Pulmonary extraction of serotonin and propranolol in patients with adult respiratory distress syndrome.

Because injury to the pulmonary vascular endothelium is associated with the development of the adult respiratory distress syndrome (ARDS), we assessed the metabolic function of pulmonary endothelial cells by the measurements of the first-pass pulmonary extraction of [14C]serotonin and [3H]propranolol in 15 patients with ARDS and 15 patients at risk for developing ARDS. Serotonin extraction ratio was lower in patients with ARDS (0.85 +/- 0.10, mean +/- SD) than in patients at risk (0.91 +/- 0.04) (p less than 0.025), and both values were significantly reduced (p less than 0.005) when compared with a control group value (0.97 +/- 0.01). The decrease in serotonin extraction was correlated with the severity of ARDS (r = -0.67) (p less than 0.001) and with pulmonary function changes over time. Propranolol extraction ratio was decreased in patients at risk (0.66 +/- 0.11) (p less than 0.005) but not in patients with ARDS (0.75 +/- 0.11), when compared with those in the control group (0.81 +/- 0.03). Low values in patients at risk were restored to normal by continuous positive airway pressure breathing. We conclude that pulmonary extraction of serotonin, an index of pulmonary endothelial cell function, correlates with the severity of ARDS.