15.4 Nutrition Flashcards
A 45-year-old man with a history of ulcerative colitis and alcohol abuse is admitted to the intensive care
unit for inotropic and ventilatory support following a laparotomy to excise a toxic megacolon. His body
mass index is 18 kg/m2.
a) Why should this patient receive early nutritional support and what are the clinical benefits? (30%)
why should this patient:
Need for early nutritional support:
> > Existing malnourishment evidenced by low BMI.
> > Chronic alcohol excess associated with malnutrition.
> > Long-term gastrointestinal disease
associated with malnutrition.
> > Inflammatory condition, recent surgery, sepsis and critical illness all contribute to a catabolic state.
> > Poor absorptive capacity.
> > Unlikely to be able to re-establish normal oral feeding within the next five days so supplementation indicated.
Clinical benefits early nutrition
Clinical benefits:
» Improved wound healing.
>> Improved weaning from ventilator, reduced risk of respiratory infection, maintenance of respiratory muscle strength all contribute to fewer ventilator-dependent days.
> > Improved immune function generally.
> > Improved rehabilitation due to
maintenance of skeletal muscle strength.
> > Reduced ICU length of stay.
> > Overall reduced mortality.
Refeeding syndrome
Whos at risk
Explain pathophysiology
Assessment of this patient according to NICE guidelines indicates that he is at risk of refeeding syndrome.
Risk factors include the following:
> > Low BMI with unintentional weight loss.
> > Poor recent nutritional intake.
> > Low serum potassium, magnesium or phosphate.
> > History of alcohol abuse.
> > Drugs including chemotherapy,
insulin, antacids and diuretics.
Chronic malnutrition causes depletion of electrolytes through reduced intake and utilisation for metabolism of fat and lipid stores.
Serum electrolyte levels are maintained better than intracellular levels due to reduced energy
for transmembrane pumping and reduced insulin-dependent pumping.
Upon refeeding, there is a sudden insulin-driven uptake of glucose into cells and accompanying electrolytes.
Serum levels of these ions, such as magnesium, phosphate, calcium and potassium, can drop precipitously.
Also, cardiac muscle is weakened by chronic malnutrition. On refeeding, the circulating volume increases due to glucose-driven osmolality, risking heart failure. Weakened respiratory muscles must attempt to cope with increased carbon dioxide production as the body reverts to more carbohydrate-based metabolism (the respiratory quotient for a carbohydrate diet being 1, but 0.7 for fat- and 0.9 for protein-based diets, respectively).
This may precipitate arrhythmias, seizures, respiratory failure, cardiac failure, coma, death.
b) What is the specific composition of a nutritional regimen for this patient? (30%)
> > This patient is at risk of refeeding syndrome due to:
• Low BMI.
- Alcohol abuse.
- Low recent oral intake likely due to illness.
- Toxic megacolon and ulcerative colitis may have resulted in electrolyte imbalance.
>> Water 30–35 ml/kg/day, but guided by fluid balance, abnormal losses and cardiac output monitoring. Avoid excessive fluid input in refeeding situation.
> > The following are normal requirements,
all of which should be cut to
one-third for the first four to seven days
of nutrition in a patient at risk of
refeeding syndrome:
- 30 kCal/kg/day.
- 60% intake from carbohydrate so 4.8 g/kg/day.
- 40% intake from fat so 1.3 g/kg/day.
- Protein 0.8–1.5 g/kg/day.
> > Electrolytes should be guided by frequent blood testing, and increased
quantities likely to be needed in refeeding situation:
• Sodium 1 mmol/kg/day.
• Potassium 2–4 mmol/kg/day.
• Phosphate 0.3–0.6 mmol/kg/day.
• Magnesium 0.2 mmol/kg/day.
>> Vitamins: • Intravenous thiamine and riboflavin: one to two pairs Pabrinex twice daily 30 minutes before starting feeding and continued for 10 days.
• Supplement vitamins A, D, E, K, C.
> > Trace elements:
• Copper, zinc, selenium, manganese.
> > Immunonutrition:
• Glutamine 0.2 g/kg/day.
ICU dietician will work within the
multidisciplinary team to optimise nutrition
of this patient.
List advantages of enteral nutrition (20%)
Cheaper.
Avoidance of line infections and the complications of line insertion.
Reduced risk of stress ulceration.
Maintenance of gut integrity, absorptive and
immune function.
Lower risk of hyperglycaemia.
Reduced risk of abnormal liver function test
results, hypertriglyceridaemia, metabolic
acidosis, electrolyte imbalance and uraemia
associated with parenteral feeding
List disadvantages of enteral nutrition (20%)
May not be absorbed.
May therefore result in malnutrition.
Risk of aspiration and pneumonia.
Necrosis and bleeding of nose or small bowel
due to erosion by feeding tube (nasogastric,
PEG or PEJ).
