patients like premature babies who require high amounts of nutrients or older patients who have digestive issues or other problems that make it hard or impossible for them to feed normally via the mouth.

Main Differences Between PPN and TPN

Both total and partial parenteral nutrition have their uses and advantages, and both of these systems have many things in common, but also some big differences. Here are the main ways in which PPN and TPN differ:

1. Total and Partial

Obviously, the main difference between TPN and PPN is that one provides a patient with the totality of their nutritional intake, while the other is only used as a partial or supplementary source of nutrients, in conjunction with other methods. A patient undergoing TPN won’t consume food in any other way, but one with PPN may also have a feeding tube or nutrients delivered by other means.

2. Formula Contents

The formulas used for TPN and PPN can also vary a lot in terms of their contents. A TPN formula needs to meet all of a patient’s nutritional needs, so it has to contain sufficient amounts of salts, fats, proteins, carbohydrates, vitamins, minerals, and other essential ingredients. PPN formulas are only partially meeting the patient’s needs, so they may not contain quite as many ingredients.

3. Formula Concentration

The formulas used for TPN and PPN may not only differ in terms of their contents and ingredients, but also in terms of their concentrations. A typical formula for TPN, for example, will be much more highly concentrated than one for PPN. This makes the formula thicker and more dense, which also affects the insertion method for TPN compared to PPN.

4. Method of Insertion

TPN and PPN also differ greatly in terms of how they are administered and how the solutions are inserted into the body. Since TPN involves a formula with a higher concentration, it can only be inserted into the larger veins of the body, in places like the neck and chest. PPN is a more diluted formula that can flow into smaller veins, so is inserted via narrow, peripheral veins.

5. Duration

Another way in which TPN and PPN can differ is in terms of how long they’re used for. Total parenteral nutrition is very much a long-term solution and it can be used for several weeks or even months at a time for patients with chronic illnesses and conditions that make it hard for them to feed. PPN is more of a temporary measure and is usually only used for a maximum duration of two weeks.

6. Purpose

The intended purpose of PPN and TPN is to feed a patient and provide them with nutrients. However, these methods of PN can be used in different situations. Usually, TPN is aimed at patients who have long-term issues that make it hard or impossible for them to feed in other ways, such as serious gastrointestinal problems. TPN is more of a temporary measure to help someone while they have surgery or while a temporary problem is resolved. 

7. Risks

It’s also worth noting that the risks of TPN and PPN can vary, as well. The solution used for TPN is considered to be more caustic, due to the presence of additional minerals, glucose, and electrolytes, while the solutions used for PPN are more mild. In addition, since these methods involve different parts of the body and different blood vessels, they may vary in terms of the complications they can cause.

FAQ

When Should Peripheral Parenteral Nutrition Be Used?

Peripheral parenteral nutrition involves the administration of fluids via vein access in a limb, rather than via a central vein (which is known as central venous nutrition, or CVN). Peripheral parenteral nutrition may be the best option if central vein access is difficult and is mainly utilized as a short-term or supplementary treatment method. It’s best suited for patients who require temporary parenteral nutrition until a more suitable form of nutrition can be found.

When Should Total Parenteral Nutrition Be Used?

There are many cases in which total parenteral nutrition is the right course of action. Since this method provides a patient with all of the nutrients their body needs, it should be used in situations when other methods like conventional feeding or feeding tubes cannot be administered. For example, someone with a severe digestive issue or an injury to the mouth or throat may not be able to consume food in the regular way, so will benefit from TPN. TPN Is also commonly used for premature babies.

Is PPN Contraindicated in Any Type of Patient?

In general, PPN may be contraindicated if alternative feeding methods are available for the patient, or if they are suffering from certain conditions, like critical cardiovascular problems, kidney failure, or decerebrate patients. 

Is TPN Contraindicated in Any Type of Patient?

In general, TPN is contraindicated in certain specific situations, including: 

• Premature or newborns with very small bowels (under 8cm)
• Patients who are decerebrate 
• Patients with critical cardiovascular or metabolic problems 
• Patients with certain kinds of kidney problems 
• Patients who are suitable for gastrointestinal feeding (use of feeding tubes)

What Are the Most Common Complications of PPN? 

There is a risk of certain complications occurring as a result of PPN treatment. One of the most common complications is phlebitis, which is inflammation of a vein. This can lead to bleeding, tissue damages, and even sepsis in the worst cases. Other potential complications include blood clots, high blood sugar, dehydration, and electrolyte imbalances.

What Are the Most Common Complications of TPN?

Some of the most common complications resulting due to TPN include phlebitis or inflammation of the vein, as well as extravasation, in which the fluids leak out from the vein into the surrounding tissue, where they may potentially cause damage. Other possible complications include blood clots in the vein, imbalances of electrolytes, and dehydration.