Parenteral nutrition support.

Continuing education and the APD program

This quiz is an ideal activity for APD members to include in your CPD log, where it relates to personal learning goals. Record the time taken, to the nearest hour, to complete the quiz and any associated research.

INTRODUCTION

When oral or enteral nutrition cannot meet a patient's needs, parenteral nutrition (PN) support may be indicated. There are many situations, however, in which the expected benefit of PN does not justify the associated risks and costs. The decision to use PN should be based on an individualised assessment of the patients condition and nutritional status, and the evidence available. (1) The dietitian is an essential part of nutrition support management, ensuring that suitable nutrition support strategies are chosen, any problems or risks are identified early, the individual patient's needs are met, and inadequate or excessive feeding is avoided. This continuing education quiz provides dietitians with basic information on PN support and useful references for further reading.

1. Which of the following conditions are not absolute indications for the use of PN?

a. Severe short bowel syndrome 

b. Distal high-output enterocutaneous fistula 

c. Severe acute pancreatitis

d. Mechanical intestinal obstruction

e. Diarrhoea

2. Which of the following factors might contribute to infection and/or sepsis in a patient being fed solely via total PN (TPN)?

a. Hyperglycaemia 

b. Disuse of the gastrointestinal tract

c. Immunosuppressive effect of the lipid emulsion

d. All of the above

3. In a three-in-one PN formulation, the 'three' refers to which components?

a. Protein, glucose and electrolytes

b. Protein, glucose and lipid

c. Protein, electrolytes and vitamins

d. Glucose, vitamins and lipid

4. The most common complication associated with stopping TPN too quickly is:

a. Hypoalbuminaemia

b. Hepatic steatosis 

c. Hypoglycaemia 

d. Cholecystitis 

5. If a patient has an allergic reaction to the parenteral lipid, what should be done?

a. Ascertain the nature of the reaction. Patients who experience anaphylaxis should not be given parenteral lipid

b. Stop the lipid immediately and continue fat-free TPN, adjusting the rate to ensure the patients energy needs are met. There are no disadvantages to using TPN without lipid

c. Provide essential fatty acids by using an oil that contains linoleic acid, in oral (if able) or topical (on the skin) form, if parenteral lipid cannot be given

d. Both a and c

6. What is the ideal type of i.v. access line for an acutely ill patient who needs the line only for TPN?

a. Multilumen central venous catheter (CVC or 'central line')

b. Subcutaneous port (such as a Portacath)

c. Peripheral i.v. catheter (PIVC)

d. Peripherally inserted central catheter ('PICC line')

e. Cuffed tunnelled CVC (such as a 'Hickman's catheter')

7. Three-in-one TPN formulations are increasingly common. Which of the following features is a disadvantage of this format?

a. Only uses one lumen of the central line

b. Less risk of bacterial contamination

c. Simpler to calculate regimen

d. Precipitate is less visible in the solution

8. Which of the following statements about TPN monitoring is/are true?

a. Triglycerides should be checked before TPN is commenced and weekly thereafter

b. Gastric aspirates and bowel activity should be noted daily to check for tolerance and absorption of nutrition support

c. Trace elements (copper, manganese, chromium, selenium) should be monitored weekly in all patients, and trace element supplementation stopped if levels are found to be high

d. All of the above

9. Which of the following is not a well-known complication in adults receiving long-term TPN?

a. Bone pain and/or fractures (in the absence of any trauma) due to metabolic bone disease 

b. Chronic liver disease 

c. Carnitine deficiency

d. Excessive weight gain

10. Mrs Brown is on TPN in intensive care, and has been ventilator-dependent for an unusually long period. She weighs 60 kg and is receiving 400 g carbohydrate, 80 g lipid and 60 g protein per day. Her liver enzyme levels are increasing. Which of the following do you suspect may be causing complications?

