Negative Nitrogen Balance:
In health, the normal dietary intake of protein is 80–120 g per day (equivalent to 12–20 g nitrogen). Approximately 2 g of nitrogen are lost in faeces and 10–18 g in urine each day, mainly in the form of urea.
During catabolism, nitrogen intake is often reduced but urinary losses increase markedly, reaching 20–30 g/day in patients with severe trauma, sepsis or burns.
Following uncomplicated surgery, this negative nitrogen balance usually lasts 5–8 days, but in patients with sepsis, burns or conditions associated with prolonged inflammation (e.g. acute pancreatitis) it may persist for many weeks