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 Table of Contents  
REVIEW ARTICLE
Year : 2016  |  Volume : 29  |  Issue : 3  |  Page : 478-486

Nutritional support in critically ill adult patients


Department of Anesthesia, ICU and Pain Management, Faculty of Medicine, Menoufia University, Menoufia, Egypt

Date of Submission28-Apr-2015
Date of Acceptance26-Jul-2015
Date of Web Publication23-Jan-2017

Correspondence Address:
Ahmed M Ragab
MBBCh, El Helal Hospital, Health Insurance Organization, El Menoufia Branch, Garwan Village, El Bagour, Menoufia Governorate, 32871
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1110-2098.198655

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  Abstract 

Objective
The aim of this study was to conduct a review of nutritional support in critically ill adult patients.
Data analysis
Data source: medical textbooks, medical journals, and medical websites with recent research studies having the keyword nutritional support in the title of the paper were searched. Study selection: systemic reviews that addressed nutritional support and studies that addressed support in critically ill adult patients were selected. Data extraction: a special search was conducted at midline with the keywords nutritional and support in the title of the paper, and suitable studies meeting the criteria were extracted and their quality and validity assessed. Data synthesis: each study was reviewed independently. The data were translated into the language most comfortable for the researcher and arranged in topics throughout the article.
Recent findings
Early nutritional support (within 48 h) is advocated in critically ill patients. The normal policy is to start with enteral nutrition (EN). If not feasible or not able to provide complete nutrition, parenteral nutrition is started to supplement EN. The caloric balance can be maintained by providing 25-35 kcal/kg/day. Nutrition should be personalized for each patient taking into consideration the state of disease and the present nutritional status of the patient. The patient's nutritional adequacy and possible side effects should be assessed regularly.
Conclusion
Early EN has been suggested to be beneficial in the critically ill. But depending on the enteral route alone might lead to underfeeding. Therefore, many patients may need a combination of EN and parenteral nutrition, adjusted as tolerance to EN increases.

Keywords: critically ill, enteral nutrition, nutritional requirements, nutritional support, parenteral nutrition


How to cite this article:
Radi AA, Aiad AA, Soliman EA, Ragab AM. Nutritional support in critically ill adult patients. Menoufia Med J 2016;29:478-86

How to cite this URL:
Radi AA, Aiad AA, Soliman EA, Ragab AM. Nutritional support in critically ill adult patients. Menoufia Med J [serial online] 2016 [cited 2020 Feb 16];29:478-86. Available from: http://www.mmj.eg.net/text.asp?2016/29/3/478/198655


  Introduction Top


Malnutrition is an alteration of body composition due to the deficiency of either total energy or proteins (and other nutrients) that results in reduced body cell mass, organ dysfunction, and abnormal serum chemistry values. It occurs usually due to the adaptive changes induced by the body in response to the stress created by the critical illness to maintain a normal homoeostasis [1] .

Unfortunately, malnutrition is very common in acutely ill patients, occurring in 30-50% of hospitalized patients. This number may be higher in critically ill patients [2] . Hospital malnutrition has been associated with an increased risk for complications, particularly in surgical patients. It also increases hospital costs and is associated with impaired immunologic function and increased morbidity and mortality in acutely ill patients [2] .

The American College of Chest Physicians has laid down certain goals for nutritional support. This includes providing nutrition support consistent with the patient's medical condition and the available route of administration, preventing development of deficiencies of various macronutrients and micronutrients, supplementing various nutrients in the doses sufficient for the existing medical condition, and preventing any complications that may be related to the route of delivery. This will improve the patient outcome and subsequently reduce mortality and morbidity [1] .


  Materials and methods Top


The guidance published by the Centre for Reviews and Dissemination was used to assess the methodology and outcomes of the studies. This review was reported in accordance with the preferred reporting items for systematic reviews and meta-analyses statement. An institutional review board and ethics committee approved this study.