a. Excessive carbohydrate

b. Excessive lipid

c. Excess energy

d. Both a and c

ANSWERS

1. Both c and e.

Traditionally, PN and 'bowel rest' was the standard nutritional intervention for patients with pancreatitis, to minimise pancreatic stimulation. However, enteral nutrition into the jejunum, beyond the ligament of Treitz, may be well tolerated while still minimising pancreatic stimulation. (2) Elemental formula may be the preferred feed option. (2,3) Some patients may even tolerate feeding into the stomach. (4) Diarrhoea in itself is not an absolute indication for PN. There are numerous causes of diarrhoea including infection, underlying disease, altered gastrointestinal anatomy medications and medical therapies. Enteral nutrition can usually be provided while the underlying cause is evaluated and treated. Malnourished patients with severe intractable diarrhoea may, in some cases, benefit from the use of supplemental PN to minimise the risk of worsening malnutrition. PN is also indicated in patients with severe short bowel syndrome where there is less than 30 cm of small bowel remaining, because the reduced bowel length has insufficient absorptive capacity to maintain adequate nutrition. Where there is greater length of small bowel, PN may still be indicated in the initial phase until sufficient intestinal adaptation has occurred. High-output fistula of the gastrointestinal tract, when it is not possible to deliver enteral feed beyond the fistula site; and mechanical intestinal obstruction, when surgery is not immediately possible, are other indications for use of PN.

2. d.

Total PN increases the risk of infectious complications. (5-7) Hyperglycaemia is a well-documented TPN-related complication that increases infection risk. (5) The gut acts as a barrier to pathogens and their endotoxin, and plays a crucial role in the immune function, helping to protect against inaction. (6) The gastrointestinal tract is often overlooked as an organ that needs to be utilised in order to maintain its integrity and functionality, much like other organs such as the kidneys. Excessive lipid infusion has been shown to interfere with immune function. (6,7)

3. b.

There are many PN solutions that provide protein and glucose together. A more recent development is the parenteral solution in a bag with a separate chamber containing lipid, which is perforated before hanging, to allow the solution to be mixed well. This kind of bag is called a 'three-in-one'.

4. c.

Insulin is produced in response to the glucose component of PN. When PN is stopped suddenly, there is a rapid decrease in both blood glucose and insulin levels. The drop in blood glucose, combined with residual insulin activity, may cause hypoglycaemia in some patients, particularly if the blood glucose level is in the low end of the normal range at the time of stopping PN. (8) This may be prevented by a more gradual decrease of the infusion rate (such as halving the rate for two to four hours before stopping), with monitoring of blood glucose levels.

5. d.

Allergic reactions to parenteral lipid are rare, but cause difficulties when they do occur, because it is easier to meet the full energy needs of many patients with a combination of glucose and fat, than with glucose alone. The combination of glucose and fat may result in better nitrogen balance (9) and glucose tolerance, particularly when the fat is given continuously rather than intermittently. (10,11) Some adverse reactions can be minimised by decreasing the amount or rate of fat infusion. This could be trialled in patients who experience symptoms that are not life-threatening (such as nausea, sweating or headache). If the patient cannot have parenteral lipid at all, the risk of essential fatty acid deficiency is real and can occur within a few weeks. Safflower oil can be given orally or rubbed into the forearms daily; a pleasant lotion can be made up by a pharmacist for this purpose. (12)

6. d.

