Maintenance of colloid osmotic pressure in critically ill surgical patients on total parenteral nutrition.

The effect of total parenteral nutrition (TPN) on plasma colloid osmotic pressure (COP) was investigated in critically ill and stable surgical patients. Normal COP ranged from 22 to 26 mm Hg (mean +/- SD 24 +/- 2). In critically ill patients COP levels dropped as low as 14 mm Hg (mean 17 +/- 2.4), and remained at these low levels despite aggressive nutritional support with 2,500 to 4,000 kcal and 100 to 170 g protein/day given as central vein parenteral nutrition. A group of stable surgical patients receiving TPN as supportive therapy was investigated as a comparison with the critically ill group. The mean COP level in this stable group was 21.8 +/- 0.6 mm Hg, at the low-normal level. Only when the critically ill patients became less catabolic, sometimes coincident with the resumption of oral intake, did COP levels rise toward normal. As long as a patient is critically ill, the low COP levels should be corrected by the addition of plasma and albumin, as TPN seems to be inadequate for this task in these surgical patients.