Search strategy

We reviewed papers on nutritional support in critically ill adult patients from Medline databases (Pub Med, Medscape, Science Direct) and also materials available on the internet. We used nutritional support/nutritional assessment/nutritional requirements/critically ill adult/intensive care unit/enteral nutrition (EN) and parenteral nutrition (PN) as search terms. In addition, we examined references from specialist databases such as Journal of Parenteral and Enteral Nutrition. The search was performed in the electronic databases from the creation of the database up to 2015.

Study selection

All studies were independently assessed for inclusion. They were included if they fulfilled the following criteria:

  • They were published in the English language
  • They were published in peer-reviewed journals
  • They focussed on nutritional support in critically ill adult patients
  • They discussed nutritional assessment, requirements, and routes in critically ill adult patients.


If a study had several publications on certain aspects we used the latest publication giving the most relevant data.

Data extraction

Studies on nutritional support outside the ICU, those on patients with chronic diseases or on paediatric patients, reports without peer review, studies not within the national research programme, and letters/comments/editorials/news and studies not focussed on nutritional support in critically ill adult patients were excluded.

Quality assessment

The quality of all selected studies was assessed. Important parameters included study design, attainment of ethical approval, evidence of a power calculation, specified eligibility criteria, appropriate controls, adequate information, and specified assessment measures. It was expected that confounding factors would be reported and controlled for and appropriate data analysis made, in addition to an explanation for missing data.

Data synthesis

A structured systematic review was performed and the results tabulated.


  Results Top


Early nutritional support (within 48 h) is advocated in critically ill patients. The usual policy is to start with EN. If not feasible or not able to provide complete nutrition, PN is started to supplement EN. The caloric balance can be maintained by providing 25-35 kcal/kg/day. Nutrition should be personalized for each patient taking into consideration the state of disease and the present nutritional status of the patient. The patient's nutritional adequacy and possible side effects should be assessed regularly.


  Discussion Top


Physiology of nutrition and metabolism

The process of metabolism involves the oxidation of basic nutrients to produce thermal energy or heat. This process converts oxygen into carbon dioxide, water and heat. The heat is dissipated through the skin and is measured as kilo calories [3] .

1 g glucose + 0.74 l O 2 yield, 0.74 l CO 2 + 3.75 kcal

The summed metabolism of all three substrates will determine the overall O 2 consumption (VO 2 ), CO 2 production (VCO 2 ) and energy expenditure (EE) in any individual patient. Because heat production is not easy to measure, VO 2 and VCO 2 can be used as indirect measures of the metabolic EE in individual subjects. This is the principle behind indirect calorimetry (IC), which is the standard method for measuring EE in the clinical sitting [3] .

Definition of critical illness

Critical illness is any disease process that causes physiological instability leading to disability or death within minutes or hours. Perturbation of the neurological and cardiorespiratory systems generally has the most immediate life-threatening effects. Fortunately such instability can be reliably detected from deviations from the normal range during simple clinical observations, such as level of consciousness, respiratory rate, heart rate, blood pressure and urinary output [4] .

The metabolic response to critical illness

The body's response to critical illness occurs in phases that clearly change over time. There appears to be an acute phase in which the modern ICU patient is undergoing acute resuscitation and the body's evolutionary metabolic response to injury is rapid catabolism [2] . If the patient survives the acute phase, this is followed by a more chronic phase of critical illness when the patient becomes quite vulnerable to recurrent infection and other complications, which can lead to a return to the acute phase. If the patient can recover sufficiently, they will enter a recovery phase, which often coincides with ICU discharge to a hospital floor or rehabilitation unit ([Figure 1]) [2],[5] .
Figure 1: The metabolic response to injury [5]. ACTH, adrenocorticotropic hormone.

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Nutritional screening

All ICU admissions should be screened to assess their need for nutrition support. Nutrition support should be recommended within 24-48 h of ICU admission (or once haemodynamically stable) for undernourished or hypercatabolic patients, ill patients expected to stay in the ICU for 3 days or more, and patients not expected to commence diet within the next 5 days or more [6] .

