NUTRITION IN ICU

Nutrition is an essential part of the care for critically ill patients, but the optimal feeding strategy for patients in the intensive care unit (ICU) is still debated and often remains a challenge for the ICU team in clinical practice.

Medical nutrition therapy (MNT)is a term that encompasses oral nutritional supplements, enteral nutrition (EN) and parenteral nutrition (PN)

Medical nutrition therapy in the ICU aims at avoiding malnutrition in primarily well-nourished patients and at preventing further deterioration of previously malnourished patients.

Malnutrition is a significant prognostic risk factor for critically ill patients, influencing major outcomes such as mortality, length of stay, duration of mechanical ventilation, and infection rates.

There is no single “golden bullet” to diagnose malnutrition, but many helpful tools and criteria. All ICU patients should be regularly screened for risk of malnutrition.

WHEN TO START NUTRITION THERAPY

Medical nutrition therapy shall be considered for all patients staying in the ICU, mainly for more than 48 hours.

A general clinical assessment should be performed to assess malnutrition in the ICU, until a specific tool has been validated.

General clinical assessment could include anamnesis, report of unintentional weight loss or decrease in physical performance before ICU admission, physical examination, general assessment of body composition, and muscle mass and strength, if possible.

ENTERAL OR PARENTERAL?

Oral diet shall be preferred over EN or PN in critically ill patients who are able to eat.

If oral intake is not possible, early EN (within 48 h) in critically ill adult patients should be performed/initiated rather than delaying EN

If oral intake is not possible, early EN (within 48 h) shall be performed/initiated in critically ill adult patients rather than early PN

In case of contraindications to oral and EN, PN should be implemented within three to seven days

Early and progressive PN can be provided instead of no nutrition in case of contraindications for EN in severely malnourished patients.

HOW MUCH?

To avoid overfeeding, early full EN and PN shall not be used in critically ill patients but shall be prescribed within three to seven days.

Continuous rather than bolus EN should be used. ROUTE

Gastric access should be used as the standard approach to initiate EN.

In patients with gastric feeding intolerance not solved with prokinetic agents, postpyloric feeding should be used.

In patients deemed to be at high risk for aspiration, post-pyloric, mainly jejunal feeding can be performed.

In critically ill patients with gastric feeding intolerance, intravenous erythromycin should be used as a first line prokinetic therapy.

Alternatively, intravenous metoclopramide or a combination of metoclopramide and erythromycin can be used as a prokinetic therapy.

ASSESSMENT OF ENERGY EXPENDITURE

In critically ill mechanically ventilated patients, EE should be determined by using indirect calorimetry.

If indirect calorimetry is used, isocaloric nutrition rather than hypocaloric nutrition can be progressively implemented after the early phase of acute illness

Hypocaloric nutrition (not exceeding 70% of EE) should be administered in the early phase of acute illness.

After day 3, caloric delivery can be increased up to 80-100% of measured EE. REQUIREMENT

The daily energy expenditure of each individual patient can be estimated or measured.

Daily energy expenditure based on sex, body weight (in kilograms), and height (in inches) is expressed as Harris–Benedict equations as shown in table below

Another more simplified predictive equation for the BEE is as follows:

BEE (kcal/day)=25 X Wt (in kg)

To allow for the thermal effect of food intake, the BEE is multiplied by 1.2 to derive the resting energy expenditure (REE), which is the energy expenditure of basal metabolism in the resting but not fasted state. Other adjustments in the BEE that allow for enhanced energy expenditure in hypermetabolic conditions are shown below:

·       Fever: BEE X 1.1 (for each °C above the normal body temperature)

·       Mild stress: BEE X 1.2

·       Moderate stress: BEE X 1.4

·       Severe stress: BEE X 1.6

The daily energy requirement should be provided by calories derived from carbohydrates and lipids, and protein intake should be used to maintain the stores of essential enzymatic and structural proteins.

Carbohydrates supply approximately 70% of the nonprotein calories Lipids should provide approximately 30% of the daily energy needs.

Protein requirement: The goal of protein intake is to match the rate of protein catabolism in the individual patient

·       Normal metabolism 0.8 to 1.0 g/kg

·       Hypercatabolism 1.2 to 1.6 g/kg

The amount of glucose (PN) or carbohydrates (EN) administered to ICU patients should not exceed 5 mg/kg/min.

