Who Needs a Gut Anyway ?

This is an up-to-date review on Chronic Intestinal Failure (CIF) and Parenteral Nutrition (PN) as a management strategy for CIF. CIF and long-term PN are important subjects, but are superficially covered in undergraduate curricula due to the perception that they are relatively specialist areas. PN, as well as being a form of acute nutritional support, is used as a life-sustaining measure for patients with CIF due to conditions such as bowel ischaemia and Crohn’s disease. Currently, around 500 patients receive long-term PN in the UK and the numbers are expected to rise with the aging population. It is a costly service, requiring a multidisciplinary team effort, along with high frequency patienthealthcare interaction. This article aims to discuss the current evidence on the causes, management and prognosis of CIF, with a particular focus on PN as a form of nutritional management. While PN seems to improve the prognosis of patients with CIF from a medical point of view, we will also explore how it affects other aspects of a patient’s life, such as their social life and mental health. Copyright Royal Medical Society. All rights reserved. The copyright is retained by the author and the Royal Medical Society, except where explicitly otherwise stated. Scans have been produced by the Digital Imaging Unit at Edinburgh University Library. Res Medica is supported by the University of Edinburgh’s Journal Hosting Service: http://journals.ed.ac.uk ISSN: 2051-7580 (Online) ISBN: 0482-3206 (Print) Res Medicais published by the Royal Medical Society, 5/5 Bristo Square, Edinburgh, EH8 9AL Res Medica, 2014, 22(1): 37-50. doi:10.2218/resmedica.v22i1.813 Res Medica 2014, Volume 22, Issue 1 Park, E et al. Who Needs a Gut Anyway? Res Medica 2014, 22(1), pp. 37-50. doi:10.2218/resmedica.v22i1.813 37 Who Needs a Gut Anyway?


Who Needs a Gut Anyway? Introduction
This is an up-to-date review on chronic intestinal failure (CIF) and parenteral nutrition (PN) as a management strategy for CIF.
CIF and long-term PN are important subjects but not covered in detail at the undergraduate level due to the perception that it is a relatively specialist area within gastroenterology.However, it is an essential aspect of gastroenterology, which must be appreciated and understood by the medical student, particularly because of its associated mortality and morbidity.As well as being a form of acute nutritional support, PN is used as a life-sustaining measure for patients with CIF due to conditions such as bowel ischaemia and Crohn's disease (CD).In the UK, there are currently around 500 patients receiving long-term home parenteral nutrition (HPN) in addition to oral nutrition and artificial enteral nutrition (EN), and the numbers are expected to rise with the ageing population. 1 It is a costly service requiring a multidisciplinary team effort along with high frequency patient-healthcare interaction.We will discuss the current evidence on the causes, management, and prognosis of CIF, with a particular focus on PN as a form of nutritional management.While PN seems to improve the prognosis of patients with CIF from a medical point of view, we will also explore how it affects other aspects of a patient's life, such as their social life and mental health.

Methods
Articles on CIF were found through PubMed, MEDLINE, and Google Scholar, their abstracts reviewed and then selected on the basis of their relevance.The following is an example of a search strategy using MeSH headings on Ovid:

Causes of CIF
Causes of CIF include congenital defects, dysmotility, obstruction, surgical resection, or disease-associated loss of absorption 3,5 The most common causes are SBS and motility disorders.SBS, which may result from congenital abnormalities or bowel resection, is the most common cause of CIF. 6,7In 1993, a multicentre survey in Europe showed that SBS represents the largest subset of patients (35%) that require HPN. 8 The length of the small intestine in healthy state ranges from 275 to 400 cm. 6SBS occurs when less than 200 cm of small bowel remains. 8A study conducted by Nightingale et al. 9 showed that the most common underlying diagnosis of SBS is CD; a relapsing inflammatory disease in which 50% of patients experience intestinal complications within 20 years. 10tients with a jejunostomy and a jejunal length of less than 100 cm are more likely to need long-term parenteral support due to excessive secretory loss. 11However, oral nutrition is usually sufficient for patients with 50 cm or more of small intestine if the colon is intact and remains in continuity. 6ronic intestinal failure can also arise from motility disorders such as extended Hirschsprung's disease and chronic intestinal pseudo-obstruction (CIPO).CIPO is a rare, disabling disorder in which total bowel length remains normal, but its function is compromised by an impairment of gastrointestinal peristalsis that mimics mechanical obstruction. 12edominant causes of CIF in children are congenital disorders such as intestinal atresia, gastroschisis, and microvillus atrophy. 5,7Other causes of CIF include small-bowel tumour and irradiation. 7

