Creaming and plasma clearance rate of intravenous fat emulsion in critically ill patients.

Intravenous fat emulsion incubated with serum or plasma in vitro may result in the aggregation of fat (creaming). Twenty critically ill patients were tested for in vitro creaming of the fat emulsion Intralipid. An intravenous fat tolerance test was used to determine the plasma clearance rate of Intralipid in each patient. Eleven patients (55%) were found to be creamers. These patients had a higher mean plasma clearance rate of Intralipid than non-creamers (5.73 +/- 0.56 vs. 2.77 +/- 0.37% per min; p < 0.001); however, the rates of both groups were within the range reported in normal healthy subjects. Mean C-reactive protein concentration was significantly higher (p < 0.01), and albumin levels were lower (p < 0.01) in creamers compared to non-creamers. Ionized calcium levels did not differ between the two groups. The results of this study indicate that in vitro creaming is common in acutely ill patients. The clinical significance of creaming is probably minimal since creamers tolerated 50 to 100 g/day of intravenous fat emulsion while receiving total parenteral nutrition. Creaming was uncommon when the fat was mixed with blood in vitro.