A 'nutrition risk in the critically ill score' (NUTRIC score) has recently been validated for screening ICU patients. The final NUTRIC score consisted of six variables, including age, baseline APACHE 2 score (Acute Physiological and Chronic Health Evaluation), baseline SOFA score (Sequential Organ Failure Assessment), number of comorbidities, days from hospital admission to ICU admission, and serum interleukin-6. These specific variables were found to be highly predictive of outcomes, such as mortality and duration of mechanical ventilation (MV), with higher NUTRIC scores predicting poor outcome [7] .

Nutritional assessment

A complete nutrition assessment includes subjective global assessment, anthropometric measurements, and dynamic nutritional assessment that includes muscle function tests, nitrogen balance, plasma proteins, cell-mediated immunity and creatinine height index.

Subjective global assessment is a well-recognized validated method that easily captures both history (including weight change, changes in food intake, gastrointestinal symptoms and functional impairment) and physical exam findings (including loss of subcutaneous fat, muscle wasting, oedema and ascites) [8] .

Anthropometry or body composition refers to the amount of fat and lean tissues in our body. If midarm muscle circumference is less than 23 cm in males and 22 cm in females, malnutrition is considered . If triceps skin-fold thickness is less than 10 mm in males and 13 mm in females, malnutrition is considered [9] .

Ideally, admission weight before interventions should be obtained. But an accurate measurement of body weight is an arduous task in critically ill patients with bulky dressings, catheters, monitoring wires, tubes and drains.

The ideal body weight (IBW), a comparison of the patient's current weight for height with the IBW, can be used as a quantifying tool in the nutrition assessment process. Interpretation of the IBW is as follows: 80-90% IBW is considered mild malnutrition, 70-79% is considered moderate malnutrition, and 0-69% is considered severe malnutrition [10] .

IBW (male) (kg) = height (cm) − 100

IBW (female) (kg) = height (cm) − 105

In an ideal situation, a measure of BMI is a useful indicator of nutritional state:



A BMI less than 18.5 meets the criterion for malnutrition [11] .

Major limitations to these measurements in the intensive care setting include fluid shifts, changes in hydration status and interobserver variability [10] .

Body composition can objectively be measured with technical devices like a skin-fold caliper, bioelectrical bioimpedance analyses, dual-energy X-ray absorptiometry, air displacement plethysmography, computed tomography, ultrasound or MRI [8] .

Serum proteins with a short half-life, such as transthyretin (prealbumin) (2 days) and transferrin (8 days), respond more quickly to declining or improving nutrition status than does albumin, which has a half-life of 20 days. Their serum levels decrease rapidly when catabolic inflammatory cytokines are released by infection or trauma [9] .

Creatinine height index is defined as the ratio of 24 h urine creatinine excreted compared with height-matched controls of the same sex. Expressed as a percentage, an index of 100% indicates normal muscle mass, provided there is normal excretion of creatinine [9] .

In addition to this, electrolytes, glucose and BUN/creatinine help assess overall clinical and fluid volume status and need to be measured if PN is to be instituted. Iron levels should be measured in the setting of unexplained anaemia, as should specific vitamin levels if clinically indicated (e.g. B12/folate in macrocytic anaemias, others based upon specific physical signs). Serum calcium, magnesium and phosphorous should also be assessed periodically, particularly in the setting of poor oral intake or diarrhoea [12] .

Nitrogen balance is measured as follows:

Nitrogen balance = nitrogen intake − nitrogen loss

Nitrogen balance (g) = [protein intake (g)/6.25] - (UUN + 4)

As UUN refers to urinary urea nitrogen in grams per 24 h, we add 4 g for correction of insensible nitrogen losses; each gram of urinary nitrogen represents 6.25 g of degraded protein [13] .

The functional ability of an individual can be measured by hand-grip dynamometry and forearm muscle dynamometry. These tests are inexpensive and easy to perform but may be difficult in the ICU. Severely malnourished patients will have reduced grip strength [10] .