The administration of intravenous lipid emulsions should be generally a part of PN.

Intravenous lipid (including non-nutritional lipid sources) should not exceed 1.5 g lipids/kg/day and should be adapted to individual tolerance.

In patients with burns > 20% body surface area, additional enteral doses of GLN (0.3-0.5 g/kg/d) should be administered for 10-15 days as soon as EN is commenced.

In critically ill trauma, additional EN doses of GLN (0.2-0.3 g/ kg/d) can be administered for the first five days with EN. In case of complicated wound healing it can be administered for a longer period of ten to 15 days.

In ICU patients except burn and trauma patients, additional enteral GLN should not be administered.

High doses of omega-3-enriched EN formula should not be given by bolus administration.

EN enriched with omega-3 FA within nutritional doses can be administered.

High doses omega-3 enriched enteral formulas should not be given on a routine basis.

Parenteral lipid emulsions enriched with EPA + DHA (Fish oil dose 0.1-0.2 g/kg/d) can be provided in patients receiving PN

To enable substrate metabolism, micronutrients (i.e. trace elements and vitamins) should be provided daily with PN. Antioxidants as high dose monotherapy should not be administered without proven deficiency.

In critically ill patients with measured low plasma levels (25-hydroxy-vitamin D

< 12.5 ng/ml, or 50 nmol/l) vitamin D3 can be supplemented.

In critically ill patients with measured low plasma levels (25-hydroxy-vitamin D

< 12.5 ng/ml, or 50 nmol/l) a high dose of vitamin D3 (500,000 UI) as a single dose can be administered within a week after admission.

EN should be delayed

·       if shock is uncontrolled and hemodynamic and tissue perfusion goals are not reached, whereas low dose EN can be started as soon as shock is controlled with fluids and vasopressors/inotropes, while remaining vigilant for signs of bowel ischemia;

·       in case of uncontrolled life-threatening hypoxemia, hypercapnia or acidosis, whereas EN can be started in patients with stable hypoxemia, and compensated or permissive hypercapnia and acidosis;

·       in patients suffering from active upper GI bleeding, whereas EN can be started when the bleeding has stopped and no signs of re- bleeding are observed;

·       in patients with overt bowel ischemia; in patients with high-output intestinal fistula if reliable

·       feeding access distal to the fistula is not achievable; in patients with abdominal compartment syndrome; and if gastric aspirate volume is above 500 ml/6 h.

Early EN should be performed

·       in patients receiving ECMO

·       in patients with traumatic brain injury

·       in patients with stroke (ischemic or haemorrhagic)

·       in patients with spinal cord injury

·       in patients with severe acute pancreatitis

·       in patients after GI surgery

·       in patients after abdominal aortic surgery

·       in patients with abdominal trauma when the continuity of the GI tract is confirmed/restored

·       in patients receiving neuromuscular blocking agents

·       in patients managed in prone position

·       in patients with open abdomen

·       regardless of the presence of bowel sounds unless bowel ischemia or obstruction is suspected in patients with diarrhoea.

SPECIAL CONSIDERATIONS

In non-intubated patients not reaching the energy target with an oral diet, oral nutritional supplements should be considered first and then EN.

In non-intubated patients with dysphagia, texture-adapted food can be considered. If swallowing is proven unsafe, EN should be administered.

In non-intubated patients with dysphagia and a very high aspiration risk, post- pyloric EN or, if not possible, temporary PN during swallowing training with removed naso-enteral tube can be performed.

In patients after abdominal or esophageal surgery, early EN can be preferred over delayed EN.

In critically ill patients with surgical complications after abdominal or esophageal surgery and unable to eat orally, EN (rather than PN) should be preferred unless discontinuity or obstruction of GI tract, or abdominal compartment syndrome is present.

In the case of an unrepaired anastomotic leak, internal or external fistula, a feeding access distal to the defect should be aimed for to administer EN.

In the case of an unrepaired anastomotic leak, internal or external fistula, or if distal feeding access is not achieved, EN should be withheld and PN may be commenced.

In case of high output stoma or fistula, the appropriateness of chyme reinfusion or enteroclysis should be evaluated and performed if adequate.

Trauma patients should preferentially receive early EN instead of early PN.