Pulmonary extraction of dobutamine in critically ill surgical patients

This study was conducted to assess the pulmonary extraction of dobutamine. Eleven patients admitted to the general surgical intensive care unit, with varying diagnoses requiring dobutamine as part of their therapeutic intervention, were included. A single simultaneous sample was drawn, at the clinically required rate of infusion, from the radial and pulmonary artery catheter sites. Total dobutamine clearance was determined using the pulmonary artery (pre-lung) sample. The mean +/- SD total dobutamine clearance was 82 +/- 67 mL.kg-1.min-1 a value which is larger than the average cardiac output of plasma of 56 +/- 20 mL.kg-1.min-1. The mean percent pulmonary extraction fraction of dobutamine was 3.6% +/- 22.5% (range -34-52), a value within the 9% coefficient of variability (CV) of the assay. However, five patients had pulmonary extraction greater than the CV of the assay. Of these five patients, three had "negative" extraction values, and two had "positive" extraction values. There was no relationship between the percent pulmonary extraction of dobutamine and the rate or duration of dobutamine infusion before sampling. The results show that the extraction of dobutamine by the lungs is minimal.