Artificial enteral nutrition
Artificial EN involves the provision of nutrients through the gastrointestinal tract and is given when a patient cannot ingest, chew, or swallow food, but can still digest and absorb nutrients. 13EN is a common method of nutritional supplementation for patients with intestinal failure, both in hospitals and the community. 14dications EN is used in patients with a partially functioning gastrointestinal tract due to both chronic and acute conditions, and ensures that they receive sufficient nutrition while simultaneously stimulating the bowel during recovery. 14Artificial EN is the firstline nutritional support for critically ill patients in general as well as for those who have undergone surgery. 15t is recommended that these patients should receive EN as tolerated, and PN only when EN does not meet the requirements for longer than several days to a week, depending on the previous nutritional state 16 ; this also applies to paediatric patients. 17

Benefits
Several reviews suggest that EN, rather than PN or surgery, is the preferred method of countering malnutrition in acute and chronic intestinal failure. 16,18Parenteral nutrition is costly, invasive, and associated with physical, social, and mental complications. 19r example, the lack of exposure to nutrients and the resulting diminished release of bile and enzymes causes atrophy and inflammation of the intestine, which in turn leads to fatty liver and elevation of liver enzymes. 4,18This is more significant when part of the bowel is bypassed.There is also increased infection risk when nutrient-rich solutions are directly infused into the bloodstream. 4There is open access from the skin into the bloodstream, which increases the risk of developing bloodstream infections, especially with skin flora.

Compared with EN, intestinal
transplantation is costly and associated with high morbidity and mortality. 19though septic complications due to the translocation of bacteria or bacterial products across a starving atrophied intestinal mucosa have been frequently reported, these are less likely to occur with EN. 20 Furthermore, probiotics in feeding solutions have been claimed to support the growth of beneficial intestinal microflora but this is still an area of investigation. 18mpan et al. 21  Guidelines on different EN regimens are constantly being updated. 22mplications There is a risk of feeding tube displacement in EN.Therefore, a small aspirate sample of gastric or intestinal fluid is taken to check the position of the tube end before administering any fluid.Nasogastric feeding can be associated with "dumping syndrome", which occurs when the patient is suddenly overloaded with feeding formula.This happens when the tube bypasses the stomach, which normally acts as a reservoir for large volumes of food entering the gastrointestinal system. 22,23

Parenteral nutrition
Parenteral nutrition is a form of nutritional support for severely malnourished patients who cannot be fed adequately by oral or enteral feeding.In contrast to enteral feeding, the nutrients are administered intravenously.Parenteral nutrition that provides total nutrition including protein, vitamins, energy, electrolytes, and trace elements is referred to as total parenteral nutrition (TPN) (Figure 2). 5,24Infection rates increase when care of the feeding line and the insertion site is poor.

Catheter-related problems
Insertion of the venous catheter may damage structures adjacent to the veins, such as the pleural membrane and other smaller veins, causing pneumothorax and haematoma. 27However, in contrast to infection, a prospective single-centre study by Cotogni et al. 29 showed that catheter dislocation is uncommon and occurred in only 5% of patients.

Metabolic complications
The most common metabolic complication in PN is hyperglycaemia.This is treated either by replacing 30% of glucose calories with fat or preferably with insulin treatment. 30Other metabolic complications include hypokalaemia and hypophosphataemia, which are common in severely malnourished patients who are refed after a long period of starvation. 5,24

Reduced quality of life
Studies on the quality of life (QoL) of PN patients provide conflicting evidence.
Patients' accounts vary greatly, depending on the severity of their complications and family environment. 27In a study conducted

Negative emotions
A non-structured interview study showed that a third of HPN patients experience anxiety with regard to treatment complications. 33They may also feel anger and grief when others are unable to understand their condition. 28Another study demonstrated that 80% of HPN patients experience depression as a consequence of losing their social life, independence, and physical mobility.Additionally, they experience problems with care providers and other complications of HPN. 26

Intestinal transplantation
Intestinal transplantation consists of the implantation of an intestinal allograft in patients with CIF, with the intention of restoring intestinal function.

Perioperative treatment
Perioperative treatment is vital to improve the chances of success for surgery.Intestinal transplantation only came into frequent use in the early 1990s with the introduction of tacrolimus, an immunosuppressive agent that minimizes the risk of organ rejection. 37crolimus is used by itself or in conjunction with other immunosuppressors or corticosteroids. 36teral nutrition is started as soon as possible after transplantation and an intestinal biopsy is performed every 48 hours to detect signs of organ rejection.
Finally, about 3 months after surgery and complete recovery, ileostomy closure is carried out and the central venous catheter is removed when the patient no longer relies on PN. 36

Prognosis
The prognosis for CIF patients receiving HPN is dependent on a number of factors, the most significant being the nature of the underlying disease. 40 general, patients taking PN have a 1-year survival rate of 86%, which decreases to 77% and 73% at 3 and 5 years, respectively. 41

Learning points
What is already known  Chronic intestinal failure (CIF) is the long-term inability of the body to maintain a healthy internal environment through nutrition. The nutritional need in CIF can be managed by enteral tube feeding, parenteral nutrition, or bowel transplant. Each method of management is associated with several side effects and complications, some more serious than others.

