Impact of sepsis, lung injury, and the role of lipid infusion on circulating prostacyclin and thromboxane A2

Objective: To investigate whether plasma levels of prostacyclin (PGI2) and thromboxane A2 (TxA2) are a function of the infusion rate of soybean-based fat emulsions, severity of systemic inflammation, and pulmonary organ failure. Design: Prospective, randomized, crossover study. Setting: Intensive care unit of a university hospital. Patients: Eighteen critically ill patients, ten presenting with severe sepsis, eight with SIRS or sepsis complicated with ARDS. Interventions: Patients were randomly assigned to receive rapid fat infusion over 6 h (rFI) or slow fat infusion over 24 h (sFI) along with parenteral nutrition. Measurements and results: The stable prostanoids 6-keto-PGF1alpha and TxB2 were measured in arterial and mixed venous blood samples, and at 6-h periods trans-pulmonary balances (TPB) were calculated. Free linoleic acid fraction was determined in arterial blood. rFI induced greater increase of linoleic acid than sFI in both groups. Enhanced prostanoid levels and correlations with linoleic acid availabilities were found, however, in ARDS patients only, revealing the highest sepsis- and lung injury scores. Averaged TPB per 24 h was positive in the sepsis group and negative in the ARDS group as rFI induced lowest TPB values for TxB2 at 6 h. Conclusion: The quantity of prostanoids formed and their subsequent utilization are dependent on the availability of precursor linoleic acid and are probably affected by the severity of SIRS or sepsis and the existence of pulmonary organ failure, respectively. Because TxA2 might be extracted by the injured lung, rapid infusion of soybean-based fat emulsions should be avoided in patients suffering from severe pulmonary organ failure.