Monitoring the optimal infusion of intravenous lipids. Detection of essential fatty acid deficiency.

Since increased amounts of the trienoic acid C20:3w9 are produced in patients with essential fatty acid (EFA) deficiency (EFAD) of the linoleic (w6) family, the trienoic (C20:3w9)-to-tetraenoic (C20:4w6) fatty acid ratio (T/T ratio) is used as a biochemical indicator of w6 EFAD. A T/T ratio above 0.02 is suggestive of w6 EFAD. Fatty acid profiles, listing the percent of individual and families of fatty acids, are useful in evaluating the effects of intravenous lipid infusions during treatment. We evaluated the condition of a patient with fat malabsorption treated with a soybean oil-based intravenous lipid solution and found that levels of linoleic acid and its derivatives did not reach reference levels, while linolenic acid and its derivatives quickly exceeded reference levels. A persistently elevated T/T ratio suggested that altered fatty acid metabolism characteristic of linoleic acid deficiency was not corrected by the treatment. Plasma levels of the EFA, ie, linoleic and linolenic acids, cannot be predicted from the lipid treatment or from the patient's clinical course; therefore, periodic measurements of EFA are required to monitor the effects of therapy. To provide the most effective therapy, the amounts and proportions of linoleic and linolenic acids provided in the intravenous infusions should be varied, as indicated by periodic monitoring of the fatty acid profile.