There are several important considerations in selecting an appropriate type of catheter. (13) Standard TPN solutions usually require a central line, rather than a peripheral catheter. ('Central' means that the tip of the catheter is located in the superior vena cava, to deliver the concentrated solution directly into a fast-flowing bloodstream.) A PICC line is inserted into a peripheral vein (usually the median cubital, basilic or cephalic veins), which reduces the incidence of infection. Insertion is safer because of the distance from major central blood vessels and underlying lung tissue. PICC lines may remain indwelling for many months. Multilumen CVCs are more difficult to insert and have an increased risk of catheter-related complications. These are required for patients requiring multiple infusions at any given time and can remain in place for approximately four to six weeks. Subcutaneous ports and cuffed tunnelled CVCs are much more complicated to insert, requiring a vascular surgeon. Both are appropriate for long-term use--for months or years--and have features that minimise infection risk. In culled, tunnelled CVCs, infections are minimised by the inbuilt cuff and by tunnelling through subcutaneous tissue before entering the bloodstream. In subcutaneous ports, infections are minimised through being completely covered by the skin, usually in the chest or arm (with access for infusion by a special needle that is removed when the infusion is complete). Finally peripheral venous catheters are suitable only for isotonic solutions with a neutral pH, and are mainly used for simple i.v. therapy (fluids and drugs) and peripheral PN (with specialised solutions). These catheters are easy to insert, with a low incidence of complications, but need to be changed within about three days.

7. d.

Three-in-one parenteral solutions may be more convenient in terms of nursing time, and reduce risk of bacterial contamination. (14) Disadvantages of the three-in-one include the larger particle size (preventing use of an antibacterial filter) and the opaque nature of the solution that makes it difficult to detect particles that may form in precipitation. Using modular components allows flexibility in adjusting macronutrients, but three-in-one solutions are easier to store, calculate and administer.

8. a.

Triglycerides may rise in patients receiving parenteral lipid, but it is essential to check baseline levels before TPN starts, to prevent a pre-existing high level from incorrectly being attributed to the TPN. (15) Gastrointestinal symptoms do not relate to tolerance, of PN, although they may be monitored in order to ascertain the possibility of reintroducing enteral intake. Trace element levels do not require frequent monitoring in all patients. Weekly monitoring may be indicated in patients with liver disease (at risk of elevated levels, particularly of manganese) (16) or increased gastrointestinal losses or malnutrition or who have been on TPN for a prolonged period (all at risk of deficiency due to depleted endogenous stores). Apparent high serum level may be due to contamination. This is common with trace elements, and trace-element-free test tubes should be obtained from the pathology laboratory to confirm a high serum level.

9. c

Although TPN does not provide carnitine, most patients do not exhibit deficiency symptoms even after many years. (Premature infants may be at risk because of their increased requirements.) (17) Metabolic bone disease is experienced by a significant number of people who are receiving long-term PN. (18) Many different causes of liver disease are associated with PN. In particular, continuous PN (i.e. not cyclic) with a lack of enteral stimulation can promote cholestasis. (19) Excessive weight gain can easily occur if the patients requirements are not reviewed regularly.

10. d.

The estimated maximum limit of glucose oxidation is 4 mg/kg/minute. (20) This would be 345 g per day for a person weighing 60 kg. Excessive carbohydrate administration can cause hyperglycaemia, fatty liver and excessive C[O.sub.2] production (and prolonged ventilator dependence). This is most likely to occur in situations of total overfeeding (21) and in this case Mrs Brown is receiving 44 Cal/kg, Recommendations for intensive care patients are usually less than 35 Cal/kg. Mrs Brown is not receiving excessive lipid. Complications from lipid infusion are usually avoided if the rate is below 0.11 g/kg/hour, (22) or 158 g for Mrs Brown.

REFERENCES

1 American Gastroenterological Association Clinical Practice and Practice Economics Committee. American Gastroenterological Association medical position statement: parenteral nutrition. Gastroenterology 2001; 121: 966-9.

2 Russell M. Acute pancreatitis: a review of pathophysiology and nutrition management. Nutr Clin Pract 2004; 19: 16-24.

3 O'Keefe S, Lee R, Anderson F et al. Physiological effects of enteral and parenteral feeding on pancreaticobiliary secretion in humans. Am J Physiol Gastrointest Liver Physiol 2003; 283: G27-36.

4 Eatock F, Brombacher G, Steven A, Imrie C, McKay C, Carter R. Nasogastric feeding in severe acute pancreatitis may be practical and safe. Int J Pancreatol 2000; 28: 23-9.

