Approximately 25-30kcal/kg/day in a normal, stable patient. Approximately 1300-1800kcal/day.
Should be provided in TPN as a combination of fat and glucose, but no evidence to mandate a particular ratio as long as minimum requirements are met. Dual energy supply minimises metabolic complications, reduces fluid retention, enhances substrate utilisation, and is associated with reduced CO2 production
Carbohydrate
2g/kg/day
Physiological maximum rate of utilisation is about 4mg/kg/minute
No point infusing glucose faster - it would just get turned into fat, and lead to hyperglycaemia in the meantime
Fat
Dietary fat is composed of triglycerides made up of four main long-chain fatty acids
Saturated - palmitic (C16) and stearic (C18)
Unsaturated - oleic (C18 with one double bond) and linoleic (C18 with two double bonds)
Linolenic (C18 with three double bonds) and medium-chain fatty acids (C6-C10) are also contained in the diet
Unsaturated fats are essential - cannot be synthesised in vivo
Emulsions are produced for parenteral nutrition containing long-chain triglycerides, which provide energy at about 9kcal/g.
Do these emulsions cause immunosuppression? Maybe. Newer emulsions might contain medium-chain fatty acids and omega-3 FAs, but evidence supporting this is sparse, especially is TPN is run at a normal rate and triglycerides are being checked regularly.
Protein
Nitrogen 0.1-0.15 g/kg/day, increasing to double that in hypermetabolic patients
