Parenteral Nutrition Q&A

Parenteral nutrition is the provision of nutrition to patients intravenously via the veins in the form of a liquid infusion. The liquid infusion typically contains a nutritionally balanced combination of protein, carbohydrate, fat, minerals, electrolytes and vitamins. The nutrients are provided into the bloodstream in a form that can be used by body cells straight away, i.e. no digestion is needed by the gastrointestinal tract. Parenteral nutrition is most commonly referred to as total parenteral nutrition; however some patients only need to receive certain nutrients intravenously.

According to the National Institute of Health and Care Excellence (NICE) Clinical Guideline on Nutrition Support in Adults,1 healthcare professionals should consider parenteral nutrition in individuals who are malnourished or at risk of malnutrition and who have either:

1) an inadequate or unsafe oral and/or enteral nutrition intake

2) a non-functional, inaccessible or perforated (leaking) gastrointestinal tract

The most common indication for parenteral nutrition is intestinal failure, in which the capacity of the gastrointestinal tract to ingest and absorb food and/or fluid is inadequate to meet the body’s needs.2 Intestinal failure reduces intestinal absorption of nutrients to the extent that macronutrients and/or water and electrolyte supplements are needed to maintain health and/or growth.3 Intestinal failure may be caused by post-operative complications, such as leakage following gastrointestinal surgery or prolonged paralytic ileus, or an inaccessible gastrointestinal tract. Peri-operative parenteral nutrition should also be given to surgical patients who are severely malnourished and cannot meet their nutritional requirements orally or enterally (via the gut).

Further examples where parenteral nutrition may be indicated are:4

• Prolonged ileus (paralysis of the small intestine) >3 days
• Short bowel syndrome or high output stoma
• Severe malabsorption
• Time to reach full enteral nutrition or oral >5 days
• Insufficient energy intakes
• Hyperemesis gravidarum (severe and prolonged vomiting in pregnancy)
• High risk of aspiration (food or fluid is breathed into the lungs or airways leading to the lungs instead of being swallowed into the oesophagus (gullet) and stomach).

Parenteral nutrition is made using a combination of ingredients that will provide glucose, fat, amino acids (the building blocks of protein), electrolytes, vitamins, minerals, trace elements and water.

Whilst standardised parenteral nutrition solutions are available in ready-made bags, parenteral nutrition solutions are often customised to individual patients' requirements in the form of tailored bags.5 There are many different ingredients used in parenteral nutrition and the ‘recipe’ used to make up a parenteral nutrition bag will vary, depending on the needs of the individual patient.

Patients who need parenteral nutrition should have their nutritional requirements determined by healthcare professionals with the relevant skills and training in the prescription of nutrition support.6 Nutritional requirements should be calculated to take into account individual needs (age, gender, body size, activity level, nutritional status and any nutritional intake from oral and/or enteral routes) and disease-specific considerations such as medical condition, organ function and fluid output or restrictions.

On evaluating a patient's individual needs, the nutrition support team will prescribe the most appropriate parenteral nutrition solution to meet those needs, and advise on the rate at which the solution should be infused.

Whilst standardised parenteral nutrition solutions are available, parenteral nutrition solutions are often customised to individual patient requirements. To address this, prescribed additions and adjustments may be made to parenteral nutrition products, for example the addition of micronutrients or trace elements, electrolytes and other nutrients.1 Additions should be made under appropriate pharmaceutically controlled environmental conditions before administration. Strict sterility remains vital as well as avoidance of physical instability, which can result in the formation of precipitates or the cracking of fat emulsions, and of chemical instability which may result in a loss of biological activity.

Parenteral nutrition is manufactured and produced under sterile, aseptic conditions to ensure that it is safe. Parenteral nutrition is highly regulated and must conform to standards set by the Medicines and Healthcare Products Regulatory Agency, the government agency responsible for regulating medicines and medical devices.

