Partial correction by exogenous lipid of abnormal patterns of polyunsaturated fatty acids in plasma phospholipids of stressed and septic surgical patients.

Polyunsaturated fatty acid (PUFA) profiles are abnormal in a variety of clinical conditions that are commonly seen in the surgical intensive care unit. PUFA profiles in the serum phospholipids were studied by capillary gas chromatography in 22 critically ill, hypermetabolic surgical intensive care unit patients. All patients received continuous total parenteral nutrition (TPN) by central vein with trace elements and vitamins. Eleven patients received daily supplementation with 50 gm of safflower oil-based lipid emulsion (TPN + L group). No lipid was administered in the other 11 patients (TPN). Both groups showed deficiencies in 18:2 omega 6 linoleic acid from the time of onset of TPN. In TPN the deficiency was progressive; in the TPN + L group, lipid administration prevented this progression but did not restore 18:2 omega 6 levels to normal. In the TPN group levels of 18:1 omega 9 and its metabolite 20:3 omega 9 (the triene of deficiency) increased over time, consistent with a mild essential fatty acid deficiency. These changes in omega 9 acids were not seen with lipid supplementation. Despite low levels of 18:2 omega 6 in both groups, the levels of omega 6 metabolites were normal or increased. Levels of 20:4 omega 6 (arachidonate) remained normal or slightly decreased in the TPN group but were decreased in the TPN + L group. Levels of arachidonate metabolites, in particular 22:5 omega 6, were increased in the lipid-supplemented group. We concluded that stressed patients receiving TPN develop mild essential fatty acid deficiency that is only partially correctable by lipid supplementation and that administration of supplemental lipid to these patients stimulates arachidonic acid conversion to 22:5 omega 6.