Immune competence, as measured by delayed cutaneous hypersensitivity, is affected by severe malnutrition. However, several diseases and drugs, such as infections, uraemia, and steroids, influence this measurement, making it a poor predictor of malnutrition in sick patients [8] .

Nutritional requirements

To measure caloric requirements, controversy remains when comparing IC with weight-based equations such as the Harris-Benedict equation (HBE). Direct measurement of resting metabolic expenditure (REE) by IC is the best way. However, ICs have several limitations as they are expensive, time-consuming and not universally available. In addition, they give unreliable results with an inspired oxygen concentration of more than 50%. REE is calculated by IC as follows [14] :

REE (kcal/day) = 3.9 (VO 2 ) + 1.1 (VCO 2 ) × 1440 (the Weir equation)

HBE is used to calculate REE to provide adequate calorie intake.

Men: REE = 66.4 + [13.7 × weight (kg)] + [5.0 × height (cm)] − [6.8 × age (years)]

Women: REE = 65.5 + [9.6 × weight (kg)] + [1.7 × height (cm)] − [4.7 × age (years)] [1]

The result is multiplied by a stress factor and activity factor according to the degree of tissue injury and severity of illness to estimate total energy expenditure. Stress factor is calculated as 1.1 for fever, for each degree Celsius, 1-1.25 for mild starvation, 1.25-1.5 for moderate to severe illness, 1.5-1.75 for severe illness, and 2.10 for severe burn. Activity factor equals 1.2 if confined to bed and equals 1.3 if out of bed [9] .

For people who are not severely ill or injured, nor at risk for refeeding syndrome, the suggested nutritional prescription for total intake should provide all of the nutritional elements in balanced amounts. The total energy required is estimated as 25-35 kcal/kg/day. Protein requirements are about 0.8-1.5 g/kg/day. Fluid required is about 30-35 ml/kg. Adequate electrolytes, minerals and vitamins should be added. Their daily requirements are shown in [Table 1]. Fibre and other special additives should be considered if appropriate [13] .
Table 1 The daily requirements of vitamins, trace elements and electrolytes[11]


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Calories can be given in three forms: carbohydrates, fat and protein. Carbohydrates provide 3.75 kcal/g. Therefore, 30-70% of total calories can be given as carbohydrate. Fat provides 9.3 kcal/g. Therefore, 20-50% of total calories can be given as fat [1] . Protein provides 5.3 kcal/g. Therefore, 15-20% of total calories can be administered as protein or amino acids. Proteins are not routinely used in calculating the daily energy provision as the delivered amino acids will be used for new protein synthesis [1] .

Routes of nutrition

Routes of nutrition include EN and PN. EN is associated with fewer complications than PN and is less expensive to administer. However, the use of EN alone often does not achieve caloric targets and hence underfeeding may occur [Table 2]. Combining PN with EN constitutes a strategy to prevent nutritional deficit but may involve the risk of overfeeding. SCCM/A.S.P.E.N. guidelines suggest that PN support therapy not be implemented for the first 7 days of ICU admission [16] . Unless an absolute contraindication to EN exists, EN should be initiated preferentially over PN in critically ill patients [4] .
Table 2 Problems associated with EN[15]


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Enteral nutrition

The main contraindications for EN are intestinal obstruction, intestinal fistulas, generalized suppurative peritonitis, bowel ischaemia, acute fulminant necrotizing pancreatitis and severe shock [14] .

Enteral access is usually decided by estimating whether a tube will be required in the short term or in the long term. Nasoenteric devices are preferred if EN is not expected to presist for more than 30 days. Percutaneous gastrostomy or jejunostomy devices are placed if EN is expected beyond 30 days, as shown in [Figure 2] [16] .
Figure 2: Routes of enteral nutrition [16].

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Methods of confirming nasogastric tube position include radiographic confirmation, bedside pH checks (pH < 5.5 confirms gastric position), observation of change in the external tube length during feeding, and auscultatory method. Methods for confirming small bowel location of feeding tubes were bile aspiration, pH change from acidic to basic, and methylene blue dye injection [6] .