It is important that patients receiving parenteral nutrition are cared for by a multidisciplinary team which is skilled both in prescribing parenteral nutrition that is specifically tailored for the individual patient, and also in providing intravenous nutrition support. It is essential that patients on parenteral nutrition are closely monitored to ensure that they are safely supported to meet their nutritional needs. Parenteral nutrition should be provided via an appropriate intravenous catheter, with a dedicated line for nutrition, and with special care to minimise any risk of infection or catheter related complications.

As parenteral nutrition is a supportive therapy, the length of time a patient may receive it varies, from a few days to longer term or even lifelong provision at home. Parenteral nutrition should be provided for as long as it is clinically necessary.

Yes. Home parenteral nutrition is provided when patients have chronic intestinal failure and cannot meet their nutritional requirements by oral or enteral feeding, but are well enough to return to their community.7

The most common underlying diseases are inflammatory bowel disease, complications following surgery, mesenteric vascular disease, radiation enteritis, and chronic small bowel disease with severe malabsorption and dysmotility syndromes. The indication for home parenteral nutrition in patients with chronic intestinal failure typically will be short bowel syndrome, fistula, bowel dysmotility and radiation enteropathy.

NICE Guidance1 recommends that people receiving parenteral nutrition in the community need to be supported by a homecare nursing team, and require a detailed and specific care plan along with good communication within the multidisciplinary team in the hospital. In addition, they should be reviewed at a specialist hospital clinic every 3-6 months. Many patients on home parenteral nutrition now experience good quality of life over ten years.

Parenteral nutrition can be given to babies and infants to provide nutrition support when enteral intake is unsafe or insufficient to meet their nutritional needs. The aim of neonatal parenteral nutrition support is to meet nutritional needs avoiding an imbalance of macronutrients, providing micronutrients, and to provide balance in fluid homeostasis and electrolytes to achieve postnatal growth and development.

The ways in which patients are provided nutrition support (oral, enteral - via the gut - nutrition, and parenteral nutrition) are not necessarily mutually exclusive.

If a patient is physically able to eat and drink and it is safe to do so, oral nutritional intake is encouraged. When oral intake is inadequate or unsafe, patients should be referred to a nutrition support team to determine the most appropriate way to meet their nutritional needs, i.e. enteral nutrition, parenteral nutrition or a combination of both.

Some patients experience optimal results on a combination of different forms of nutrition support. This may change over time, according to a patient’s condition and progress, for example a patient may continue to receive parenteral nutrition whilst establishing an adequate intake from oral or enteral nutrition. A nutrition support team should assess these needs.

Parenteral nutrition should only be withdrawn once adequate oral or enteral nutrition is tolerated and nutritional status is stable. Withdrawal should be planned on a staged basis, including a daily review of the patient’s progress.

It is important to assess a patient’s fluid status when considering parenteral nutrition and fluids. Fluid and electrolyte disturbances can have a profound immediate effect on health and imbalances can result in dehydration or fluid overload.3

Accurate assessment of a patient’s fluid balance helps to determine the volume of fluid that should be provided to the patient on a daily basis and the fluid and electrolyte composition of the parenteral nutrition regimen should be altered accordingly. It is imperative that an accurate fluid balance is monitored as fluid requirements can change rapidly.

In general, parenteral nutrition will provide most, or all, of a patient’s fluid requirement, and additional intravenous fluids are not usually necessary provided if the patient is able to tolerate the volume of parenteral nutrition and infusion rate provided.

NICE Guideline 32 states that patients on parenteral nutrition need close monitoring, particularly if their clinical condition is metabolically unstable.1 A multidisciplinary nutrition support team should take responsibility for coordinating metabolic and nutritional management. Anthropometric measurements (e.g. weight, and body muscle and fat) should be monitored monthly. Catheter care is essential to avoid the risk of complications such as infections (which can lead to sepsis and central vein thrombosis). It is also important that the parenteral nutrition access site is checked regularly. Fluid balance should be monitored by recording the output of urine and other bodily fluids and a daily glycaemic (blood sugar) and insulin profile is required to avoid potential overload. A weekly full laboratory analysis of biochemistry and haematology is also required and changes over time should be monitored.4

Patients that are established on parenteral nutrition and are metabolically stable, and who receive parenteral nutrition at home, need measurement of haematology along with tests for liver-function, creatinine and electrolytes, calcium, magnesium, phosphate and albumin about every 3 months. Measurement of trace elements, vitamins A, E, D, B12 and folic acid should be done at 12 month intervals. Testing for bone mineral density is also recommended on an annual basis.

