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Parenteral Nutrition

Parenteral nutrition is indicated in patients who cannot eat or tolerate enteral feeds. Parenteral nutrition can be delivered as:


(i) 2 to 2.5 liters of 5% Dextrose:
This can provide enough glucose per day to suppress gluconeogenesis. However, it cannot provide adequate nutritional support to achieve the caloric goals. This can suffice for an otherwise well-nourished, ‘not so stressed’ patient for the first few days of the post-operative period.


(ii) Peripheral Parenteral nutrition:
This is a useful method of supplying aminoacids with low concentration of glucose to provide adequate protein sparing effect in a patient with stress added to starvation. This can maintain nutrition for 1 to 2 weeks of the post-operative period or as long as the patient’s peripheral veins last. Peripheral Parenteral nutrition is recommended when one wants to avoid using central veins and is based on the principle that peripheral veins by and large tolerate low osmolar solutions (≤800 mOsmol/L). Osmolarity of a solution can be reduced by decreasing the glucose component drastically and substituting lipid solutions to provide the necessary calories as lipids are low osmolar solutions.


Osmolarity of solutions:

Solution
Osmolarity
Energy (kcal/l)
Saline (0.9% NaCl)
290
Nil
Glucose 5%
252
200
Glucose 10%
505
400
Glucose 20%
1010
800
Glucose 25%
1262
1000
Glucose 50%
2525
2000
Glucose 10%
260
900
Glucose 20%
260
1800
Glucose 30%
200
2700

(iii) Peripheral Parenteral nutrition:
This is a combination of aminoacids, concentrated glucose and lipid solutions, which can be used to provide required calories and proteins for an indefinite period. Here the high concentration of glucose increases the osmolarity of the solutions, which thus cannot be given through the peripheral veins, and hence central venous access becomes mandatory. Most often the internal jugular or subclavian veins are used and this allows a painless route of administration of high concentration solutions for longer periods as required in most critically ill patients.


Parenteral Nutrition-Access

Subclavian vein:
Ideal access
Advantages: stable position, enabling proper dressing and least possibility of sepsis Disadvantages: pneumothorax (commonest complication)

Internal jugular vein:
Second best choice
Advantages: Less chances of pneumothorax and easy access
Disadvantages: Unstable position, discomfort in neck movements, accidental puncture of internal carotid artery (commonest complication).

Femoral vein:
Should be strictly avoided
Disadvantages: high risk of infection and thrombophlebitis as it is an area which is difficult to keep clean

Peripheral vein:
High incidence and thrombophlebitis
Only low osmolarity solutions can be given [≤800 mOsm/lit]