What this study adds
 Where possible, enteral nutrition should be encouraged at all times as it can speed up the recovery process by physiologically stimulating the bowel and successfully covering the nutritional requirements with least side effects. Parenteral nutrition, while associated with a number of significant physical, social, and psychological side effects, is the preferred method of nutritional support in patients whose bowel is not viable for enteral nutrition. Bowel transplantation, although potentially curative, is associated with significant mortality and must be applied only in carefully selected cases. Patients on long-term HPN are supported by a dedicated nutritional support team, who play a crucial role in supporting patients not only medically but also emotionally and mentally.
1. exp "Parenteral Nutrition, Total"/ or exp "Parenteral Nutrition"/ (21019) 2. exp "Quality of Life"/ (113933) 3. 1 and 2 (333) 4. exp "Parenteral Nutrition, Home"/ (940) 5. 2 and 4 (161) Limited knowledge of total parenteral nutrition (TPN) meant that background reading and meetings with experts in the field had to be undertaken.A meeting was organized with a specialist nurse who provided background information on the use of TPN in NHS Lothian.Review articles were useful in providing links to relevant primary literature.References for both primary and secondary literature were shared and organized on an online group which was set up on Zotero.Chronic intestinal failure Chronic intestinal failure (CIF) is defined as the long-term inability to sustain development and growth through oral nutrition, 2 or the inability to maintain protein-energy, fluid, electrolyte, or micronutrient balance. 3The jejunum and ileum are the main absorptive surfaces of the gastrointestinal tract, although iron and calcium are preferentially absorbed in the duodenum.Jejunum and ileum absorb and process most of the ingested nutrients including amino acids, glucose, fat, electrolytes, vitamins, and bile salts.Approximately 1 m of functioning small intestine must remain to allow adequate absorption of nutrients.Surgery or disease that leaves less than this causes short bowel syndrome (SBS) and intestinal failure. 4Chronic intestinal failure was considered a fatal state or one with poor prognosis, before life-saving techniques such as artificial enteral nutrition (EN), parenteral nutritional (PN) support, and bowel transplant surgery were developed. 2Such treatments have given CIF patients a better prognosis, although complications and side effects, such as diarrhoea, infections, and sepsis, may occur. 5 conducted a prospective, randomized controlled trial involving 28 patients who were treated in intensive care for multiple injuries.They found that patients who started EN immediately after admission were less likely to develop multiple organ failure and intestinal permeability than patients starting EN after 24 hours.This study was limited due to a small sample size and the absence of blinding.The cause of illness and extent of damage to patients before treatment may also have varied greatly.Many studies have provided data suggesting that early EN may have beneficial effects on successful coverage of nutritional requirements, infectious complications, and length of stay in the ICU or hospital.Where possible, and clinically indicated, EN should be employed.Even in intestinal failure, it is advantageous to give continuous EN at slow speed.Sometimes, patients eat small meals 5 or 6 times a day and, if insufficient, they may receive supplementary nocturnal tube feeding.Complementary PN is indicated in cases where the above measures fail.AdministrationThere are several ways to access the stomach and intestines in EN.The less invasive methods involve nasogastric, nasoduodenal, and nasojejunal tubes (Figure1).These methods are used for short-term EN or when the physical condition of the patient makes it unsafe to perform more invasive procedures.Nasal tubes can be inserted and advanced down into the stomach, the duodenum, or the jejunum.The feed is administered continuously (small amount of feed given without break throughout the day) or cyclically (for instance, every 12 or 24 hours).

Figure 2 .
Figure 2. Total Parenteral Nutrition48 refers to the inflammation of the vein leading to thrombus formation.It is common in PN patients, especially if the catheter is inserted into a vein with low blood flow.Signs of thrombophlebitis are erythema and tenderness over the area of the cannulated vein.If major thrombophlebitis is suspected, an ultrasound is performed to confirm the diagnosis, and anticoagulants such as heparin, urokinase, or plasminogen activator can be administered to dissolve the clot. 5If unresolved, a new catheter is inserted into a healthy vein.
in 48 HPN patients by Persoon et al. 31 involving surveys and structured openended interviews, 92% reported at least one psychosocial problem while 50% reported at least one physical problem.A review of 38 articles by Baxter et al. 32 investigated the QoL of patients receiving HPN due to underlying diseases such as cancer or intestinal failure.Collectively, this showed a mixture of positive and negative impacts of HPN on aspects such as emotional function, social function, nutritional status, and employment status.The different impact of HPN on QoL depends on the severity of the underlying indication for their HPN.32