Nutrition in Critically Ill Flashcards
Multifactorial cause of catabolic state in critically ill (5)
- Systemic inflammatory response
- Hypermetabolism
- Multiple organ dysfunction
- Infectious complications
- Malnutrition
Physiologic adaptation to starvation
Pathologic adaptation to starvation in critically ill patients
Physiologic metabolism to starvation
1. Lowering blood glucose to near 3 mmol/L
- Suppresses insulin secretion
- Fat hydrolysis -> FFA release
2. Use of FFA - conversion to ketone bodies
- Theoretically: 15kg of fat can last for 67 days
(9kcal each g = 135,000kcal total)
- Conservation of glucose to feed the brain
4. Prolonged starvation - gluconeogenesis from amino acids -> protein catabolism
Pathologic metabolism in critically ill
1. Adrenal axis and system inflammation promotes protein breakdown and insulin resistance
2. Insulin fails to control blood glucose level and muscle catabolism
3. Poor mobilisation of FFA due to adipose tissue poor perfusion
4. Increased energy expenditure from baseline
History and shift to nutritional therapy in critically ill
Over past 20 years, there is a sift away from NBM to nutrition support to currently nutrition therapy
Nutrition support - nutrition as fuel to support critical illness
Nutrition therapy - nutrition intervention to modulate immunologic and inflammatory response
Goals of nutrition therapy in critically ill
- Nutrition consistent with patient’s condition
- Prevent nutrient deficiencies
- Avoid complications related to delivering nutrition
- Improve patient outcomes
Assessment of nutritional status in critically ill
- Historically
- Current practice
Historically: albumin and anthropometric measurements
–> Highly inaccurate - acute phase reactant, fluid resuscitation altered the levels
Current practice: ASPEN and SCCM guidelines (2016)
- NUTRIC score or NRS-2002
- Early enteral nutrition beneficial to critically ill (within 48 hours)
Enteral or parenteral nutrition?
RCTs meta-analysis: no difference in survival
However: enteral feeding is preferred unless absolute contraindications (ischaemic or bowel obstruction)
Reasons:
1. Reduction in infectious complications
2. Significantly less expensive
3. Prevents gut bacterial translocation - NBM rapidly causes gut luminal mucosa atrophy
(even small trophic feeds increase blood flow to guy and preserve GI structures)
4. Strengthens gut-associated lymphoid tissue
5. Lesser side effects compared to PN
When should enteral nutrition be initiated in critically ill patients?
Early enteral nutrition - within 48 hours of ICU admission
- Bowel sounds and flatus may not necessary be present for EN initiation
- Once resuscitated and haemodynamically stable with static or reducing vasopressors (no longer in shock)
(complications of ischaemic bowel due to EN in critically ill patients in shock) - Watch for feeding intolerance - abdominal distention, vomiting
RCTs meta-analysis:
1. Early EN reduces mortality and reduces infectious complications
2. Early EN does not affect duration of ventilation or ICU length of stay
NUTRIC Score
Quantify risk of critically ill patients developing adverse events that MAY BE MODIFIED by aggressive nutrition therapy
Comprises of:
- Age
- APACHE II score
- SOFA score
- Comorbids
- Days from hospital to ICU admission
- IL-6 levels
0-4 (0-5 with IL6): low score - low malnutrition risk
5-9 (6-10 with IL6): high score - worse outcome in mortality and ventilation, will benefit from aggressive nutrition therapy
How many calories should critically ill patients receive?
How to estimate energy expenditure?
Varies, and optimal calorie in unclear
Standard practice:
- Calories: 25-30 kcal/kg IBW
- Proteins: 1-1.2 g/kg per day IBW
(modified in severely obese - lower calories, more proteins)
Escalation:
Start within 48 hours of ICU admission
Acute phase - 70% TEE (hypocaloric)
Gradually increase to 100%
Methods of estimation
1. Indirect calorimetry - total energy expenditure (TEE)
2. Resting energy expenditure, multiplied by stress factor 1 to 2 -> estimate TEE
3. Equations: Harris-Benedict, Ireton-Jones, Weir
Composition of enteral nutrition in critically ill
A. Protein: 1-1.2 g/kg ABW (2-2.5g/kg IBW)
- More protein instead of total calories is associated with improved outcome
- Whole protein recommended instead of peptide based formula
B. Fat: 25-50% of calories
- Insufficient evidence on high fat or low fat feeding
C. Calories: 25-30 kcal/kg IBW
Choice of formulas
1. Arginine based - surgery, trauma (contraindicated in sepsis - increases mortality)
2. Anti-oxidants (Vit C, E) and minerals (selenium, zinc, copper) - burns, trauma, mechanical ventilation
3. Glutamine - RCTs no benefit, PN glutamine harmful -> avoided
4. Omega-3 FA - conflicting evidence
5. Low phosphate and potassium - CKD
Should critically ill patients in shock and/or receiving vasopressors receive enteral nutrition?
