Gastroenterology training and education

Discuss nutrition in ITU?

• Current literature strongly favours using enteral nutrition as the first line method for feeding ITU patients.
• Further there is no significant difference in the efficacy of gastric versus jejunal feeding in ITU patients.
• Use of prokinetics should be considered in patients intolerant to enteral feeding.
• Whole protein formulas are appropriate in most cases. There is no advantage of a peptide based formula.
• ESPEN (2006) guidelines favours early (<24hr) feeding of haemodynamically stable patients.
• EN is indicated in all patients who are not expected to be on full oral diet within 3 days
• During the acute phase of illness, provision of higher amounts of nutrients is associated with a less favourable outcome. Hence during the first 72-96 hours calorie intake in excess of 20-25 Kcal/kg/day (25-30 Kcal.kg/day for undernourished/chronic catabolic state patients) may be associated with less favorable outcome. During he recovery phase, aim to provide 25-Approve User Registration30 Kcal/kg/day.
• Indication of parenteral nutrition- only if pts are intolerant of EN or to provide supplemental PN if sufficient EN cannot be fed.
• Evidence for the use of glutamine- Glutamine should be added to EN in burned and trauma patients. Glutamine is a conditionally essential immunonutrient that is derived from muscle protein breakdown.
• Consider supplementation with omega-3-fatty acids, arginine and nucleotides (immune modulating formula) in elective upper GI patients, pts with mild sepsis (APACHE II <15), trauma and ARDS pts. However ICU patients with very severe illness and who do not tolerate more than 700 ml EN/day  should not receive a immune modulating formula

Parenteral nutrition in ICU

What is the indication for PN in ICU?

Patients who are not expected to be on oral nutrition within 3 days should receive PN if EN is contraindicated or if they do not tolerate EN. All patients who are not expected to be on a full oral diet within 3 days and who do not receive sufficient enteral nutrition for > 24h should receive complementary parenteral nutrition

What are the energy and substrate requirements?

• Energy requirements as above in EN section of ICU nutrition. Provide energy as close as possible to the measured energy expenditure to decrease negative energy balance
• The minimal requirements for glucose are about 2g/kg BW/day and they should not exceed 5-6 g/kg/day.
• Hyperglycemia should be avoided to prevent infectious complications. Tight glucose control (4.5-6.1 mmol/l) may lead to decreased mortality in surgical ICU patients. Whether a target below 8.3 mmol/L is equally effective and perhaps safer remains unknown
• IV lipids (LCT, MCT or mixed emulsions) can be administered safely at a rate of 0.7 up to 1.5 g/kg/d.
• Soybean oil-based lipid emulsions (LCT) high in linoleic acid are largely used in the ICU and remain the reference emulsion. LCT/MCT lipid emulsions show a clinical advantage to LCT alone but no improvement in survival.
• A balanced amino acids mixture should be infused at 1.3 – 1.5 g/kg ideal body weight/day in patients receiving adequate energy supply. In acute patients receiving hypocaloric feeding protein requirements were increased by about 25-30%.
• The amino acid solution should include 0.2 to 0.4 g/kgBW /day of glutamine (0.3 to 0.6 g/kg/day alanyl-glutamine).
• It is the most abundant free amino acid that under normal conditions is not an essential amino acid. However in the critically ill, its demand is increased for immune activity and repair.  A low plasma level is associated with a worse outcome. Various studies have shown reduced mortality or improved morbidity with reduced infections, improved glycaemic control or reductions in length of stay. Where the dipeptide cannot be incorporated within the PN feed it has been shown safe to administer through a peripheral line.
• Any prescription of PN includes 1 daily dose of multivitamins and 1 daily dose of trace elements. Parenteral feeding solutions (unlike enteral solutions) contain no trace elements or vitamins for stability reasons; this implies that they must be prescribed separately. However, clinicians very often forget to prescribe them, as they consider the PN bags to be analogue to the enteral complete feeding solutions.
• The micronutrients are invariably prescribed as “1 daily dose”, whatever the bodyweight or metabolic rate. When PN is prolonged, and if the patient remains critically ill, determination of plasma concentrations on monthly basis enables detection of gross deficiencies that should be supplied by the individual trace element: selenium and zinc are particularly at risk.

Some patients have specific substitution requirements that should be considered separately from PN requirements:

• Continuous renal replacement therapy causes a continuous loss in the effluent varying between 1-2  adult doses of selenium, zinc and thiamine per day that should be given in addition to basal requirements.
• Major burns cause large exudative Cu, Se and Zn losses
• In alcoholic patients- thiamine supplements (100-300 mg/day) are needed during the first 3 days in the ICU to prevent neurological side effects associated with PN glucose delivery.

There is no specific solution for these patients: it is therefore tempting to administer 2 or 3 vials of existing preparations to achieve an adequate dose. However this may cause toxicity.  A compromise solution may be the development of new basic multiple trace element preparation to which additional trace elements can be added for patients with increased trace element losses such as selenium and zinc

Are there any advantages of specific lipid formulations?

There are a number of different formulations of parenteral lipids:

• Soybean oil-based (e.g., Intralipid, Livolipid, etc); these are often referred to as long chain triglycerides (LCT)
• Mixtures (usually 50:50) of LCT and MCT e.g., Lipofundin
• Mixture (20:80) of LCT and olive oil (Clinoleic)
• Mixtures of lipids including fish oil (e.g. 30:30:25:15 mixture of LCT, MCT, olive oil and fish oil  (SMOFLipid); 40:50:10 mixture of LCT, MCT and fish oil (Lipoplus, also known as Lipidem)
• Fish oil for use as a supplement to be diluted with soybean oil (Omegaven).

Intravenous fish oil, providing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) decreases the synthesis of inflammatory cytokines, when compared to LCT/MCT. A multicenter study showed that IV fish oil had favorable effects on survival, infection rate, antibiotic requirements and length of stay when administered in doses between 0.1 and 0.2 g/kg/day. The best effects were observed in abdominal sepsis.

Although there is a theoretical basis for the inclusion of fish oil as a component of a lipid mixture such as seen in SMOFLipid, there is very little direct evidence of the efficacy of such mixtures. LCT/MCT, olive oil and fish oil enriched emulsions show clinical advantages on Omega 6 fatty acids emulsions, except in terms of survival.

ESPEN currently recommends use of fish oil enriched lipid emulsions in abdominal sepsis and surgical patients requiring ICU.

Discuss lipid biochemistry?

• Fatty acids are classified as saturated (no double bonds in the chain) or unsaturated (one or more double bonds in the chain), with the latter sub classified as monounsaturated (one double bond in the chain) or polyunsaturated (two or more double bonds in the chain).
• According to the chain length, fatty acids are termed short chain (< 8 carbons), medium chain (8 to 14 carbons) or long chain (16 or more carbons).
• With regard to the position of the double bond within the fatty acid chain three families are typically distinguished: omega-9, omega-6 and omega-3 (sometimes referred to as n-9, n-6 and n-3).
• Many fatty acids can be synthesized within the human body but two fatty acids (linoleic acid and alpha-linolenic acid) cannot. These fatty acids are required to be supplied to humans and are referred to as essential fatty acids. The essential fatty acids are synthesized in plants and are found in high  amounts in plant oils (e.g. corn, sunflower, soybean). They can be further metabolized to longer  chain, more unsaturated fatty acids including arachidonic acid (omega-6), and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (both omega-3).
• Fish oil contains EPA and DHA. Olive oil contains the omega-9 monounsaturated fatty acid oleic acid.

Ref

1. ESPEN guidelines