5 McCowen K, Friel C, Sternberg J et al. Hypocaloric total parenteral nutrition: effectiveness in prevention of hyperglycemia and infectious complications--a randomised clinical trial. Crit Care Med 2000; 28: 3606-11.

6 Raper S, Maynard N. Feeding the critically ill patient. Br J Nurs 1992; 1: 273-80.

7 Klein C, Stanek G, Wiles C. Overfeeding macronutrients to critically ill adults: metabolic complications. J Am Diet Assoc 1998; 98: 795-806.

8 Krzywda E, Andris D, Whipple J et al. Glucose reponse to abrupt initiation and discontinuation of total parenteral nutrition. J Parenteral Enteral Nutr 1993; 17: 64-7.

9 MacFie J, Smith R, Hill R. Glucose or fat as a nonprotein energy source? Gastroenterology 1981; 80: 103-7.

10 Jensen G, Mascioli E, Seidner D et al. Parenteral infusion of long- and medium-chain triglycerides and reticuloendothelial system function in man. J Parenteral Enteral Nutr 1990; 14: 467-71.

11 MacFie J, Courtney D, Brennan T. Continuous versus intermittent infusion of fat emulsions during total parenteral nutrition: clinical trial. Nutrition 1991; 7: 99-103.

12 Speerhas R. Inquire here: how can a clinician diagnose essential fatty acid deficiency (EFAD) and how can EFAD be treated? Support Line 2002; 24: 23-4.

13 Horattas M, Trupiano J, Hopkins S, Pasini D, Martino C, Murty A. Changing concepts in long-term central venous access: catheter selection and cost savings. Am J Infect Control 2001; 29: 32-40.

14 Didier M, Fischer S, Maki D. Total nutrient admixtures appear safer than lipid emulsion alone as regards microbial contamination. J Parenteral Enteral Nutr 1998; 22: 291-6.

15 American Society for Parenteral and Enteral Nutrition (ASPEN): Board of Directors. Guidelines for the use of parenteral and enteral nutrition in adult and paediatric patients. J Parenteral Enteral Nutr 2002; 26 (Suppl 1): 1SA-138SA.

16 Fitzgerald K, Mikalunas V, Rubin H, McCarthey R, Vanagunas A, Craig R. Hypermanganesemia in patients receiving total parenteral nutrition. J Parenteral Enteral Nutr 1999; 23: 333-6.

17 Worthley L, Fishlock R, Snoswell A. Carnitine deficiency with hyperbilirubinemia, generalised skeletal muscle weakness and reactive hypoglycemia in a patient on long-term parenteral nutrition. J Parenteral Enteral Nutr 1983; 7: 176-80.

18 Shike M, Harrison J, Sturtridge W et al. Metabolic bone disease in patients receiving long-term total parenteral nutrition. Ann Intern Med 1980; 92: 343-50.

19 Quigley E, Marsh M, Shaffer J, Marking R. Hepatobiliary complications of total parenteral nutrition. Gastroenterology 1993: 104: 286-301.

20 Wolfe R, O'Donnell T, Stone M, Richmand D, Burke J. Investigation of factors determining the optimal glucose infusion rate in total parenteral nutrition. Metabolism 1980; 29: 892-900.

21 Lo H, Lin C, Tsai L. Effects of hypercaloric feeding on nutrition status and carbon dioxide production in patients with long-term mechanical ventilation. J Parenteral Enteral Nutr 2005; 29: 380-87.

22 Miles J. Intravenous fat emulsions in nutritional support. Curr Opin Gastroenterol 1991; 7: 306-11.

This quiz has been prepared by the NSW Enteral/Parenteral Nutrition Interest Group. Correspondence should be directed to Suzie Ferrie, IG Convenor, Department of Nutrition and Dietetics, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia, or at [e-mail]