Nutrition in Critical Care

Question 1

What are the 3 key principles of nutrition in the ICU

Answer 1

1. Optimize enteral nutrition within 48 hours ICU admission
2. Avoid forced starvation
3. Judicious use of supplemental parenteral nutrition

Question 2

How is nutritional assessment conducted in the ICU

Answer 2

1. Malnutrition Universal Screening Tool (MUST) (not validated for ICU pts)
2. Nutrition Risk in the Critically Ill (NUTRIC) (not validated for ICU pts)
3. Clinical assessment
   - pre-ICU weight loss
   - decline of physical performance prior to ICU admission
   - Examine muscle mass/ body composition / strength

Patients admitted to ICU > 48 hrs are considered high risk for malnutrition

Question 3

What is the aim of nutrition in acute illness

Answer 3

Meet energy expenditure (EE) to decrease negative energy balance

Question 4

How should energy expenditure ideally be determined

Answer 4

Indirect calorimetry (IC) using: (BEST)
1. VO2 (PAWC)
2. VCO2 (Ventilator)

Feeding equations (less accurate than above)
1. Harris-Benedict
2. Schofield

Question 5

How much energy per ml do ‘low energy formulations’ provide

Answer 5

<0.9 kcal/ml

Question 6

How much energy per ml do ‘normal energy formulations’ provide

Answer 6

0.9 - 1.2 kcal/ml

Question 7

How much energy per ml do ‘high energy formulations’ provide?

Answer 7

> 1.2 kcal/ml

Question 8

How much protein do high protein formulations provide

Answer 8

These formulas contain 20% or more of total energy from protein.

Question 9

What are high lipid formulas

Answer 9

These formulas contain more than 40% of total energy from lipids

Question 10

Which patient groups should not receive standard formulation enteral nutrition?

Answer 10

1. Volume restriction - require concentrated enteral nutrition
2. Renal failure ± volume overload ± electrolyte abN - require electrolye restricted (renal) enteral nutrition formulations

Question 11

Is routine supplementation with the following indicated:
1. Omega 3
2. Antioxidants
3. Glutamine
4. Ornithine ketoglutarate
5. Arginine
6. Pre-biotics
7. Beta-hydroxy-beta-methylbutyrate (HMB)
8. Immune modulators

Answer 11

No

Question 12

How should enteral feeding be initiated in critically ill patients

Answer 12

Start the standard formulation at 10 to 30 ml/hour increasing over six days and increasing more incrementally to the target rate in more severely critically ill patients.

INFREQUENT pausing of enteral nutrition for issues such as
- high gastric residual volumes
- Diarrhoea
- Vomiting

may be required.

Question 13

When should gastric residual volumes be measured?

Answer 13

If the patient exhibits a clinical change e.g.
1. Abdominal pain
2. Abdominal distension
3. Deterioration in haemodynamics/overall status

Question 14

When should post pyloric feeding be used

Answer 14

When gastric feeding is not tolerated or is contraindicated or it may be considered in those with a high risk of aspiration

Question 15

Classify feeding formulations

Answer 15

Concentrated
- requiring volume restriction

Predigested (no compelling evidence for benefit)
(Previously called semi-elemental, elemental)
- Malabsorptive syndromes unresponsive to pancreatic enzyme supplementation
- Persistent diarrhoea with standard feed
- thoracic duct leak (chylothorax/chylous ascites)
- ?? short gut or marginal gut function ??

Critical illness
- Renal formulae for fluid and electrolyte restriction
- Glycaemic control formulae for patients receiving bolus feeding

Question 16

Describe the nutritional characteristics of typical standard enteral nutrition

Answer 16

Isotonic to plasma
1 kcal/ml
Lactose free
Intact protein content 40g / 1000 kcal
Non-protein calorie : Nitrogen ratio is 130

CHO - Mix of simple and complex
Fat - Mainly long chain
Essential vit, minerals, micronutrients

Question 17

What is the theoretical advantage to low CHO/High fat enteral nutrition

Answer 17

Lower CHO means less CO2 production –> smaller Ve necessary to control PaCO2 –> reduced weaning time.

Question 18

How does the protein content in the renal enteral nutrition formulation differ from the standard formulation. Discuss.

Answer 18

Standard formulation = 40g / 1000 kcal

Renal formulation = 44g /1000 kcal

Historically, low protein enteral nutrition was developed for patients with renal disease because of the widespread belief that protein restriction delays the progression of renal disease.
—-> multiple trials show that patients with renal failure can tolerate protein intake as high as 2.5g / kg /day during critical illness.

Question 19

What are the characteristics of renal enteral feeding formulations

Answer 19

1. Promote fluid and specific electrolyte restriction (K, PO4)

Question 20

Which electrolyte cannot be effectively restricted by any of the enteral feeding formulations

Answer 20

Calcium. All enteral formulae exceed calcium removal capacity in patients on haemodialysis

Question 21

When should standard enteral feeding formulations be used in renal patients

Answer 21

1. Normal volume and electrolyte status
2. Patients on continuous renal replacement therapy

standard feeds preferred.

Question 22

What is a reasonable calorie goal for a patient of normal weight

Answer 22

25 kcal/kg/day

Question 23

When should gastric residual volumes be measured

Answer 23

Clini

Question 24

Classify the complications of enteral nutrition

Answer 24

1. Aspiration
2. Diarrhoea ( 15% vs 6 % with non-enteral) - mechanism unknown
3. Metabolic (hyperglycaemia, micronutrient deficiency and re-feeding syndrome)
4. Dehydration - minimal water contained in standard formulations
5. Constipation

Question 25

Define the re-feeding syndrome

Answer 25

The typical clinical complications that occur due to fluid and electrolyte shifts during nutritional rehabilitation of significantly malnourished patients.

Question 26

List the most important and common characteristics of the re-feeding syndrome

Answer 26

1. Hypophosphataemia 2. Hypokalaemia + hypoMg 3. Volume overload with peripheral oedema 4. CCF 5. Rhabdomyolysis 6. Seizures 7. Haemolysis 8. Respiratory insufficiency

Question 27

Describe the pathophysiology of the re-feeding syndrome

Answer 27

PO4 depleted (malnourished). --> Nutritional replenishment --> insulin release 1. --> cellular uptake PO4 --> reduced serum PO4 2. --> Increased synthesis of ADP/2,3 DPG --> use up PO4 --> subsequent lack of phosphorylated intermediates --> tissue hypoxia, myocardial dysfunction, respiratory failure (diaphragm), haemolysis, rhabdomyolysis, seizures.

Question 28

How much water is in standard enteral feeding formulations

Answer 28

20 ml/kg (for formulations containing 25 kcal/kg with 1 kcal/ml) not enough. Must supplement and monitor volume status