No.
Criteria to initiation of enteral feeding
1. Stabilised shock, adequately resuscitated
2. Stable or reducing vasopressors
3. Downtrending lactate
High risk of ischaemic bowel in critically ill patient in shock
Continuous or bolus enteral nutrition?
Continuous feeding preferred
(One pseudorandom study - aggressive early EN via bolus feeding harmful)
Continuous: small volume continuously over 24 hour period
Bolus: large volume over short period
Monitoring of enteral feeding tolerance
- Abdomen distention
- Bowel output
- Vomiting
- Pain (or haemodynamics)
- +/- gastric residual (aspirate) volume (GRV)
New guidelines: aspirate volume checks provide no clinical benefit
Positioning of patient during enteral feeding
Semi-recumbent (30-45 degree)
Evidence: conflicting results
1. Drakulovic 1999: significant reduction in pneumonia in semi-recumbent
2. Nieuwenhoven 2006: no statistical significance
Define high gastric output
Motility agents in critically ill
High gastric output > 500mL after 6 hours OR vomiting
- Start prokinetics
- Pause EN, restart at half rate
- If intolerance persists, KIV nasojejunal tube
- Attempt EN up to 7 days
Choice of motility agents
1. Metoclopramide 10mg Q8H
2. Erythromycin
3. Emerging: PO naloxone
(reverses side effects of opioid narcotics on GI tract - allows higher EN volume, reduced GRVs, reduce ventilator associated pneumonia)
Contraindications to Enteral Feeding
- Ischaemic bowel
- Intestinal obstruction, perforation, leak
- Severe malabsorption
- Severe short gut syndrome
- Uncontrolled shock
- Uncontrolled respiratory failure
- Abdominal compartment syndrome (IAP > 20)
- Active upper GI bleeding
(Previous taboos are no longer contraindicated)
1. Pancreatitis - feeding more beneficial
2. Enterocutaneous fistulae
3. GI surgery - early gut motility improves outcome
Complications of enteral feeding
A. Gastrointestinal
- Nausea, vomiting, diarrhoea/constipation
- Aspiration
- Ischaemic bowel
B. Mechanical
- Feeding tube obstruction
- Nasal or gastic mucosa erosion and bleeding
- Infection
- Perforation
- Accidental insertion into pulmonary tree
- Tube displacement or dislodgement
- Sinusitis
C. Metabolic
- Hyperglycaemia
- Electrolyte derangement
- Overfeeding
- Refeeding syndrome
Strategies to reduce enteral feeding complications
Insertion
1. Soft and well lubricated tube
2. Tube position verified radiographically
Feeding
3. Semi-recumbent position (30-45 degree)
4. Small-bowel feeding tube
5. Continuous feeding
6. +/- PO naxolon for opioids side effect reversal
7. Motility agents
Diarrhoea
8. Rule out infective causes in diarrhoea
9. Stool bulking agents in diarrhoea or change formula
Biochemical monitoring
10. Monitor blood sugar
11. Monitor electrolytes for refeeding syndrome (hypokalaemia, hypophosphataemia)
12. Thiamine replacement
Feeding tolerance
13. Monitor abdominal distention, vomiting, diarrhoea
14. +/- monitor aspirate volume
Gastric or small bowel feeding tube?
Meta-analysis: small bowel feeding has no added improvement, but has reduction in pneumonia
However, small bowel tubes are less feasible / difficult to insert and require endoscopic / fluoroscopic guidance
Parenteral nutrition in critically ill
ASPEN-SCCM guideline recommendations:
1. 7-10 days ICU admission who are not malnourished and have lower nutritional risk, but not feasible for enteral feeding or only receiving fraction of goal calories
2. On admission malnourished, high nutritional risk and enteral feeds not possible
Complications of parenteral nutrition
A. Mechanical
1. Catheter related complications - pneumothorax, thromboembolism, CRBSI
B. Metabolic
2. Hyperglycaemia
3. Electrolyte abnormalities
4. Transaminitis, ALP, hyperbilirubinaemia
4A. Steatosis, fatty liver
4B. Acalculous cholecystitis
History and evolution of feeding in acute pancreatitis
20 years ago - NBM, fed TPN
Research have proven improved outcomes in patients who receive early enteral feeding within 48 hours of admission, EVEN in severe acute pancreatitis
No difference when fed gastrically or jejunally
- However gastric feeding may fail due to mechanical pressure of swollen retroperitoneum compressing onto gastic outlet
Propofol use and nutrition content
Propofol contains 10% lipid emulsion
(provides 1.1 kcal/mL)
Risk of hypertriglyceridaemia leading to acute pancreatitis
Monitor TG levels in patient receiving high dose of propofol
