Immediate intralipid clearance from plasma in critically ill patients after a single-dose injection

Plasma fractional removal rates (k2) of Intralipid injected in parallel with 125I albumin were analyzed in five healthy males and nine critically ill patients. The k2 values of critically ill patients were similar to those of healthy subjects. However, the initial plasma concentrations of Intralipid calculated by extrapolation to zero-time (y0) were markedly different. The mean y0 value in the critically ill patients was 43% that of healthy subjects. No plasma loss of 125I albumin occurred throughout the test. Intralipid to 125I albumin plasma concentration ratios during the removal phase paralleled the curves obtained from the iv fat tolerance test. This suggests that these ratios depend on Intralipid clearance rather than leakage from the circulation. The immediate loss of Intralipid suggests that the pulmonary vasculature, the first capillary bed through which the emulsion passes, could be the site where a substantial uptake of the emulsion occurs in critically ill patients.