Surfactant phosphatidylcholine in thermally injured pigs

OBJECTIVE: To investigate the effect of a thermal injury on pulmonary surfactant phosphatidylcholine kinetics. DESIGN: Random, controlled study. SETTING: University research laboratory. SUBJECTS: Yorkshire swine (n = 8) with and without a 40% total body surface area burn. INTERVENTIONS: A new isotope tracer methodology was used to quantify surfactant phosphatidylcholine kinetics. Four days after burn, [1,2-13C2]acetate and [U-(13)C16]palmitate were infused continuously for 8 hrs to quantify surfactant phosphatidylcholine synthesis, secretion, recycling, and irreversible loss. MEASUREMENTS AND MAIN RESULTS: The total surfactant phosphatidylcholine pool size was reduced from the control value of 2.65 +/- 0.05 to 1.61 +/- 0.08 micromol/g wet lung in burned animals (p <.05), as was the proportional contribution of palmitate to lung surfactant phosphatidylcholine composition. This reduction was associated with a significant decrease in lung dynamic compliance from the control value of 66 +/- 6 to 55 +/- 6 mL/cm H2O for burned pigs (p <.05). The most prominent response of lung phosphatidylcholine kinetics was a decrease in the total lung phosphatidylcholine synthesis from a control value of 12.7 +/- 1.2 to 5.5 +/- 0.3 nmol phosphatidylcholine-bound palmitate x hr(-1) x g of wet lung(-1) in burned animals (p<.05). CONCLUSIONS: Pulmonary phosphatidylcholine content and palmitate composition decrease after burn injury because of a decrease in the rate of phosphatidylcholine synthesis. These responses likely contribute to impaired lung compliance.