Gastric feeding is quite beneficial as the stomach is the primary organ that helps in initiating digestion and sterilizing the gastric contents. However, gastric atony and a higher risk of developing aspiration pneumonitis are a few disadvantages associated with gastric feeding [14] .

Jejunal feeding allows the full use of the gut in critically ill patients at high risk of aspiration, or who have demonstrated gastric feed intolerance. The main disadvantage is difficulty in placement. This can be overcome by endoscopic or fluoroscopic guidance [14] .

It is preferable to give EN by continuous infusion rather than as intermittent boluses. Both calories and infusion rate are increased over time and the desired level is reached over a few days so as to prevent diarrhoea. This method is all the more important in the case of jejunostomy or nasojejunal tube usage as there is no reservoir (stomach). It is started at 25 ml/h and can be increased by 25 ml every hour [14] .

In monitoring EN tolerance, guidelines recommend that gastric residual volumes between 250 and 500 ml should prompt clinicians to take measures to reduce the risk of aspiration, such as elevation of the head of the bed, but that automatic cessation of enteral feeding should not occur for gastric residual volumes less than 500 ml unless other signs of intolerance are present, such as nausea, vomiting and distention [6] .

Enteral formulae

Standard formulae contain the reference values for macronutrients and micronutrients for a healthy population. Most of them contain whole protein, lipid and fibre [7] . Disease-specific formulae are adapted to the needs of a specific disease and/or digestive or metabolic disorder (e.g. branched chain amino acid formula for hepatic failure and immune-enhancing formula for critical illness) [7] . Immune-modulating formula is derived by adding ω-3 fatty acids, arginine and nucleotides to a complete formula to enhance immune functions.

Normal-energy formula provide 0.9-1.2 kcal/ml, any formula above this range is considered high-energy formula, and any formula below this is considered low-energy formula [17] . Polymeric formulae contain intact proteins derived from cow's milk or soya beans, complex carbohydrates from starches, and fats in addition to the trace elements, vitamins, minerals and fibre. These feeds are usually made lactose free as lactose intolerance is common in critically ill patients. They are preferred for duodenal and jejunal administration [1] .

Peptide-based formula contains protein predominantly in peptide form (2-50 amino acid chains) [17] . Elemental formulae contain the various macronutrients in a readily absorbable form - e.g. proteins in the form of peptides or amino acids, fats in the form of medium-chain triglycerides, and carbohydrates in the form of monosaccharides or disaccharides. It is indicated in patients with severe form of malabsorption states [1] .

High lipid formulae contain more than 40% of total energy from lipids. High monounsaturated fatty acid formulae contain 20% or more of total energy from monounsaturated fatty acid [17] .

Complications of EN include diarrhoea, distention, aspiration and infection. One of the most important risk factors for the development of ventilator-associated pneumonia is an enteral-feeding catheter [18] .

Mechanical complications of EN include the following: obstruction of the feeding tube with medications, erosion of nasal or gastric mucosa with risk of bleeding, infection or perforation; displacement of the tube with risk of aspiration; and sinusitis. To minimize these complications, tubes should be soft and well lubricated for insertion, and tube position should always be verified radiographically before use. Tube obstruction can be minimized by flushing water on a regular basis [4] .

Parenteral nutrition

Ideally, PN should be given through a tunnelled subclavian vein central line. However, peripheral vein nutrition can be used with solution osmolality less than 900 mOsm/l in short-term feeding [16] .

Total parenteral nutrition (TPN) solutions should contain a balanced mix of protein, carbohydrates and lipid, together with water, vitamins, electrolytes and minerals. Protein is provided as a balanced solution of essential (40%) and nonessential (60%) amino acids. Lipid emulsions are used because it is possible to supply a large amount of energy in a small volume (9 kcal/g), which is nonirritant to veins. Glucose (4 kcal/g) is used as the main source of carbohydrate, but requires close control of blood sugar. Feeds with a high proportion of glucose may delay weaning from ventilation in some patients, because they sometimes cause excess carbon dioxide production [15] .

