A critically ill surgical patient requires parenteral nutrition (PN). Nitrogen requirement is estimated at 0.25 g/kg/day. Body weight is 70 kg. What is the required amino acid input per day, and which complication is most specific to PN administered through a peripheral vein rather than a central catheter?

• A 17.5 g nitrogen/day as amino acids; specific peripheral PN complication is catheter-related bloodstream infection (CRBSI)
• B 1.25 g protein/kg/day amino acids (87.5 g protein); thrombophlebitis and central vein thrombosis are the peripheral PN complications
• C 17.5 g nitrogen/day; specific peripheral PN complication is thrombophlebitis of peripheral vein due to hyperosmolar solution ✓
• D 25 g nitrogen input; specific complication of peripheral PN is hyperglycaemia due to high dextrose concentration

Explanation

Nitrogen requirement = 0.25 g/kg/day × 70 kg = 17.5 g N/day. Protein (amino acids) = 17.5 × 6.25 = 109 g amino acids/day. Peripheral PN must use low-osmolality formulations (< 800-900 mOsmol/L) to avoid thrombophlebitis; the principal limitation and specific complication of peripheral PN is chemical thrombophlebitis of peripheral veins due to the hyperosmolar nature of PN solutions. Central PN (via PICC or central catheter) allows higher osmolality solutions. CRBSI is a complication of central venous access, not specific to peripheral PN. Hyperglycaemia is a metabolic complication of PN regardless of route.

Reference: Bailey & Love's Short Practice of Surgery, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.