NICE Guideline 321 recommends that parenteral nutrition in an acute hospital setting should be managed by a multidisciplinary nutrition support team, which may include doctors, dietitians, a specialist nutrition nurse, other nurses, pharmacists, biochemistry and microbiology laboratory support staff, and other allied healthcare professionals (for example speech and language specialists).

For patients receiving parenteral nutrition at home in the community, it is essential that a co-ordinated multidisciplinary nutrition support team, which includes input from specialist nutrition nurses, senior dietitians, GPs, senior pharmacists and district and/or homecare company nurses, is closely involved in their care.1,3 A close relationship between the multidisciplinary team and patients and/or their carers is essential for diagnoses, prescription, arrangements and managing potential problems.

Compounding in relation to parenteral nutrition describes the manufacturing of a bag of nutrients to support the unique nutritional needs of a patient. Compounding companies combine or process appropriate ingredients using various tools.

Aseptic manufacture is the process by which a sterile (aseptic) product is packaged in a sterile container in a way that avoids any contamination of the product in order to maintain its sterility.

The complex process of compounding parenteral nutrition takes place in specialist aseptic units and may involve combining approximately 10-15 different nutrition products. This must be carried out without causing any adverse chemical reactions, which could result in patient harm, and also to maintain the sterility of the product.

Parenteral nutrition solutions are a very complex combination of a large number of ingredients. Over time there can be reactions between these ingredients, and it is important that advice from the manufacturer regarding shelf life is observed. The shelf life of a product will depend on the combination of ingredients, the type of bag the ingredients are packaged in, the storage conditions and how the parenteral nutrition product was made.

Parenteral nutrition and its provision, particularly in the community, may include not only the product but also a number of associated services.

Homecare companies often deliver the feeds, fluids and flushes for the venous access device (once a week or fortnightly), provide a refrigerator to store them in, the pump, drip stand, dressing trolley, cleaning materials and any other equipment necessary. Nurses employed by homecare companies may also help to facilitate discharge from hospital, provide training for the patient or a carer to make the connections and disconnections themselves, or provide a full home parenteral nutrition nursing service long term.

In the hospital the funding of parenteral nutrition is covered by specialised commissioning, whereas home parenteral nutrition is covered under Home Parenteral Nutrition Framework.

Knowledge of parenteral nutrition and confidence to administer it varies considerably among healthcare professionals and Trusts. NICE Guidance CG321 statement states that “there is no minimum length of time for the duration in which parenteral nutrition should be given”. BSNA conducted an online survey8 in 2015 to understand the current practices for providing parenteral nutrition and the view of parenteral nutrition amongst healthcare professionals in the UK. The survey highlighted that CG32 is used to different extents amongst healthcare professionals, which may result in parenteral nutrition being administered inconsistently.

Qualitative research from the survey also found that healthcare professionals believe greater clarification of the current guidance is needed.

It is important that parenteral nutrition training is accessible to all healthcare professionals involved in the administration of parenteral nutrition. Increasing knowledge and understanding of parenteral nutrition will ensure that it is used appropriately and safely.

The availability of formal parenteral nutrition training, the way in which it is delivered, and the level of knowledge of parenteral nutrition among healthcare professionals is inconsistent across Trusts. According to a BSNA survey,8 which was conducted in 2015 to understand the current practices for providing parenteral nutrition, a fifth of healthcare professionals reported that their Trust did not provide parenteral nutrition training. Healthcare professionals have called for training to be delivered through online tutorials, practical courses and via more detailed guidance in order to support their development of knowledge and confidence about parenteral nutrition. A list of the range of training courses is available here.