Once prepared, these nutrient components are delivered with the assistance of an inline filter (filters impurities and bacteria) and an infusion pump [16] . PN may be delivered through a 2-in-1 system (one solution containing amino acids, dextrose, electrolytes, vitamins, minerals and fluids and one solution containing intravenous fat emulsions) or through a 3-in-1 system (all nutrients mixed in one container) [19] .

Complications of PN include hyperglycaemia (a blood glucose target of 7-9 mmol/l is recommended to prevent it), electrolyte disturbances, hepatic dysfunction, cardiac arrhythmias, and catheter-related complications such as malposition, pneumothorax and catheter-related sepsis [16] .

Catheter-related sepsis can be prevented by using a full aseptic technique, using the line for PN only and applying the Biopatch Ethicon, Inc. Johnson & Johnson, Cornelia, GA, USA (a commercially available chlorhexidine-impregnated sponge) over the exit site of the catheter and changing it weekly. Ethanol also can be instilled into the lumen of the catheter when cyclic PN is not being infused [16] .

General complications of nutritional support

General complications of nutritional support include refeeding syndrome, overfeeding and hyperglycaemia. Overfeeding can cause uraemia, hyperglycaemia, hyperlipidaemia, hypertriglyceridaemia, fatty liver (hepatic steatosis), hyperazotemia, hypercapnia (especially with excess carbohydrates), fluid overload and metabolic acidosis [11],[20] .

Refeeding syndrome is usually seen if the period of fasting exceeds 5 days or more and is seen within 4 days of restarting the feed. During resumption of feeding with the onset of normoglycaemia, various minerals and electrolytes, especially potassium, magnesium and phosphates, are rapidly used up, leading to their acute intracellular deficiency, although the serum levels may be normal. This leads to cardiac failure, arrhythmias, confusion, coma, convulsions and respiratory failure ([Figure 3]) [1] .
Figure 3: Refeeding syndrome [20].

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To prevent the above-mentioned complications, energy intake is restricted to about 50-70% of the total energy requirements during the first 3-5 days, along with close monitoring of electrolytes and multivitamins, and restoring circulatory volume and fluid balance and monitoring the overall clinical status closely [1] .

Monitoring of patients on nutritional support

While receiving EN or PN, the patient must be monitored for changes in body composition, blood chemistry, blood glucose, triglycerides and protein synthesis. Daily weight and the total volume of patient intake and output need to be monitored in addition to assessing other markers of hydration and volume status. Electrolytes and markers of renal function should be monitored routinely. Maintaining blood glucose levels to 80-110 mg/dl in all patients who are critically ill, regardless of pre-existing diabetes mellitus, is recommended. The protocol for monitoring nutritional support is shown in [Table 3] [21] .
Table 3 Suggested monitoring protocol for nutritional support [21]


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Nutritional additives

Nutritional additives include glutamine, arginine, fibre, ω-3 fatty acids and antioxidants (such as zinc, selenium, and vitamins E and C). Their indications and contraindications are shown in [Table 4]. Various trials have shown that glutamine can reduce the incidence of catheter-related infections in critically ill patients but its effect on overall mortality is still controversial [1] .
Table 4 Special indications and contraindications of nutritional additives[22]

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Arginine is important in modulating blood flow through its role in nitric oxide production and thus has been found to be beneficial in postoperative patients. However, it causes harmful effects in septic patients and should not be used [1],[2] .

All guidelines specifically recommend the use of ω-3 fatty acids in acute lung injury and acute respiratory distress syndrome [23] .

Combination of immunonutrients as a supplement to the enteral feed has been found to reduce the incidence of infections and duration of MV [1] . Antioxidants either singly or in combination, and by both parenteral and enteral routes, should be considered in critically ill patients, particularly in those with burns or trauma and receiving MV [22],[23] .

