Providing Nutrition on the ICU
Chief dietician, John Radcliffe Hospital, Oxford
Focus on types of feeding routes used in critical care
A number of potential feeding routes are available in the critically ill patient. These include:
- Oral nutritional support
- Nasogastric tube feeding
- Nasojejunal tube feeding
- Gastrostomy tube feeding
- Jejunostomy tube feeding
- Parenteral nutritional support
Oral nutritional support
Fortification of meals or modification of food texture may be required for those ICU patients who can swallow safely. Common techniques are the use of nourishing drinks and encouraging small meals with energy dense snacks and supplements. Supplements include complete sip feeds and puddings, glucose polymer powders and fat liquids.
Nasogastric (NG) tube feeding
This is the most commonly seen type of feeding on the ICU, employing either a Ryles or fine bore tube passed into the stomach. This mode of feeding is dependent on normal gastric emptying and a functioning gut.
Nasojejunal (NJ) tube feeding
NJ tubes are often employed in the presence of either abnormal pylorus function or delayed gastric emptying. Some centres prefer to feed patients with severe pancreatitis by NJ route in an attempt to ameliorate the production of pancreatic secretions, although current available evidence in favour of this approach is not conclusive. NJ feeding can be considered in patients in the prone position in an attempt to minimise the risk of pulmonary aspiration.
Gastrostomy tube feeding
These include surgically placed gastrostomies, percutaneous endoscopically placed gastrostomies (PEGs) and radiologically placed gastrostomies (RIGs). These techniques are indicated for prolonged tube feeding e.g. head injured patients, patients with inaccessible upper GI tracts or after extensive maxillofacial surgery.
Jejunostomy tube feeding
These include the surgically placed (JEJ), percutaneous endoscopically placed jejunostomy (PEJ), radiologically placed jejunostomy or percutaneous gastrojejunostomy (PEG/J) placed endoscopically or radiologically. These techniques are indicated in proximal problems of the GI tract e.g. post oesophagectomy and gastrectomy.
see Parental Nutrition resource.
Focus on the use of prokinetics
If NG feeding is poorly established, most intensive care feeding protocols include recommendations on the use of prokinetics as a first line prior to NJ placement or initiation of parental nutrition. Three common approaches to delayed gastric emptying or high NG aspirates are:
- Use of laxatives if the bowels have not opened
- Metoclopramide IV to encourage stomach emptying
- Erythromycin IV to promote intestinal motility
Focus on the use of Pro/symbiotics
A recent systematic review was unable to determine any benefit or the use of pro/symbiotics in ICU patients. However, there is increasing interest in the use of pro/symbiotics to prevent reoccurrence of C. Difficile infection, decrease diarrhoea days and recolonise the bowel post eradication or following long term broad spectrum antibiotic use.
Focus on the types of feeds used
There are a wide range of commercially prepared enteral feeds available. These include:
- Standard feeds
- Energy dense feeds
- Disease specific feeds
- Low sodium feeds
- High protein feeds
- Immune enhancing feeds
Provide 1kcal/ml with or without fibre (lower osmolality)
Energy dense feeds
Provide1.2-1.5kcal/ml with or without fibre. These are suitable for patients with either a lower fluid requirement or not tolerating high rates of feed (ml/hr).
Disease specific feeds
Normally provide 2kcal/ml because of fluid restriction and are low in electrolytes. These feeds are not suitable for patients on renal replacement therapy for any length of time because the protein content is too low. Using a standard or higher protein feed and filtering off the additional fluid and electrolytes is recommended in this case.
These are ‘part digested’ to peptides/amino acids, fatty acids and glucose. These are used in patients with pancreatitis, inflammatory bowel disease and diarrhoea that has not responded to fibre alteration of the feed.
Low sodium feeds
The evidence for the benefit of low sodium feeds is poor. However, low sodium feeds are occasionally used in fluid restricted patients with a high sodium level. Rationalising other sources of sodium intake (e.g.that contained in medications) is recommended prior to changing the feed to a low sodium one.
High protein feeds
These feeds are protein enriched for patients with proportionally higher protein needs.
Immune enhancing feeds
At present there is no consensus or evidence base to recommend the use of immune enhancing enteral nutrition in critical care, the so called ‘immunonutrition’. These feeds contain one or more of arginine, omega 3 fatty acids, RNA and glutamine. Theoretical advantages to the use of immune enhancing feeds include antioxidant, immunomodulatory and anti-inflammatory properties. There is some evidence in trauma patients that enteral glutamine enriched feeds are associated with a reduction in incidence of infections. The mechanism is thought to involve decreases in muscle catabolism, enhanced antioxidant and immune stimulating profile that help maintain the mucosal integrity of the gut. One study in ARDS patients showed that the use of high fat, low carbohydrate feeds enriched in eicosapentaenoic and g linolenic acids and antioxidants reduced both the length of ICU stay and decreased the number of days ventilated. This is thought to occur through a dampening of the pulmonary inflammatory response and accompanying decreased carbon dioxide production.
Focus on monitoring nutrition provision and status in the critically ill
Continued monitoring is essential considering the variables and estimations used when estimating nutritional requirements.
Short term monitoring
- Blood biochemistry
- Feed volume received vs feed volume prescribed
- Bowel motion and gastric aspirates
- Any changes in stress/ patient activity
Longer term monitoring
This includes the same as short term monitoring plus:
- Trace elements (vitamins and minerals)
- Urinary urea for nitrogen balance
- Urinary electrolytes
- Anthropometric measurements (to determine fat and muscle mass and strength)
- Indirect calorimetry (machine that works out kcal requirements based on oxygen consumed, carbon dioxide produced and heat generated)
Focus on Enterostomies
Patients who have colostomies/ileostomies/jejunostomies may have specific nutritional problems depending on the output from the stoma and the length of the remaining bowel.
Colostomies only tend to cause nutritional concern if a high output/diarrhoea is present. Normal feeding is indicated with alteration of the fibre content as indicated. Specific attention should be given to magnesium, sodium and potassium levels. Requirements are likely to be higher due to the increased losses from the higher output stoma. If non-infective, anti-diarrhoeals such as loperamide and codeine phosphate can be useful in controlling output.
Ileostomies and jejunostomies require a similar approach to management but closer attention should be paid to electrolyte levels. Occasionally fluid restrictions or the use of isotonic liquids is needed to control high output stomas. Enteral water should be avoided in these patients as it is hypotonic and will increase stoma output (give IV hydration instead).
In patients with enterostomies being fed enterally, the need for additional parental nutrition and IV vitamins is often dependent on the function of the remaining gut e.g. short bowel syndrome.
Important medications affecting or interacting with nutritional state
Feeds need to be stopped 2 hrs before and after dose to prevent decreased drug absorption
1ml 1% provides 0.9kcal
Enteral nutrition can influence the anticoagulant effect due to the Vitamin K content of the feeds
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