Nutritional requirements in special diseases

Trauma and sepsis are characterized by a severe catabolic process requiring an additional 10-20% increase in calorie requirement, and so is the requirement of proteins. The electrolyte and trace element requirements are also increased, and close monitoring is required. Hyperglycaemia can be a common finding and may require inclusion of insulin infusion. Lipids, however, may have to be decreased because of increased incidence of hypertriglyceridaemia [1] . Patients with thermal injuries require 30-35 kcal/kg/24 h and high protein intake of 2-2.5 g/kg/day [14] .

In acute renal failure patients, protein intake should be restricted to 0.5 g/kg/day and fluid to 0.8-1 l/day. Protein intake can be increased to 1 g/kg/day once dialysis begins as amino acids will be lost during haemodialysis or haemofiltration. Also, in enteral feeds, a carbohydrate: fat ratio of 60: 40 should be used. Special precautions should be taken while supplementing electrolytes such as K, Mg and PO 4 , through frequent monitoring [14] .

In patients with hepatic dysfunction, protein intake should be maintained at 1 g/kg/day if encephalopathy is not present and reduced to 0.3 g/kg/day if encephalopathy is present. Also, carbohydrate: fat intake ratio has to be kept at 60 : 40 [14] .

In patients with chronic obstructive pulmonary disease, the ratio of carbohydrate: fat has to be kept at 40 : 60. Conversely, in patients with acute respiratory distress syndrome, lipid emulsions should be avoided and carbohydrate: fat ratio should be kept at 65 : 35 [14] .

In patients with cardiac failure, salt and water intake should be restricted. Carbohydrate: fat ratio is to be kept at 60 : 40. PN is to be given over 3-4 days with half of the total calorie requirements [14] .

Regarding neurocritical patients, total calorie intake ranges from 20 to 30 kcal/kg/day, with protein intake higher than 20% of total calories (hyperproteic diet) [24] .

In severe pancreatitis, peptide-based jejunal feed should be given. But in ileus and necrotizing pancreatitis, there is no other alternative but to give TPN [14] .

The obese, critically ill patient may be expected to have a greater number of underlying comorbidities and subsequently more complications [6] . Postpyloric feeding is preferred here. High-protein hypocaloric feeding (70-80% of the calculated target) should be provided. IC is the preferred method for measuring REE [6] .

Uncomplicated surgery has been associated with energy requirements of 1.0-1.5 × BMR, whereas complicated surgery requires 1.25-1.4 × BMR in order to meet the patient's needs. In general, 25 kcal/kg/day is an acceptable target intake. Protein requirements in the range of 1.25-2.0 g/kg/day have been recommended [25] .

In our critically ill cancer patients, IC is the method of choice for determining caloric need, but if it is not available or feasible HBE without added stress and activity factors is more accurate than the clinically estimated REE [26] .

In geriatric patients, REE declines by 1-2% per decade after the third decade of life, possibly because of loss of fat-free mass. Thus, illness severity increases energy and protein requirements. A volume of 20 kcal/kg has been suggested, but that simple method is fraught with inaccuracy. Of the reviewed equations, the 2003 Penn State equation has the best prediction accuracy (85%) [27] .

One of the aims of treatment of gastrointestinal diseases such as short bowel syndrome is reduction of TPN dependence. Evaluating the location and severity of gastrointestinal impairment helps to decide the location of tube placement. Gastric tube is indicated in oral or oesophageal diseases. If the stomach does not function or has been surgically removed, the tube is placed in the small intestine. The choice of formula is also important as mentioned before [28] .

The treatment of dyslipidaemia of metabolic syndrome should be focussed on lowering LDL and increasing HDL. Combination lipid-lowering therapy is frequently needed. Nicotinic acid and fibric acid derivatives both act to reduce triglycerides and increase HDL cholesterol. They are frequently used with statin medications [29] .


  Conclusion Top


Early EN has been suggested to be beneficial in the critically ill. But depending on enteral route alone might lead to underfeeding. Therefore, many patients may need combinations of EN and PN, adjusted as tolerance to EN increases.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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